Publications by authors named "Serap Aksoy"

161 Publications

Viviparity and habitat restrictions may influence the evolution of male reproductive genes in tsetse fly (Glossina) species.

BMC Biol 2021 Sep 23;19(1):211. Epub 2021 Sep 23.

Department of Biology and Biotechnology, University of Pavia, Pavia, Italy.

Background: Glossina species (tsetse flies), the sole vectors of African trypanosomes, maintained along their long evolutionary history a unique reproductive strategy, adenotrophic viviparity. Viviparity reduces their reproductive rate and, as such, imposes strong selective pressures on males for reproductive success. These species live in sub-Saharan Africa, where the distributions of the main sub-genera Fusca, Morsitans, and Palpalis are restricted to forest, savannah, and riverine habitats, respectively. Here we aim at identifying the evolutionary patterns of the male reproductive genes of six species belonging to these three main sub-genera. We then interpreted the different patterns we found across the species in the light of viviparity and the specific habitat restrictions, which are known to shape reproductive behavior.

Results: We used a comparative genomic approach to build consensus evolutionary trees that portray the selective pressure acting on the male reproductive genes in these lineages. Such trees reflect the long and divergent demographic history that led to an allopatric distribution of the Fusca, Morsitans, and Palpalis species groups. A dataset of over 1700 male reproductive genes remained conserved over the long evolutionary time scale (estimated at 26.7 million years) across the genomes of the six species. We suggest that this conservation may result from strong functional selective pressure on the male imposed by viviparity. It is noteworthy that more than half of these conserved genes are novel sequences that are unique to the Glossina genus and are candidates for selection in the different lineages.

Conclusions: Tsetse flies represent a model to interpret the evolution and differentiation of male reproductive biology under different, but complementary, perspectives. In the light of viviparity, we must take into account that these genes are constrained by a post-fertilization arena for genomic conflicts created by viviparity and absent in ovipositing species. This constraint implies a continuous antagonistic co-evolution between the parental genomes, thus accelerating inter-population post-zygotic isolation and, ultimately, favoring speciation. Ecological restrictions that affect reproductive behavior may further shape such antagonistic co-evolution.
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http://dx.doi.org/10.1186/s12915-021-01148-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8461966PMC
September 2021

Infection with endosymbiotic Spiroplasma disrupts tsetse (Glossina fuscipes fuscipes) metabolic and reproductive homeostasis.

PLoS Pathog 2021 Sep 16;17(9):e1009539. Epub 2021 Sep 16.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America.

Tsetse flies (Glossina spp.) house a population-dependent assortment of microorganisms that can include pathogenic African trypanosomes and maternally transmitted endosymbiotic bacteria, the latter of which mediate numerous aspects of their host's metabolic, reproductive, and immune physiologies. One of these endosymbionts, Spiroplasma, was recently discovered to reside within multiple tissues of field captured and laboratory colonized tsetse flies grouped in the Palpalis subgenera. In various arthropods, Spiroplasma induces reproductive abnormalities and pathogen protective phenotypes. In tsetse, Spiroplasma infections also induce a protective phenotype by enhancing the fly's resistance to infection with trypanosomes. However, the potential impact of Spiroplasma on tsetse's viviparous reproductive physiology remains unknown. Herein we employed high-throughput RNA sequencing and laboratory-based functional assays to better characterize the association between Spiroplasma and the metabolic and reproductive physiologies of G. fuscipes fuscipes (Gff), a prominent vector of human disease. Using field-captured Gff, we discovered that Spiroplasma infection induces changes of sex-biased gene expression in reproductive tissues that may be critical for tsetse's reproductive fitness. Using a Gff lab line composed of individuals heterogeneously infected with Spiroplasma, we observed that the bacterium and tsetse host compete for finite nutrients, which negatively impact female fecundity by increasing the length of intrauterine larval development. Additionally, we found that when males are infected with Spiroplasma, the motility of their sperm is compromised following transfer to the female spermatheca. As such, Spiroplasma infections appear to adversely impact male reproductive fitness by decreasing the competitiveness of their sperm. Finally, we determined that the bacterium is maternally transmitted to intrauterine larva at a high frequency, while paternal transmission was also noted in a small number of matings. Taken together, our findings indicate that Spiroplasma exerts a negative impact on tsetse fecundity, an outcome that could be exploited for reducing tsetse population size and thus disease transmission.
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http://dx.doi.org/10.1371/journal.ppat.1009539DOI Listing
September 2021

spp. and spp. in spp.: Detection Using Molecular Approaches

Turkiye Parazitol Derg 2021 08;45(3):211-215

Niğde Ömer Halisdemir University, Bor Vocational School, Bor-Niğde, Turkey

Objective: This study aimed to detect the presence of and endosymbionts in flies through molecular approaches.

