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Davis CN, Crump RE, Sutherland SA, Spencer SEF, Corbella A, Chansy S, Lebuki J, Miaka EM, Rock KS. Comparison of stochastic and deterministic models for gambiense sleeping sickness at different spatial scales: A health area analysis in the DRC. PLoS Comput Biol 2024; 20:e1011993. [PMID: 38557869 PMCID: PMC11008881 DOI: 10.1371/journal.pcbi.1011993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 04/11/2024] [Accepted: 03/11/2024] [Indexed: 04/04/2024] Open
Abstract
The intensification of intervention activities against the fatal vector-borne disease gambiense human African trypanosomiasis (gHAT, sleeping sickness) in the last two decades has led to a large decline in the number of annually reported cases. However, while we move closer to achieving the ambitious target of elimination of transmission (EoT) to humans, pockets of infection remain, and it becomes increasingly important to quantitatively assess if different regions are on track for elimination, and where intervention efforts should be focused. We present a previously developed stochastic mathematical model for gHAT in the Democratic Republic of Congo (DRC) and show that this same formulation is able to capture the dynamics of gHAT observed at the health area level (approximately 10,000 people). This analysis was the first time any stochastic gHAT model has been fitted directly to case data and allows us to better quantify the uncertainty in our results. The analysis focuses on utilising a particle filter Markov chain Monte Carlo (MCMC) methodology to fit the model to the data from 16 health areas of Mosango health zone in Kwilu province as a case study. The spatial heterogeneity in cases is reflected in modelling results, where we predict that under the current intervention strategies, the health area of Kinzamba II, which has approximately one third of the health zone's cases, will have the latest expected year for EoT. We find that fitting the analogous deterministic version of the gHAT model using MCMC has substantially faster computation times than fitting the stochastic model using pMCMC, but produces virtually indistinguishable posterior parameterisation. This suggests that expanding health area fitting, to cover more of the DRC, should be done with deterministic fits for efficiency, but with stochastic projections used to capture both the parameter and stochastic variation in case reporting and elimination year estimations.
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Affiliation(s)
- Christopher N. Davis
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, The University of Warwick, Coventry, United Kingdom
- School of Life Sciences, The University of Warwick, Coventry, United Kingdom
- Mathematics Institute, The University of Warwick, Coventry, United Kingdom
| | - Ronald E. Crump
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, The University of Warwick, Coventry, United Kingdom
- Mathematics Institute, The University of Warwick, Coventry, United Kingdom
| | - Samuel A. Sutherland
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, The University of Warwick, Coventry, United Kingdom
- Warwick Medical School, The University of Warwick, Coventry, United Kingdom
| | - Simon E. F. Spencer
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, The University of Warwick, Coventry, United Kingdom
- Department of Statistics, The University of Warwick, Coventry, United Kingdom
| | - Alice Corbella
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, The University of Warwick, Coventry, United Kingdom
- Department of Statistics, The University of Warwick, Coventry, United Kingdom
| | - Shampa Chansy
- Programme National de Lutte contre la Trypanosomiase Humaine Africaine (PNLTHA), Kinshasa, Democratic Republic of the Congo
| | - Junior Lebuki
- Programme National de Lutte contre la Trypanosomiase Humaine Africaine (PNLTHA), Kinshasa, Democratic Republic of the Congo
| | - Erick Mwamba Miaka
- Programme National de Lutte contre la Trypanosomiase Humaine Africaine (PNLTHA), Kinshasa, Democratic Republic of the Congo
| | - Kat S. Rock
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, The University of Warwick, Coventry, United Kingdom
- Mathematics Institute, The University of Warwick, Coventry, United Kingdom
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Doherty JF, Ames T, Brewster LI, Chiang J, Cyr E, Kelsey CR, Lee JP, Liu B, Lo IHY, Nirwal GK, Mohammed YG, Phelan O, Seyfourian P, Shannon DM, Tochor NK, Matthews BJ. An update and review of arthropod vector sensory systems: Potential targets for behavioural manipulation by parasites and other disease agents. ADVANCES IN PARASITOLOGY 2024; 124:57-89. [PMID: 38754927 DOI: 10.1016/bs.apar.2024.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
For over a century, vector ecology has been a mainstay of vector-borne disease control. Much of this research has focused on the sensory ecology of blood-feeding arthropods (black flies, mosquitoes, ticks, etc.) with terrestrial vertebrate hosts. Of particular interest are the cues and sensory systems that drive host seeking and host feeding behaviours as they are critical for a vector to locate and feed from a host. An important yet overlooked component of arthropod vector ecology are the phenotypic changes observed in infected vectors that increase disease transmission. While our fundamental understanding of sensory mechanisms in disease vectors has drastically increased due to recent advances in genome engineering, for example, the advent of CRISPR-Cas9, and high-throughput "big data" approaches (genomics, proteomics, transcriptomics, etc.), we still do not know if and how parasites manipulate vector behaviour. Here, we review the latest research on arthropod vector sensory systems and propose key mechanisms that disease agents may alter to increase transmission.
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Affiliation(s)
| | - Tahnee Ames
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | | | - Jonathan Chiang
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Elsa Cyr
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Cameron R Kelsey
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Jeehan Phillip Lee
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Bingzong Liu
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Ivan Hok Yin Lo
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Gurleen K Nirwal
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | | | - Orna Phelan
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Parsa Seyfourian
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
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Morrison LJ, Steketee PC, Tettey MD, Matthews KR. Pathogenicity and virulence of African trypanosomes: From laboratory models to clinically relevant hosts. Virulence 2023; 14:2150445. [PMID: 36419235 DOI: 10.1080/21505594.2022.2150445] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
African trypanosomes are vector-borne protozoa, which cause significant human and animal disease across sub-Saharan Africa, and animal disease across Asia and South America. In humans, infection is caused by variants of Trypanosoma brucei, and is characterized by varying rate of progression to neurological disease, caused by parasites exiting the vasculature and entering the brain. Animal disease is caused by multiple species of trypanosome, primarily T. congolense, T. vivax, and T. brucei. These trypanosomes also infect multiple species of mammalian host, and this complexity of trypanosome and host diversity is reflected in the spectrum of severity of disease in animal trypanosomiasis, ranging from hyperacute infections associated with mortality to long-term chronic infections, and is also a main reason why designing interventions for animal trypanosomiasis is so challenging. In this review, we will provide an overview of the current understanding of trypanosome determinants of infection progression and severity, covering laboratory models of disease, as well as human and livestock disease. We will also highlight gaps in knowledge and capabilities, which represent opportunities to both further our fundamental understanding of how trypanosomes cause disease, as well as facilitating the development of the novel interventions that are so badly needed to reduce the burden of disease caused by these important pathogens.
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Affiliation(s)
- Liam J Morrison
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Pieter C Steketee
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Mabel D Tettey
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Keith R Matthews
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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4
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Hargrove JW, Van Sickle J. Improved models for the relationship between age and the probability of trypanosome infection in female tsetse, Glossina pallidipes Austen. BULLETIN OF ENTOMOLOGICAL RESEARCH 2023; 113:469-480. [PMID: 37194504 DOI: 10.1017/s0007485323000159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Between 1990 and 1999, at Rekomitjie Research Station, Zambezi Valley, Zimbabwe, 29,360 female G. pallidipes were dissected to determine their ovarian category and trypanosome infection status. Overall prevalences were 3.45 and 2.66% for T. vivax and T. congolense, respectively, declining during each year as temperatures increased from July - December. Fits to age-prevalence data using Susceptible-Exposed-Infective (SEI) and SI compartmental models were statistically better than those obtained using a published catalytic model, which made the unrealistic assumption that no female tsetse survived more than seven ovulations. The improved models require knowledge of fly mortality, estimated separately from ovarian category distributions. Infection rates were not significantly higher for T. vivax than for T. congolense. For T. congolense in field-sampled female G. pallidipes, we found no statistical support for a model where the force of infection was higher at the first feed than subsequently. The long survival of adult female tsetse, combined with feeding at intervals ≤3 days, ensures that post-teneral feeds, rather than the first feed, play the dominant role in the epidemiology of T. congolense infections in G. pallidipes. This is supported by estimates that only about 3% of wild hosts at Rekomitjie were harbouring sufficient T. congolense to ensure that tsetse feeding off them take an infected meal, so that the probability of ingesting an infected meal is low at every meal.
