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Kajero OT, Janoušková E, Bakare EA, Belizario V, Divina B, Alonte AJ, Manalo SM, Paller VG, Betson M, Prada JM. OUP accepted manuscript. Trans R Soc Trop Med Hyg 2022; 116:727-735. [PMID: 35169848 PMCID: PMC9356178 DOI: 10.1093/trstmh/trac002] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 10/01/2021] [Accepted: 01/11/2022] [Indexed: 12/02/2022] Open
Abstract
Background A large number of studies have assessed risk factors for infection with soil-transmitted helminths (STH), but few have investigated the interactions between the different parasites or compared these between host species across hosts. Here, we assessed the associations between Ascaris, Trichuris, hookworm, strongyle and Toxocara infections in the Philippines in human and animal hosts. Methods Faecal samples were collected from humans and animals (dogs, cats and pigs) in 252 households from four villages in southern Philippines and intestinal helminth infections were assessed by microscopy. Associations between worm species were assessed using multiple logistic regression. Results Ascaris infections showed a similar prevalence in humans (13.9%) and pigs (13.7%). Hookworm was the most prevalent infection in dogs (48%); the most prevalent infection in pigs was strongyles (42%). The prevalences of hookworm and Toxocara in cats were similar (41%). Statistically significant associations were observed between Ascaris and Trichuris and between Ascaris and hookworm infections in humans, and also between Ascaris and Trichuris infections in pigs. Dual and triple infections were observed, which were more common in dogs, cats and pigs than in humans. Conclusions Associations are likely to exist between STH species in humans and animals, possibly due to shared exposures and transmission routes. Individual factors and behaviours will play a key role in the occurrence of co-infections, which will have effects on disease severity. Moreover, the implications of co-infection for the emergence of zoonoses need to be explored further.
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Affiliation(s)
- Olumayowa T Kajero
- School of Veterinary Medicine, Faculty of Health & Medical Sciences, University of Surrey, GU2 7AL, UK
| | - Eva Janoušková
- School of Veterinary Medicine, Faculty of Health & Medical Sciences, University of Surrey, GU2 7AL, UK
| | - Emmanuel A Bakare
- Biomathematics and Applied Mathematical Modelling Research Group, Modelling Simulation and Data Science Network, Department of Mathematics, Federal University Oye-Ekiti, 371104, Ekiti, Nigeria
| | - Vicente Belizario
- College of Public Health, University of Philippines, Manila, 1000, Philippines
| | - Billy Divina
- Department of Veterinary Paraclinical Sciences, College of Veterinary Medicine, University of the Philippines Los Baños, 4030, Philippines
| | - Allen Jethro Alonte
- Animal Biology Division, Institute of Biological Sciences, University of the Philippines, Los Baños, 4030, Philippines
| | - Sheina Macy Manalo
- Department of Veterinary Paraclinical Sciences, College of Veterinary Medicine, University of the Philippines Los Baños, 4030, Philippines
| | - Vachel Gay Paller
- Department of Veterinary Paraclinical Sciences, College of Veterinary Medicine, University of the Philippines Los Baños, 4030, Philippines
| | - Martha Betson
- School of Veterinary Medicine, Faculty of Health & Medical Sciences, University of Surrey, GU2 7AL, UK
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Hamelin FM, Allen LJS, Bokil VA, Gross LJ, Hilker FM, Jeger MJ, Manore CA, Power AG, Rúa MA, Cunniffe NJ. Coinfections by noninteracting pathogens are not independent and require new tests of interaction. PLoS Biol 2019; 17:e3000551. [PMID: 31794547 PMCID: PMC6890165 DOI: 10.1371/journal.pbio.3000551] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 11/04/2019] [Indexed: 12/26/2022] Open
Abstract
If pathogen species, strains, or clones do not interact, intuition suggests the proportion of coinfected hosts should be the product of the individual prevalences. Independence consequently underpins the wide range of methods for detecting pathogen interactions from cross-sectional survey data. However, the very simplest of epidemiological models challenge the underlying assumption of statistical independence. Even if pathogens do not interact, death of coinfected hosts causes net prevalences of individual pathogens to decrease simultaneously. The induced positive correlation between prevalences means the proportion of coinfected hosts is expected to be higher than multiplication would suggest. By modelling the dynamics of multiple noninteracting pathogens causing chronic infections, we develop a pair of novel tests of interaction that properly account for nonindependence between pathogens causing lifelong infection. Our tests allow us to reinterpret data from previous studies including pathogens of humans, plants, and animals. Our work demonstrates how methods to identify interactions between pathogens can be updated using simple epidemic models. If pathogen species, strains, or clones do not interact, intuition suggests the proportion of coinfected hosts can be obtained by simply multiplying the individual prevalences. However, even simple epidemiological models show this to be untrue. This study develops new tests for interaction between pathogens that account for this surprising lack of statistical independence.
