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Evolution of tetraspanin antigens in the zoonotic Asian blood fluke Schistosoma japonicum. Parasit Vectors 2023; 16:97. [PMID: 36918965 PMCID: PMC10012309 DOI: 10.1186/s13071-023-05706-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 02/17/2023] [Indexed: 03/16/2023] Open
Abstract
BACKGROUND Despite successful control efforts in China over the past 60 years, zoonotic schistosomiasis caused by Schistosoma japonicum remains a threat with transmission ongoing and the risk of localised resurgences prompting calls for a novel integrated control strategy, with an anti-schistosome vaccine as a core element. Anti-schistosome vaccine development and immunisation attempts in non-human mammalian host species, intended to interrupt transmission, and utilising various antigen targets, have yielded mixed success, with some studies highlighting variation in schistosome antigen coding genes (ACGs) as possible confounders of vaccine efficacy. Thus, robust selection of target ACGs, including assessment of their genetic diversity and antigenic variability, is paramount. Tetraspanins (TSPs), a family of tegument-surface antigens in schistosomes, interact directly with the host's immune system and are promising vaccine candidates. Here, for the first time to our knowledge, diversity in S. japonicum TSPs (SjTSPs) and the impact of diversifying selection and sequence variation on immunogenicity in these protiens were evaluated. METHODS SjTSP sequences, representing parasite populations from seven provinces across China, were gathered by baiting published short-read NGS data and were analysed using in silico methods to measure sequence variation and selection pressures and predict the impact of selection on variation in antigen protein structure, function and antigenic propensity. RESULTS Here, 27 SjTSPs were identified across three subfamilies, highlighting the diversity of TSPs in S. japonicum. Considerable variation was demonstrated for several SjTSPs between geographical regions/provinces, revealing that episodic, diversifying positive selection pressures promote amino acid variation/variability in the large extracellular loop (LEL) domain of certain SjTSPs. Accumulating polymorphisms in the LEL domain of SjTSP-2, -8 and -23 led to altered structural, functional and antibody binding characteristics, which are predicted to impact antibody recognition and possibly blunt the host's ability to respond to infection. Such changes, therefore, appear to represent a mechanism utilised by S. japonicum to evade the host's immune system. CONCLUSION Whilst the genetic and antigenic geographic variability observed amongst certain SjTSPs could present challenges to vaccine development, here we demonstrate conservation amongst SjTSP-1, -13 and -14, revealing their likely improved utility as efficacious vaccine candidates. Importantly, our data highlight that robust evaluation of vaccine target variability in natural parasite populations should be a prerequisite for anti-schistosome vaccine development.
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Rennar GA, Gallinger TL, Mäder P, Lange-Grünweller K, Haeberlein S, Grünweller A, Grevelding CG, Schlitzer M. Disulfiram and dithiocarbamate analogues demonstrate promising antischistosomal effects. Eur J Med Chem 2022; 242:114641. [PMID: 36027862 DOI: 10.1016/j.ejmech.2022.114641] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 07/14/2022] [Accepted: 07/27/2022] [Indexed: 11/03/2022]
Abstract
Schistosomiasis is a neglected tropical disease with more than 200 million new infections per year. It is caused by parasites of the genus Schistosoma and can lead to death if left untreated. Currently, only two drugs are available to combat schistosomiasis: praziquantel and, to a limited extent, oxamniquine. However, the intensive use of these two drugs leads to an increased probability of the emergence of resistance. Thus, the search for new active substances and their targeted development are mandatory. In this study the substance class of "dithiocarbamates" and their potential as antischistosomal agents is highlighted. These compounds are derived from the basic structure of the human aldehyde dehydrogenase inhibitor disulfiram (tetraethylthiuram disulfide, DSF) and its metabolites. Our compounds revealed promising activity (in vitro) against adults of Schistosoma mansoni, such as the reduction of egg production, pairing stability, vitality, and motility. Moreover, tegument damage as well as gut dilatations or even the death of the parasite were observed. We performed detailed structure-activity relationship studies on both sides of the dithiocarbamate core leading to a library of approximately 300 derivatives (116 derivatives shown here). Starting with 100 μm we improved antischistosomal activity down to 25 μm by substitution of the single bonded sulfur atom for example with different benzyl moieties and integration of the two residues on the nitrogen atom into a cyclic structure like piperazine. Its derivatization at the 4-nitrogen with a sulfonyl group or an acyl group led to the most active derivatives of this study which were active at 10 μm. In light of this SAR study, we identified 17 derivatives that significantly reduced motility and induced several other phenotypes at 25 μm, and importantly five of them have antischistosomal activity also at 10 μm. These derivatives were found to be non-cytotoxic in two human cell lines at 100 μm. Therefore, dithiocarbamates seem to be interesting new candidates for further antischistosomal drug development.
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Affiliation(s)
- Georg A Rennar
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Marbacher, Weg 6, 35032, Marburg, Germany
| | - Tom L Gallinger
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Marbacher, Weg 6, 35032, Marburg, Germany
| | - Patrick Mäder
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Marbacher, Weg 6, 35032, Marburg, Germany
| | - Kerstin Lange-Grünweller
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Marbacher, Weg 6, 35032, Marburg, Germany
| | - Simone Haeberlein
- BFS, Institute of Parasitology, Justus-Liebig-Universität Gießen, Schubertstraße 81, 35392, Gießen, Germany
| | - Arnold Grünweller
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Marbacher, Weg 6, 35032, Marburg, Germany
| | - Christoph G Grevelding
- BFS, Institute of Parasitology, Justus-Liebig-Universität Gießen, Schubertstraße 81, 35392, Gießen, Germany.
| | - Martin Schlitzer
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Marbacher, Weg 6, 35032, Marburg, Germany.
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Lund AJ, Wade KJ, Nikolakis ZL, Ivey KN, Perry BW, Pike HNC, Paull SH, Liu Y, Castoe TA, Pollock DD, Carlton EJ. Integrating genomic and epidemiologic data to accelerate progress toward schistosomiasis elimination. eLife 2022; 11:79320. [PMID: 36040013 PMCID: PMC9427098 DOI: 10.7554/elife.79320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/11/2022] [Indexed: 11/13/2022] Open
Abstract
The global community has adopted ambitious goals to eliminate schistosomiasis as a public health problem, and new tools are needed to achieve them. Mass drug administration programs, for example, have reduced the burden of schistosomiasis, but the identification of hotspots of persistent and reemergent transmission threaten progress toward elimination and underscore the need to couple treatment with interventions that reduce transmission. Recent advances in DNA sequencing technologies make whole-genome sequencing a valuable and increasingly feasible option for population-based studies of complex parasites such as schistosomes. Here, we focus on leveraging genomic data to tailor interventions to distinct social and ecological circumstances. We consider two priority questions that can be addressed by integrating epidemiological, ecological, and genomic information: (1) how often do non-human host species contribute to human schistosome infection? and (2) what is the importance of locally acquired versus imported infections in driving transmission at different stages of elimination? These questions address processes that can undermine control programs, especially those that rely heavily on treatment with praziquantel. Until recently, these questions were difficult to answer with sufficient precision to inform public health decision-making. We review the literature related to these questions and discuss how whole-genome approaches can identify the geographic and taxonomic sources of infection, and how such information can inform context-specific efforts that advance schistosomiasis control efforts and minimize the risk of reemergence.
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Affiliation(s)
- Andrea J Lund
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado AnschutzAuroraUnited States
| | - Kristen J Wade
- Department of Biochemistry & Molecular Genetics, University of Colorado School of MedicineAuroraUnited States
| | - Zachary L Nikolakis
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - Kathleen N Ivey
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - Blair W Perry
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - Hamish NC Pike
- Department of Biochemistry & Molecular Genetics, University of Colorado School of MedicineAuroraUnited States
| | - Sara H Paull
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado AnschutzAuroraUnited States
| | - Yang Liu
- Sichuan Centers for Disease Control and PreventionChengduChina
| | - Todd A Castoe
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - David D Pollock
- Department of Biochemistry & Molecular Genetics, University of Colorado School of MedicineAuroraUnited States
| | - Elizabeth J Carlton
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado AnschutzAuroraUnited States
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Kebede T, Bech N, Allienne JF, Olivier R, Erko B, Boissier J. Genetic evidence for the role of non-human primates as reservoir hosts for human schistosomiasis. PLoS Negl Trop Dis 2020; 14:e0008538. [PMID: 32898147 PMCID: PMC7500647 DOI: 10.1371/journal.pntd.0008538] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 09/18/2020] [Accepted: 06/29/2020] [Indexed: 12/20/2022] Open
Abstract
Background Schistosomiasis is a chronic parasitic disease, that affects over 207 million people and causes over 200,000 deaths annually, mainly in sub-Saharan Africa. Although many health measures have been carried out to limit parasite transmission, significant numbers of non-human primates such as Chlorocebus aethiops (Ch. aethiops) (vervet) and Papio anubis (baboon) are infected with S. mansoni, notably in Ethiopia, where they are expected to have potentially significant implications for transmission and control efforts. Objective The objective of this study was to assess and compare the genetic diversity and population structure of S. mansoni isolates from human and non-human primates free-ranging in close proximity to villages in selected endemic areas of Ethiopia. Methods A cross-sectional study was conducted in three transmission sites: Bochesa, Kime and Fincha. A total of 2,356 S. mansoni miracidia were directly isolated from fecal specimens of 104 hosts (i.e. 60 human hosts and 44 non-human primates). We performed DNA extraction and PCR amplification using fourteen microsatellite loci. Results At population scale we showed strong genetic structure between the three sample sites. At the definitive host scale, we observed that host factors can shape the genetic composition of parasite infra-populations. First, in male patients, we observed a positive link between parasite genetic diversity and the age of the patients. Second, we observed a difference in genetic diversity which was high in human males, medium in human females and low in non-human primates (NHPs). Finally, whatever the transmission site no genetic structure was observed between human and non-human primates, however, there appears to be little barriers, if any, host specificity of the S. mansoni populations with cross-host infections. Conclusion Occurrence of infection of a single host with multiple S. mansoni strains and inter- and intra-host genetic variations was observed. Substantial genetic diversity and gene flow across the S. mansoni population occurred at each site and non-human primates likely play a role in local transmission and maintenance of infection. Therefore, public health and wildlife professionals should work together to improve disease control and elimination strategies. Schistosomiasis is a chronic disease caused by flukes (trematodes). The definitive host spectrum of schistosomes, whether human, non-human primates (NHPs) or other mammals, is highly dependent on the schistosome species concerned. Genetic diversity and population structure studies of S. mansoni have provided insights into the variation of natural populations. Understanding S. mansoni genetic diversity and population structure of isolates from human and non-human primate hosts living in close proximity showed the occurrence of infection of a single host with multiple S. mansoni strains and inter- and intra-host genetic variations. In this article, the researchers assert the fact that genetic approach reveals that parasites from the three different sites are independent. Thus, we could consider the three sites as geographical replicates showing the influence of NHPs in parasitic transmission in Ethiopia. This study provides insights into the epidemiology, genetic diversity and population structure of S. mansoni in human and non-human primates in Ethiopia, all of which are crucial for the control of schistosomiasis.