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Affiliation(s)
- J W Hargrove
- SACEMA, University of Stellenbosch, Stellenbosch, South Africa
| | - J Van Sickle
- Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, USA
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Lisack J, Morriswood B, Engstler M. Response to comment on 'Unexpected plasticity in the life cycle of Trypanosoma Brucei'. eLife 2022; 11:e75922. [PMID: 35103593 PMCID: PMC8806184 DOI: 10.7554/elife.75922] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 12/20/2021] [Indexed: 01/23/2023] Open
Abstract
We thank Keith Matthews and Stephen Larcombe for their thoughtful comment, which follows the good tradition of public scientific discourse (Matthews and Larcombe, 2022). While their remarks have prompted us to take another critical look at our data, we think that they neither alter our conclusions nor offer a practical alternative explanation. In essence, we see two possible interpretations of our experiments: either the trypanosome life cycle can accommodate a more flexible role for the slender stage, or the definition of the stumpy stage needs to be radically changed. While the first interpretation - which we favour - would not falsify any published work, the second one - which Matthews and Larcombe are proposing - would contradict the literature. Hence, we favour a model with an unexpected phenotypic plasticity for the slender stage and a certain degree of stochasticity in the trypanosome life cycle.
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Affiliation(s)
- Jaime Lisack
- Department of Cell and Developmental Biology, University of WürzburgWürzburgGermany
| | - Brooke Morriswood
- Department of Cell and Developmental Biology, University of WürzburgWürzburgGermany
| | - Markus Engstler
- Department of Cell and Developmental Biology, University of WürzburgWürzburgGermany
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Matthews KR, Larcombe S. Comment on 'Unexpected plasticity in the life cycle of Trypanosoma brucei'. eLife 2022; 11:74985. [PMID: 35103595 PMCID: PMC8806180 DOI: 10.7554/elife.74985] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 12/20/2021] [Indexed: 12/18/2022] Open
Abstract
Schuster et al. make the important observation that small numbers of trypanosomes can infect tsetse flies, and further argue that this can occur whether the infecting parasites are developmentally ‘slender’ or ‘stumpy’(Schuster et al., 2021). We welcome their careful experiments but disagree that they require a rethink of the trypanosome life-cycle. Instead, the study reveals that stumpy forms are more likely to successfully infect flies, the key limit on parasite transmission, and we predict this advantage would be greatly amplified in tsetse infections in the field. Further, we argue that stumpy forms are defined by a suite of molecular adaptations for life-cycle progression, with morphology being a secondary feature. Finally, their dominance in chronic infections means most natural tsetse infections would involve stumpy forms, even in small numbers. Our interpretation does not require re-evaluation of the obligatory life cycle of the parasite, where stumpy forms are selected to sustain transmission.
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Affiliation(s)
- Keith R Matthews
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Stephen Larcombe
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
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7
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Naitore C, Villinger J, Kibet CK, Kalayou S, Bargul JL, Christoffels A, Masiga DK. The developmentally dynamic microRNA transcriptome of Glossina pallidipes tsetse flies, vectors of animal trypanosomiasis. BIOINFORMATICS ADVANCES 2021; 2:vbab047. [PMID: 36699416 PMCID: PMC9710702 DOI: 10.1093/bioadv/vbab047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 11/25/2021] [Accepted: 12/24/2021] [Indexed: 01/28/2023]
Abstract
Summary MicroRNAs (miRNAs) are single stranded gene regulators of 18-25 bp in length. They play a crucial role in regulating several biological processes in insects. However, the functions of miRNA in Glossina pallidipes, one of the biological vectors of African animal trypanosomosis in sub-Saharan Africa, remain poorly characterized. We used a combination of both molecular biology and bioinformatics techniques to identify miRNA genes at different developmental stages (larvae, pupae, teneral and reproductive unmated adults, gravid females) and sexes of G. pallidipes. We identified 157 mature miRNA genes, including 12 novel miRNAs unique to G. pallidipes. Moreover, we identified 93 miRNA genes that were differentially expressed by sex and/or in specific developmental stages. By combining both miRanda and RNAhybrid algorithms, we identified 5550 of their target genes. Further analyses with the Gene Ontology term and KEGG pathways for these predicted target genes suggested that the miRNAs may be involved in key developmental biological processes. Our results provide the first repository of G. pallidipes miRNAs across developmental stages, some of which appear to play crucial roles in tsetse fly development. Hence, our findings provide a better understanding of tsetse biology and a baseline for exploring miRNA genes in tsetse flies. Availability and implementation Raw sequence data are available from NCBI Sequence Read Archives (SRA) under Bioproject accession number PRJNA590626. Supplementary information Supplementary data are available at Bioinformatics Advances online.
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Affiliation(s)
- Careen Naitore
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya,Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology (JKUAT), P.O. Box 62000, Nairobi 00200, Kenya
| | - Jandouwe Villinger
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya,To whom correspondence should be addressed. or
| | - Caleb K Kibet
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya
| | - Shewit Kalayou
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya
| | - Joel L Bargul
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya,Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology (JKUAT), P.O. Box 62000, Nairobi 00200, Kenya
| | - Alan Christoffels
- South African Medical Research Council Bioinformatics Unit, South African National Bioinformatics Institute (SANBI), University of the Western Cape, Bellville 7530, South Africa
| | - Daniel K Masiga
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772, Nairobi 00100, Kenya,To whom correspondence should be addressed. or
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8
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Das AM, Chitnis N, Burri C, Paris DH, Patel S, Spencer SEF, Miaka EM, Castaño MS. Modelling the impact of fexinidazole use on human African trypanosomiasis (HAT) transmission in the Democratic Republic of the Congo. PLoS Negl Trop Dis 2021; 15:e0009992. [PMID: 34843475 PMCID: PMC8659363 DOI: 10.1371/journal.pntd.0009992] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 12/09/2021] [Accepted: 11/12/2021] [Indexed: 11/18/2022] Open
Abstract
Gambiense human African trypanosomiasis is a deadly disease that has been declining in incidence since the start of the Century, primarily due to increased screening, diagnosis and treatment of infected people. The main treatment regimen currently in use requires a lumbar puncture as part of the diagnostic process to determine disease stage and hospital admission for drug administration. Fexinidazole is a new oral treatment for stage 1 and non-severe stage 2 human African trypanosomiasis. The World Health Organization has recently incorporated fexinidazole into its treatment guidelines for human African trypanosomiasis. The treatment does not require hospital admission or a lumbar puncture for all patients, which is likely to ease access for patients; however, it does require concomitant food intake, which is likely to reduce adherence. Here, we use a mathematical model calibrated to case and screening data from Mushie territory, in the Democratic Republic of the Congo, to explore the potential negative impact of poor compliance to an oral treatment, and potential gains to be made from increases in the rate at which patients seek treatment. We find that reductions in compliance in treatment of stage 1 cases are projected to result in the largest increase in further transmission of the disease, with failing to cure stage 2 cases also posing a smaller concern. Reductions in compliance may be offset by increases in the rate at which cases are passively detected. Efforts should therefore be made to ensure good adherence for stage 1 patients to treatment with fexinidazole and to improve access to care. Sleeping sickness is a parasitic disease present in parts of Central and West Africa that is fatal if left untreated. Current case management requires unpleasant procedures such as a lumbar puncture and intravenous drug administration, but has high compliance rates as the treatment is given by hospital staff to patients. In this study, we explore the impact of a new oral treatment on compliance rates for treatment using a mathematical model fitted to data on sleeping sickness cases and screening activities. We also look at the possibility of patients being more likely to seek and access treatment since the new treatment can be used without a lumbar puncture if the patient does not display clinically severe symptoms. We find that reduced compliance, especially from patients suffering from the first less severe stage of the disease, will lead to more sleeping sickness cases and delay elimination, but increases in the number of patients seeking treatment will likely counter effects of reduced compliance.