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Affiliation(s)
- Frédéric M. Hamelin
- IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, Rennes, France
| | - Linda J. S. Allen
- Department of Mathematics and Statistics, Texas Tech University, Lubbock, Texas, United States of America
| | - Vrushali A. Bokil
- Department of Mathematics, Oregon State University, Corvallis, Oregon, United States of America
| | - Louis J. Gross
- National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Frank M. Hilker
- Institute of Environmental Systems Research, School of Mathematics and Computer Science, Osnabrück University, Osnabrück, Germany
| | - Michael J. Jeger
- Centre for Environmental Policy, Imperial College London, Ascot, United Kingdom
| | - Carrie A. Manore
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Alison G. Power
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, United States of America
| | - Megan A. Rúa
- Department of Biological Sciences, Wright State University, Dayton, Ohio, United States of America
| | - Nik J. Cunniffe
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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3
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Prospects for the elimination of schistosomiasis and soil-transmitted helminthiasis: exploring disease trends through time at the Barombi crater lakes, South-West Cameroon. Parasitology 2018; 145:1700-1714. [PMID: 30246664 DOI: 10.1017/s0031182018001531] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In Cameroon, there is a national programme engaged in the control of schistosomiasis and soil-transmitted helminthiasis. In certain locations, the programme is transitioning from morbidity control towards local interruption of parasite transmission. The volcanic crater lake villages of Barombi Mbo and Barombi Kotto are well-known transmission foci and are excellent context-specific locations to assess appropriate disease control interventions. Most recently they have served as exemplars of expanded access to deworming medications and increased environmental surveillance. In this paper, we review infection dynamics through time, beginning with data from 1953, and comment on the short- and long-term success of disease control. We show how intensification of local control is needed to push towards elimination and that further environmental surveillance, with targeted snail control, is needed to consolidate gains in preventive chemotherapy as well as empower local communities to take ownership of interventions.
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Abstract
Estimating the public health impact of endemic helminth infections is an important component of control strategies that aim not only to reduce the number of infections in a community, but also to improve community health. This is not straightforward, as the risk of morbidity in an infected individual can be influenced by a number of factors, and different infections can cause similar symptoms. Here, Mark Booth describes how attributable risk analysis techniques based on 232 tables can be used to address these problems, and how they were applied to estimate the public health impact of Schistosoma japonicum infections in three villages in China.
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Affiliation(s)
- M Booth
- Department of Public Health and Epidemiology, Swiss Tropical Institute, CH-4002 Basel, Switzerland
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5
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Sturrock HJW, Gething PW, Clements ACA, Brooker S. Optimal survey designs for targeting chemotherapy against soil-transmitted helminths: effect of spatial heterogeneity and cost-efficiency of sampling. Am J Trop Med Hyg 2010; 82:1079-87. [PMID: 20519603 DOI: 10.4269/ajtmh.2010.09-0702] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Implementation of helminth control programs requires information on the distribution and prevalence of infection to target mass treatment to areas of greatest need. In the absence of data, the question of how many schools/communities should be surveyed depends on the spatial heterogeneity of infection and the cost efficiency of surveys. We used geostatistical techniques to quantify the spatial heterogeneity of soil-transmitted helminths in multiple settings in eastern Africa, and using the example of Kenya, conducted conditional simulation to explore the implications of alternative sampling strategies in identifying districts requiring mass treatment. Cost analysis is included in the simulations using data from actual field surveys and control programs. The analysis suggests that sampling four or five schools in each district provides a cost-efficient strategy in identifying districts requiring mass treatment, and that efficiency of sampling was relatively insensitive to the number of children sampled per school.