Methods: In total, 40 Musca spp. (20 female and 20 male) were used. Before DNA extraction, the flies were dissected and their heads, wings and legs were detached from their bodies under a stereomicroscope. Genomic DNA was analysed by standard polymerase chain reaction (PCR) using primers against Musca beta-tubulin. Afterward, the samples were examined for the presence of spp. using primers against and . Furthermore, the DNA samples were analysed by PCR to detect the presence of using primers against the 16S rRNA.

Results: No positivity was detected in Musca flies, as shown by the negative PCR results for wsp and . positivity was detected in 5% (1/20) of the female Musca flies but not in the male flies (0/20).

Conclusion: spp. were not detected in Musca flies. Of the total Musca flies, only one was positive for spp. To our knowledge, this is the first study to detect the presence of in flies.
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http://dx.doi.org/10.4274/tpd.galenos.2021.35229DOI Listing
August 2021

A machine learning approach to integrating genetic and ecological data in tsetse flies () for spatially explicit vector control planning.

Evol Appl 2021 Jul 5;14(7):1762-1777. Epub 2021 May 5.

Department of Ecology and Evolutionary Biology Yale University New Haven CT USA.

Vector control is an effective strategy for reducing vector-borne disease transmission, but requires knowledge of vector habitat use and dispersal patterns. Our goal was to improve this knowledge for the tsetse species , a vector of human and animal African trypanosomiasis, which are diseases that pose serious health and socioeconomic burdens across sub-Saharan Africa. We used random forest regression to (i) build and integrate models of .  habitat suitability and genetic connectivity across Kenya and northern Tanzania and (ii) provide novel vector control recommendations. Inputs for the models included field survey records from 349 trap locations, genetic data from 11 microsatellite loci from 659 flies and 29 sampling sites, and remotely sensed environmental data. The suitability and connectivity models explained approximately 80% and 67% of the variance in the occurrence and genetic data and exhibited high accuracy based on cross-validation. The bivariate map showed that suitability and connectivity vary independently across the landscape and was used to inform our vector control recommendations. Post hoc analyses show spatial variation in the correlations between the most important environmental predictors from our models and each response variable (e.g., suitability and connectivity) as well as heterogeneity in expected future climatic change of these predictors. The bivariate map suggests that vector control is most likely to be successful in the Lake Victoria Basin and supports the previous recommendation that .  from most of eastern Kenya should be managed as a single unit. We further recommend that future monitoring efforts should focus on tracking potential changes in vector presence and dispersal around the Serengeti and the Lake Victoria Basin based on projected local climatic shifts. The strong performance of the spatial models suggests potential for our integrative methodology to be used to understand future impacts of climate change in this and other vector systems.
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http://dx.doi.org/10.1111/eva.13237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8288027PMC
July 2021

Paratransgenic manipulation of a tsetse microRNA alters the physiological homeostasis of the fly's midgut environment.

PLoS Pathog 2021 Jun 9;17(6):e1009475. Epub 2021 Jun 9.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America.

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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http://dx.doi.org/10.1371/journal.ppat.1009475DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8216540PMC
June 2021

The genome of the stable fly, Stomoxys calcitrans, reveals potential mechanisms underlying reproduction, host interactions, and novel targets for pest control.

BMC Biol 2021 03 10;19(1):41. Epub 2021 Mar 10.

Department of Computer Science & Engineering, Department of Biochemistry & Biophysics, Texas A & M University, College Station, TX, USA.

Background: The stable fly, Stomoxys calcitrans, is a major blood-feeding pest of livestock that has near worldwide distribution, causing an annual cost of over $2 billion for control and product loss in the USA alone. Control of these flies has been limited to increased sanitary management practices and insecticide application for suppressing larval stages. Few genetic and molecular resources are available to help in developing novel methods for controlling stable flies.

Results: This study examines stable fly biology by utilizing a combination of high-quality genome sequencing and RNA-Seq analyses targeting multiple developmental stages and tissues. In conjunction, 1600 genes were manually curated to characterize genetic features related to stable fly reproduction, vector host interactions, host-microbe dynamics, and putative targets for control. Most notable was characterization of genes associated with reproduction and identification of expanded gene families with functional associations to vision, chemosensation, immunity, and metabolic detoxification pathways.