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Affiliation(s)
- Aatreyee M. Das
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
| | - Nakul Chitnis
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Christian Burri
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Daniel H. Paris
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Swati Patel
- Department of Statistics, University of Warwick, Coventry, United Kingdom
- Department of Mathematics, Oregon State University, Corvallis, Oregon, United States of America
| | | | - Erick M. Miaka
- Programme National de Lutte contre la Trypanosomiase Humaine Africaine, Kinshasa, the Democratic Republic of the Congo
| | - M. Soledad Castaño
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
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Yang L, Weiss BL, Williams AE, Aksoy E, de Silva Orfano A, Son JH, Wu Y, Vigneron A, Karakus M, Aksoy S. Paratransgenic manipulation of a tsetse microRNA alters the physiological homeostasis of the fly's midgut environment. PLoS Pathog 2021; 17:e1009475. [PMID: 34107000 PMCID: PMC8216540 DOI: 10.1371/journal.ppat.1009475] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 06/21/2021] [Accepted: 05/13/2021] [Indexed: 12/27/2022] Open
Abstract
Tsetse flies are vectors of parasitic African trypanosomes, the etiological agents of human and animal African trypanosomoses. Current disease control methods include fly-repelling pesticides, fly trapping, and chemotherapeutic treatment of infected people and animals. Inhibiting tsetse's ability to transmit trypanosomes by strengthening the fly's natural barriers can serve as an alternative approach to reduce disease. The peritrophic matrix (PM) is a chitinous and proteinaceous barrier that lines the insect midgut and serves as a protective barrier that inhibits infection with pathogens. African trypanosomes must cross tsetse's PM in order to establish an infection in the fly, and PM structural integrity negatively correlates with trypanosome infection outcomes. Bloodstream form trypanosomes shed variant surface glycoproteins (VSG) into tsetse's gut lumen early during the infection establishment, and free VSG molecules are internalized by the fly's PM-producing cardia. This process results in a reduction in the expression of a tsetse microRNA (miR275) and a sequential molecular cascade that compromises PM integrity. miRNAs are small non-coding RNAs that are critical in regulating many physiological processes. In the present study, we investigated the role(s) of tsetse miR275 by developing a paratransgenic expression system that employs tsetse's facultative bacterial endosymbiont, Sodalis glossinidius, to express tandem antagomir-275 repeats (or miR275 sponges). This system induces a constitutive, 40% reduction in miR275 transcript abundance in the fly's midgut and results in obstructed blood digestion (gut weights increased by 52%), a significant increase (p-value < 0.0001) in fly survival following infection with an entomopathogenic bacteria, and a 78% increase in trypanosome infection prevalence. RNA sequencing of cardia and midgut tissues from paratransgenic tsetse confirmed that miR275 regulates processes related to the expression of PM-associated proteins and digestive enzymes as well as genes that encode abundant secretory proteins. Our study demonstrates that paratransgenesis can be employed to study microRNA regulated pathways in arthropods that house symbiotic bacteria.
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Affiliation(s)
- Liu Yang
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
| | - Brian L. Weiss
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
| | - Adeline E. Williams
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
- Department of Microbiology, Immunology, Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Emre Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Alessandra de Silva Orfano
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
| | - Jae Hak Son
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
| | - Yineng Wu
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
| | - Aurelien Vigneron
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
- Department of Evolutionary Ecology, Institute for Organismic and Molecular Evolution, Johannes Gutenberg University, Mainz, Germany
| | - Mehmet Karakus
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
- Department of Medical Microbiology, Faculty of Medicine, University of Health Sciences, Istanbul, Turkey
| | - Serap Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
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10
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Medina Munoz M, Brenner C, Richmond D, Spencer N, Rio RVM. The holobiont transcriptome of teneral tsetse fly species of varying vector competence. BMC Genomics 2021; 22:400. [PMID: 34058984 PMCID: PMC8166097 DOI: 10.1186/s12864-021-07729-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 05/21/2021] [Indexed: 12/13/2022] Open
Abstract
Background Tsetse flies are the obligate vectors of African trypanosomes, which cause Human and Animal African Trypanosomiasis. Teneral flies (newly eclosed adults) are especially susceptible to parasite establishment and development, yet our understanding of why remains fragmentary. The tsetse gut microbiome is dominated by two Gammaproteobacteria, an essential and ancient mutualist Wigglesworthia glossinidia and a commensal Sodalis glossinidius. Here, we characterize and compare the metatranscriptome of teneral Glossina morsitans to that of G. brevipalpis and describe unique immunological, physiological, and metabolic landscapes that may impact vector competence differences between these two species. Results An active expression profile was observed for Wigglesworthia immediately following host adult metamorphosis. Specifically, ‘translation, ribosomal structure and biogenesis’ followed by ‘coenzyme transport and metabolism’ were the most enriched clusters of orthologous genes (COGs), highlighting the importance of nutrient transport and metabolism even following host species diversification. Despite the significantly smaller Wigglesworthia genome more differentially expressed genes (DEGs) were identified between interspecific isolates (n = 326, ~ 55% of protein coding genes) than between the corresponding Sodalis isolates (n = 235, ~ 5% of protein coding genes) likely reflecting distinctions in host co-evolution and adaptation. DEGs between Sodalis isolates included genes involved in chitin degradation that may contribute towards trypanosome susceptibility by compromising the immunological protection provided by the peritrophic matrix. Lastly, G. brevipalpis tenerals demonstrate a more immunologically robust background with significant upregulation of IMD and melanization pathways. Conclusions These transcriptomic differences may collectively contribute to vector competence differences between tsetse species and offers translational relevance towards the design of novel vector control strategies. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-021-07729-5.
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Affiliation(s)
- Miguel Medina Munoz
- Department of Biology, Eberly College of Arts and Sciences, West Virginia University, Morgantown, WV, 26505, USA
| | - Caitlyn Brenner
- Department of Biology, Washington and Jefferson College, Washington, PA, 15301, USA
| | - Dylan Richmond
- Department of Biology, Eberly College of Arts and Sciences, West Virginia University, Morgantown, WV, 26505, USA
| | - Noah Spencer
- Department of Biology, Eberly College of Arts and Sciences, West Virginia University, Morgantown, WV, 26505, USA
| | - Rita V M Rio
- Department of Biology, Eberly College of Arts and Sciences, West Virginia University, Morgantown, WV, 26505, USA.
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11
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Chilongo K, Manyangadze T, Samson M. Human-associated scarcity of hosts for tsetse flies (Diptera: Glossinidae) is related to an increase in prevalence of trypanosome infection in flies in north-eastern Zambia. Trop Anim Health Prod 2021; 53:305. [PMID: 33950335 DOI: 10.1007/s11250-021-02749-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 04/26/2021] [Indexed: 10/21/2022]
Abstract
Occurrence of nutritional stress (due to depletion of fat reserves) in tsetse flies, associated with inadequate levels of access to blood meals, enhances susceptibility of the flies to trypanosome infection. Thus, in a tsetse-infested area, a spatial gradient of reducing tsetse habitat quality is potentially a gradient of increasing prospects for occurrence of stress in tsetse flies. This study investigated prevalence of trypanosome infection in Glossina morsitans morsitans and G. pallidipes along a transect line hypothesised to represent such a gradient, in relation to the edge of the tsetse belt and distribution of human settlements. This was undertaken in three sites located in Lundazi, Mpika and Rufunsa districts, respectively, in north-eastern Zambia. Human settlement was concentrated at the edge of the tsetse belt in the Mpika and Rufunsa sites and evenly distributed along transect line in the Lundazi site. Tsetse fly samples were collected using black-screen fly rounds and Epsilon traps. Detection of trypanosome infection was by dissection and microscopy in Lundazi and Mpika sites and loop-mediated isothermal amplification (LAMP) test in Rufunsa site. Multiple logistic regression models were applied to determine whether the following factors, 'change in distance from edge of tsetse belt', 'tsetse sampling method' and 'sex of tsetse fly', had effect on 'prevalence of trypanosome infection' in the tsetse flies. Only 'increase in distance from the edge of tsetse belt' for G. m. morsitans was significantly associated with 'prevalence of trypanosome infection' in the flies, in the Mpika and Rufunsa sites. Distance was associated with reduced likelihood of infection with 'one or more subgenera of trypanosomes' and with 'Nannomonas trypanosomes', in the case of 'all sites collectively', 'Lundazi and Mpika sites collectively', Mpika site alone, and Rufunsa site alone. Per site, increase in distance entailed reduced prospects for Trypanozoon infection but only in the Mpika and Rufunsa sites. We conclude that in the Mpika and Rufunsa sites, increase in distance from human settlements entailed reduced likelihood of trypanosome infection, likely due to reducing tsetse habitat degradation, increasing availability of hosts, and hence increasing levels of nutrition and fat reserves, thus enhancing tsetse immunity against trypanosome infection.