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Affiliation(s)
- Hugh J W Sturrock
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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6
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de Silva N, Hall A. Using the prevalence of individual species of intestinal nematode worms to estimate the combined prevalence of any species. PLoS Negl Trop Dis 2010; 4:e655. [PMID: 20405050 PMCID: PMC2854118 DOI: 10.1371/journal.pntd.0000655] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 03/02/2010] [Indexed: 11/18/2022] Open
Abstract
Objectives To assess if a probabilistic model could be used to estimate the combined prevalence of infection with any species of intestinal nematode worm when only the separate prevalence of each species is reported, and to estimate the extent to which simply taking the highest individual species prevalence underestimates the combined prevalence. Methods Data were extracted from community surveys that reported both the proportion infected with individual species and the combined proportion infected, for a minimum sample of 100 individuals. The predicted combined proportion infected was calculated based on the assumption that the probability of infection with one species was independent of infection with another species, so the probability of combined infections was multiplicative. Findings Thirty-three reports describing 63 data sets from surveys conducted in 20 countries were identified. A strong correlation was found between the observed and predicted combined proportion infected (r = 0.996, P<0.001). When the observed and predicted values were plotted against each other, a small correction of the predicted combined prevalence by dividing by a factor of 1.06 achieved a near perfect correlation between the two sets of values. The difference between the single highest species prevalence and the observed combined prevalence was on average 7% or smaller at a prevalence of ≤40%, but at prevalences of 40–80%, the difference was about 12%. Conclusions A simple probabilistic model of combined infection with a small correction factor is proposed as a novel method to estimate the number of individuals that would benefit from mass deworming when data are reported only for separate species. Mixed infections with roundworm, whipworm and hookworm are common, but survey reports often give only the separate prevalence of each type. However, the combined prevalence is important to estimate accurately the number of individuals who would benefit from control programmes and to make decisions about the frequency of treatment. Previous work suggests that mixed infections involving hookworm occur randomly, but that roundworm and whipworm infections are found together more frequently than would be expected by chance. We used 63 data sets from community surveys that reported both the proportions infected with individual types of worms and the combined proportion infected with any worm. We then calculated the proportion that would be infected with any type of worm if infections had occurred randomly and compared it with the observed combined proportion infected. We found a strong correlation between the observed and predicted combined proportions infected. A small downward correction of the predicted proportion infected by dividing by a factor of 1.06 brought it to a value that nearly equalled the observed proportion infected almost all the time. This simple model could be applied to published survey data to estimate accurately the number of individuals that would benefit from mass deworming.
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Affiliation(s)
- Nilanthi de Silva
- Department of Parasitology, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka.
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Brooker S, Clements ACA, Bundy DAP. Global epidemiology, ecology and control of soil-transmitted helminth infections. ADVANCES IN PARASITOLOGY 2009; 62:221-61. [PMID: 16647972 PMCID: PMC1976253 DOI: 10.1016/s0065-308x(05)62007-6] [Citation(s) in RCA: 359] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Soil-transmitted helminth (STH) infections are among the most prevalent of chronic human infections worldwide. Based on the demonstrable impact on child development, there is a global commitment to finance and implement control strategies with a focus on school-based chemotherapy programmes. The major obstacle to the implementation of cost-effective control is the lack of accurate descriptions of the geographical distribution of infection. In recent years, considerable progress has been made in the use of geographical information systems (GIS) and remote sensing (RS) to better understand helminth ecology and epidemiology, and to develop low-cost ways to identify target populations for treatment. This review explores how this information has been used practically to guide large-scale control programmes. The use of satellite-derived environmental data has yielded new insights into the ecology of infection at a geographical scale that has proven impossible to address using more traditional approaches, and has in turn allowed spatial distributions of infection prevalence to be predicted robustly by statistical approaches. GIS/RS have increasingly been used in the context of large-scale helminth control programmes, including not only STH infections but also those focusing on schistosomiasis, filariasis and onchocerciasis. The experience indicates that GIS/RS provides a cost-effective approach to designing and monitoring programmes at realistic scales. Importantly, the use of this approach has begun to transition from being a specialist approach of international vertical programmes to becoming a routine tool in developing public sector control programmes. GIS/RS is used here to describe the global distribution of STH infections and to estimate the number of infections in school-age children in sub-Saharan Africa (89.9 million) and the annual cost of providing a single anthelmintic treatment using a school-based approach (US$5.0-7.6 million). These are the first estimates at a continental scale to explicitly include the fine spatial distribution of infection prevalence and population, and suggest that traditional methods have overestimated the situation. The results suggest that continent-wide control of parasites is, from a financial perspective, an attainable goal.