Conclusions: The combined sequencing, assembly, and curation of the male stable fly genome followed by RNA-Seq and downstream analyses provide insights necessary to understand the biology of this important pest. These resources and new data will provide the groundwork for expanding the tools available to control stable fly infestations. The close relationship of Stomoxys to other blood-feeding (horn flies and Glossina) and non-blood-feeding flies (house flies, medflies, Drosophila) will facilitate understanding of the evolutionary processes associated with development of blood feeding among the Cyclorrhapha.
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http://dx.doi.org/10.1186/s12915-021-00975-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7944917PMC
March 2021

Vector-borne Zoonotic Diseases in Turkey: Rising Threats on Public Health

Turkiye Parazitol Derg 2020 09;44(3):168-175

Yale School of Public Health, Department of Epidemiology of Microbial Diseases, USA

Vector-borne zoonotic diseases (VBZDs) are a major problem for public health and animal welfare all over the world. In recent years, there has been an alarming increase in VBZDs, mainly caused by new or re-emerging arboviruses, bacteria and parasites. The World Health Organization enumerated 10 threats to global health for 2019, notably emphasizing climate change and emerging pathogens as growing priorities. It is important to review potential threats and develop new control programs for rising threats against human health and safety. Changes in host and vector population diversity and density may affect pathogen transmission patterns and influence VBZD emergence processes. In addition to environmental and climate-related changes, human and animal migratory patterns pose future threats. The geographic location and habitat features of Turkey support the establishment of many arthropod species as vectors of various diseases. To date, a total of 107 zoonotic infections have been reported originating from Turkey. Arthropods transmit 19 of 107 such infections, including 2 mosquito-borne, 9 tick-borne, 1 sandfly-borne, 3 flea-borne, 1 simuliid-borne, 1 mite-borne and 2 fly-borne diseases. In this review, we focus on the present status of knowledge on VBZDs as a rising threat to public health in Turkey to provide a foundation for future control efforts.
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http://dx.doi.org/10.4274/tpd.galenos.2020.6985DOI Listing
September 2020

Molecular characterization and expression patterns of heat shock proteins in Spodoptera littoralis, heat shock or immune response?

Cell Stress Chaperones 2021 01 15;26(1):29-40. Epub 2020 Aug 15.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, USA.

The Egyptian cotton leaf worm, Spodoptera littoralis (Boisd.), is a major agricultural lepidopterous pest causing extensive damage in a variety of crops including vegetable, cotton, fodder, and fiber crops. Heat shock protein (HSP) family members play important roles in protecting insects against environmental stressors. In this study, we characterized three putative heat shock proteins (SpliHsp70, SpliHsp90, and SpliHSF) from S. littoralis and analyzed their expression levels in response to heat, cold, ultraviolet irradiation, Bacillus thuringiensis, and Spodoptera littoralis nucleopolyhedrovirus treatments. Significant upregulation of SpliHsp70 was observed in female pupae, while the highest expression levels of SpliHsp90 and SpliHSF were found in female adults. Heat shock triggered increases in SpliHsp levels compared to cold treatment. SpliHsp90 exhibited the highest expression levels during the first 30 min of UV treatment. Both bacterial and viral pathogenic agents effected the regulation of Hsps in S. littoralis. These findings suggest that SpliHsp genes might play significant roles in the response to biotic and abiotic stress, as well as in the regulation of developmental stages.
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http://dx.doi.org/10.1007/s12192-020-01149-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7736435PMC
January 2021

Phylogeography and population structure of the tsetse fly Glossina pallidipes in Kenya and the Serengeti ecosystem.

PLoS Negl Trop Dis 2020 02 24;14(2):e0007855. Epub 2020 Feb 24.

Department of Ecology and Evolutionary Biology, Yale University, Connecticut, United States of America.

Glossina pallidipes is the main vector of animal African trypanosomiasis and a potential vector of human African trypanosomiasis in eastern Africa where it poses a large economic burden and public health threat. Vector control efforts have succeeded in reducing infection rates, but recent resurgence in tsetse fly population density raises concerns that vector control programs require improved strategic planning over larger geographic and temporal scales. Detailed knowledge of population structure and dispersal patterns can provide the required information to improve planning. To this end, we investigated the phylogeography and population structure of G. pallidipes over a large spatial scale in Kenya and northern Tanzania using 11 microsatellite loci genotyped in 600 individuals. Our results indicate distinct genetic clusters east and west of the Great Rift Valley, and less distinct clustering of the northwest separate from the southwest (Serengeti ecosystem). Estimates of genetic differentiation and first-generation migration indicated high genetic connectivity within genetic clusters even across large geographic distances of more than 300 km in the east, but only occasional migration among clusters. Patterns of connectivity suggest isolation by distance across genetic breaks but not within genetic clusters, and imply a major role for river basins in facilitating gene flow in G. pallidipes. Effective population size (Ne) estimates and results from Approximate Bayesian Computation further support that there has been recent G. pallidipes population size fluctuations in the Serengeti ecosystem and the northwest during the last century, but also suggest that the full extent of differences in genetic diversity and population dynamics between the east and the west was established over evolutionary time periods (tentatively on the order of millions of years). Findings provide further support that the Serengeti ecosystem and northwestern Kenya represent independent tsetse populations. Additionally, we present evidence that three previously recognized populations (the Mbeere-Meru, Central Kenya and Coastal "fly belts") act as a single population and should be considered as a single unit in vector control.
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http://dx.doi.org/10.1371/journal.pntd.0007855DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7058365PMC
February 2020