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Affiliation(s)
- Tadesse Kebede
- Department of Microbiology, Immunology and Parasitology, School of Medicine, Addis Ababa University, Addis Ababa, Ethiopia
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
- Laboratoire Interactions Hôtes-Pathogènes-Environnements (IHPE), UMR 5244 CNRS, University of Perpignan, IFREMER, Univ. Montpellier, F-66860 Perpignan, France
- * E-mail:
| | - Nicolas Bech
- Laboratory of Ecologie et Biologie des Interactions (EBI), UMR CNRS 7267, Poitiers University, Poitiers, France
| | - Jean-François Allienne
- Laboratoire Interactions Hôtes-Pathogènes-Environnements (IHPE), UMR 5244 CNRS, University of Perpignan, IFREMER, Univ. Montpellier, F-66860 Perpignan, France
| | - Rey Olivier
- Laboratoire Interactions Hôtes-Pathogènes-Environnements (IHPE), UMR 5244 CNRS, University of Perpignan, IFREMER, Univ. Montpellier, F-66860 Perpignan, France
| | - Berhanu Erko
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Jerome Boissier
- Laboratoire Interactions Hôtes-Pathogènes-Environnements (IHPE), UMR 5244 CNRS, University of Perpignan, IFREMER, Univ. Montpellier, F-66860 Perpignan, France
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Zou HY, Yu QF, Qiu C, Webster JP, Lu DB. Meta-analyses of Schistosoma japonicum infections in wild rodents across China over time indicates a potential challenge to the 2030 elimination targets. PLoS Negl Trop Dis 2020; 14:e0008652. [PMID: 32877407 PMCID: PMC7491725 DOI: 10.1371/journal.pntd.0008652] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 09/15/2020] [Accepted: 07/27/2020] [Indexed: 01/14/2023] Open
Abstract
China once suffered greatly from schistosomiasis japonica, a major zoonotic disease. Nearly 70 years of multidisciplinary efforts have achieved great progress in disease control, with infections in both humans and bovines significantly reduced to very low levels. However, reaching for the target of complete interruption of transmission at the country level by 2030 still faces great challenges, with areas of ongoing endemicity and/or re-emergence within previously 'eliminated' regions. The objectives of this study were, by using meta-analytical methods, to estimate the overall prevalence of Schistosoma japonicum infections in abundant commensal rodent species in mainland China after the introduction of praziquantel for schistosomiasis treatment in humans and bovines in 1980s. In doing so we thereby aimed to further assess the role of wild rodents as potential reservoirs in ongoing schistosome transmission. Published studies on infection prevalence of S. japonicum in wild rodents in mainland China since 1980 were searched across five electronic bibliographic databases and lists of article references. Eligible studies were selected based on inclusion and exclusion criteria. Risks of within and across study biases, and the variations in prevalence estimates attributable to heterogeneities were assessed. The pooled infection prevalence and its 95% confidence intervals (CIs) were calculated with the Freeman-Tukey double arcsine transformation. We identified a total of 37 relevant articles involving 61 field studies which contained eligible data on 8,795 wild rodents across mainland China. The overall pooled infection prevalence was 3.86% (95% CI: 2.16-5.93%). No significant change in the overall pooled prevalence was observed between 1980-2003 (n = 23 studies) and 2004-current (n = 38 studies). However, whilst the estimated prevalence decreased over time in the marshland and lake regions, there was an apparent increase in prevalence within hilly and mountainous regions. Among seven provinces, a significant prevalence reduction was only seen in Jiangsu where most endemic settings are classified as the marshland and lakes. These estimates changed over season, ranging from 0.58% in spring to 22.39% in winter, in association with increases in rodent density. This study systematically analyzed S. japonicum infections in wild rodents from the published literature over the last forty years after the introduction of praziquantel for schistosomiasis treatment in humans and bovines in 1980s. Although numbers of schistosomiasis cases in humans and bovines have been greatly reduced, no such comparable overall change of infection prevalence in rodents was detected. Furthermore, there appeared to be an increase in S. japonicum prevalence in rodents over time within hilly and mountainous regions. Rodents have been projected to become the dominant wildlife in human-driven environments and the main reservoir of zoonotic diseases in general within tropical zones. Our findings thus suggest that it is now necessary to include monitoring and evaluation of potential schistosome infection within rodents, particularly in hilly and mountainous regions, if we are ever to reach the new 2030 elimination goals and to maximize the impact of future public, and indeed One Health, interventions across, regional, national and international scales.
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Affiliation(s)
- Hui-Ying Zou
- Department of Epidemiology and Statistics, School of Public Health, Soochow University, Suzhou, China
- Key Laboratory of National Health and Family Planning Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi, China
| | - Qiu-Fu Yu
- Department of Epidemiology and Statistics, School of Public Health, Soochow University, Suzhou, China
- Key Laboratory of National Health and Family Planning Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi, China
| | - Chen Qiu
- Department of Epidemiology and Statistics, School of Public Health, Soochow University, Suzhou, China
- Key Laboratory of National Health and Family Planning Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi, China
| | - Joanne P. Webster
- Key Laboratory of National Health and Family Planning Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi, China
- Centre for Emerging, Endemic and Exotic Diseases (CEEED), Department of Pathology and Population Sciences, Royal Veterinary College, University of London, London, United Kingdom
| | - Da-Bing Lu
- Department of Epidemiology and Statistics, School of Public Health, Soochow University, Suzhou, China
- Key Laboratory of National Health and Family Planning Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi, China
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Gu MJ, Li YW, Emery AM, Li SZ, Jiang YZ, Dong HF, Zhao QP. The genetic variation of different developmental stages of Schistosoma japonicum: do the distribution in snails and pairing preference benefit the transmission? Parasit Vectors 2020; 13:360. [PMID: 32690109 PMCID: PMC7372819 DOI: 10.1186/s13071-020-04240-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 07/15/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Schistosoma japonicum is a waterborne parasite that causes schistosomiasis in humans and in more than 40 animal species. Schistosoma japonicum shows distinct genetic differentiation among geographical populations and multiple hosts, but the genetic diversity of different developmental stages of S. japonicum from is less studied. Such studies could elucidate ecological mechanisms in disease transmission by analysing feedbacks in individual physiology and population state. METHODS After infection using cercariae from a pool of snails shedding together (Method I) and infection using mixed equal numbers of cercariae from individually shed snails (Method II), different developmental stages of S. japonicum were genotyped with microsatellite loci, including 346 cercariae, 701 adult worms and 393 miracidia. Genetic diversity and molecular variation were calculated at different population levels. Kinships (I') among cercariae at intra-snail and inter-snail levels were evaluated. Genetic distance (Dsw) was compared between paired and unpaired worms, and partner changing was investigated through paternity identification for miracidia. RESULTS The cercaria clones in individual snails varied from 1 to 8 and the kinship of cercariae within individual snails was significant higher (P < 0.001) than that among different snails after deleting near-identical multi-locus genotypes (niMLGs). The allelic diversity of worms in Method I was lower (P < 0.001) than that in Method II, and allele frequency among mice in Method I was also less consistent. The parents of some miracidia were worms that were not paired when collected. The Dsw between each female of paired and unpaired males was much larger (P < 0.001) than that between the female and male in each pair. CONCLUSIONS Most of the infected snails contained multiple miracidia clones. The aggregation of genetically similar S. japonicum miracidia in individual snails and the unbalanced distribution of miracidia among snails suggests a non-uniform genetic distribution of cercariae among snails in the field. This further influenced the genetic structure of adult worms from infections with different cercariae sampling methods. Schistosoma japonicum in mice can change paired partner, preferring to mate with genetically similar worms. These characteristics provide implications for understanding the balance in genetic diversity of S. japonicum related to the transmission of schistosomiasis.
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Affiliation(s)
- Meng-Jie Gu
- Department of Parasitology, School of Basic Medical Sciences, Wuhan University, Wuhan, 430071 Hubei China
| | - Yan-Wei Li
- Department of Parasitology, School of Basic Medical Sciences, Wuhan University, Wuhan, 430071 Hubei China
- Hubei Provincial Center for Disease Control and Prevention, Wuhan, 430072 Hubei China
| | - Aidan M. Emery
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD UK
| | - Shi-Zhu Li
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, National Center for Tropical Diseases Research, WHO Collaborating Center for Tropical Diseases, Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai, 200025 China
| | - Yong-Zhong Jiang
- Hubei Provincial Center for Disease Control and Prevention, Wuhan, 430072 Hubei China
| | - Hui-Fen Dong
- Department of Parasitology, School of Basic Medical Sciences, Wuhan University, Wuhan, 430071 Hubei China
| | - Qin-Ping Zhao
- Department of Parasitology, School of Basic Medical Sciences, Wuhan University, Wuhan, 430071 Hubei China
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Betson M, Alonte AJI, Ancog RC, Aquino AMO, Belizario VY, Bordado AMD, Clark J, Corales MCG, Dacuma MG, Divina BP, Dixon MA, Gourley SA, Jimenez JRD, Jones BP, Manalo SMP, Prada JM, van Vliet AHM, Whatley KCL, Paller VGV. Zoonotic transmission of intestinal helminths in southeast Asia: Implications for control and elimination. ADVANCES IN PARASITOLOGY 2020; 108:47-131. [PMID: 32291086 DOI: 10.1016/bs.apar.2020.01.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intestinal helminths are extremely widespread and highly prevalent infections of humans, particularly in rural and poor urban areas of low and middle-income countries. These parasites have chronic and often insidious effects on human health and child development including abdominal problems, anaemia, stunting and wasting. Certain animals play a fundamental role in the transmission of many intestinal helminths to humans. However, the contribution of zoonotic transmission to the overall burden of human intestinal helminth infection and the relative importance of different animal reservoirs remains incomplete. Moreover, control programmes and transmission models for intestinal helminths often do not consider the role of zoonotic reservoirs of infection. Such reservoirs will become increasingly important as control is scaled up and there is a move towards interruption and even elimination of parasite transmission. With a focus on southeast Asia, and the Philippines in particular, this review summarises the major zoonotic intestinal helminths, risk factors for infection and highlights knowledge gaps related to their epidemiology and transmission. Various methodologies are discussed, including parasite genomics, mathematical modelling and socio-economic analysis, that could be employed to improve understanding of intestinal helminth spread, reservoir attribution and the burden associated with infection, as well as assess effectiveness of interventions. For sustainable control and ultimately elimination of intestinal helminths, there is a need to move beyond scheduled mass deworming and to consider animal and environmental reservoirs. A One Health approach to control of intestinal helminths is proposed, integrating interventions targeting humans, animals and the environment, including improved access to water, hygiene and sanitation. This will require coordination and collaboration across different sectors to achieve best health outcomes for all.
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Affiliation(s)
- Martha Betson
- University of Surrey, Guildford, Surrey, United Kingdom.
| | | | - Rico C Ancog
- University of the Philippines Los Baños, Laguna, Philippines
| | | | | | | | - Jessica Clark
- University of Surrey, Guildford, Surrey, United Kingdom
| | | | | | - Billy P Divina
- University of the Philippines Los Baños, Laguna, Philippines
| | | | | | | | - Ben P Jones
- University of Surrey, Guildford, Surrey, United Kingdom
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8
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Neves MI, Webster JP, Walker M. Estimating helminth burdens using sibship reconstruction. Parasit Vectors 2019; 12:441. [PMID: 31522688 PMCID: PMC6745796 DOI: 10.1186/s13071-019-3687-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 08/28/2019] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Sibship reconstruction is a form of parentage analysis that can be used to identify the number of helminth parental genotypes infecting individual hosts using genetic data on only their offspring. This has the potential to be used for estimating individual worm burdens when adult parasites are otherwise inaccessible, the case for many of the most globally important human helminthiases and neglected tropical diseases. Yet methods of inferring worm burdens from sibship reconstruction data on numbers of unique parental genotypes are lacking, limiting the method's scope of application. RESULTS We developed a novel statistical method for estimating female worm burdens from data on the number of unique female parental genotypes derived from sibship reconstruction. We illustrate the approach using genotypic data on Schistosoma mansoni (miracidial) offspring collected from schoolchildren in Tanzania. We show how the bias and precision of worm burden estimates critically depends on the number of sampled offspring and we discuss strategies for obtaining sufficient sample sizes and for incorporating judiciously formulated prior information to improve the accuracy of estimates. CONCLUSIONS This work provides a novel approach for estimating individual-level worm burdens using genetic data on helminth offspring. This represents a step towards a wider scope of application of parentage analysis techniques. We discuss how the method could be used to assist in the interpretation of monitoring and evaluation data collected during mass drug administration programmes targeting human helminthiases and to help resolve outstanding questions on key population biological processes that govern the transmission dynamics of these neglected tropical diseases.
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Affiliation(s)
- M Inês Neves
- Department of Pathobiology and Population Sciences, Royal Veterinary College, University of London, Hawkshead Lane, Hatfield, UK. .,London Centre for Neglected Tropical Disease Research, London, UK.
| | - Joanne P Webster
- Department of Pathobiology and Population Sciences, Royal Veterinary College, University of London, Hawkshead Lane, Hatfield, UK.,London Centre for Neglected Tropical Disease Research, London, UK
| | - Martin Walker
- Department of Pathobiology and Population Sciences, Royal Veterinary College, University of London, Hawkshead Lane, Hatfield, UK.,London Centre for Neglected Tropical Disease Research, London, UK
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Angeles JMM, Goto Y, Kirinoki M, Leonardo LR, Moendeg KJ, Ybañez AP, Rivera PT, Villacorte EA, Inoue N, Chigusa Y, Kawazu SI. Detection of canine Schistosoma japonicum infection using recombinant thioredoxin peroxidase-1 and tandem repeat proteins. J Vet Med Sci 2019; 81:1413-1418. [PMID: 31391359 PMCID: PMC6863713 DOI: 10.1292/jvms.19-0126] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Humans and dogs live very close together and share various pathogens causing zoonotic
parasitoses like schistosomiasis. A previous population genetics study done for
schistosomes in the Philippines suggested that there is a high transmission level of
Schistosoma japonicum among humans and dogs proving that the latter are
important reservoirs for this zoonotic parasite. A more sensitive and specific test
detecting schistosome infection in dogs will therefore strengthen the zoonotic
surveillance, which might help in the possible elimination of this ancient disease. In
this study, recombinant thioredoxin peroxidase-1 (SjTPx-1) and tandem repeat proteins
(Sj1TR, Sj2TR, Sj4TR, Sj7TR) previously tested on human and water buffalo samples were
used to assess its diagnostic applicability to dogs. Fifty-nine dog serum and stool
samples were collected in the schistosomiasis-endemic municipalities of Calatrava, Negros
Occidental and Catarman, Northern Samar in the Philippines and examined using the ELISA as
compared to microscopy and fecal sample-based PCR. Samples positive for Babesia
gibsoni and Dirofilaria immitis were also used to check for
cross-reaction. Results showed that SjTPx-1 (80% sensitivity, 92.3% specificity) and Sj7TR
(73.3% sensitivity, 92.3% specificity) have good potentials for diagnosing S.
japonicum infection in dogs. These diagnostic antigens will therefore improve
the surveillance in the transmission of the parasites from dogs to humans.