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Affiliation(s)
- S Brooker
- Department of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine, Keppel Street, London, UK
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8
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Hillier SD, Booth M, Muhangi L, Nkurunziza P, Khihembo M, Kakande M, Sewankambo M, Kizindo R, Kizza M, Muwanga M, Elliott AM. Plasmodium falciparum and helminth coinfection in a semi urban population of pregnant women in Uganda. J Infect Dis 2008; 198:920-7. [PMID: 18721060 PMCID: PMC2886962 DOI: 10.1086/591183] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Helminth infections and malaria are widespread in the tropics. Recent studies suggest helminth infections may increase susceptibility to Plasmodium falciparum infection. If confirmed, this increased susceptibility could be particularly important during pregnancy-induced immunosuppression. OBJECTIVE To evaluate the geographical distribution of P. falciparum-helminth coinfection and the associations between P. falciparum infection and infection with various parasite species in pregnant women in Entebbe, Uganda. METHODS A cross-sectional study was conducted at baseline during a trial of antihelminthic drugs during pregnancy. Helminth and P. falciparum infections were quantified in 2,507 asymptomatic women. Subjects' socioeconomic and demographic characteristics and geographical details were recorded. RESULTS Hookworm and Mansonella perstans infections were associated with P. falciparum infection, but the effect of hookworm infection was seen only in the absence of M. perstans infection. The odds ratio [OR] for P. falciparum infection, adjusted for age, tribe, socioeconomic status, HIV infection status, and location was as follows: for individuals infected with hookworm but not M. perstans, 1.53 (95% confidence interval [CI], 1.09-2.14); for individuals infected with M. perstans but not hookworm, 2.33 (95% CI, 1.47-3.69); for individuals infected with both hookworm and M. perstans, 1.85 (CI, 1.24-2.76). No association was observed between infection with Schistosoma mansoni, Trichuris, or Strongyloides species and P. falciparum infection. CONCLUSIONS Hookworm-P. falciparum coinfection and M. perstans-P. falciparum coinfection among pregnant women in Entebbe is more common than would be expected by chance. Further studies are needed to elucidate the mechanism of this association. A helminth-induced increase in susceptibility to P. falciparum could have important consequences for pregnancy outcome and responses to P. falciparum infection in infancy.
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Affiliation(s)
- Stephen D Hillier
- The University of Birmingham Medical School, Birmingham, United Kingdom.
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9
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Pullan R, Brooker S. The health impact of polyparasitism in humans: are we under-estimating the burden of parasitic diseases? Parasitology 2008; 135:783-94. [PMID: 18371242 PMCID: PMC2645487 DOI: 10.1017/s0031182008000346] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Parasitic infections are widespread throughout the tropics and sub-tropics, and infection with multiple parasite species is the norm rather than the exception. Despite the ubiquity of polyparasitism, its public health significance has been inadequately studied. Here we review available studies investigating the nutritional and pathological consequences of multiple infections with Plasmodium and helminth infection and, in doing so, encourage a reassessment of the disease burden caused by polyparasitism. The available evidence is conspicuously sparse but is suggestive that multiple human parasite species may have an additive and/or multiplicative impact on nutrition and organ pathology. Existing studies suffer from a number of methodological limitations and adequately designed studies are clearly necessary. Current methods of estimating the potential global morbidity due to parasitic diseases underestimate the health impact of polyparasitism, and possible reasons for this are presented. As international strategies to control multiple parasite species are rolled-out, there is a number of options to investigate the complexity of polyparasitism, and it is hoped that that the parasitological research community will grasp the opportunity to understand better the health of polyparasitism in humans.
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Affiliation(s)
- R Pullan
- Department of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
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10
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Fleming FM, Brooker S, Geiger SM, Caldas IR, Correa-Oliveira R, Hotez PJ, Bethony JM. Synergistic associations between hookworm and other helminth species in a rural community in Brazil. Trop Med Int Health 2006; 11:56-64. [PMID: 16398756 DOI: 10.1111/j.1365-3156.2005.01541.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE To identify possible synergistic associations of hookworm and other helminths. METHOD Cross-sectional survey of all households within 10 km2 of Americaninhas, a rural community in Minas Gerais, Brazil. We determined the prevalence and intensity of single and multiple helminth species infection in an age-stratified sample of 1332 individuals from 335 households. RESULTS Hookworm was the most prevalent helminth infection (68.2%), followed by Ascaris lumbricoides (48.8%) and Schistosoma mansoni (45.3%). Overall, 60.6% of individuals harboured mixed helminth infections. Multivariate analysis indicated significant positive associations for co-infection with hookworm and S. mansoni and for co-infection with hookworm and A. lumbricoides. Co-infections with hookworm and A. lumbricoides resulted in higher egg counts for both, suggesting a synergistic relationship between these species, although, we found important age differences in this relationship. However, the intensity of S. mansoni or A. lumbricoides co-infection did not differ from that of mono-infection. CONCLUSION These results have implications for the epidemiology, immunology and control of multiple helminth infections. More research is needed to examine the rates of re-infection and immune responses after chemotherapy, and to what extent the effects of polyparasitism are altered by chemotherapy.