What constitutes a neglected tropical disease?

PLoS Negl Trop Dis 2020 01 30;14(1):e0008001. Epub 2020 Jan 30.

Vector Molecular Biology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States of America.

The World Health Organization (WHO) currently classifies 20 diseases and conditions as neglected tropical diseases (NTDs). However, since its inception in 2007, PLOS Neglected Tropical Diseases has considered an expanded list that includes additional diseases with the chronic and/or debilitating, and poverty-promoting features of NTDs. Described here is an update of our current scope, which attempts to embrace all of the NTDs, and a discussion of the status of some of the more debated medical conditions in terms of whether or not they constitute an NTD.
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http://dx.doi.org/10.1371/journal.pntd.0008001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6991948PMC
January 2020

World neglected tropical diseases day.

PLoS Negl Trop Dis 2020 01 29;14(1):e0007999. Epub 2020 Jan 29.

Vector Molecular Biology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States of America.

January 30, 2020 is the first-ever World Neglected Tropical Diseases Day (World NTD Day), a day when we celebrate the achievements made towards control of the world's NTDs, yet recognize the daunting challenges we face in the control and elimination of these conditions.
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http://dx.doi.org/10.1371/journal.pntd.0007999DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6988912PMC
January 2020

Single-cell RNA sequencing of from tsetse salivary glands unveils metacyclogenesis and identifies potential transmission blocking antigens.

Proc Natl Acad Sci U S A 2020 02 21;117(5):2613-2621. Epub 2020 Jan 21.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520;

Tsetse-transmitted African trypanosomes must develop into mammalian-infectious metacyclic cells in the fly's salivary glands (SGs) before transmission to a new host. The molecular mechanisms that underlie this developmental process, known as metacyclogenesis, are poorly understood. Blocking the few metacyclic parasites deposited in saliva from further development in the mammal could prevent disease. To obtain an in-depth perspective of metacyclogenesis, we performed single-cell RNA sequencing (scRNA-seq) from a pool of 2,045 parasites collected from infected tsetse SGs. Our data revealed three major cell clusters that represent the epimastigote, and pre- and mature metacyclic trypanosome developmental stages. Individual cell level data also confirm that the metacyclic pool is diverse, and that each parasite expresses only one of the unique metacyclic variant surface glycoprotein (mVSG) coat protein transcripts identified. Further clustering of cells revealed a dynamic transcriptomic and metabolic landscape reflective of a developmental program leading to infectious metacyclic forms preadapted to survive in the mammalian host environment. We describe the expression profile of proteins that regulate gene expression and that potentially play a role in metacyclogenesis. We also report on a family of nonvariant surface proteins (Fam10) and demonstrate surface localization of one member (named SGM1.7) on mature metacyclic parasites. Vaccination of mice with recombinant SGM1.7 reduced parasitemia early in the infection. Future studies are warranted to investigate Fam10 family proteins as potential trypanosome transmission blocking vaccine antigens. Our experimental approach is translationally relevant for developing strategies to prevent other insect saliva-transmitted parasites from infecting and causing disease in mammalian hosts.
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http://dx.doi.org/10.1073/pnas.1914423117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007551PMC
February 2020

The impact of vector migration on the effectiveness of strategies to control gambiense human African trypanosomiasis.

PLoS Negl Trop Dis 2019 12 5;13(12):e0007903. Epub 2019 Dec 5.

Center for Infectious Disease Modeling and Analysis, Yale School of Public Health, New Haven, CT, United States of America.

Background: Several modeling studies have been undertaken to assess the feasibility of the WHO goal of eliminating gambiense human African trypanosomiasis (g-HAT) by 2030. However, these studies have generally overlooked the effect of vector migration on disease transmission and control. Here, we evaluated the impact of vector migration on the feasibility of interrupting transmission in different g-HAT foci.