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Affiliation(s)
- Jose Ma M Angeles
- Department of Parasitology, College of Public Health, University of the Philippines, Manila 1000, Philippines.,National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Yasuyuki Goto
- Laboratory of Molecular Immunology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Masashi Kirinoki
- Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi 321-0293, Japan
| | - Lydia R Leonardo
- Department of Parasitology, College of Public Health, University of the Philippines, Manila 1000, Philippines
| | - Kharleezelle J Moendeg
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.,Department of Biology, School of Science and Engineering, Ateneo de Manila University, Quezon City 1108, Philippines
| | - Adrian P Ybañez
- College of Veterinary Medicine (Barili Campus) and Center for Vector-Borne and Protozoan Diseases (Main Campus), Cebu Technological University, Cebu City 6000, Philippines
| | - Pilarita T Rivera
- Department of Parasitology, College of Public Health, University of the Philippines, Manila 1000, Philippines
| | - Elena A Villacorte
- Department of Parasitology, College of Public Health, University of the Philippines, Manila 1000, Philippines
| | - Noboru Inoue
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Yuichi Chigusa
- Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi 321-0293, Japan
| | - Shin-Ichiro Kawazu
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
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10
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Villar-Torres M, Repullés-Albelda A, Montero FE, Raga JA, Blasco-Costa I. Neither Diplectanum nor specific: a dramatic twist to the taxonomic framework of Diplectanum (Monogenea: Diplectanidae). Int J Parasitol 2019; 49:365-374. [PMID: 30776372 DOI: 10.1016/j.ijpara.2018.11.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 11/24/2018] [Accepted: 11/26/2018] [Indexed: 11/15/2022]
Abstract
The taxonomy of the genus Diplectanum has been exclusively based on morphological features, with 28 nominal species parasitic on perciform fishes recognised. We used molecular data, to our knowledge for the first time, to evaluate the taxonomic framework of Diplectanum, infer the relationships amongst species attributed to this genus, re-assess the degree of host specificity and explore the population genetic structure of Diplectanum spp. parasitising Mediterranean sciaenids, which are potential target fish species for aquaculture diversification in the region. A minimum of 10 specimens of Diplectanum spp. were sequenced per host species (Argyrosomus regius, Sciaena umbra, Umbrina canariensis and Umbrina cirrosa) and locality (Burriana, Sant Carles de la Ràpita and Santa Pola (Spain)) together with five individuals of the type species Diplectanum aequans. Sequences of partial 28S rDNA and internal transcribed spacer region of Diplectanum spp. were analysed together with those from other Diplectanidae spp. in GenBank using Bayesian inference and maximum likelihood phylogenetic methods. Population genetic analyses were performed using cytochrome c oxidase subunit I gene sequences for a diplectanid species with a wide distribution across host species and localities. Results showed that Diplectanum was not monophyletic, nor were the specimens infecting sciaenids. Instead they formed two separate clades, 26.1-28.6% divergent for the internal transcribed spacer and 13.2-16.9% for the 28S region from D. aequans. Altogether, our results suggest that these specimens represent two distinct new genera from Diplectanum and five putative species with low host specificity. It is likely that morphological variability has led to the description of more species than were detected by molecular methods. In contrast to other monogeneans, Diplectaninae gen. spp. are chiefly generalists. Nonetheless, intraspecific genetic divergence in the internal transcribed spacer region of Diplectaninae gen. spp., and population genetic analyses of one presumed generalist species, Diplectaninae gen. sp. 1.2, showed significant variation between subpopulations living on different hosts. The intraspecific genetic structure by host also suggests different cross-infection potential amongst sciaenid species.
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Affiliation(s)
- Mar Villar-Torres
- Cavanilles Institute of Biodiversity and Evolutionary Biology, Science Park, University of Valencia, PO Box 22085, 46071 Valencia, Spain.
| | - Aigües Repullés-Albelda
- Cavanilles Institute of Biodiversity and Evolutionary Biology, Science Park, University of Valencia, PO Box 22085, 46071 Valencia, Spain
| | - Francisco Esteban Montero
- Cavanilles Institute of Biodiversity and Evolutionary Biology, Science Park, University of Valencia, PO Box 22085, 46071 Valencia, Spain
| | - Juan Antonio Raga
- Cavanilles Institute of Biodiversity and Evolutionary Biology, Science Park, University of Valencia, PO Box 22085, 46071 Valencia, Spain
| | - Isabel Blasco-Costa
- Natural History Museum of Geneva, PO Box 6434, CH-1211 Geneva 6, Switzerland
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11
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Mäder P, Rennar GA, Ventura AMP, Grevelding CG, Schlitzer M. Chemotherapy for Fighting Schistosomiasis: Past, Present and Future. ChemMedChem 2018; 13:2374-2389. [DOI: 10.1002/cmdc.201800572] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Indexed: 01/22/2023]
Affiliation(s)
- Patrick Mäder
- Department of Pharmaceutical Chemistry; Philipps-Universität Marburg; Marbacher Weg 6 35032 Marburg Germany
| | - Georg A. Rennar
- Department of Pharmaceutical Chemistry; Philipps-Universität Marburg; Marbacher Weg 6 35032 Marburg Germany
| | - Alejandra M. Peter Ventura
- Department of Pharmaceutical Chemistry; Philipps-Universität Marburg; Marbacher Weg 6 35032 Marburg Germany
| | - Christoph G. Grevelding
- Institute of Parasitology, BFS; Justus-Liebig-Universität Gießen; Schubertstraße 81 35392 Gießen Germany
| | - Martin Schlitzer
- Department of Pharmaceutical Chemistry; Philipps-Universität Marburg; Marbacher Weg 6 35032 Marburg Germany
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12
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Antonovics J, Wilson AJ, Forbes MR, Hauffe HC, Kallio ER, Leggett HC, Longdon B, Okamura B, Sait SM, Webster JP. The evolution of transmission mode. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0083. [PMID: 28289251 PMCID: PMC5352810 DOI: 10.1098/rstb.2016.0083] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/05/2016] [Indexed: 12/31/2022] Open
Abstract
This article reviews research on the evolutionary mechanisms leading to different transmission modes. Such modes are often under genetic control of the host or the pathogen, and often in conflict with each other via trade-offs. Transmission modes may vary among pathogen strains and among host populations. Evolutionary changes in transmission mode have been inferred through experimental and phylogenetic studies, including changes in transmission associated with host shifts and with evolution of the unusually complex life cycles of many parasites. Understanding the forces that determine the evolution of particular transmission modes presents a fascinating medley of problems for which there is a lack of good data and often a lack of conceptual understanding or appropriate methodologies. Our best information comes from studies that have been focused on the vertical versus horizontal transmission dichotomy. With other kinds of transitions, theoretical approaches combining epidemiology and population genetics are providing guidelines for determining when and how rapidly new transmission modes may evolve, but these are still in need of empirical investigation and application to particular cases. Obtaining such knowledge is a matter of urgency in relation to extant disease threats.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.
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Affiliation(s)
- Janis Antonovics
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Anthony J Wilson
- Integrative Entomology group, Vector-borne Viral Diseases programme, The Pirbright Institute, Pirbright GU24 0NF, UK
| | - Mark R Forbes
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B7
| | - Heidi C Hauffe
- Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trentino, Italy
| | - Eva R Kallio
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, 40014 Jyvaskyla, Finland.,Department of Ecology, University of Oulu, PO Box 3000, 90014 Oulu, Finland
| | - Helen C Leggett
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Ben Longdon
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, UK
| | - Beth Okamura
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW5 7BD, UK
| | - Steven M Sait
- School of Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Joanne P Webster
- Department of Pathology and Pathogen Biology, Centre for Emerging, Endemic and Exotic Diseases, Royal Veterinary College, University of London, London AL9 7TA, UK
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13
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Moendeg KJ, Angeles JMM, Nakao R, Leonardo LR, Fontanilla IKC, Goto Y, Kirinoki M, Villacorte EA, Rivera PT, Inoue N, Chigusa Y, Kawazu SI. Geographic strain differentiation of Schistosoma japonicum in the Philippines using microsatellite markers. PLoS Negl Trop Dis 2017; 11:e0005749. [PMID: 28692692 PMCID: PMC5519200 DOI: 10.1371/journal.pntd.0005749] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 07/20/2017] [Accepted: 06/25/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Microsatellites have been found to be useful in determining genetic diversities of various medically-important parasites which can be used as basis for an effective disease management and control program. In Asia and Africa, the identification of different geographical strains of Schistosoma japonicum, S. haematobium and S. mansoni as determined through microsatellites could pave the way for a better understanding of the transmission epidemiology of the parasite. Thus, the present study aims to apply microsatellite markers in analyzing the populations of S. japonicum from different endemic areas in the Philippines for possible strain differentiation. METHODOLOGY/ PRINCIPAL FINDINGS Experimental mice were infected using the cercariae of S. japonicum collected from infected Oncomelania hupensis quadrasi snails in seven endemic municipalities. Adult worms were harvested from infected mice after 45 days of infection and their DNA analyzed against ten previously characterized microsatellite loci. High genetic diversity was observed in areas with high endemicity. The degree of genetic differentiation of the parasite population between endemic areas varies. Geographical separation was considered as one of the factors accounting for the observed difference between populations. Two subgroups have been observed in one of the study sites, suggesting that co-infection with several genotypes of the parasite might be present in the population. Clustering analysis showed no particular spatial structuring between parasite populations from different endemic areas. This result could possibly suggest varying degrees of effects of the ongoing control programs and the existing gene flow in the populations, which might be attributed to migration and active movement of infected hosts from one endemic area to another. CONCLUSIONS/ SIGNIFICANCE Based on the results of the study, it is reasonable to conclude that genetic diversity could be one possible criterion to assess the infection status in highly endemic areas. Genetic surveillance using microsatellites is therefore important to predict the ongoing gene flow and degree of genetic diversity, which indirectly reflects the success of the control program in schistosomiasis-endemic areas.
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Affiliation(s)
- Kharleezelle J. Moendeg
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan
- Department of Biology, School of Science and Engineering, Ateneo de Manila University, Quezon City, Manila, Philippines
| | - Jose Ma M. Angeles
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan
| | - Ryo Nakao
- Laboratory of Parasitology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Lydia R. Leonardo
- Department of Parasitology, College of Public Health, University of the Philippines Manila, Philippines
| | | | - Yasuyuki Goto
- Laboratory of Molecular Immunology, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Masashi Kirinoki
- Department of Tropical Medicine and Parasitology, Dokkyo Medical University School of Medicine, Tochigi, Japan
| | - Elena A. Villacorte
- Department of Parasitology, College of Public Health, University of the Philippines Manila, Philippines
| | - Pilarita T. Rivera
- Department of Parasitology, College of Public Health, University of the Philippines Manila, Philippines
| | - Noboru Inoue
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan
| | - Yuichi Chigusa
- Department of Tropical Medicine and Parasitology, Dokkyo Medical University School of Medicine, Tochigi, Japan
| | - Shin-ichiro Kawazu
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan
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14
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Webster JP, Borlase A, Rudge JW. Who acquires infection from whom and how? Disentangling multi-host and multi-mode transmission dynamics in the 'elimination' era. Philos Trans R Soc Lond B Biol Sci 2017; 372:20160091. [PMID: 28289259 PMCID: PMC5352818 DOI: 10.1098/rstb.2016.0091] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2016] [Indexed: 12/21/2022] Open
Abstract
Multi-host infectious agents challenge our abilities to understand, predict and manage disease dynamics. Within this, many infectious agents are also able to use, simultaneously or sequentially, multiple modes of transmission. Furthermore, the relative importance of different host species and modes can itself be dynamic, with potential for switches and shifts in host range and/or transmission mode in response to changing selective pressures, such as those imposed by disease control interventions. The epidemiology of such multi-host, multi-mode infectious agents thereby can involve a multi-faceted community of definitive and intermediate/secondary hosts or vectors, often together with infectious stages in the environment, all of which may represent potential targets, as well as specific challenges, particularly where disease elimination is proposed. Here, we explore, focusing on examples from both human and animal pathogen systems, why and how we should aim to disentangle and quantify the relative importance of multi-host multi-mode infectious agent transmission dynamics under contrasting conditions, and ultimately, how this can be used to help achieve efficient and effective disease control.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.