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Affiliation(s)
- Fiona M Fleming
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK
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Faulkner H, Turner J, Behnke J, Kamgno J, Rowlinson MC, Bradley JE, Boussinesq M. Associations between filarial and gastrointestinal nematodes. Trans R Soc Trop Med Hyg 2005; 99:301-12. [PMID: 15708389 DOI: 10.1016/j.trstmh.2004.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Revised: 04/26/2004] [Accepted: 05/04/2004] [Indexed: 11/29/2022] Open
Abstract
The possibility that positive or negative associations occur between the filarial nematode Onchocerca volvulus and the gastrointestinal nematodes Ascaris lumbricoides and Trichuris trichiura was investigated in 205 children attending three schools in central Cameroon. Despite the closeness of their locations, marked differences between the schools were detected with respect to the number of species carried, the prevalence of O. volvulus and T. trichiura and the interaction between the prevalence of these two species. The number of species carried and these same prevalences varied significantly across the narrow age range of the study group. In addition, we observed an interaction between the prevalences of O. volvulus and A. lumbricoides that was dependent upon school but independent of host age and sex. Quantitative analyses revealed that the abundances of O. volvulus, A. lumbricoides and T. trichiura were affected by both school and age whereas host sex was significant only for O. volvulus. Finally, we observed significant positive interactions between the intensities of A. lumbricoides and T. trichiura and between O. volvulus and T. trichiura, that were school, age and sex independent. Our data suggest that associations do occur between filarial and gastrointestinal nematodes and that certain individuals are prone to multiple and high-level infections.
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Affiliation(s)
- Helen Faulkner
- School of Biology, University of Nottingham, Nottingham NG7 2RD, UK
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12
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Jackson JA, Turner JD, Rentoul L, Faulkner H, Behnke JM, Hoyle M, Grencis RK, Else KJ, Kamgno J, Bradley JE, Boussinesq M. Cytokine response profiles predict species-specific infection patterns in human GI nematodes. Int J Parasitol 2004; 34:1237-44. [PMID: 15491586 DOI: 10.1016/j.ijpara.2004.07.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Revised: 07/27/2004] [Accepted: 07/29/2004] [Indexed: 11/23/2022]
Abstract
This study investigated associations between pre-treatment cytokine expression and infection patterns, before and after de-worming, in humans exposed to two gastrointestinal nematode species. Quantitative measures of Ascaris lumbricoides and Trichuris trichiura infection (based on faecal egg counts) were estimated immediately before and 8-9 months after treatment in a Cameroonian population. Whole blood cytokine responses to parasite-derived antigens were assayed immediately pre-treatment. An overall measure of the tendency towards species-specific infection (increasing with A. lumbricoides faecal egg counts and decreasing with T. trichiura faecal egg counts) was significantly positively related to IL-10 levels in older (14-57 year) hosts. There was a significant negative influence of IL-5 on reinfection probability in T. trichiura but not A. lumbricoides. This effect coincided with reduced reinfection success in T. trichiura compared to A. lumbricoides. T(H)2 cytokine expression by younger hosts (4-13 year) was negatively associated with contemporary A. lumbricoides faecal egg counts before treatment. Following treatment, the pre-treatment T(H)2 cytokine expression data for younger hosts (now reflecting responsiveness 8-9 months in the past) were negatively associated with T. trichiura faecal egg counts. Taken together, these observations suggest a successional interaction between T(H)2-driven immune responses and species infection over time. However, any differential effects of the measured immune responses on species-specific recruitment, maturation and mortality were superimposed upon (and outweighed by) the effects of other factors favouring coinfection.
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Affiliation(s)
- J A Jackson
- School of Biology, Nottingham University, Nottingham NG7 2RD, UK
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13
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Booth M, Vennervald BJ, Kenty L, Butterworth AE, Kariuki HC, Kadzo H, Ireri E, Amaganga C, Kimani G, Mwatha JK, Otedo A, Ouma JH, Muchiri E, Dunne DW. Micro-geographical variation in exposure to Schistosoma mansoni and malaria, and exacerbation of splenomegaly in Kenyan school-aged children. BMC Infect Dis 2004; 4:13. [PMID: 15147584 PMCID: PMC421731 DOI: 10.1186/1471-2334-4-13] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Accepted: 05/17/2004] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Schistosoma mansoni and Plasmodium falciparum are common infections of school aged children in Kenya. They both cause enlargement of the spleen, but their relative contribution to the condition of splenomegaly remains unknown in areas where both infections are endemic. Here, we have investigated whether relatively high exposure to both infections has a clinically measurable effect on this condition. METHODS 96 children aged 6-16 years living along a ten kilometre stretch and within 4 km south of a river that is a source of both S. mansoni and malaria infections were examined clinically for splenomegaly along the mid clavicular line (MCL) and mid axillary line (MAL). The survey was conducted outside the malaria transmission season. The consistency of the organ was recorded as soft, firm or hard. Mapping of the locations of houses and the course of the river was undertaken. Egg counts were mapped at the household level, as were IgG3 responses to Plasmodium falciparum schizont antigen (anti-Pfs IgG3), in order to identify areas with relatively high exposure to both infections, either infection or neither infection. ANOVA was used to test for differences in egg counts, IgG3 levels and the magnitude of spleen enlargement between these areas. RESULTS 4 contiguous sectors were identified, one where anti-Pfs IgG3 responses and S. mansoni egg counts were both high, one where only anti-Pfs IgG3 responses were high, one where only egg counts were high, and one where both anti-Pfs IgG3 responses and egg counts were low. Spleen MAL and MCL values were significantly higher amongst children from the sector with highest IgG3 levels and highest egg counts but similar amongst children from elsewhere. Both egg counts and anti-Pfs IgG3 responses were significantly higher in children with MAL values > or =4 cm. Hardening of spleens was associated with proximity of domicile to the river. CONCLUSIONS Micro-geographical variation in exposure to S. mansoni and malaria infections can be exploited to investigate the chronic impact of these two infections. These results provide firm evidence that relatively high exposure to both infections exacerbates splenomegaly even outside the malaria transmission season. Major implications include assessing the burden of infection in school age-children.