Methods: We developed a g-HAT transmission model of a single tsetse population cluster that accounts for migration of tsetse fly into this population. We used a model calibration approach to constrain g-HAT incidence to ranges expected for high, moderate and low transmission settings, respectively. We used the model to evaluate the effectiveness of current intervention measures, including medical intervention through enhanced screening and treatment, and vector control, for interrupting g-HAT transmission in disease foci under each transmission setting.

Results: We showed that, in low transmission settings, under enhanced medical intervention alone, at least 70% treatment coverage is needed to interrupt g-HAT transmission within 10 years. In moderate transmission settings, a combination of medical intervention and a vector control measure with a daily tsetse mortality greater than 0.03 is required to achieve interruption of disease transmission within 10 years. In high transmission settings, interruption of disease transmission within 10 years requires a combination of at least 70% medical intervention coverage and at least 0.05 tsetse daily mortality rate from vector control. However, the probability of achieving elimination in high transmission settings decreases with an increased tsetse migration rate.

Conclusion: Our results suggest that the WHO 2030 goal of G-HAT elimination is, at least in theory, achievable. But the presence of tsetse migration may reduce the probability of interrupting g-HAT transmission in moderate and high transmission foci. Therefore, optimal vector control programs should incorporate monitoring and controlling of vector density in buffer areas around foci of g-HAT control efforts.
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http://dx.doi.org/10.1371/journal.pntd.0007903DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6894748PMC
December 2019

Thermal stress responses of Sodalis glossinidius, an indigenous bacterial symbiont of hematophagous tsetse flies.

PLoS Negl Trop Dis 2019 11 18;13(11):e0007464. Epub 2019 Nov 18.

Yale School of Public Health, Department of Epidemiology of Microbial Diseases, New Haven, Connecticut, United States of America.

Tsetse flies (Diptera: Glossinidae) house a taxonomically diverse microbiota that includes environmentally acquired bacteria, maternally transmitted symbiotic bacteria, and pathogenic African trypanosomes. Sodalis glossinidius, which is a facultative symbiont that resides intra and extracellularly within multiple tsetse tissues, has been implicated as a mediator of trypanosome infection establishment in the fly's gut. Tsetse's gut-associated population of Sodalis are subjected to marked temperature fluctuations each time their ectothermic fly host imbibes vertebrate blood. The molecular mechanisms that Sodalis employs to deal with this heat stress are unknown. In this study, we examined the thermal tolerance and heat shock response of Sodalis. When grown on BHI agar plates, the bacterium exhibited the most prolific growth at 25oC, and did not grow at temperatures above 30oC. Growth on BHI agar plates at 31°C was dependent on either the addition of blood to the agar or reduction in oxygen levels. Sodalis was viable in liquid cultures for 24 hours at 30oC, but began to die upon further exposure. The rate of death increased with increased temperature. Similarly, Sodalis was able to survive for 48 hours within tsetse flies housed at 30oC, while a higher temperature (37oC) was lethal. Sodalis' genome contains homologues of the heat shock chaperone protein-encoding genes dnaK, dnaJ, and grpE, and their expression was up-regulated in thermally stressed Sodalis, both in vitro and in vivo within tsetse fly midguts. Arrested growth of E. coli dnaK, dnaJ, or grpE mutants under thermal stress was reversed when the cells were transformed with a low copy plasmid that encoded the Sodalis homologues of these genes. The information contained in this study provides insight into how arthropod vector enteric commensals, many of which mediate their host's ability to transmit pathogens, mitigate heat shock associated with the ingestion of a blood meal.
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http://dx.doi.org/10.1371/journal.pntd.0007464DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6887450PMC
November 2019

Comparative genomic analysis of six Glossina genomes, vectors of African trypanosomes.

Genome Biol 2019 09 2;20(1):187. Epub 2019 Sep 2.

McDonnell Genome Institute, Washington University School of Medicine, St. Louis, MO, USA.

Background: Tsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity.

Results: Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges.

Conclusions: Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.
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http://dx.doi.org/10.1186/s13059-019-1768-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6721284PMC
September 2019

Tsetse peritrophic matrix influences for trypanosome transmission.

Authors:
Serap Aksoy

J Insect Physiol 2019 10 16;118:103919. Epub 2019 Aug 16.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, 60 College St, LEPH 624, New Haven, CT 06520, United States. Electronic address:

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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http://dx.doi.org/10.1016/j.jinsphys.2019.103919DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6853167PMC
October 2019

Spatio-temporal distribution of Spiroplasma infections in the tsetse fly (Glossina fuscipes fuscipes) in northern Uganda.

PLoS Negl Trop Dis 2019 08 1;13(8):e0007340. Epub 2019 Aug 1.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, United States of America.