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Affiliation(s)
- Kalinga Chilongo
- School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa.,Department of Veterinary Services, Ministry of Fisheries and Livestock, Lusaka, Zambia
| | - Tawanda Manyangadze
- College of Health Sciences, Department of Public Health, Howard College, University of KwaZulu-Natal, Durban, 4041, South Africa.,Faculty of Science and Engineering, Geography Department, Bindura University of Science Education, Bag, 1020, Bindura, Zimbabwe
| | - Mukaratirwa Samson
- School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa. .,One Health Center for Zoonoses and Tropical Veterinary Medicine, Ross University School of Veterinary Medicine, St Kitts, Basseterre, Saint Kitts and Nevis.
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12
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Davis CN, Rock KS, Antillón M, Miaka EM, Keeling MJ. Cost-effectiveness modelling to optimise active screening strategy for gambiense human African trypanosomiasis in endemic areas of the Democratic Republic of Congo. BMC Med 2021; 19:86. [PMID: 33794881 PMCID: PMC8017623 DOI: 10.1186/s12916-021-01943-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 02/16/2021] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Gambiense human African trypanosomiasis (gHAT) has been brought under control recently with village-based active screening playing a major role in case reduction. In the approach to elimination, we investigate how to optimise active screening in villages in the Democratic Republic of Congo, such that the expenses of screening programmes can be efficiently allocated whilst continuing to avert morbidity and mortality. METHODS We implement a cost-effectiveness analysis using a stochastic gHAT infection model for a range of active screening strategies and, in conjunction with a cost model, we calculate the net monetary benefit (NMB) of each strategy. We focus on the high-endemicity health zone of Kwamouth in the Democratic Republic of Congo. RESULTS High-coverage active screening strategies, occurring approximately annually, attain the highest NMB. For realistic screening at 55% coverage, annual screening is cost-effective at very low willingness-to-pay thresholds (20.4 per disability adjusted life year (DALY) averted), only marginally higher than biennial screening (14.6 per DALY averted). We find that, for strategies stopping after 1, 2 or 3 years of zero case reporting, the expected cost-benefits are very similar. CONCLUSIONS We highlight the current recommended strategy-annual screening with three years of zero case reporting before stopping active screening-is likely cost-effective, in addition to providing valuable information on whether transmission has been interrupted.
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Affiliation(s)
- Christopher N Davis
- Mathematics Institute, University of Warwick, Coventry, CV4 7AL, UK.
- Zeeman Institute (SBIDER), University of Warwick, Coventry, CV4 7AL, UK.
| | - Kat S Rock
- Mathematics Institute, University of Warwick, Coventry, CV4 7AL, UK
- Zeeman Institute (SBIDER), University of Warwick, Coventry, CV4 7AL, UK
| | - Marina Antillón
- Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel, 4051, Switzerland
- University of Basel, Petersplatz 1, Basel, 4051, Switzerland
| | - Erick Mwamba Miaka
- Programme National de Lutte contre la Trypanosomiase Humaine Africaine (PNLTHA), Ave Coisement Liberation et Bd Triomphal No 1, Commune de Kasavubu, Kinshasa, Democratic Republic of Congo
| | - Matt J Keeling
- Mathematics Institute, University of Warwick, Coventry, CV4 7AL, UK
- Zeeman Institute (SBIDER), University of Warwick, Coventry, CV4 7AL, UK
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
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Davis CN, Rock KS, Mwamba Miaka E, Keeling MJ. Village-scale persistence and elimination of gambiense human African trypanosomiasis. PLoS Negl Trop Dis 2019; 13:e0007838. [PMID: 31658269 PMCID: PMC6837580 DOI: 10.1371/journal.pntd.0007838] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 11/07/2019] [Accepted: 10/10/2019] [Indexed: 11/18/2022] Open
Abstract
Gambiense human African trypanosomiasis (gHAT) is one of several neglected tropical diseases that is targeted for elimination by the World Health Organization. Recent years have seen a substantial decline in the number of globally reported cases, largely driven by an intensive process of screening and treatment. However, this infection is highly focal, continuing to persist at low prevalence even in small populations. Regional elimination, and ultimately global eradication, rests on understanding the dynamics and persistence of this infection at the local population scale. Here we develop a stochastic model of gHAT dynamics, which is underpinned by screening and reporting data from one of the highest gHAT incidence regions, Kwilu Province, in the Democratic Republic of Congo. We use this model to explore the persistence of gHAT in villages of different population sizes and subject to different patterns of screening. Our models demonstrate that infection is expected to persist for long periods even in relatively small isolated populations. We further use the model to assess the risk of recrudescence following local elimination and consider how failing to detect cases during active screening events informs the probability of elimination. These quantitative results provide insights for public health policy in the region, particularly highlighting the difficulties in achieving and measuring the 2030 elimination goal.
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Affiliation(s)
- Christopher N. Davis
- MathSys CDT, Mathematics Institute, University of Warwick, Coventry, United Kingdom
- Zeeman Institute (SBIDER), University of Warwick, Coventry, United Kingdom
| | - Kat S. Rock
- Zeeman Institute (SBIDER), University of Warwick, Coventry, United Kingdom
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Erick Mwamba Miaka
- Programme National de Lutte contre la Trypanosomiase Humaine Africaine (PNLTHA), Ave Coisement Liberation et Bd Triomphal No 1, Commune de Kasavubu, Kinshasa, Demecratic Republic of the Congo
| | - Matt J. Keeling
- Zeeman Institute (SBIDER), University of Warwick, Coventry, United Kingdom
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
- * E-mail:
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Aksoy S. Tsetse peritrophic matrix influences for trypanosome transmission. JOURNAL OF INSECT PHYSIOLOGY 2019; 118:103919. [PMID: 31425686 PMCID: PMC6853167 DOI: 10.1016/j.jinsphys.2019.103919] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 08/09/2019] [Accepted: 08/09/2019] [Indexed: 06/10/2023]
Abstract
Tsetse flies are important vectors of parasitic African trypanosomes, agents of human and animal trypanosomiasis. Easily administrable and effective tools for disease control in the mammalian host are still lacking but reduction of the tsetse vector populations can reduce disease. An alternative approach is to reduce the transmission of trypanosomes in the tsetse vector. The gut peritrophic matrix (PM) has emerged as an important regulator of parasite transmission success in tsetse. Tsetse has a Type II PM that is constitutively produced by cells in the cardia organ. Tsetse PM lines the entire gut and functions as an immunological barrier to prevent the gut epithelia from responding to commensal environmental microbes present in the gut lumen. Tsetse PM also functions as a physical barrier to trypanosome infections that enter into the gut lumen in an infective blood meal. For persistence in the gut, African trypanosomes have developed an adaptive manipulative process to transiently reduce PM efficacy. The process is mediated by mammalian trypanosome surface coat proteins, Variant Surface Glycoproteins (VSGs) which are shed in the gut lumen and taken up by cardia cells. The mechanism of PM reduction involves a tsetse microRNA (miR-275) which acts thru the Wnt signaling pathway. The PM efficacy is once again reduced later in the infection process to enable the gut established parasites to reenter into the gut lumen to colonize the salivary glands, an essential process for transmission. The ability to modulate PM integrity can lead to innovative approaches to reduce disease transmission.
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Affiliation(s)
- Serap Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, 60 College St, LEPH 624, New Haven, CT 06520, United States.