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Affiliation(s)
- Mark Booth
- Division of Microbiology and Parasitology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK
| | | | - LeeCarol Kenty
- Division of Microbiology and Parasitology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK
| | - Anthony E Butterworth
- Biomedical Research and Training Institute, P.O. Box CY 1753, Causeway, Harare, Zimbabwe
| | - Henry C Kariuki
- Division of Vector Borne Diseases, Ministry of Health, P.O Box 54840, Nairobi, Kenya
| | | | - Edmund Ireri
- Kenya Medical Research Institute, Nairobi, Kenya
| | | | | | | | - Amos Otedo
- Kenya Medical Research Institute, Nairobi, Kenya
| | | | - Eric Muchiri
- Division of Vector Borne Diseases, Ministry of Health, P.O Box 54840, Nairobi, Kenya
| | - David W Dunne
- Division of Microbiology and Parasitology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK
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Tchuem Tchuenté LA, Behnke JM, Gilbert FS, Southgate VR, Vercruysse J. Polyparasitism with Schistosoma haematobium and soil-transmitted helminth infections among school children in Loum, Cameroon. Trop Med Int Health 2003; 8:975-86. [PMID: 14629763 DOI: 10.1046/j.1360-2276.2003.01120.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Prevalence and abundance of Schistosoma haematobium and soil-transmitted helminths (STH) were assessed among a total of 1600 pupils (urine, n = 1190; faecal samples, n = 1454) attending five schools in Loum, Littoral Province, Cameroon, with the specific aim of assessing the extent of polyparasitism and the extent to which infections were focused in particular subsets of the study group. Prevalence of S. haematobium was 62.8% with an abundance (arithmetic mean of egg counts) of 54 eggs/10 ml urine. For the STH these were 47.7% and 619 eggs per gram of faeces (EPG) for Trichuris trichiura, 65.5% and 3636 EPG for Ascaris lumbricoides, and 1.4% and <0.1 EPG for hookworms. Most children (90.3%) were infected with at least one of these four species, the largest proportion (34.3%) carrying two species; 27.4% carried three and 1.1% carried concurrently all four species of parasites. The average number of species harboured increased with age, as did the prevalences of S. haematobium and T. trichiura but not that of A. lumbricoides. All STH showed marked differences in prevalence between the five schools but only T. trichiura varied significantly between sexes. Mean abundance of infection varied significantly between age classes, among schools and between the sexes, with females showing heavier mean EPGs for A. lumbricoides and T. trichiura and males higher mean eggs/10 ml urine for S. haematobium infections. A highly significant association was detected between A. lumbricoides and T. trichiura, that was not context-dependent. This was confirmed in quantitative analyses after controlling for differences in abundance between schools, sexes and age classes. A weaker context-dependent association (prevalence data) was detected between S. haematobium and A. lumbricoides (sex- and age-dependent) but quantitative associations between these two species, as well as between S. haematobium and T. trichiura, were not convincing.
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Affiliation(s)
- L-A Tchuem Tchuenté
- Laboratory of General Biology, Faculty of Sciences, University of Yaoundé, Yaoundé, Cameroon.
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Howard SC, Donnelly CA, Kabatereine NB, Ratard RC, Brooker S. Spatial and intensity-dependent variations in associations between multiple species helminth infections. Acta Trop 2002; 83:141-9. [PMID: 12088855 DOI: 10.1016/s0001-706x(02)00093-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Estimated associations between infections with different helminth species can be used to predict the proportion of a population infected with multiple species infections. This is an important measure of disease burden, as those with multiple infections are often at an increased risk of morbidity. In this paper, we investigate variation amongst the estimated associations between Ascaris lumbricoides, Trichuris trichiura and hookworm, over a number of different spatial levels among schoolchildren in Cameroon. Associations between species were largely homogeneous within districts, provinces and ecological zones, although variation between these regions was identified, implying that a single measure of association may not be appropriate in different epidemiological settings. Further data collected amongst school children in Kenya and Uganda were analysed, to assess the dependence of the associations on the intensity of infection. It was found that the strength of the association between A. lumbricoides and T. trichiura increased with intensity, such that those with more intense infections with one species are increasingly likely to harbour concurrent intense infections with the other species. The implications of these results are discussed in relation to the estimation of the disease burden due to multiple helminth species.