Tsetse flies (Glossina spp.) are vectors of parasitic trypanosomes, which cause human (HAT) and animal African trypanosomiasis (AAT) in sub-Saharan Africa. In Uganda, Glossina fuscipes fuscipes (Gff) is the main vector of HAT, where it transmits Gambiense disease in the northwest and Rhodesiense disease in central, southeast and western regions. Endosymbionts can influence transmission efficiency of parasites through their insect vectors via conferring a protective effect against the parasite. It is known that the bacterium Spiroplasma is capable of protecting its Drosophila host from infection with a parasitic nematode. This endosymbiont can also impact its host's population structure via altering host reproductive traits. Here, we used field collections across 26 different Gff sampling sites in northern and western Uganda to investigate the association of Spiroplasma with geographic origin, seasonal conditions, Gff genetic background and sex, and trypanosome infection status. We also investigated the influence of Spiroplasma on Gff vector competence to trypanosome infections under laboratory conditions. Generalized linear models (GLM) showed that Spiroplasma probability was correlated with the geographic origin of Gff host and with the season of collection, with higher prevalence found in flies within the Albert Nile (0.42 vs 0.16) and Achwa River (0.36 vs 0.08) watersheds and with higher prevalence detected in flies collected in the intermediate than wet season. In contrast, there was no significant correlation of Spiroplasma prevalence with Gff host genetic background or sex once geographic origin was accounted for in generalized linear models. Additionally, we found a potential negative correlation of Spiroplasma with trypanosome infection, with only 2% of Spiroplasma infected flies harboring trypanosome co-infections. We also found that in a laboratory line of Gff, parasitic trypanosomes are less likely to colonize the midgut in individuals that harbor Spiroplasma infection. These results indicate that Spiroplasma infections in tsetse may be maintained by not only maternal but also via horizontal transmission routes, and Spiroplasma infections may also have important effects on trypanosome transmission efficiency of the host tsetse. Potential functional effects of Spiroplasma infection in Gff could have impacts on vector control approaches to reduce trypanosome infections.
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http://dx.doi.org/10.1371/journal.pntd.0007340DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6692048PMC
August 2019

Mutualist-Provisioned Resources Impact Vector Competency.

mBio 2019 06 4;10(3). Epub 2019 Jun 4.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, Connecticut, USA

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 B) production by the tsetse fly ( spp.) essential mutualist, , aids auxotrophic African trypanosomes in completing their life cycle within this obligate vector. We show that the expression of folate biosynthesis genes changes with the progression of trypanosome infection within tsetse. The disruption of 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 , which exhibits low trypanosome vector competency and houses incapable of producing folate. Folate-supplemented flies were significantly more susceptible to trypanosome infection, further demonstrating that this vitamin facilitates parasite infection establishment. Our cumulative results provide evidence that 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. 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 provisions folate (vitamin B) 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.
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http://dx.doi.org/10.1128/mBio.00018-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6550517PMC
June 2019

Colonization of the tsetse fly midgut with commensal Kosakonia cowanii Zambiae inhibits trypanosome infection establishment.

PLoS Pathog 2019 02 28;15(2):e1007470. Epub 2019 Feb 28.

Yale School of Public Health, Department of Epidemiology of Microbial Diseases, New Haven, Connecticut, United States of America.

Tsetse flies (Glossina spp.) vector pathogenic trypanosomes (Trypanosoma spp.) in sub-Saharan Africa. These parasites cause human and animal African trypanosomiases, which are debilitating diseases that inflict an enormous socio-economic burden on inhabitants of endemic regions. Current disease control strategies rely primarily on treating infected animals and reducing tsetse population densities. However, relevant programs are costly, labor intensive and difficult to sustain. As such, novel strategies aimed at reducing tsetse vector competence require development. Herein we investigated whether Kosakonia cowanii Zambiae (Kco_Z), which confers Anopheles gambiae with resistance to Plasmodium, is able to colonize tsetse and induce a trypanosome refractory phenotype in the fly. Kco_Z established stable infections in tsetse's gut and exhibited no adverse effect on the fly's survival. Flies with established Kco_Z infections in their gut were significantly more refractory to infection with two distinct trypanosome species (T. congolense, 6% infection; T. brucei, 32% infection) than were age-matched flies that did not house the exogenous bacterium (T. congolense, 36% infected; T. brucei, 70% infected). Additionally, 52% of Kco_Z colonized tsetse survived infection with entomopathogenic Serratia marcescens, compared with only 9% of their wild-type counterparts. These parasite and pathogen refractory phenotypes result from the fact that Kco_Z acidifies tsetse's midgut environment, which inhibits trypanosome and Serratia growth and thus infection establishment. Finally, we determined that Kco_Z infection does not impact the fecundity of male or female tsetse, nor the ability of male flies to compete with their wild-type counterparts for mates. We propose that Kco_Z could be used as one component of an integrated strategy aimed at reducing the ability of tsetse to transmit pathogenic trypanosomes.
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http://dx.doi.org/10.1371/journal.ppat.1007470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6394900PMC
February 2019

The population genomics of multiple tsetse fly (Glossina fuscipes fuscipes) admixture zones in Uganda.