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Affiliation(s)
- Joanne P Webster
- Department of Pathology and Pathogen Biology, Centre for Emerging, Endemic and Exotic Diseases, Royal Veterinary College, University of London, Hatfield AL9 7TA, UK
| | - Anna Borlase
- Department of Pathology and Pathogen Biology, Centre for Emerging, Endemic and Exotic Diseases, Royal Veterinary College, University of London, Hatfield AL9 7TA, UK
| | - James W Rudge
- Communicable Diseases Policy Research Group, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
- Faculty of Public Health, Mahidol University, 420/1 Rajavithi Road, Bangkok 10400, Thailand
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15
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Pitaksakulrat O, Kiatsopit N, Laoprom N, Webster BL, Webster JP, Lamberton PHL, Laha T, Andrews RH, Petney TN, Blair D, Carlton EJ, Spear RC, Sithithaworn P. Preliminary genetic evidence of two different populations of Opisthorchis viverrini in Lao PDR. Parasitol Res 2017; 116:1247-1256. [PMID: 28238124 DOI: 10.1007/s00436-017-5401-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 02/03/2017] [Indexed: 11/28/2022]
Abstract
Opisthorchis viverrini is a major public health concern in Southeast Asia. Various reports have suggested that this parasite may represent a species complex, with genetic structure in the region perhaps being dictated by geographical factors and different species of intermediate hosts. We used four microsatellite loci to analyze O. viverrini adult worms originating from six species of cyprinid fish in Thailand and Lao PDR. Two distinct O. viverrini populations were observed. In Ban Phai, Thailand, only one subgroup occurred, hosted by two different fish species. Both subgroups occurred in fish from That Luang, Lao PDR, but were represented to very different degrees among the fish hosts there. Our data suggest that, although geographical separation is more important than fish host specificity in influencing genetic structure, it is possible that two species of Opisthorchis, with little interbreeding, are present near Vientiane in Lao PDR.
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Affiliation(s)
- Opal Pitaksakulrat
- Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.,Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.,Faculty of Veterinary Science, Prince of Songkla University, Songkhla, 90110, Thailand
| | - Nadda Kiatsopit
- Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.,Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand
| | - Nonglak Laoprom
- Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.,Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.,Department of General Science, Faculty of Science and Engineering, Kasetsart University, Chalermphrakiat Sakon Nakhon Province Campus, Sakon Nakhon, 47000, Thailand
| | - Bonnie L Webster
- Department of Life Sciences, Parasites and Vectors Division, Natural History Museum, London, SW7 5BD, UK.,The London Centre for Neglected Tropical Disease Research (LCNTDR), Imperial College, Faculty of Medicine (St Mary's Campus), Norfolk Place, London, W2 1PG, UK
| | - Joanne P Webster
- Department of Infectious Disease Epidemiology, Imperial College, Faculty of Medicine (St Mary's Campus), Norfolk Place, London, W2 1PG, UK.,Department of Pathology and Pathogen Biology, Centre for Emerging, Endemic and Exotic Diseases (CEEED), Royal Veterinary College, University of London, Hertfordshire, London, AL9 7TA, UK
| | - Poppy H L Lamberton
- Institute of Biodiversity, Animal Health and Comparative Medicine, and Wellcome Centre for Molecular Parasitology, Graham Kerr Building, The University of Glasgow, Glasgow, G12 8QQ, UK
| | - Thewarach Laha
- Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand
| | - Ross H Andrews
- Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.,Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.,Department of Infectious Disease Epidemiology, Imperial College, Faculty of Medicine (St Mary's Campus), Norfolk Place, London, W2 1PG, UK.,Cholangiocarcinoma Screening and Care Program, (CASCAP) Khon Kaen University, Khon Kaen, 40002, Thailand
| | - Trevor N Petney
- Cholangiocarcinoma Screening and Care Program, (CASCAP) Khon Kaen University, Khon Kaen, 40002, Thailand.,Institute of Zoology 1: Ecology and Parasitology, Karlsruhe Institute of Technology, KornblumenStrasse 13, Karlsruhe, Germany
| | - David Blair
- Centre for Tropical Diversity and Climate change, James Cook University, Townsville, Australia
| | - Elizabeth J Carlton
- Department of Environmental and Occupational Health, Colorado School of Public Health, 13001 E. 17th Place, B119, Aurora, CO, 8004510, USA
| | - Robert C Spear
- Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, USA
| | - Paiboon Sithithaworn
- Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand. .,Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.
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16
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Schurer JM, Mosites E, Li C, Meschke S, Rabinowitz P. Community-based surveillance of zoonotic parasites in a 'One Health' world: A systematic review. One Health 2016; 2:166-174. [PMID: 28616494 PMCID: PMC5462647 DOI: 10.1016/j.onehlt.2016.11.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 11/01/2016] [Indexed: 11/17/2022] Open
Abstract
The One Health (OH) concept provides an integrated framework for observing and improving health issues involving human, animal, and environmental factors, and has been applied in particular to zoonotic disease problems. We conducted a systematic review of English and Chinese language peer-reviewed and grey literature databases to identify zoonotic endoparasite research utilizing an OH approach in community-based settings. Our review identified 32 articles where specimens collected simultaneously from all three OH domains (people, animals, and the environment) were assessed for endoparasite infection or exposure. Study sites spanned 23 countries, and research teams brought together an average of seven authors from two countries. Surveillance of blood-borne and gastrointestinal protozoa were most frequently reported (19 of 32; 59%), followed by trematodes, nematodes, and cestodes. Laboratory techniques varied greatly between studies, and only 16 identified parasites using Polymerase Chain Reaction (PCR) in all three OH domains. Our review identified important gaps in parasitology research operating under an OH framework. We recommend that investigators working in the realm of zoonotic disease strive to evaluate all three OH domains by integrating modern molecular tools as well as techniques provided by economists and social scientists.
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Affiliation(s)
- JM Schurer
- Department of Veterinary Microbiology, University of Saskatchewan, 52 Campus Drive, Saskatoon S7N 5B4, Canada
- Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific Street, Seattle 98195, United States
- Corresponding author at: 52 Campus Drive, Saskatoon S7N 5B4, Canada.52 Campus DriveSaskatoonS7N 5B4Canada
| | - E Mosites
- Paul G. Allen School for Global Animal Health, Washington State University, P.O. Box 647090, Pullman 99164-7090, United States
| | - C Li
- Irma Lerma Rangel College of Pharmacy, Texas A & M University, 1010 West Ave B, Kingsville 78363, United States
| | - S Meschke
- Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific Street, Seattle 98195, United States
| | - P Rabinowitz
- Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific Street, Seattle 98195, United States
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17
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Santos-Vega M, Martinez PP, Pascual M. Climate forcing and infectious disease transmission in urban landscapes: integrating demographic and socioeconomic heterogeneity. Ann N Y Acad Sci 2016; 1382:44-55. [PMID: 27681053 DOI: 10.1111/nyas.13229] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 08/15/2016] [Accepted: 08/18/2016] [Indexed: 01/23/2023]
Abstract
Urbanization and climate change are the two major environmental challenges of the 21st century. The dramatic expansion of cities around the world creates new conditions for the spread, surveillance, and control of infectious diseases. In particular, urban growth generates pronounced spatial heterogeneity within cities, which can modulate the effect of climate factors at local spatial scales in large urban environments. Importantly, the interaction between environmental forcing and socioeconomic heterogeneity at local scales remains an open area in infectious disease dynamics, especially for urban landscapes of the developing world. A quantitative and conceptual framework on urban health with a focus on infectious diseases would benefit from integrating aspects of climate forcing, population density, and level of wealth. In this paper, we review what is known about these drivers acting independently and jointly on urban infectious diseases; we then outline elements that are missing and would contribute to building such a framework.
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Affiliation(s)
| | - Pamela P Martinez
- Ecology and Evolution Department, University of Chicago, Chicago, Illinois
| | - Mercedes Pascual
- Ecology and Evolution Department, University of Chicago, Chicago, Illinois
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18
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Huo GN, Liu L, He HB, Attwood SW. An investigation into the potential effects of infrapopulation structure and other sources of sampling error, on population genetic studies of the transmission of Schistosoma japonicum (Trematoda: Digenea). Parasit Vectors 2016; 9:165. [PMID: 27000844 PMCID: PMC4802887 DOI: 10.1186/s13071-016-1454-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 03/15/2016] [Indexed: 02/05/2023] Open
Abstract
Background Schistosoma japonicum remains a major challenge to human and animal health. Earlier microsatellite-based studies reported possible definitive-host-specific private alleles within S. japonicum, opening the possibility that different definitive hosts might harbour different parasite strains. Previous investigations have also detected near-identical multilocus genotypes in populations of adult worms - possibly the result of mutations occurring during the asexual (intramolluscan) phase of clonal expansion. Research has also revealed extensive deviations from Hardy-Weinberg Proportions (HWP) and conflicting results among studies. The present study was performed to examine some of the potential effects of infrapopulation structure on microsatellite-based studies of the transmission ecology of S. japonicum. Potential sources of bias considered included organotropic distribution of worms, non-random mating and corrections for clonal expansion. Results Stool samples from naturally infected hosts were used to infect snails in the laboratory and thereby expose mice. 274 individual worms were typed at seven microsatellite loci. Removal of individuals bearing duplicate MLGs (as a correction for presumed clonal expansion) had an impact on both HWP and organotropic genetic differentiation. The study found no evidence that heterozygote deficiencies were caused by a Wahlund effect. Female-male pairings appeared to be random and there was no evidence for mate choice by heterozygosity. There was some indication that excess heterozygosity, induced by clonal expansion, can offset heterozygote deficiencies caused by small population size or populations fragmented by parasite control efforts. Conclusions The view is supported that miracidia are preferable to adult worms in investigations into host-specific parasite lineages. Where adults must be used, extreme care should be taken with regard to sampling if infrapopulations of small animals are compared with those of larger animals; this is because of organotropic patterns in genetic variation and the tendency to sample from different organs in differently sized hosts. As corrections for clones may accentuate signals of population subdivision, corrections should only be made if tests for clonal expansion prove positive. Finally, evidence for heterozygote deficiency caused by small sample size, calls for carefully designed random and comprehensive sampling strategies for S. japonicum in China, where control efforts have greatly fragmented parasite populations. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1454-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Guan-Nan Huo
- State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, Chengdu, People's Republic of China
| | - Liang Liu
- State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, Chengdu, People's Republic of China
| | - Hong-Bin He
- Hunan Institute of Parasitic Diseases, Yueyang, Hunan, People's Republic of China
| | - Stephen W Attwood
- State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, Chengdu, People's Republic of China. .,Department of Life Sciences, The Natural History Museum, London, UK.
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19
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Webster JP, Gower CM, Knowles SCL, Molyneux DH, Fenton A. One health - an ecological and evolutionary framework for tackling Neglected Zoonotic Diseases. Evol Appl 2016; 9:313-33. [PMID: 26834828 PMCID: PMC4721077 DOI: 10.1111/eva.12341] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 10/20/2015] [Indexed: 12/27/2022] Open
Abstract
Understanding the complex population biology and transmission ecology of multihost parasites has been declared as one of the major challenges of biomedical sciences for the 21st century and the Neglected Zoonotic Diseases (NZDs) are perhaps the most neglected of all the Neglected Tropical Diseases (NTDs). Here we consider how multihost parasite transmission and evolutionary dynamics may affect the success of human and animal disease control programmes, particularly neglected diseases of the developing world. We review the different types of zoonotic interactions that occur, both ecological and evolutionary, their potential relevance for current human control activities, and make suggestions for the development of an empirical evidence base and theoretical framework to better understand and predict the outcome of such interactions. In particular, we consider whether preventive chemotherapy, the current mainstay of NTD control, can be successful without a One Health approach. Transmission within and between animal reservoirs and humans can have important ecological and evolutionary consequences, driving the evolution and establishment of drug resistance, as well as providing selective pressures for spill-over, host switching, hybridizations and introgressions between animal and human parasites. Our aim here is to highlight the importance of both elucidating disease ecology, including identifying key hosts and tailoring control effort accordingly, and understanding parasite evolution, such as precisely how infectious agents may respond and adapt to anthropogenic change. Both elements are essential if we are to alleviate disease risks from NZDs in humans, domestic animals and wildlife.