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Affiliation(s)
- S C Howard
- Stroke Prevention Research Unit, Department of Clinical Neurology, University of Oxford, Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, UK.
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Abstract
Parasitic worm infections are amongst the most widespread of all chronic human infections. It is estimated that there are more than 3 billion infections in the world today. In many low income countries it is often more common to be infected than not to be. Indeed, a child growing up in an endemic community can expect be infected soon after weaning, and to be infected and constantly reinfected for the rest of her or his life. Infection is most common amongst the poorest and most disadvantaged communities, and is typically most intense in children of school going age. As the risk of morbidity is directly related to intensity of infection, it follows that children are the most at risk from the morbid effects of disease. Multiparasite infections are also common in such communities and there is evidence that individuals harbouring such infections may suffer exacerbated morbidity, making children even more vulnerable. Thus, these infections pose a serious threat to the health and development of children in low income countries. For many years, the need to control these infections has lain uncontested, and with the advent of broad-spectrum anthelminthic drugs that are cheap, safe and simple to deliver, control has at last become a viable option for many communities. Furthermore, there is now increased emphasis being placed on a multispecies approach as a cost-effective mechanism to control the morbidity of virtually all the major helminthic infections of humans.
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Affiliation(s)
- L J Drake
- Wellcome Trust Centre for the Epidemiology of Infections Disease, University of Oxford.
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Flores A, Esteban JG, Angles R, Mas-Coma S. Soil-transmitted helminth infections at very high altitude in Bolivia. Trans R Soc Trop Med Hyg 2001; 95:272-7. [PMID: 11490995 DOI: 10.1016/s0035-9203(01)90232-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
A cross-sectional study of soil-transmitted helminthiases in the Northern Bolivian Altiplano was carried out over the 6-year period 1992-97. Prevalences, intensities and associations were analysed from coprological results obtained in 31 surveys (28 in schools and 3 in individuals of all age-groups) performed in 24 Aymara communities located between the city of La Paz and Lake Titicaca, at an altitude of 3800-4200 m. Ascaris lumbricoides and Trichuris trichiura were detected, with local prevalences in the range 1.2-28.0% and 0.0-24.0%, respectively. Significant differences in prevalence rates of trichuriasis were detected, with highest prevalences in male schoolchildren and in subjects aged > 40 years. The global intensity ranged from 24 to 86,544 eggs per gram of faeces (epg) and from 24 to 4560 epg for ascariasis and trichuriasis, respectively. Higher intensities were noted in girls. A. lumbricoides egg counts were statistically significantly higher in the 5-8-years age-group. A positive association between A. lumbricoides and T. trichiura infections was detected. The proportion of heavy infections for A. lumbricoides was 0.1% and 1.0% in the school and community surveys, respectively. No heavy infection for T. trichiura was detected. The very high altitude and its severe environmental conditions may determine the relatively low prevalences and intensities in this area.
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Affiliation(s)
- A Flores
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain
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Morales GA, Pinto de Morales L, Arteaga C, Matinella L, Rojas H. [Prevalence of intestinal helminthiasis in 100 municipalities in Venezuela (1989-1992)]. Rev Soc Bras Med Trop 1999; 32:263-70. [PMID: 10380565 DOI: 10.1590/s0037-86821999000300007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A total of 113,254 individuals from 100 venezuelan municipalities were studied by mean of Kato-Katz coprological examination and the geohelminth prevalences were established. The national prevalences of T. trichiura, A. lumbricoides and Anquilostomideos were 32.6%, 26.9% and 5.6% respectively+. For T. trichiura the highest values were obtained for the following municipalities: Arévalo González (54.6%) in Miranda state, Urama (76.9%) in Carabobo state and Punta de Piedra (78.4%) in Sucre state. For A. lumbricoides the highest values were determined in Punta de Piedra (63%), Tunapuy (61.9%) in Sucre state and Arévalo González (62.7%) in Miranda state. For hookworm the highest values were detected in El Amparo (39.5%) and San Camilo (35.9%) in the state of Apure. In relation to the age, the highest prevalence of Ascariosis and Trichuriosis were determined in pre-school and school children and for hookworm in adolescents and adults. A high variability between the municipalities belonging to the same state for the three geohelminths was observed.