Mol Ecol 2019 01;28(1):66-85

Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut.

Understanding the mechanisms that enforce, maintain or reverse the process of speciation is an important challenge in evolutionary biology. This study investigates the patterns of divergence and discusses the processes that form and maintain divergent lineages of the tsetse fly Glossina fuscipes fuscipes in Uganda. We sampled 251 flies from 18 sites spanning known genetic lineages and the four admixture zones between them. We apply population genomics, hybrid zone and approximate Bayesian computation to the analysis of three types of genetic markers: 55,267 double-digest restriction site-associated DNA (ddRAD) SNPs to assess genome-wide admixture, 16 microsatellites to provide continuity with published data and accurate biogeographic modelling, and a 491-bp fragment of mitochondrial cytochrome oxidase I and II to infer maternal inheritance patterns. Admixture zones correspond with regions impacted by the reorganization of Uganda's river networks that occurred during the formation of the West African Rift system over the last several hundred thousand years. Because tsetse fly population distributions are defined by rivers, admixture zones likely represent both old and new regions of secondary contact. Our results indicate that older hybrid zones contain mostly parental types, while younger zones contain variable hybrid types resulting from multiple generations of interbreeding. These findings suggest that reproductive barriers are nearly complete in the older admixture zones, while nearly absent in the younger admixture zones. Findings are consistent with predictions of hybrid zone theory: Populations in zones of secondary contact transition rapidly from early to late stages of speciation or collapse all together.
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http://dx.doi.org/10.1111/mec.14957DOI Listing
January 2019

Symbiotic microbes affect the expression of male reproductive genes in Glossina m. morsitans.

BMC Microbiol 2018 11 23;18(Suppl 1):169. Epub 2018 Nov 23.

Department of Biology and Biotechnology, University of Pavia, 27100, Pavia, Italy.

Background: Tsetse flies (Diptera, Glossinidae) display unique reproductive biology traits. Females reproduce through adenotrophic viviparity, nourishing the growing larva into their modified uterus until parturition. Males transfer their sperm and seminal fluid, produced by both testes and male accessory glands, in a spermatophore capsule transiently formed within the female reproductive tract upon mating. Both sexes are obligate blood feeders and have evolved tight relationships with endosymbionts, already shown to provide essential nutrients lacking in their diet. However, the partnership between tsetse and its symbionts has so far been investigated, at the molecular, genomic and metabolomics level, only in females, whereas the roles of microbiota in male reproduction are still unexplored.

Results: Here we begin unravelling the impact of microbiota on Glossina m. morsitans (G. morsitans) male reproductive biology by generating transcriptomes from the reproductive tissues of males deprived of their endosymbionts (aposymbiotic) via maternal antibiotic treatment and dietary supplementation. We then compared the transcriptional profiles of genes expressed in the male reproductive tract of normal and these aposymbiotic flies. We showed that microbiota removal impacts several male reproductive genes by depressing the activity of genes in the male accessory glands (MAGs), including sequences encoding seminal fluid proteins, and increasing expression of genes in the testes. In the MAGs, in particular, the expression of genes related to mating, immunity and seminal fluid components' synthesis is reduced. In the testes, the absence of symbionts activates genes involved in the metabolic apparatus at the basis of male reproduction, including sperm production, motility and function.

Conclusions: Our findings mirrored the complementary roles male accessory glands and testes play in supporting male reproduction and open new avenues for disentangling the interplay between male insects and endosymbionts. From an applied perspective, unravelling the metabolic and functional relationships between tsetse symbionts and male reproductive physiology will provide fundamental information useful to understanding the biology underlying improved male reproductive success in tsetse. This information is of particular importance in the context of tsetse population control via Sterile Insect Technique (SIT) and its impact on trypanosomiasis transmission.
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http://dx.doi.org/10.1186/s12866-018-1289-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251095PMC
November 2018

Effect of antibiotic treatment and gamma-irradiation on cuticular hydrocarbon profiles and mate choice in tsetse flies (Glossina m. morsitans).

BMC Microbiol 2018 11 23;18(Suppl 1):145. Epub 2018 Nov 23.