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Affiliation(s)
- Joanne P. Webster
- Department of Pathology and Pathogen BiologyCentre for Emerging, Endemic and Exotic Diseases (CEEED)Royal Veterinary CollegeUniversity of LondonHertfordshireUK
| | - Charlotte M. Gower
- Department of Pathology and Pathogen BiologyCentre for Emerging, Endemic and Exotic Diseases (CEEED)Royal Veterinary CollegeUniversity of LondonHertfordshireUK
| | | | - David H. Molyneux
- Department of ParasitologyLiverpool School of Tropical MedicineLiverpoolUK
| | - Andy Fenton
- Institute of Integrative BiologyUniversity of LiverpoolLiverpoolUK
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Angeles JMM, Leonardo LR, Goto Y, Kirinoki M, Villacorte EA, Hakimi H, Moendeg KJ, Lee S, Rivera PT, Inoue N, Chigusa Y, Kawazu SI. Water buffalo as sentinel animals for schistosomiasis surveillance. Bull World Health Organ 2015; 93:511-2. [PMID: 26170512 PMCID: PMC4490807 DOI: 10.2471/blt.14.143065] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 01/14/2015] [Accepted: 01/23/2015] [Indexed: 11/27/2022] Open
Affiliation(s)
- Jose Ma M Angeles
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-13, Inada-cho Obihiro, Hokkaido, Japan 080-8555
| | - Lydia R Leonardo
- Department of Parasitology, University of the Philippines, Manila, Philippines
| | - Yasuyuki Goto
- Laboratory of Molecular Immunology, University of Tokyo, Tokyo, Japan
| | - Masashi Kirinoki
- Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi, Japan
| | - Elena A Villacorte
- Department of Parasitology, University of the Philippines, Manila, Philippines
| | - Hassan Hakimi
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-13, Inada-cho Obihiro, Hokkaido, Japan 080-8555
| | - Kharleezelle J Moendeg
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-13, Inada-cho Obihiro, Hokkaido, Japan 080-8555
| | - Seungyeon Lee
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-13, Inada-cho Obihiro, Hokkaido, Japan 080-8555
| | - Pilarita T Rivera
- Department of Parasitology, University of the Philippines, Manila, Philippines
| | - Noboru Inoue
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-13, Inada-cho Obihiro, Hokkaido, Japan 080-8555
| | - Yuichi Chigusa
- Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi, Japan
| | - Shin-ichiro Kawazu
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-13, Inada-cho Obihiro, Hokkaido, Japan 080-8555
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Chelomina GN, Tatonova YV, Hung NM, Ngo HD. Genetic diversity of the Chinese liver fluke Clonorchis sinensis from Russia and Vietnam. Int J Parasitol 2014; 44:795-810. [DOI: 10.1016/j.ijpara.2014.06.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 06/01/2014] [Accepted: 06/02/2014] [Indexed: 11/24/2022]
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Webster JP, Molyneux DH, Hotez PJ, Fenwick A. The contribution of mass drug administration to global health: past, present and future. Philos Trans R Soc Lond B Biol Sci 2014; 369:20130434. [PMID: 24821920 DOI: 10.1098/rstb.2013.0434] [Citation(s) in RCA: 178] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mass drug administration (MDA) is a means of delivering safe and inexpensive essential medicines based on the principles of preventive chemotherapy, where populations or sub-populations are offered treatment without individual diagnosis. High-coverage MDA in endemic areas aims to prevent and alleviate symptoms and morbidity on the one hand and can reduce transmission on the other, together improving global health. MDA is the recommended strategy of the World Health Organisation to control or eliminate several neglected tropical diseases (NTDs). More than 700 million people now receive these essential NTD medicines annually. The combined cost of integrated NTD MDA has been calculated to be in the order of $0.50 per person per year. Activities have recently been expanded due, in part, to the proposed attempt to eliminate certain NTDs in the coming two decades. More than 1.9 billion people need to receive MDA annually across several years if these targets are to be met. Such extensive coverage will require additional avenues of financial support, expanded monitoring and evaluation focusing on impact and drug efficacy, as well as new diagnostic tools and social science strategies to encourage adherence. MDA is a means to help reduce the burden of disease, and hence poverty, among the poorest sector of populations. It has already made significant improvements to global health and productivity and has the potential for further successes, particularly where incorporated into sanitation and education programmes. However logistical, financial and biological challenges remain.
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Affiliation(s)
- Joanne P Webster
- Department of Infectious Disease Epidemiology, School of Public Health, Imperial College Faculty of Medicine, , St Mary's Campus, London W2 1PG, UK
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Abstract
Parasite virulence, or the damage a parasite does to its host, is measured in terms of both host costs (reductions in host growth, reproduction and survival) and parasite benefits (increased transmission and parasite numbers) in the literature. Much work has shown that ecological and genetic factors can be strong selective forces in virulence evolution. This review uses kin selection theory to explore how variations in host ecological parameters impact the genetic relatedness of parasite populations and thus virulence. We provide a broad overview of virulence and population genetics studies and then draw connections to existing knowledge about natural parasite populations. The impact of host movement (transporting parasites) and host resistance (filtering parasites) on the genetic structure and virulence of parasite populations is explored, and empirical studies of these factors using Plasmodium and trematode systems are proposed.
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French MD, Churcher TS, Basáñez MG, Norton AJ, Lwambo NJ, Webster JP. Reductions in genetic diversity of Schistosoma mansoni populations under chemotherapeutic pressure: the effect of sampling approach and parasite population definition. Acta Trop 2013; 128:196-205. [PMID: 22440199 DOI: 10.1016/j.actatropica.2012.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 03/02/2012] [Accepted: 03/04/2012] [Indexed: 10/28/2022]
Abstract
Detecting potential changes in genetic diversity in schistosome populations following chemotherapy with praziquantel (PZQ) is crucial if we are to fully understand the impact of such chemotherapy with respect to the potential emergence of resistance and/or other evolutionary outcomes of interventions. Doing so by implementing effective, and cost-efficient sampling protocols will help to optimise time and financial resources, particularly relevant to a disease such as schistosomiasis currently reliant on a single available drug. Here we explore the effect on measures of parasite genetic diversity of applying various field sampling approaches, both in terms of the number of (human) hosts sampled and the number of transmission stages (miracidia) sampled per host for a Schistosoma mansoni population in Tanzania pre- and post-treatment with PZQ. In addition, we explore population structuring within and between hosts by comparing the estimates of genetic diversity obtained assuming a 'component population' approach with those using an 'infrapopulation' approach. We found that increasing the number of hosts sampled, rather than the number of miracidia per host, gives more robust estimates of genetic diversity. We also found statistically significant population structuring (using Wright's F-statistics) and significant differences in the measures of genetic diversity depending on the parasite population definition. The relative advantages, disadvantages and, hence, subsequent reliability of these metrics for parasites with complex life-cycles are discussed, both for the specific epidemiological and ecological scenario under study here and for their future application to other areas and schistosome species.
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McWilliam HEG, Piedrafita D, Li Y, Zheng M, He Y, Yu X, McManus DP, Meeusen ENT. Local immune responses of the Chinese water buffalo, Bubalus bubalis, against Schistosoma japonicum larvae: crucial insights for vaccine design. PLoS Negl Trop Dis 2013; 7:e2460. [PMID: 24086786 PMCID: PMC3784499 DOI: 10.1371/journal.pntd.0002460] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 08/17/2013] [Indexed: 01/03/2023] Open
Abstract
Asian schistosomiasis is a zoonotic parasitic disease infecting up to a million people and threatening tens of millions more. Control of this disease is hindered by the animal reservoirs of the parasite, in particular the water buffalo (Bubalus bubalis), which is responsible for significant levels of human transmission. A transmission-blocking vaccine administered to buffaloes is a realistic option which would aid in the control of schistosomiasis. This will however require a better understanding of the immunobiology of schistosomiasis in naturally exposed buffaloes, particularly the immune response to migrating schistosome larvae, which are the likely targets of an anti-schistosome vaccine. To address this need we investigated the immune response at the major sites of larval migration, the skin and the lungs, in previously exposed and re-challenged water buffaloes. In the skin, a strong allergic-type inflammatory response occurred, characterised by leukocyte and eosinophil infiltration including the formation of granulocytic abscesses. Additionally at the local skin site, interleukin-5 transcript levels were elevated, while interleukin-10 levels decreased. In the skin-draining lymph node (LN) a predominant type-2 profile was seen in stimulated cells, while in contrast a type-1 profile was detected in the lung draining LN, and these responses occurred consecutively, reflecting the timing of parasite migration. The intense type-2 immune response at the site of cercarial penetration is significantly different to that seen in naive and permissive animal models such as mice, and suggests a possible mechanism for immunity. Preliminary data also suggest a reduced and delayed immune response occurred in buffaloes given high cercarial challenge doses compared with moderate infections, particularly in the skin. This study offers a deeper understanding into the immunobiology of schistosomiasis in a natural host, which may aid in the future design of more effective vaccines. Schistosomiasis is caused by a parasitic blood fluke, and in parts of Asia it infects both humans and livestock such as water buffaloes. This makes controlling the disease more difficult, because both humans and livestock must be treated regularly. A vaccine given to buffaloes is likely to reduce human infection rates and improve buffalo health by providing long-lasting protection from re-infection; at present no vaccines are available. Older buffaloes are known to have some immunity to schistosomiasis which is acquired over time; however how this occurs is not understood. In this study we investigated the immune response of buffalo against the schistosome larvae, which are vulnerable to immune attack, and hence are the ideal stage to target for vaccination. We found that the buffalo produces a profound allergic type-2 response as larvae penetrate the skin, with significant cellular infiltrates and abscesses. When the larvae move next to the lungs, a uniquely type-1 response was induced. This skin response is much greater than more susceptible animals such as mice, and may be a mechanism for larval killing in the buffalo. This study offers insight into the immunobiology of an important host for schistosomiasis and may help in designing better vaccines.
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Affiliation(s)
- Hamish E. G. McWilliam
- Biotechnology Research Laboratories, School of Biomedical Sciences, Monash University, Melbourne, Victoria, Australia
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Melbourne, Victoria, Australia
- * E-mail:
| | - David Piedrafita
- Biotechnology Research Laboratories, School of Biomedical Sciences, Monash University, Melbourne, Victoria, Australia
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Melbourne, Victoria, Australia
| | - Yuesheng Li
- Hunan Institute of Parasitic Diseases, Yueyang, Hunan, China
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Mao Zheng
- Hunan Institute of Parasitic Diseases, Yueyang, Hunan, China
| | - Yongkang He
- Hunan Institute of Parasitic Diseases, Yueyang, Hunan, China
| | - Xinling Yu
- Hunan Institute of Parasitic Diseases, Yueyang, Hunan, China
| | - Donald P. McManus
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Els N. T. Meeusen
- Biotechnology Research Laboratories, School of Biomedical Sciences, Monash University, Melbourne, Victoria, Australia
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Melbourne, Victoria, Australia
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Steinauer ML, Christie MR, Blouin MS, Agola LE, Mwangi IN, Maina GM, Mutuku MW, Kinuthia JM, Mkoji GM, Loker ES. Non-invasive sampling of schistosomes from humans requires correcting for family structure. PLoS Negl Trop Dis 2013; 7:e2456. [PMID: 24069499 PMCID: PMC3777896 DOI: 10.1371/journal.pntd.0002456] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 08/12/2013] [Indexed: 12/04/2022] Open
Abstract
For ethical and logistical reasons, population-genetic studies of parasites often rely on the non-invasive sampling of offspring shed from their definitive hosts. However, if the sampled offspring are naturally derived from a small number of parents, then the strong family structure can result in biased population-level estimates of genetic parameters, particularly if reproductive output is skewed. Here, we document and correct for the strong family structure present within schistosome offspring (miracidia) that were collected non-invasively from humans in western Kenya. By genotyping 2,424 miracidia from 12 patients at 12 microsatellite loci and using a sibship clustering program, we found that the samples contained large numbers of siblings. Furthermore, reproductive success of the breeding schistosomes was skewed, creating differential representation of each family in the offspring pool. After removing the family structure with an iterative jacknifing procedure, we demonstrated that the presence of relatives led to inflated estimates of genetic differentiation and linkage disequilibrium, and downwardly-biased estimates of inbreeding coefficients (FIS). For example, correcting for family structure yielded estimates of FST among patients that were 27 times lower than estimates from the uncorrected samples. These biased estimates would cause one to draw false conclusions regarding these parameters in the adult population. We also found from our analyses that estimates of the number of full sibling families and other genetic parameters of samples of miracidia were highly intercorrelated but are not correlated with estimates of worm burden obtained via egg counting (Kato-Katz). Whether genetic methods or the traditional Kato-Katz estimator provide a better estimate of actual number of adult worms remains to be seen. This study illustrates that family structure must be explicitly accounted for when using offspring samples to estimate the genetic parameters of adult parasite populations. Genetic epidemiology uses genetic data to uncover patterns of disease processes. To acquire data for these analyses, individual pathogens are collected and scored at genetic markers, and the resultant data are analyzed to infer biological patterns about the pathogen populations. In lieu of invasive sampling of adult pathogens in humans, researchers have relied on non-invasive sampling of parasite offspring (often shed in fecal samples). One potential problem with this approach is that analyses using the offspring data will be biased because many of the offspring are related and family sizes are likely to be unequal. We show that this sampling issue is relevant in a natural transmission zone in western Kenya and that it yields biases in three important parameters: genetic differentiation, inbreeding coefficients, and estimates of the amount of non-random association between loci (linkage disequilibrium). We also develop a method to remove these biases by removing the sibling structure present in the dataset. Finally, we suggest that our measure of family number, as well as other genetic measures, may be useful measures of the worm burdens in patients.