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15
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Matetovici I, De Vooght L, Van Den Abbeele J. Innate immunity in the tsetse fly (Glossina), vector of African trypanosomes. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2019; 98:181-188. [PMID: 31075296 DOI: 10.1016/j.dci.2019.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 05/05/2019] [Accepted: 05/06/2019] [Indexed: 06/09/2023]
Abstract
Tsetse flies (Glossina sp.) are medically and veterinary important vectors of African trypanosomes, protozoan parasites that cause devastating diseases in humans and livestock in sub-Saharan Africa. These flies feed exclusively on vertebrate blood and harbor a limited diversity of obligate and facultative bacterial commensals. They have a well-developed innate immune system that plays a key role in protecting the fly against invading pathogens and in modulating the fly's ability to transmit African trypanosomes. In this review, we briefly summarize our current knowledge on the tsetse fly innate immune system and its interaction with the bacterial commensals and the trypanosome parasite.
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Affiliation(s)
- Irina Matetovici
- Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp, Nationalestraat 155, B-2000, Antwerp, Belgium
| | - Linda De Vooght
- Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp, Nationalestraat 155, B-2000, Antwerp, Belgium
| | - Jan Van Den Abbeele
- Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp, Nationalestraat 155, B-2000, Antwerp, Belgium.
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Abstract
Parasites elicit several physiological changes in their host to enhance transmission. Little is known about the functional association between parasitism and microbiota-provisioned resources typically dedicated to animal hosts and how these goods may be rerouted to optimize parasite development. This study is the first to identify a specific symbiont-generated metabolite that impacts insect vector competence by facilitating parasite establishment and, thus, eventual transmission. Specifically, we demonstrate that the tsetse fly obligate mutualist Wigglesworthia provisions folate (vitamin B9) that pathogenic African trypanosomes exploit in an effort to successfully establish an infection in the vector’s MG. This process is essential for the parasite to complete its life cycle and be transmitted to a new vertebrate host. Disrupting metabolic contributions provided by the microbiota of arthropod disease vectors may fuel future innovative control strategies while also offering minimal nontarget effects. Many symbionts supplement their host’s diet with essential nutrients. However, whether these nutrients also enhance parasitism is unknown. In this study, we investigated whether folate (vitamin B9) production by the tsetse fly (Glossina spp.) essential mutualist, Wigglesworthia, aids auxotrophic African trypanosomes in completing their life cycle within this obligate vector. We show that the expression of Wigglesworthia folate biosynthesis genes changes with the progression of trypanosome infection within tsetse. The disruption of Wigglesworthia folate production caused a reduction in the percentage of flies that housed midgut (MG) trypanosome infections. However, decreased folate did not prevent MG trypanosomes from migrating to and establishing an infection in the fly’s salivary glands, thus suggesting that nutrient requirements vary throughout the trypanosome life cycle. We further substantiated that trypanosomes rely on symbiont-generated folate by feeding this vitamin to Glossina brevipalpis, which exhibits low trypanosome vector competency and houses Wigglesworthia incapable of producing folate. Folate-supplemented G. brevipalpis flies were significantly more susceptible to trypanosome infection, further demonstrating that this vitamin facilitates parasite infection establishment. Our cumulative results provide evidence that Wigglesworthia provides a key metabolite (folate) that is “hijacked” by trypanosomes to enhance their infectivity, thus indirectly impacting tsetse species vector competency. Parasite dependence on symbiont-derived micronutrients, which likely also occurs in other arthropod vectors, represents a relationship that may be exploited to reduce disease transmission.
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17
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A fine-tuned vector-parasite dialogue in tsetse's cardia determines peritrophic matrix integrity and trypanosome transmission success. PLoS Pathog 2018; 14:e1006972. [PMID: 29614112 PMCID: PMC5898766 DOI: 10.1371/journal.ppat.1006972] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 04/13/2018] [Accepted: 03/13/2018] [Indexed: 01/19/2023] Open
Abstract
Arthropod vectors have multiple physical and immunological barriers that impede the development and transmission of parasites to new vertebrate hosts. These barriers include the peritrophic matrix (PM), a chitinous barrier that separates the blood bolus from the midgut epithelia and modulates vector-pathogens interactions. In tsetse flies, a sleeve-like PM is continuously produced by the cardia organ located at the fore- and midgut junction. African trypanosomes, Trypanosoma brucei, must bypass the PM twice; first to colonize the midgut and secondly to reach the salivary glands (SG), to complete their transmission cycle in tsetse. However, not all flies with midgut infections develop mammalian transmissible SG infections—the reasons for which are unclear. Here, we used transcriptomics, microscopy and functional genomics analyses to understand the factors that regulate parasite migration from midgut to SG. In flies with midgut infections only, parasites fail to cross the PM as they are eliminated from the cardia by reactive oxygen intermediates (ROIs)—albeit at the expense of collateral cytotoxic damage to the cardia. In flies with midgut and SG infections, expression of genes encoding components of the PM is reduced in the cardia, and structural integrity of the PM barrier is compromised. Under these circumstances trypanosomes traverse through the newly secreted and compromised PM. The process of PM attrition that enables the parasites to re-enter into the midgut lumen is apparently mediated by components of the parasites residing in the cardia. Thus, a fine-tuned dialogue between tsetse and trypanosomes at the cardia determines the outcome of PM integrity and trypanosome transmission success. Insects are responsible for transmission of parasites that cause deadly diseases in humans and animals. Understanding the key factors that enhance or interfere with parasite transmission processes can result in new control strategies. Here, we report that a proportion of tsetse flies with African trypanosome infections in their midgut can prevent parasites from migrating to the salivary glands, albeit at the expense of collateral damage. In a subset of flies with gut infections, the parasites manipulate the integrity of a midgut barrier, called the peritrophic matrix, and reach the salivary glands for transmission to the next mammal. Either targeting parasite manipulative processes or enhancing peritrophic matrix integrity could reduce parasite transmission.
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18
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Bateta R, Wang J, Wu Y, Weiss BL, Warren WC, Murilla GA, Aksoy S, Mireji PO. Tsetse fly (Glossina pallidipes) midgut responses to Trypanosoma brucei challenge. Parasit Vectors 2017; 10:614. [PMID: 29258576 PMCID: PMC5738168 DOI: 10.1186/s13071-017-2569-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 12/04/2017] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Tsetse flies (Glossina spp.) are the prominent vector of African trypanosome parasites (Trypanosoma spp.) in sub-Saharan Africa, and Glossina pallidipes is the most widely distributed species in Kenya. This species displays strong resistance to infection by parasites, which are typically eliminated in the midgut shortly after acquisition from the mammalian host. Although extensive molecular information on immunity for the related species Glossina morsitans morsitans exists, similar information is scarce for G. pallidipes. METHODS To determine temporal transcriptional responses of G. pallidipes to Trypanosoma brucei brucei challenge, we conducted Illumina based RNA-seq on midgut organ and carcass from teneral females G. pallidipes at 24 and 48 h post-challenge (hpc) with T. b. brucei relative to their respective controls that received normal blood meals (without the parasite). We used a suite of bioinformatics tools to determine differentially expressed and enriched transcripts between and among tissues, and to identify expanded transcripts in G. pallidipes relative to their orthologs G. m. morsitans. RESULTS Midgut transcripts induced at 24 hpc encoded proteins were associated with lipid remodelling, proteolysis, collagen metabolism, apoptosis, and cell growth. Midgut transcripts induced at 48 hpc encoded proteins linked to embryonic growth and development, serine endopeptidases and proteosomal degradation of the target protein, mRNA translation and neuronal development. Temporal expression of immune responsive transcripts at 48 relative to 24 hpc was pronounced, indicative of a gradual induction of host immune responses the following challenge. We also searched for G. m. morsitans orthologous groups that may have experienced expansions in the G. pallidipes genome. We identified ten expanded groups in G. pallidipes with putative immunity-related functions, which may play a role in the higher refractoriness exhibited by this species. CONCLUSIONS There appears to be a lack of strong immune responses elicited by gut epithelia of teneral adults. This in combination with a compromised peritrophic matrix at this stage during the initial phase of T. b. brucei challenge may facilitate the increased parasite infection establishment noted in teneral flies relative to older adults. Although teneral flies are more susceptible than older adults, the majority of tenerals are still able to eliminate parasite infections. Hence, robust responses elicited at a later time point, such as 72 hpc, may clear parasite infections from the majority of flies. The expanded G. m. morsitans orthologous groups in G. pallidipes may also be functionally associated with the enhanced refractoriness to trypanosome infections reported in G. pallidipes relative to G. m. morsitans.