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Affiliation(s)
- G A Morales
- Laboratório de Parasitologia, Instituto de Investigaciones Veterinarias, CENIAP-FONAIAP, Araqua, Venezuela
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Needham C, Kim HT, Hoa NV, Cong LD, Michael E, Drake L, Hall A, Bundy DA. Epidemiology of soil-transmitted nematode infections in Ha Nam Province, Vietnam. Trop Med Int Health 1998; 3:904-12. [PMID: 9855404 DOI: 10.1046/j.1365-3156.1998.00324.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Baseline epidemiological data are presented from a parasitological survey conducted in Thuy Loi commune, Ha Nam province, Vietnam; a farming community where night soil is routinely used as fertilizer for crops. 177 households were visited and 543 individuals (aged 1-88 years) recruited to the study. Helminth infection intensity was assessed by Kato-Katz to determine the density of parasite eggs per gram of stool (epg). Ascaris lumbricoides, Trichuris trichiura and hookworm infections were the only species detected. 83% of individuals were infected with A. lumbricoides (mean epg = 11,971), 94% with T. trichiura (mean epg = 793) and 59% with hookworm (mean epg = 302). Age-dependent patterns of infection prevalence and intensity were similar for A. lumbricoides and T. trichiura, but markedly different for hookworm infection. Similarly, age-dependency in the k-values for the three infections was due to covariance with the respective mean intensities with age rather than to independent age effects, with similar patterns for A. lumbricoides and T. trichiura, and a different pattern for hookworm. Three major conclusions can be drawn from the multiple-species analyses: There is positive interaction between A. lumbricoides and T. trichiura infections; high-intensity A. lumbricoides infections are significantly associated with high-intensity T. trichiura infections; and there is positive interaction between these two species such that infection intensity of A. lumbricoides is higher in individuals with concurrent T. trichiura infection than in individuals without and vice versa.
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Affiliation(s)
- C Needham
- Wellcome Trust Centre for the Epidemiology of Infectious Disease, University of Oxford, UK
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Booth M, Mayombana C, Kilima P. The population biology and epidemiology of schistosome and geohelminth infections among schoolchildren in Tanzania. Trans R Soc Trop Med Hyg 1998; 92:491-5. [PMID: 9861359 DOI: 10.1016/s0035-9203(98)90886-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
A study of helminth infections was undertaken among 3244 schoolchildren from 28 schools in Morogoro Rural District, Tanzania. Schistosoma haematobium was the most common infection, followed by hookworms, Ascaris lumbricoides, S. mansoni, and Trichuris trichiura. Infection prevalence of each species varied among schools and age groups, but not between sexes. There was no relationship between the prevalences of different infections among schools, except for a strong negative correlation between the prevalence of hookworm and S. mansoni infections. Within each age group, there was little excess overlap in the distribution of each infection; thus the number of multiple infections was low whereas the number of individuals harbouring at least one infection was relatively high. More children than expected carried infections of A. lumbricoides and S. mansoni, and the clustering effect increased with age. Only 2 schools had high overall infection prevalences of both geohelminths and schistosomes. Logistic regression analysis of morbidity and parasitological data indicated that individuals with multiple species infections were not at increased risk of morbidity (on a multiplicative scale) compared to individuals with single species infections. This was attributed in part to the low egg counts observed for each parasite species. The results implied little interaction between schistosome and geohelminth infections in the region, both in parasitological terms and in the context of their combined effects on health. Implications for the feasibility and benefits of combined control of geohelminths and schistosomes are discussed.
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Affiliation(s)
- M Booth
- Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland.
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Booth M, Li Y, Tanner M. Helminth infections, morbidity indicators and schistosomiasis treatment history in three villages, Dongting Lake region, PR China. Trop Med Int Health 1996; 1:464-74. [PMID: 8765454 DOI: 10.1046/j.1365-3156.1996.d01-93.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In order to estimate the public health impact of helminth infections, and to provide baseline data for interventions, parasitological and morbidity surveys were conducted among inhabitants of three villages in Dongting Lake region, Hunan Province, China. Ascaris lumbricoides was found to be the most common helminth infection, followed by Trichuris trichiura and Schistosoma japonicum. Left liver enlargement was the most common indicator of morbidity. Observed numbers of multiple species infections closely correlated with expected figures generated from a simple probabilistic model. Heterogeneity was observed in age and sex-standardized infection and morbidity prevalences among the villages and occupations. Males had higher levels of infection, were more likely to suffer morbidity, and were more likely to have been treated for schistosomiasis than women. The prevalence of each morbidity indicator was positively correlated with the number of times of treatment for schistosomiasis, and negatively correlated with number of years since last treatment. The results imply that treatment history for S. japonicum infection may be a good indicator of current morbidity risk.
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Affiliation(s)
- M Booth
- Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland
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