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Affiliation(s)
- Michelle L. Steinauer
- College of Osteopathic Medicine of the Pacific Northwest, Western University of Health Sciences, Lebanon, Oregon, United States of America
- * E-mail:
| | - Mark R. Christie
- Department of Zoology, Oregon State University, Corvallis, Oregon, United States of America
| | - Michael S. Blouin
- Department of Zoology, Oregon State University, Corvallis, Oregon, United States of America
| | - Lelo E. Agola
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Ibrahim N. Mwangi
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Geoffrey M. Maina
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Martin W. Mutuku
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Joseph M. Kinuthia
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Gerald M. Mkoji
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Eric S. Loker
- Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
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Thétiot-Laurent SAL, Boissier J, Robert A, Meunier B. Chemotherapie gegen Schistosomiasis. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201208390] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Thétiot-Laurent SAL, Boissier J, Robert A, Meunier B. Schistosomiasis chemotherapy. Angew Chem Int Ed Engl 2013; 52:7936-56. [PMID: 23813602 DOI: 10.1002/anie.201208390] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Indexed: 01/08/2023]
Abstract
After malaria, schistosomiasis (or bilharzia) is the second most prevalent disease in Africa, and is occurring in over 70 countries in tropical and subtropical regions. It is estimated that 600 million people are at risk of infection, 200 million people are infected, and at least 200,000 deaths per year are associated with the disease. All schistosome species are transmitted through contact with fresh water that is infested with free-swimming forms of the parasite, which is known as cercariae and produced by snails. When located in the blood vessels of the host, larval and adult schistosomes digest red cells to acquire amino acids for growth and development. Vaccine candidates have been unsuccessful up to now. Against such devastating parasitic disease, the antischistosomal arsenal is currently limited to a single drug, praziquantel, which has been used for more than 35 years. Because the question of the reduction of the activity of praziquantel was raised recently, it is thus urgent to create new and safe antischistosomal drugs that should be combined with praziquantel to develop efficient bitherapies.
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Affiliation(s)
- Sophie A-L Thétiot-Laurent
- Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, BP 44099, 31077 Toulouse cedex 4, France
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Zhou YB, Liang S, Jiang QW. Factors impacting on progress towards elimination of transmission of schistosomiasis japonica in China. Parasit Vectors 2012; 5:275. [PMID: 23206326 PMCID: PMC3519747 DOI: 10.1186/1756-3305-5-275] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 11/27/2012] [Indexed: 11/10/2022] Open
Abstract
Over the past decades China has made a great stride in controlling schistosomiasis, eliminating transmission of Schistosoma japonicum in 5 provinces and remarkably reducing transmission intensities in the rest of the seven endemic provinces. Recently, an integrated control strategy, which focuses on interventions on humans and bovines, has been implemented throughout endemic areas in China. This strategy assumes that a reduction in transmission of S. japonicum from humans and bovines to the intermediate Oncomelania snail host would eventually block the transmission of this parasite, and has yielded effective results in some endemic areas. Yet the transmission of S. japonicum is relatively complicated--in addition to humans and bovines, more than 40 species of mammalians can serve as potential zoonotic reservoirs. Here, we caution that some factors--potential roles of other mammalian reservoirs and human movement in sustaining the transmission, low sensitivity/specificity of current diagnostic tools for infections, praziquantel treatment failures, changes in environmental and socio-economic factors such as flooding in key endemic areas--may pose great obstacles towards transmission interruption of the parasite. Assessing potential roles of these factors in the transmission and implications for current control strategies aiming at transmission interruption is needed.
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Affiliation(s)
- Yi-Biao Zhou
- Department of Epidemiology, School of Public Health, Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, China
- Key Laboratory of Public Health Safety, Ministry of Education (Fudan University), 138 Yi Xue Yuan Road, Shanghai 200032, China
| | - Song Liang
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, FL, 32610, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32610, USA
| | - Qing-Wu Jiang
- Department of Epidemiology, School of Public Health, Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, China
- Key Laboratory of Public Health Safety, Ministry of Education (Fudan University), 138 Yi Xue Yuan Road, Shanghai 200032, China
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Zhao GH, Li J, Blair D, Li XY, Elsheikha HM, Lin RQ, Zou FC, Zhu XQ. Biotechnological advances in the diagnosis, species differentiation and phylogenetic analysis of Schistosoma spp. Biotechnol Adv 2012; 30:1381-9. [DOI: 10.1016/j.biotechadv.2012.02.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 01/08/2012] [Accepted: 02/08/2012] [Indexed: 11/26/2022]
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Gobert GN, You H, Jones MK, McInnes R, McManus DP. Differences in genomic architecture between two distinct geographical strains of the blood fluke Schistosoma japonicum reveal potential phenotype basis. Mol Cell Probes 2012; 27:19-27. [PMID: 22940009 DOI: 10.1016/j.mcp.2012.08.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 08/10/2012] [Accepted: 08/11/2012] [Indexed: 10/28/2022]
Abstract
The Chinese (SjC) and Philippine (SjP) strains of the blood fluke Schistosoma japonicum have been shown to present clearly different phenotypes in fecundity, pathology, drug sensitivity and immunology. We used microarray based comparative genomic hybridisation (aCGH) to investigate structural differences in the genomes of the two strains and identified seven distinct regions of the S. japonicum genome that present differential aCGH representing either deletion or duplication regions in SjP. Within these regions, genes predicted to be associated with the recognised phenotypic differences were identified and that may provide new insights into the biology and evolution of the two strains, with implications for the epidemiology and control of schistosomiasis japonica in China and the Philippines.
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Affiliation(s)
- Geoffrey N Gobert
- Queensland Institute of Medical Research-QIMR, 300 Herston Road, Herston, Qld 4006, Australia.
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Zhao QP, Jiang MS, Dong HF, Nie P. Diversification of Schistosoma japonicum in Mainland China revealed by mitochondrial DNA. PLoS Negl Trop Dis 2012; 6:e1503. [PMID: 22348161 PMCID: PMC3279335 DOI: 10.1371/journal.pntd.0001503] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 12/15/2011] [Indexed: 12/11/2022] Open
Abstract
Background Schistosoma japonicum still causes severe parasitic disease in mainland China, but mainly in areas along the Yangtze River. However, the genetic diversity in populations of S. japonicum has not been well understood across its geographical distribution, and such data may provide insights into the epidemiology and possible control strategies for schistosomiasis. Methodology/Principal Findings In this study infected Oncomelania snails were collected from areas in the middle and lower (ML) reaches of the Yangtze River, including Hubei, Hunan, Anhui, Jiangxi and Jiangsu provinces, and in the upper reaches of the river, including Sichuan and Yunnan provinces in southwest (SW) China. The adult parasites obtained from experimentally infected mice using isolated cercariae were sequenced individually for several fragments of mitochondrial regions, including Cytb-ND4L-ND4, 16S-12S and ND1. Populations in the ML reaches exhibited a relatively high level of diversity in nucleotides and haplotypes, whereas a low level was observed for populations in the SW, using either each single fragment or the combined sequence of the three fragments. Pairwise analyses of F-statistics (Fst) revealed a significant genetic difference between populations in the ML reaches and those in the SW, with limited gene flow and no shared haplotypes in between. It is rather obvious that genetic diversity in the populations of S. japonicum was significantly correlated with the geographical distance, and the geographical separation/isolation was considered to be the major factor accounting for the observed difference between populations in the ML reaches and those in the SW in China. Conclusions S. japonicum in mainland China exhibits a high degree of genetic diversity, with a similar pattern of genetic diversity as observed in the intermediate host snails in the same region in China. Despite the existing threat of schistosomiasis in some rural areas along the Yangtze River, the genetic diversity of Schistosoma japonicum has not been investigated across its wide geographical distribution in China, and such information may provide insight into the disease epidemiology and the development of its control measures. In this study, the adult parasites, obtained through infecting mice with cercariae from snails of the genus Oncomelania collected from a wide range of localities in currently endemic areas of schistosomiasis in the middle and lower (ML) reaches of the Yangtze River, and in Sichuan and Yunnan provinces in the upper reaches of the river in southwest (SW) China, were sequenced individually for mitochondrial genes. In general, a relatively high degree of genetic variation was observed in populations in the ML reaches in terms of nucleotide and haplotype diversity, but a low level was observed in populations in the SW. The significant difference in genetic diversity as revealed by F-statistics, and the existence of no shared haplotypes, were observed between populations in the ML reaches and those in the SW, indicating the effect of geographical separation/isolation upon the schistosomes and probably the parasite-snail system in China.
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Affiliation(s)
- Qin Ping Zhao
- Department of Parasitology, School of Basic Medical Science, Wuhan University, Wuhan, Hubei Province, China
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China
| | - Ming Sen Jiang
- Department of Parasitology, School of Basic Medical Science, Wuhan University, Wuhan, Hubei Province, China
| | - Hui Fen Dong
- Department of Parasitology, School of Basic Medical Science, Wuhan University, Wuhan, Hubei Province, China
| | - Pin Nie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China
- * E-mail:
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Hauswald AK, Remais JV, Xiao N, Davis GM, Lu D, Bale MJ, Wilke T. Stirred, not shaken: genetic structure of the intermediate snail host Oncomelania hupensis robertsoni in an historically endemic schistosomiasis area. Parasit Vectors 2011; 4:206. [PMID: 22029536 PMCID: PMC3226449 DOI: 10.1186/1756-3305-4-206] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 10/26/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Oncomelania hupensis robertsoni is the sole intermediate host for Schistosoma japonicum in western China. Given the close co-evolutionary relationships between snail host and parasite, there is interest in understanding the distribution of distinct snail phylogroups as well as regional population structures. Therefore, this study focuses on these aspects in a re-emergent schistosomiasis area known to harbour representatives of two phylogroups - the Deyang-Mianyang area in Sichuan Province, China. Based on a combination of mitochondrial and nuclear DNA, the following questions were addressed: 1) the phylogeography of the two O. h. robertsoni phylogroups, 2) regional and local population structure in space and time, and 3) patterns of local dispersal under different isolation-by-distance scenarios. RESULTS The phylogenetic analyses confirmed the existence of two distinct phylogroups within O. h. robertsoni. In the study area, phylogroups appear to be separated by a mountain range. Local specimens belonging to the respective phylogroups form monophyletic clades, indicating a high degree of lineage endemicity. Molecular clock estimations reveal that local lineages are at least 0.69-1.58 million years (My) old and phylogeographical analyses demonstrate that local, watershed and regional effects contribute to population structure. For example, Analyses of Molecular Variances (AMOVAs) show that medium-scale watersheds are well reflected in population structures and Mantel tests indicate isolation-by-distance effects along waterways. CONCLUSIONS The analyses revealed a deep, complex and hierarchical structure in O. h. robertsoni, likely reflecting a long and diverse evolutionary history. The findings have implications for understanding disease transmission. From a co-evolutionary standpoint, the divergence of the two phylogroups raises species level questions in O. h. robertsoni and also argues for future studies relative to the distinctness of the respective parasites. The endemicity of snail lineages at the regional level supports the concept of endemic schistosomiasis areas and calls for future geospatial analyses for a better understanding of respective boundaries. Finally, local snail dispersal mainly occurs along waterways and can be best described by using cost distance, thus potentially enabling a more precise modelling of snail, and therefore, parasite dispersal.
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Affiliation(s)
- Anne-Kathrin Hauswald
- Department of Animal Ecology & Systematics, Justus Liebig University, Heinrich-Buff-Ring 26-32 IFZ, Giessen, Germany
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Lymbery AJ, Thompson RCA. The molecular epidemiology of parasite infections: tools and applications. Mol Biochem Parasitol 2011; 181:102-16. [PMID: 22027028 DOI: 10.1016/j.molbiopara.2011.10.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 10/10/2011] [Accepted: 10/12/2011] [Indexed: 10/16/2022]
Abstract
Molecular epidemiology, broadly defined, is the application of molecular genetic techniques to the dynamics of disease in a population. In this review, we briefly describe molecular and analytical tools available for molecular epidemiological studies and then provide an overview of how they can be applied to better understand parasitic disease. A range of new molecular tools have been developed in recent years, allowing for the direct examination of parasites from clinical or environmental samples, and providing access to relatively cheap, rapid, high throughput molecular assays. At the same time, new analytical approaches, in particular those derived from coalescent theory, have been developed to provide more robust estimates of evolutionary processes and demographic parameters from multilocus, genotypic data. To date, the primary application of molecular epidemiology has been to provide specific and sensitive identification of parasites and to resolve taxonomic issues, particularly at the species level and below. Population genetic studies have also been used to determine the extent of genetic diversity among populations of parasites and the degree to which this diversity is associated with different host cycles or epidemiologically important phenotypes. Many of these studies have also shed new light on transmission cycles of parasites, particularly the extent to which zoonotic transmission occurs, and on the prevalence and importance of mixed infections with different parasite species or intraspecific variants (polyparasitism). A major challenge, and one which is now being addressed by an increasing number of studies, is to find and utilize genetic markers for complex traits of epidemiological significance, such as drug resistance, zoonotic potential and virulence.
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Affiliation(s)
- A J Lymbery
- Fish Health Unit, School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch WA 6150, Australia.
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Conlan JV, Sripa B, Attwood S, Newton PN. A review of parasitic zoonoses in a changing Southeast Asia. Vet Parasitol 2011; 182:22-40. [PMID: 21846580 DOI: 10.1016/j.vetpar.2011.07.013] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Parasitic zoonoses are common and widely distributed in the Southeast Asian region. However, the interactions between parasites, hosts and vectors are influenced by environmental, socio-cultural and livestock production changes that impact on the distribution, prevalence and severity of disease. In this review we provide an update on new knowledge in the context of ongoing changes for the food-borne pig associated zoonoses Taenia solium and Trichinella spp., the food-borne trematodes Opisthorchis viverrini and Clonorchis sinensis, the water-borne trematodes Schistosoma spp., the vector-borne zoonotic protozoa Plasmodium knowlesi and Leishmania spp. and the soil-borne zoonotic hookworm Ancylostoma ceylanicum. These various changes need to be considered when assessing or developing regional control programs or devising new research initiatives in a changing SE Asia.