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Affiliation(s)
- Rosemary Bateta
- Department of Biochemistry, Biotechnology Research Institute, Kenya Agricultural and Livestock Research Organization, P.O. Box 362, Kikuyu, Kenya
- Department of Biochemistry and Molecular Biology, Egerton University, P.O. Box 536, Njoro, Kenya
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT USA
| | - Jingwen Wang
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT USA
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200433 China
- Ministry of Education Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, 200433 China
| | - Yineng Wu
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT USA
| | - Brian L. Weiss
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT USA
| | - Wesley C. Warren
- McDonnell Genome Institute, Washington University School of Medicine, 4444 Forest Park Ave., Campus Box 8501, St Louis, MO 63108 USA
| | - Grace A. Murilla
- Department of Biochemistry, Biotechnology Research Institute, Kenya Agricultural and Livestock Research Organization, P.O. Box 362, Kikuyu, Kenya
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT USA
| | - Serap Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT USA
| | - Paul O. Mireji
- Department of Biochemistry, Biotechnology Research Institute, Kenya Agricultural and Livestock Research Organization, P.O. Box 362, Kikuyu, Kenya
- Department of Biochemistry and Molecular Biology, Egerton University, P.O. Box 536, Njoro, Kenya
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT USA
- Centre for Geographic Medicine Research - Coast, Kenya Medical Research Institute, P. O. Box 428-80108, Kilifi, Kenya
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Ngonyoka A, Gwakisa PS, Estes AB, Salekwa LP, Nnko HJ, Hudson PJ, Cattadori IM. Patterns of tsetse abundance and trypanosome infection rates among habitats of surveyed villages in Maasai steppe of northern Tanzania. Infect Dis Poverty 2017; 6:126. [PMID: 28866983 PMCID: PMC5582388 DOI: 10.1186/s40249-017-0340-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 07/26/2017] [Indexed: 12/03/2022] Open
Abstract
Background Changes of land cover modify the characteristics of habitat, host-vector interaction and consequently infection rates of disease causing agents. In this paper, we report variations in tsetse distribution patterns, abundance and infection rates in relation to habitat types and age in the Maasai Steppe of northern Tanzania. In Africa, Tsetse-transmitted trypanosomiasis negatively impacted human life where about 40 million people are at risk of contracting the disease with dramatic socio-economical consequences, for instance, loss of livestock, animal productivity, and manpower. Methods We trapped tsetse flies in dry and wet seasons between October 2014 and May 2015 in selected habitats across four villages: Emboreet, Loiborsireet, Kimotorok and Oltukai adjacent to protected areas. Data collected include number and species of tsetse flies caught in baited traps, PCR identification of trypanosome species and extraction of monitored Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectrometer (MODIS). Results Our findings demonstrate the variation of tsetse fly species abundance and infection rates among habitats in surveyed villages in relation to NDVI and host abundance. Results have shown higher tsetse fly abundance in Acacia-swampy ecotone and riverine habitats for Emboreet and other villages, respectively. Tsetse abundance was inconsistent among habitats in different villages. Emboreet was highly infested with Glossina swynnertoni (68%) in ecotone and swampy habitats followed by G. morsitans (28%) and G. pallidipes (4%) in riverine habitat. In the remaining villages, the dominant tsetse fly species by 95% was G. pallidipes in all habitats. Trypanosoma vivax was the most prevalent species in all infected flies (95%) with few observations of co-infections (with T. congolense or T. brucei). Conclusions The findings of this study provide a framework to mapping hotspots of tsetse infestation and trypanosomiasis infection and enhance the communities to plan for effective control of trypanosomiasis. Electronic supplementary material The online version of this article (doi:10.1186/s40249-017-0340-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Anibariki Ngonyoka
- School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania. .,Department of Conservation Biology, School of Biological Sciences, University of Dodoma, Dodoma, Tanzania.
| | - Paul S Gwakisa
- School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania.,Genome Sciences Center, Department of Microbiology, Parasitology and Immunology. College of Veterinary and Medical Sciences, Sokoine University of Agriculture, Morogoro, Tanzania
| | - Anna B Estes
- School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania.,Centre for Infectious Disease Dynamics, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, USA
| | - Linda P Salekwa
- Genome Sciences Center, Department of Microbiology, Parasitology and Immunology. College of Veterinary and Medical Sciences, Sokoine University of Agriculture, Morogoro, Tanzania
| | - Happiness J Nnko
- School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania.,Department of Geography and Environmental studies, University of Dodoma, Dodoma, Tanzania
| | - Peter J Hudson
- School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania.,Centre for Infectious Disease Dynamics, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, USA
| | - Isabella M Cattadori
- Centre for Infectious Disease Dynamics, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, USA
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Aksoy E, Vigneron A, Bing X, Zhao X, O'Neill M, Wu YN, Bangs JD, Weiss BL, Aksoy S. Mammalian African trypanosome VSG coat enhances tsetse's vector competence. Proc Natl Acad Sci U S A 2016; 113:6961-6. [PMID: 27185908 PMCID: PMC4922192 DOI: 10.1073/pnas.1600304113] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Tsetse flies are biological vectors of African trypanosomes, the protozoan parasites responsible for causing human and animal trypanosomiases across sub-Saharan Africa. Currently, no vaccines are available for disease prevention due to antigenic variation of the Variant Surface Glycoproteins (VSG) that coat parasites while they reside within mammalian hosts. As a result, interference with parasite development in the tsetse vector is being explored to reduce disease transmission. A major bottleneck to infection occurs as parasites attempt to colonize tsetse's midgut. One critical factor influencing this bottleneck is the fly's peritrophic matrix (PM), a semipermeable, chitinous barrier that lines the midgut. The mechanisms that enable trypanosomes to cross this barrier are currently unknown. Here, we determined that as parasites enter the tsetse's gut, VSG molecules released from trypanosomes are internalized by cells of the cardia-the tissue responsible for producing the PM. VSG internalization results in decreased expression of a tsetse microRNA (mir-275) and interferes with the Wnt-signaling pathway and the Iroquois/IRX transcription factor family. This interference reduces the function of the PM barrier and promotes parasite colonization of the gut early in the infection process. Manipulation of the insect midgut homeostasis by the mammalian parasite coat proteins is a novel function and indicates that VSG serves a dual role in trypanosome biology-that of facilitating transmission through its mammalian host and insect vector. We detail critical steps in the course of trypanosome infection establishment that can serve as novel targets to reduce the tsetse's vector competence and disease transmission.