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Affiliation(s)
- James V Conlan
- School of Veterinary and Biomedical Sciences, Murdoch University, WA, Australia.
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Piao X, Cai P, Liu S, Hou N, Hao L, Yang F, Wang H, Wang J, Jin Q, Chen Q. Global expression analysis revealed novel gender-specific gene expression features in the blood fluke parasite Schistosoma japonicum. PLoS One 2011; 6:e18267. [PMID: 21494327 PMCID: PMC3071802 DOI: 10.1371/journal.pone.0018267] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 02/24/2011] [Indexed: 01/17/2023] Open
Abstract
Background Schistosoma japonicum is one of the remarkable
Platyhelminths that are endemic in China and Southeast Asian countries. The
parasite is dioecious and can reside inside the host for many years. Rapid
reproduction by producing large number of eggs and count-react host
anti-parasite responses are the strategies that benefit long term survival
of the parasite. Praziquantel is currently the only drug that is effective
against the worms. Development of novel antiparasite reagents and
immune-prevention measures rely on the deciphering of parasite biology. The
decoding of the genomic sequence of the parasite has made it possible to
dissect the functions of genes that govern the development of the parasite.
In this study, the polyadenylated transcripts from male and female
S. japonicum were isolated for deep sequencing and the
sequences were systematically analysed. Results First, the number of genes actively expressed in the two sexes of S.
japonicum was similar, but around 50% of genes were
biased to either male or female in expression. Secondly, it was, at the
first time, found that more than 50% of the coding region of the
genome was transcribed from both strands. Among them, 65% of the
genes had sense and their cognate antisense transcripts co-expressed,
whereas 35% had inverse relationship between sense and antisense
transcript abundance. Further, based on gene ontological analysis, more than
2,000 genes were functionally categorized and biological pathways that are
differentially functional in male or female parasites were elucidated. Conclusions Male and female schistosomal parasites differ in gene expression patterns,
many metabolic and biological pathways have been identified in this study
and genes differentially expressed in gender specific manner were presented.
Importantly, more than 50% of the coding regions of the S.
japonicum genome transcribed from both strands, antisense
RNA-mediated gene regulation might play a critical role in the parasite
biology.
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Affiliation(s)
- Xianyu Piao
- Laboratory of Parasitology, Institute of
Pathogen Biology/Institute of Basic Medical Sciences, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, China
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
| | - Pengfei Cai
- Laboratory of Parasitology, Institute of
Pathogen Biology/Institute of Basic Medical Sciences, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, China
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
| | - Shuai Liu
- Laboratory of Parasitology, Institute of
Pathogen Biology/Institute of Basic Medical Sciences, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, China
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
| | - Nan Hou
- Laboratory of Parasitology, Institute of
Pathogen Biology/Institute of Basic Medical Sciences, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, China
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
| | - Lili Hao
- College of Life Science and Technology,
Southwest University of Nationalities, Chengdu, Sichuan, China
| | - Fan Yang
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
| | - Heng Wang
- Laboratory of Parasitology, Institute of
Pathogen Biology/Institute of Basic Medical Sciences, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, China
| | - Jianwei Wang
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
| | - Qi Jin
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
| | - Qijun Chen
- Laboratory of Parasitology, Institute of
Pathogen Biology/Institute of Basic Medical Sciences, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, China
- State Key Laboratory for Molecular Virology
and Genetic Engineering, Institute of Pathogen Biology, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing, China
- Key Laboratory of Zoonosis, Ministry of
Education, Institute of Zoonosis, Jilin University, Changchun, China
- * E-mail:
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Norton AJ, Gower CM, Lamberton PHL, Webster BL, Lwambo NJS, Blair L, Fenwick A, Webster JP. Genetic consequences of mass human chemotherapy for Schistosoma mansoni: population structure pre- and post-praziquantel treatment in Tanzania. Am J Trop Med Hyg 2010; 83:951-7. [PMID: 20889898 DOI: 10.4269/ajtmh.2010.10-0283] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Recent shifts in global health policy have led to the implementation of mass drug administration (MDA) for neglected tropical diseases. Here we show how population genetic analyses can provide vital insights into the impact of such MDA on endemic parasite populations. We show that even a single round of MDA produced a genetic bottleneck with reductions in a range of measures of genetic diversity of Schistosoma mansoni. Phylogenetic analyses and indices of population differentiation indicated that schistosomes collected in the same schools in different years were more dissimilar than those from different schools collected within either of the study's 2 years, in addition to distinguishing re-infection from non-clearance (that might indicate putatively resistant parasites) from within those children infected at both baseline and follow-up. Such unique results illustrate the importance of genetic monitoring and examination of long lived multi-cellular parasites such as these under novel or increased chemotherapeutic selective pressures.
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Affiliation(s)
- Alice J Norton
- Department of Infectious Disease Epidemiology, Imperial College, Faculty of Medicine, London, United Kingdom.
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Johansen MV, Sithithaworn P, Bergquist R, Utzinger J. Towards improved diagnosis of zoonotic trematode infections in Southeast Asia. ADVANCES IN PARASITOLOGY 2010; 73:171-95. [PMID: 20627143 DOI: 10.1016/s0065-308x(10)73007-4] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Humans in Southeast Asia are at risk for at least 70 species of food-borne and water-borne trematodes, including blood flukes, intestinal flukes, liver flukes and lung flukes, which are shared with a great variety of animals. Co-infection with several other zoonotic trematodes is pervasive, and hence differential diagnosis represents a major challenge. Many zoonotic trematodes are commonly overlooked, leading to unreliable prevalence data, underappreciation of their veterinary and public health burden and impact, and general neglect with respect to treatment and control. Additionally, many eggs are indistinguishable by microscopy. For example, failure to address this diagnostic dilemma has resulted in overestimation of Clonorchis sinensis prevalence and underestimation of minute intestinal flukes. Test insensitivity is becoming a problem of prime interest as surveillance is gaining in importance and various control programmes now regularly register progress. Hence, the likelihood of underestimating the true burden of disease is growing in well-controlled areas when the faecal egg excretion among infected individuals approaches zero. While antibody testing has ultimate sensitivity, its use as a test of cure remains contentious. On the other hand, employing faecal egg detection as the diagnostic 'gold' standard makes many positive antibody test results (incorrectly) appear false. Polymerase chain reaction (PCR)-based diagnostics could solve this dilemma, but more experience is needed and costs must be brought down to permit large-scale use of this approach. The future development of virtual microscopy to be used for diagnosis of parasitic infections in the field could make ordinary microscopy obsolete by electronically capturing specimens at point-of-contact in remote areas.
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Affiliation(s)
- Maria Vang Johansen
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg C, Denmark
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Schistosomiasis in the People's Republic of China: the era of the Three Gorges Dam. Clin Microbiol Rev 2010; 23:442-66. [PMID: 20375361 DOI: 10.1128/cmr.00044-09] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The potential impact of the Three Gorges Dam (TGD) on schistosomiasis transmission in China has invoked considerable global concern. The TGD will result in changes in the water level and silt deposition downstream, favoring the reproduction of Oncomelania snails. Combined with blockages of the Yangtze River's tributaries, these changes will increase the schistosomiasis transmission season within the marshlands along the middle and lower reaches of the Yangtze River. The changing schistosome transmission dynamics necessitate a comprehensive strategy to control schistosomiasis. This review discusses aspects of the epidemiology and transmission of Schistosoma japonicum in China and considers the pathology, clinical outcomes, diagnosis, treatment, immunobiology, and genetics of schistosomiasis japonica together with an overview of current progress in vaccine development, all of which will have an impact on future control efforts. The use of synchronous praziquantel (PZQ) chemotherapy for humans and domestic animals is only temporarily effective, as schistosome reinfection occurs rapidly. Drug delivery requires a substantial infrastructure to regularly cover all parts of an area of endemicity. This makes chemotherapy expensive and, as compliance is often low, a less than satisfactory control option. There is increasing disquiet about the possibility that PZQ-resistant schistosomes will develop. Consequently, as mathematical modeling predicts, vaccine strategies represent an essential component in the future control of schistosomiasis in China. With the inclusion of focal mollusciciding, improvements in sanitation, and health education into the control scenario, China's target of reducing the level of schistosome infection to less than 1% by 2015 may be achievable.
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Lu DB, Wang TP, Rudge JW, Donnelly CA, Fang GR, Webster JP. Evolution in a multi-host parasite: Chronobiological circadian rhythm and population genetics of Schistosoma japonicum cercariae indicates contrasting definitive host reservoirs by habitat. Int J Parasitol 2009; 39:1581-8. [DOI: 10.1016/j.ijpara.2009.06.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 06/03/2009] [Accepted: 06/10/2009] [Indexed: 11/16/2022]
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Contrasting reservoirs for Schistosoma japonicum between marshland and hilly regions in Anhui, China--a two-year longitudinal parasitological survey. Parasitology 2009; 137:99-110. [PMID: 19723358 DOI: 10.1017/s003118200999103x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Schistosoma japonicum remains highly endemic in many counties in China and has recently re-emerged, to a large extent, in previously controlled areas. To test the hypothesis that small rodents and less agriculturally important domestic animals such as dogs and cats may play an important role in the transmission and potential re-emergence of this disease, an annual investigation of S. japonicum among humans, domestic animals and rodents, combined with detailed surveys of the snail intermediate host, was performed across 3 marshland villages and 3 hilly villages in Anhui province of China over 2 consecutive years. The highest infection prevalence and intensity observed across all mammals was in rodents in the hilly region; while in the marshland, bovines were suspected as the main reservoirs. However, relatively high infection prevalence levels were also found in dogs and cats in both regions. Such results may have implications for the current human- and bovine-oriented control policy for this medically and veterinarily important disease, particularly within the hilly regions of mainland China.
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Agola LE, Steinauer ML, Mburu DN, Mungai BN, Mwangi IN, Magoma GN, Loker ES, Mkoji GM. Genetic diversity and population structure of Schistosoma mansoni within human infrapopulations in Mwea, central Kenya assessed by microsatellite markers. Acta Trop 2009; 111:219-25. [PMID: 19427295 PMCID: PMC2763435 DOI: 10.1016/j.actatropica.2009.04.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 04/20/2009] [Accepted: 04/29/2009] [Indexed: 10/20/2022]
Abstract
A recently developed high-throughput technique that allows multi-locus microsatellite analysis of individual miracidia of Schistosoma mansoni was used to assess the levels of genetic diversity and population structure in 12 infrapopulations of the parasite, each infrapopulation derived from an infected school child from the Mwea area, central Kenya. The mean number of alleles per locus was in the range 8.22-10.22, expected heterozygosity in Hardy-Weinberg equilibrium was 0.68-0.70, and pairwise F(ST) values ranged from 0.16% to 3.98% for the 12 infrapopulations. Although the genetic diversity within each infrapopulation of S. mansoni in this area was generally high, low levels of genetic structure were observed, suggestive of high levels of gene flow among infrapopulations. Private alleles were found in 8 of the 12 infrapopulation, the highest number of private alleles recorded per infrapopulation was 3. Our data suggest that the level of gene flow among infrapopulations of S. mansoni in Mwea is extremely high, thus providing opportunity for spread of rare alleles, including those that may confer character traits such as drug resistance and virulence.
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Affiliation(s)
- L E Agola
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya.
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Abstract
Molecular approaches are providing new insights into the genetic diversity of schistosomes and their intermediate snail hosts. For instance, molecular tools based on the polymerase chain reaction are being developed for the diagnosis of schistosomiasis and the detection of prepatent schistosome infections in snails at transmission sites. Robust phylogenies of the different species of Schistosoma, Bulinus and Biomphalaria have been determined and novel methods are available to identify the different and cryptic taxa involved. Microsatellite analyses and mitochondrial DNA sequencing methods have been developed and are contributing to a better understanding of the genetic structure of both schistosome and snail populations. New sampling procedures to capture DNA of eggs and larval stages of schistosomes in field situations are facilitating more detailed and ethically advantageous studies on parasite heterogeneity. Knowledge of the genetic diversity of schistosome and snail populations adds a further dimension to the monitoring and surveillance of disease, and the implementation of new molecular-based approaches will be of increasing importance in helping to assess the impact of schistosomiasis control strategies.