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Affiliation(s)
- Emre Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Aurélien Vigneron
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - XiaoLi Bing
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Xin Zhao
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Michelle O'Neill
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Yi-Neng Wu
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - James D Bangs
- Department of Microbiology and Immunology, University at Buffalo (SUNY), Buffalo, NY 14214
| | - Brian L Weiss
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520;
| | - Serap Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520;
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Cunningham LJ, Lingley JK, Haines LR, Ndung’u JM, Torr SJ, Adams ER. Illuminating the Prevalence of Trypanosoma brucei s.l. in Glossina Using LAMP as a Tool for Xenomonitoring. PLoS Negl Trop Dis 2016; 10:e0004441. [PMID: 26890882 PMCID: PMC4758712 DOI: 10.1371/journal.pntd.0004441] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 01/16/2016] [Indexed: 11/23/2022] Open
Abstract
Background As the reality of eliminating human African trypanosomiasis (HAT) by 2020 draws closer, the need to detect and identify the remaining areas of transmission increases. Here, we have explored the feasibility of using commercially available LAMP kits, designed to detect the Trypanozoon group of trypanosomes, as a xenomonitoring tool to screen tsetse flies for trypanosomes to be used in future epidemiological surveys. Methods and Findings The DNA extraction method was simplified and worked with the LAMP kits to detect a single positive fly when pooled with 19 negative flies, and the absolute lowest limit of detection that the kits were able to work at was the equivalent of 0.1 trypanosome per ml. The DNA from Trypanosoma brucei brucei could be detected six days after the fly had taken a blood meal containing dead trypanosomes, and when confronted with a range of non-target species, from both laboratory-reared flies and wild-caught flies, the kits showed no evidence of cross-reacting. Conclusion We have shown that it is possible to use a simplified DNA extraction method in conjunction with the pooling of tsetse flies to decrease the time it would take to screen large numbers of flies for the presence of Trypanozoon trypanosomes. The use of commercially-available LAMP kits provides a reliable and highly sensitive tool for xenomonitoring and identifying potential sleeping sickness transmission sites. Recent control efforts have reduced the global incidence of Gambiense human African trypanosomiasis (HAT) to <5,000 cases per year, strengthening the prospect of eliminating the disease as a public health problem by 2020. To meet this goal, new methods for identifying transmission must be explored to provide a cost-effective way of identifying hotspots and areas of re-emergence; commercial loop-mediated isothermal amplification (LAMP) kits that detect the trypanosome subgenus, responsible for the two forms of sleeping sickness, have been developed. The LAMP kits were tested to assess their sensitivity, specificity and suitability as a method of screening the vector of the disease, Glossina, for Trypanozoon infection, in xenomonitoring campaigns. A simplified DNA extraction process that worked in conjunction with the LAMP kits on pooled samples demonstrated a faster method of processing large numbers of flies compared to other molecular tools. The kits performed well in our experiments and demonstrated the ability of detecting low levels of target DNA, equivalent to 0.1 trypanosome per ml. The lack of cross reaction with non-target species of trypanosomes makes the kits reliable in so far as they will only react with the Trypanozoon group of parasites of which the two human forms of the disease belong, however, further species-specific tests would need to be undertaken to identify HAT areas on selected samples.
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Affiliation(s)
- Lucas J. Cunningham
- Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- * E-mail:
| | - Jessica K. Lingley
- Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Lee R. Haines
- Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Joseph M. Ndung’u
- Neglected Tropical Disease Programme, Foundation for Innovation New Diagnostics (FIND), Geneva, Switzerland
| | - Stephen J. Torr
- Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Emily R. Adams
- Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Warwick Medical School, University of Warwick, Coventry, United Kingdom
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22
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Imhof S, Roditi I. The Social Life of African Trypanosomes. Trends Parasitol 2015; 31:490-498. [PMID: 26433252 DOI: 10.1016/j.pt.2015.06.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 05/28/2015] [Accepted: 06/24/2015] [Indexed: 01/03/2023]
Abstract
The unicellular parasite Trypanosoma brucei shuttles between its definitive host, the tsetse fly, and various mammals including humans. In the fly digestive tract, T. brucei must first migrate to the ectoperitrophic space, establish a persistent infection of the midgut and then migrate to the salivary glands before being transmitted to a new mammalian host. In 2010, it was shown that insect stages of the parasite (procyclic forms) exhibit social motility (SoMo) when cultured on a semi-solid surface, and it was postulated that this behaviour might reflect a migration step in the tsetse fly. Now, almost 5 years after the initial report, several new publications shed some light on the biological function of SoMo and provide insights into the underlying signalling pathways.
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Affiliation(s)
- Simon Imhof
- Institute of Cell Biology, University of Bern, Bern, Switzerland; Graduate School for Biomedical and Cellular Science, University of Bern, Bern, Switzerland
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Bern, Switzerland.
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23
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Saada EA, DeMarco SF, Shimogawa MM, Hill KL. "With a Little Help from My Friends"-Social Motility in Trypanosoma brucei. PLoS Pathog 2015; 11:e1005272. [PMID: 26679190 PMCID: PMC4683075 DOI: 10.1371/journal.ppat.1005272] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Edwin A. Saada
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Stephanie F. DeMarco
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Michelle M. Shimogawa
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Kent L. Hill
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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24
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Rock KS, Torr SJ, Lumbala C, Keeling MJ. Quantitative evaluation of the strategy to eliminate human African trypanosomiasis in the Democratic Republic of Congo. Parasit Vectors 2015; 8:532. [PMID: 26490248 PMCID: PMC4618948 DOI: 10.1186/s13071-015-1131-8] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 10/02/2015] [Indexed: 12/03/2022] Open
Abstract
Background The virulent vector-borne disease, Gambian human African trypanosomiasis (HAT), is one of several diseases targeted for elimination by the World Health Organization. This article utilises human case data from a high-endemicity region of the Democratic Republic of Congo in conjunction with a suite of novel mechanistic mathematical models to address the effectiveness of on-going active screening and treatment programmes and compute the likely time to elimination as a public health problem (i.e. <1 case per 10,000 per year). Methods The model variants address uncertainties surrounding transmission of HAT infection including heterogeneous risk of exposure to tsetse bites, non-participation of certain groups during active screening campaigns and potential animal reservoirs of infection. Results Model fitting indicates that variation in human risk of tsetse bites and participation in active screening play a key role in transmission of this disease, whilst the existence of animal reservoirs remains unclear. Active screening campaigns in this region are calculated to have been effective, reducing the incidence of new human infections by 52–53 % over a 15-year period (1998–2012). However, projections of disease dynamics in this region indicate that the elimination goal may not be met until later this century (2059–2092) under the current intervention strategy. Conclusions Improvements to active detection, such as screening those who have not previously participated and raising overall screening levels, as well as beginning widespread vector control in the area have the potential to ensure successful and timely elimination. Electronic supplementary material The online version of this article (doi:10.1186/s13071-015-1131-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kat S Rock
- Life Sciences, Warwick University, Coventry, CV4 7AL, UK. .,WIDER, Warwick University, Coventry, CV4 7AL, UK.
| | - Steve J Torr
- WIDER, Warwick University, Coventry, CV4 7AL, UK.,Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Crispin Lumbala
- Programme National de Lutte contre la Trypanosomiase Humaine Africaine (PNLTHA), Kinshasa, Democratic Republic of Congo
| | - Matt J Keeling
- Life Sciences, Warwick University, Coventry, CV4 7AL, UK.,WIDER, Warwick University, Coventry, CV4 7AL, UK.,Mathematics Institute, Warwick University, Coventry, CV4 7AL, UK
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25
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Mbewe NJ, Mweempwa C, Guya S, Wamwiri FN. Microbiome frequency and their association with trypanosome infection in male Glossina morsitans centralis of Western Zambia. Vet Parasitol 2015; 211:93-8. [PMID: 25983231 DOI: 10.1016/j.vetpar.2015.04.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 04/27/2015] [Accepted: 04/30/2015] [Indexed: 01/24/2023]
Abstract
Tsetse flies (Diptera: Glossinidae) are considered primary cyclical vectors that transmit pathogenic trypanosomes in Africa. They harbour a variety of microbes including Wolbachia, Sodalis and the salivary gland hypertrophy virus (SGHV) which are all vertically transmitted. Knowledge on tsetse microbiome and their interactions may identify novel strategies for tsetse fly and trypanosomiasis control. Area-wide application of such strategies requires an understanding of the natural microbiome frequency in the different species and subspecies of Glossina in their geographical populations. Consequently, this study determined the prevalence of Sodalis, Wolbachia, SGHV and trypanosome infections in Glossina morsitanscentralis from two sites of Western Zambia. We also explored possible associations of the microbes with trypanosome infections. Male G. morsitanscentralis samples were collected from two sites (Lyoni and Lusinina) in Western Zambia. The age structure of the flies at each site was determined using the wing fray method. DNA was extracted from the samples and analyzed for Wolbachia, Sodalis, SGHV and trypanosome presence using PCR. Associations and measures of associations between trypanosome infection and microbes in the fly were determined. The flies from the two locations (Lusinina, n=45 and Lyoni, n=24) had a similar age structure with their median fray category not being significantly different (p=0.698). The overall prevalence of Wolbachia was 72.5% (95% CI: 61.6-83.3%), Sodalis was 15.9% (95% CI: 7.1-24.8%), SGHV was 31.9% (95% CI: 20.6-43.2%) and Trypanosoma species was 23.2% (95% CI: 13-33.4%). The prevalence of Wolbachia was significantly higher in Lusinina than Lyoni (p=0.000). However this was not the case for Sodalis, SGHV and Trypanosoma species. Despite the low number of flies that were positive for both trypanosome and Sodalis (6; 8.7%), a statistically significant association (p=0.013; AOR 6.2; 95% CI: 1.5-25.8) was observed in G. morsitanscentralis. The study showed that the prevalence of microbiota may vary within the same species of the tsetse depending on the geographical location as was the case of Wolbachia. Further it showed that infection with Sodalis could affect vector competence. The study concludes that Sodalis could be an ideal candidate for symbiont-mediated trypanosomiasis control interventions in G. morsitanscentralis.
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Affiliation(s)
- Njelembo J Mbewe
- Department of Veterinary Services, Tsetse and Trypanosomiasis Control Section, Chilanga, 350001, Zambia.
| | - Cornelius Mweempwa
- Department of Veterinary Services, Tsetse and Trypanosomiasis Control Section, Chilanga, 350001, Zambia
| | - Samuel Guya
- Kenya Agriculture and Livestock Research Organisation,Biotechnology Research Institute, Kikuyu, 362 00902, Kenya
| | - Florence N Wamwiri
- Kenya Agriculture and Livestock Research Organisation,Biotechnology Research Institute, Kikuyu, 362 00902, Kenya
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26
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A Glycosylation Mutant of Trypanosoma brucei Links Social Motility Defects In Vitro to Impaired Colonization of Tsetse Flies In Vivo. EUKARYOTIC CELL 2015; 14:588-92. [PMID: 25862152 DOI: 10.1128/ec.00023-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/03/2015] [Indexed: 01/10/2023]
Abstract
Transmission of African trypanosomes by tsetse flies requires that the parasites migrate out of the midgut lumen and colonize the ectoperitrophic space. Early procyclic culture forms correspond to trypanosomes in the lumen; on agarose plates they exhibit social motility, migrating en masse as radial projections from an inoculation site. We show that an Rft1(-/-) mutant needs to reach a greater threshold number before migration begins, and that it forms fewer projections than its wild-type parent. The mutant is also up to 4 times less efficient at establishing midgut infections. Ectopic expression of Rft1 rescues social motility defects and restores the ability to colonize the fly. These results are consistent with social motility reflecting movement to the ectoperitrophic space, implicate N-glycans in the signaling cascades for migration in vivo and in vitro, and provide the first evidence that parasite-parasite interactions determine the success of transmission by the insect host.
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27
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Rock KS, Stone CM, Hastings IM, Keeling MJ, Torr SJ, Chitnis N. Mathematical models of human african trypanosomiasis epidemiology. ADVANCES IN PARASITOLOGY 2015; 87:53-133. [PMID: 25765194 DOI: 10.1016/bs.apar.2014.12.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Human African trypanosomiasis (HAT), commonly called sleeping sickness, is caused by Trypanosoma spp. and transmitted by tsetse flies (Glossina spp.). HAT is usually fatal if untreated and transmission occurs in foci across sub-Saharan Africa. Mathematical modelling of HAT began in the 1980s with extensions of the Ross-Macdonald malaria model and has since consisted, with a few exceptions, of similar deterministic compartmental models. These models have captured the main features of HAT epidemiology and provided insight on the effectiveness of the two main control interventions (treatment of humans and tsetse fly control) in eliminating transmission. However, most existing models have overestimated prevalence of infection and ignored transient dynamics. There is a need for properly validated models, evolving with improved data collection, that can provide quantitative predictions to help guide control and elimination strategies for HAT.
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Affiliation(s)
- Kat S Rock
- Mathematics Institute/WIDER, University of Warwick, Coventry, UK
| | - Chris M Stone
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - Ian M Hastings
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Matt J Keeling
- Mathematics Institute/WIDER, University of Warwick, Coventry, UK
| | - Steve J Torr
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK; Warwick Medical School, University of Warwick, Coventry, UK
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
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28
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Beschin A, Van Den Abbeele J, De Baetselier P, Pays E. African trypanosome control in the insect vector and mammalian host. Trends Parasitol 2014; 30:538-47. [DOI: 10.1016/j.pt.2014.08.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 08/19/2014] [Accepted: 08/21/2014] [Indexed: 12/21/2022]
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29
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Aksoy S, Weiss BL, Attardo GM. Trypanosome Transmission Dynamics in Tsetse. CURRENT OPINION IN INSECT SCIENCE 2014; 3:43-49. [PMID: 25580379 PMCID: PMC4286356 DOI: 10.1016/j.cois.2014.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Tsetse flies (Diptera:Glossinidae) are vectors of African trypanosomes. Tsetse undergo viviparous reproductive biology, and depend on their obligate endosymbiont (genus Wigglesworthia) for the maintenance of fecundity and immune system development. Trypanosomes establish infections in the midgut and salivary glands of the fly. Tsetse's resistance to trypanosome infection increases as a function of age. Among the factors that mediate resistance to parasites are antimicrobial peptides (AMPs) produced by the Immune deficiency (Imd) signaling pathway, peptidoglycan recognition protein (PGRP) LB, tsetse-EP protein and the integrity of the midgut peritrophic matrix (PM) barrier. The presence of obligate Wigglesworthia during larval development is essential for adult immune system maturation and PM development. Thus, Wigglesworthia prominently influences the vector competency of it's tsetse host.
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30
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Weiss BL, Savage AF, Griffith BC, Wu Y, Aksoy S. The peritrophic matrix mediates differential infection outcomes in the tsetse fly gut following challenge with commensal, pathogenic, and parasitic microbes. THE JOURNAL OF IMMUNOLOGY 2014; 193:773-82. [PMID: 24913976 DOI: 10.4049/jimmunol.1400163] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The insect gut is lined by a protective, chitinous peritrophic matrix (PM) that separates immunoreactive epithelial cells from microbes present within the luminal contents. Tsetse flies (Glossina spp.) imbibe vertebrate blood exclusively and can be exposed to foreign microorganisms during the feeding process. We used RNA interference-based reverse genetics to inhibit the production of a structurally robust PM and then observed how this procedure impacted infection outcomes after per os challenge with exogenous bacteria (Enterobacter sp. and Serratia marcescens strain Db11) and parasitic African trypanosomes. Enterobacter and Serratia proliferation was impeded in tsetse that lacked an intact PM because these flies expressed the antimicrobial peptide gene, attacin, earlier in the infection process than did their counterparts that housed a fully developed PM. After challenge with trypanosomes, attacin expression was latent in tsetse that lacked an intact PM, and these flies were thus highly susceptible to parasite infection. Our results suggest that immunodeficiency signaling pathway effectors, as opposed to reactive oxygen intermediates, serve as the first line of defense in tsetse's gut after the ingestion of exogenous microorganisms. Furthermore, tsetse's PM is not a physical impediment to infection establishment, but instead serves as a barrier that regulates the fly's ability to immunologically detect and respond to the presence of these microbes. Collectively, our findings indicate that effective insect antimicrobial responses depend largely upon the coordination of multiple host and microbe-specific developmental factors.
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Affiliation(s)
- Brian L Weiss
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06520
| | - Amy F Savage
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06520
| | - Bridget C Griffith
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06520
| | - Yineng Wu
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06520
| | - Serap Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06520
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31
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Abbeele JVD, Rotureau B. New insights in the interactions between African trypanosomes and tsetse flies. Front Cell Infect Microbiol 2013; 3:63. [PMID: 24137569 PMCID: PMC3797390 DOI: 10.3389/fcimb.2013.00063] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 09/24/2013] [Indexed: 11/24/2022] Open
Affiliation(s)
- Jan Van Den Abbeele
- Unit of Veterinary Protozoology, Department of Biomedical Sciences, Institute of Tropical Medicine, Group ParasitologyAntwerpen, Belgium
- Laboratory of Zoophysiology, Department of Physiology, University of GhentGhent, Belgium
| | - Brice Rotureau
- Trypanosome Cell Biology Unit, Institut Pasteur, CNRS URA 2581Paris, France
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