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45
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Impact of temporal changes and host factors on the genetic structure of a population of Opisthorchis viverrini sensu lato in Khon Kaen Province (Thailand). Parasitology 2009; 136:1057-63. [DOI: 10.1017/s0031182009006441] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
SUMMARYThe population genetics of 317 individual Opisthorchis viverrini from Khon Kaen Province Thailand, from 4 different years and 4 cyprinid fish species was examined using multilocus enzyme electrophoresis of enolase (Enol), phosphoglucomutase (Pgm) and triose phosphate isomerase (Tpi). Allele and genotype frequencies for Enol and Pgm were consistent irrespective of year or host species. No heterozygote deficiency was detected for Enol. Significant heterozygote deficiencies were detected in 3 of 4 years for Pgm. For Tpi, allele frequencies of the most common allele and genotype frequency varied between years and among individuals from different host species. Heterozygote deficiencies for Tpi were detected in 2 years. No significant heterozygous deficiencies were detected among O. virerrini from different fish species in 2005, except at Pgm and Tpi from Puntioplites protozsron. There was no statistical significance in pairwise FST values between O. viverrini from Cyclocheilichthys armatus in different years or different host species in 2005. Significant departures from Hardy-Weinberg expectations and a high rate of gene flow in a population of O. viverrini are discussed in terms of self- and cross-fertilisation, natural selection, non-random mating, the Wahlund effect, presence of null alleles, intensity of infection, biology and ecology of their intermediate cyprinid hosts.
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Gray DJ, Williams GM, Li Y, Chen H, Forsyth SJ, Li RS, Barnett AG, Guo J, Ross AG, Feng Z, McManus DP. A cluster-randomised intervention trial against Schistosoma japonicum in the Peoples' Republic of China: bovine and human transmission. PLoS One 2009; 4:e5900. [PMID: 19521532 PMCID: PMC2690852 DOI: 10.1371/journal.pone.0005900] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2009] [Accepted: 05/08/2009] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Zoonotic schistosomiasis japonica is a major public health problem in China. Bovines, particularly water buffaloes, are thought to play a major role in the transmission of schistosomiasis to humans in China. Preliminary results (1998-2003) of a praziquantel (PZQ)-based pilot intervention study we undertook provided proof of principle that water buffaloes are major reservoir hosts for S. japonicum in the Poyang Lake region, Jiangxi Province. METHODS AND FINDINGS Here we present the results of a cluster-randomised intervention trial (2004-2007) undertaken in Hunan and Jiangxi Provinces, with increased power and more general applicability to the lake and marshlands regions of southern China. The trial involved four matched pairs of villages with one village within each pair randomly selected as a control (human PZQ treatment only), leaving the other as the intervention (human and bovine PZQ treatment). A sentinel cohort of people to be monitored for new infections for the duration of the study was selected from each village. Results showed that combined human and bovine chemotherapy with PZQ had a greater effect on human incidence than human PZQ treatment alone. CONCLUSIONS The results from this study, supported by previous experimental evidence, confirms that bovines are the major reservoir host of human schistosomiasis in the lake and marshland regions of southern China, and reinforce the rationale for the development and deployment of a transmission blocking anti-S. japonicum vaccine targeting bovines. TRIAL REGISTRATION Australian New Zealand Clinical Trials Registry ACTRN12609000263291.
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Affiliation(s)
- Darren J. Gray
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
- School of Population Health, The University of Queensland, Brisbane, Australia
| | - Gail M. Williams
- School of Population Health, The University of Queensland, Brisbane, Australia
| | - Yuesheng Li
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
- Hunan Institute of Parasitic Diseases, WHO Collaborating Centre for Research and Control on Schistosomiasis in Lake Region, Huabanqiao Road, Yueyang, People's Republic of China
| | - Honggen Chen
- Jiangxi Provincial Institute of Parasitic Diseases, Nanchang, People's Republic of China
| | - Simon J. Forsyth
- School of Population Health, The University of Queensland, Brisbane, Australia
| | - Robert S. Li
- School of Population Health, The University of Queensland, Brisbane, Australia
| | - Adrian G. Barnett
- School of Public Health, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Jiagang Guo
- National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Allen G. Ross
- School of Public Health, Griffith University, Meadowbrook, Queensland, Australia
| | - Zheng Feng
- National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Donald P. McManus
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
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Rudge JW, Lu DB, Fang GR, Wang TP, Basáñez MG, Webster JP. Parasite genetic differentiation by habitat type and host species: molecular epidemiology of Schistosoma japonicum in hilly and marshland areas of Anhui Province, China. Mol Ecol 2009; 18:2134-47. [PMID: 19389178 DOI: 10.1111/j.1365-294x.2009.04181.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Schistosoma japonicum, a parasite of significant public health importance in parts of China and Southeast Asia, is a true generalist pathogen with over 40 species of mammals suspected as definitive host reservoirs. In order to characterize levels of parasite gene flow across host species and identify the most important zoonotic reservoirs, S. japonicum larvae (miracidia) were sampled from a range of definitive host species in two contrasting habitat types within Anhui Province, China: a low-lying marshland region, and a hilly region, where animal reservoir populations may be predicted to differ substantially. Miracidia samples were genotyped using seven multiplexed microsatellite markers. Hierarchical F-statistics and clustering analyses revealed substantial geographical structuring of S. japonicum populations within Anhui, with strong parasite genetic differentiation between habitat types. Within most villages, there was very little or no parasite genetic differentiation among host species, suggesting frequent S. japonicum gene flow, and thus also transmission, across species. Moreover, the data provide novel molecular evidence that rodents and dogs are potentially very important infection reservoirs in hilly regions, in contrast to bovines in the marshland regions. The parasite genetic differentiation between habitat types might therefore be associated with contrasting host reservoirs. The high levels of parasite gene flow observed across host species in sympatric areas have important implications for S. japonicum control, particularly in hilly regions where control of infection among wild rodent populations could be challenging.
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Affiliation(s)
- James W Rudge
- Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, UK.
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Gray DJ, Williams GM, Li Y, McManus DP. Transmission dynamics of Schistosoma japonicum in the lakes and marshlands of China. PLoS One 2008; 3:e4058. [PMID: 19115007 PMCID: PMC2605259 DOI: 10.1371/journal.pone.0004058] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Accepted: 11/23/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Schistosoma japonicum is a major public health concern in China, with over one million people infected and another 40 million living in areas at risk of infection. Unlike the disease caused by S. mansoni and S. haematobium, schistosomiasis japonica is a zoonosis, involving a number of different mammalian species as reservoir hosts. As a result of a number of published reports from China, it has long been considered that bovines, particularly water buffaloes, play a major role in human S. japonicum transmission there, and a drug-based intervention study (1998-2003) around the Poyang Lake in Jiangxi Province provided proof of concept that water buffaloes are, indeed, major reservoirs of human infection in this setting. METHODS AND FINDINGS In this study we incorporated recently obtained epidemiological information to model the steady-state S. japonicum transmission as well as the impact of the removal of S. japonicum transmission attributable to water buffaloes on human infection rates across six different endemic scenarios within three villages in the Dongting (Hunan) and Poyang (Jiangxi) lakes of southern China. Similar results were obtained for all scenarios. Steady-state S. japonicum infection rates remained constant and human prevalence and incidence were predicted to fall considerably over time. The model showed that the contribution of S. japonicum water buffalo transmission to human infection ranged from 39.1% to 99.1% and predicted that the removal of water buffalo transmission would reduce parasite reproductive rates below 1. This indicates that without the contribution of water buffaloes, S. japonicum transmission is interrupted and unsustainable. These scenarios are generalizable to other endemic villages in the lake and marshland areas of China where a similar cycle of snail infection and infection/reinfection of humans and bovines occurs. CONCLUSIONS Along with previous epidemiological data, our findings strongly support water buffaloes as an important component of the transmission cycle that affects humans in the lake and marshlands region of China, a feature which appears to differ from the situation prevalent in the Philippines where their contribution is less pronounced. Our conclusions underscore the rationale for removal, replacement or treatment of water buffaloes, and for the development and deployment of a transmission blocking buffalo vaccine against S. japonicum for this setting to achieve the goal of transmission control. The Chinese Government has recently commenced a new integrated national strategy to improve on existing approaches to control schistosomiasis in the lake and marshlands region by reducing bovines and humans as a source of S. japonicum infection to Oncomelania snails.
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Affiliation(s)
- Darren J. Gray
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Herston, Brisbane, Queensland, Australia
- School of Population Health, The University of Queensland, Herston, Brisbane, Queensland, Australia
| | - Gail M. Williams
- School of Population Health, The University of Queensland, Herston, Brisbane, Queensland, Australia
| | - Yuesheng Li
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Herston, Brisbane, Queensland, Australia
- Hunan Institute of Parasitic Diseases, WHO Collaborating Centre for Research and Control on Schistosomiasis in Lake Region, Yueyang, People's Republic of China
| | - Donald P. McManus
- Molecular Parasitology Laboratory, Queensland Institute of Medical Research, Herston, Brisbane, Queensland, Australia
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Rudge JW, Carabin H, Balolong E, Tallo V, Shrivastava J, Lu DB, Basáñez MG, Olveda R, McGarvey ST, Webster JP. Population genetics of Schistosoma japonicum within the Philippines suggest high levels of transmission between humans and dogs. PLoS Negl Trop Dis 2008; 2:e340. [PMID: 19030225 PMCID: PMC2582952 DOI: 10.1371/journal.pntd.0000340] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Accepted: 10/31/2008] [Indexed: 11/30/2022] Open
Abstract
Background Schistosoma japonicum, which remains a major public health problem in the Philippines and mainland China, is the only schistosome species for which zoonotic transmission is considered important. While bovines are suspected as the main zoonotic reservoir in parts of China, the relative contributions of various non-human mammals to S. japonicum transmission in the Philippines remain to be determined. We examined the population genetics of S. japonicum in the Philippines in order to elucidate transmission patterns across host species and geographic areas. Methodology/Principal Findings S. japonicum miracidia (hatched from eggs within fecal samples) from humans, dogs, pigs and rats, and cercariae shed from snail-intermediate hosts, were collected across two geographic areas of Samar Province. Individual isolates were then genotyped using seven multiplexed microsatellite loci. Wright's FST values and phylogenetic trees calculated for parasite populations suggest a high frequency of parasite gene-flow across definitive host species, particularly between dogs and humans. Parasite genetic differentiation between areas was not evident at the definitive host level, possibly suggesting frequent import and export of infections between villages, although there was some evidence of geographic structuring at the snail–intermediate host level. Conclusions/Significance These results suggest very high levels of transmission across host species, and indicate that the role of dogs should be considered when planning control programs. Furthermore, a regional approach to treatment programs is recommended where human migration is extensive. Schistosomiasis is a disease caused by parasitic worms known as schistosomes, which infect about 200 million people worldwide. In the Philippines, as in China, the species of schistosome (Schistosoma japonicum) which causes the disease infects not only humans, but also many other species of mammals. In China, bovines are thought to be particularly important for harboring and transmitting S. japonicum, whereas in the Philippines infections in bovines are relatively rare. However, dogs, rats and pigs are often infected with S. japonicum in the Philippines, although the extent to which infections in these animals may give rise to human infections is unclear. To help answer this question, we characterized the genetic variation of the parasite in Samar province of the Philippines, and found that S. japonicum samples from humans, dogs, rats and pigs were genetically very similar, with no significant genetic difference between samples from humans and dogs. This suggests that in the Philippines this parasite is frequently transmitted between different mammalian species, particularly between dogs and humans. Reducing levels of infections in dogs may therefore help to reduce infections in humans. The results also suggest high levels of transmission between geographic areas, thus regional co-ordination of treatment programs is recommended.
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Affiliation(s)
- James W Rudge
- Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London, United Kingdom.
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Webster JP, Gower CM, Norton AJ. Evolutionary concepts in predicting and evaluating the impact of mass chemotherapy schistosomiasis control programmes on parasites and their hosts. Evol Appl 2008; 1:66-83. [PMID: 25567492 PMCID: PMC3352399 DOI: 10.1111/j.1752-4571.2007.00012.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Accepted: 12/05/2007] [Indexed: 11/28/2022] Open
Abstract
Schistosomiasis is a parasitic disease of significant medical and veterinary importance in many regions of the world. Recent shifts in global health policy have led towards the implementation of mass chemotherapeutic control programmes at the national scale in previously 'neglected' countries such as those within sub-Saharan Africa. Evolutionary theory has an important role to play in the design, application and interpretation of such programmes. Whilst celebrating the rapid success achieved to date by such programmes, in terms of reduced infection prevalence, intensity and associated human morbidity, evolutionary change in response to drug selection pressure may be predicted under certain circumstances, particularly in terms of the development of potential drug resistance, evolutionary changes in parasite virulence, transmission and host use, and/or competitive interactions with co-infecting pathogens. Theoretical and empirical data gained to date serve to highlight the importance of careful monitoring and evaluation of parasites and their hosts whenever and wherever chemotherapy is applied and where parasite transmission remains.
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Affiliation(s)
- Joanne P Webster
- Department of Infectious Disease Epidemiology, Imperial College Faculty of Medicine Norfolk Place, London, UK
| | - Charlotte M Gower
- Department of Infectious Disease Epidemiology, Imperial College Faculty of Medicine Norfolk Place, London, UK
| | - Alice J Norton
- Department of Infectious Disease Epidemiology, Imperial College Faculty of Medicine Norfolk Place, London, UK
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