Insect Symbiosis Research Group, Max Planck Institute for Chemical Ecology, Jena, Germany.

Background: Symbiotic microbes represent a driving force of evolutionary innovation by conferring novel ecological traits to their hosts. Many insects are associated with microbial symbionts that contribute to their host's nutrition, digestion, detoxification, reproduction, immune homeostasis, and defense. In addition, recent studies suggest a microbial involvement in chemical communication and mating behavior, which can ultimately impact reproductive isolation and, hence, speciation. Here we investigated whether a disruption of the microbiota through antibiotic treatment or irradiation affects cuticular hydrocarbon profiles, and possibly mate choice behavior in the tsetse fly, Glossina morsitans morsitans. Four independent experiments that differentially knock down the multiple bacterial symbionts of tsetse flies were conducted by subjecting tsetse flies to ampicillin, tetracycline, or gamma-irradiation and analyzing their cuticular hydrocarbon profiles in comparison to untreated controls by gas chromatography - mass spectrometry. In two of the antibiotic experiments, flies were mass-reared, while individual rearing was done for the third experiment to avoid possible chemical cross-contamination between individual flies.

Results: All three antibiotic experiments yielded significant effects of antibiotic treatment (particularly tetracycline) on cuticular hydrocarbon profiles in both female and male G. m. morsitans, while irradiation itself had no effect on the CHC profiles. Importantly, tetracycline treatment reduced relative amounts of 15,19,23-trimethyl-heptatriacontane, a known compound of the female contact sex pheromone, in two of the three experiments, suggesting a possible implication of microbiota disturbance on mate choice decisions. Concordantly, both female and male flies preferred non-treated over tetracycline-treated flies in direct choice assays.

Conclusions: While we cannot exclude the possibility that antibiotic treatment had a directly detrimental effect on fly vigor as we are unable to recolonize antibiotic treated flies with individual symbiont taxa, our results are consistent with an effect of the microbiota, particularly the obligate nutritional endosymbiont Wigglesworthia, on CHC profiles and mate choice behavior. These findings highlight the importance of considering host-microbiota interactions when studying chemical communication and mate choice in insects.
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http://dx.doi.org/10.1186/s12866-018-1292-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251160PMC
November 2018

Analysis of the gut-specific microbiome from field-captured tsetse flies, and its potential relevance to host trypanosome vector competence.

BMC Microbiol 2018 11 23;18(Suppl 1):146. Epub 2018 Nov 23.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, USA.

Background: The tsetse fly (Glossina sp.) midgut is colonized by maternally transmitted and environmentally acquired bacteria. Additionally, the midgut serves as a niche in which pathogenic African trypanosomes reside within infected flies. Tsetse's bacterial microbiota impacts many aspects of the fly's physiology. However, little is known about the structure of tsetse's midgut-associated bacterial communities as they relate to geographically distinct fly habitats in east Africa and their contributions to parasite infection outcomes. We utilized culture dependent and independent methods to characterize the taxonomic structure and density of bacterial communities that reside within the midgut of tsetse flies collected at geographically distinct locations in Kenya and Uganda.

Results: Using culture dependent methods, we isolated 34 strains of bacteria from four different tsetse species (G. pallidipes, G. brevipalpis, G. fuscipes and G. fuscipleuris) captured at three distinct locations in Kenya. To increase the depth of this study, we deep sequenced midguts from individual uninfected and trypanosome infected G. pallidipes captured at two distinct locations in Kenya and one in Uganda. We found that tsetse's obligate endosymbiont, Wigglesworthia, was the most abundant bacterium present in the midgut of G. pallidipes, and the density of this bacterium remained largely consistent regardless of whether or not its tsetse host was infected with trypanosomes. These fly populations also housed the commensal symbiont Sodalis, which was found at significantly higher densities in trypanosome infected compared to uninfected flies. Finally, midguts of field-captured G. pallidipes were colonized with distinct, low density communities of environmentally acquired microbes that differed in taxonomic structure depending on parasite infection status and the geographic location from which the flies were collected.

Conclusions: The results of this study will enhance our understanding of the tripartite relationship between tsetse, its microbiota and trypanosome vector competence. This information may be useful for developing novel disease control strategies or enhancing the efficacy of those already in use.
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http://dx.doi.org/10.1186/s12866-018-1284-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251097PMC
November 2018

Genetic Differentiation of Tsetse Flies in Southern Kenya.

Am J Trop Med Hyg 2018 10;99(4):945-953

Department of Ecology & Evolutionary Biology, Yale University, New Haven, Connecticut.

The tsetse fly , the major vector of the parasite that causes animal African trypanosomiasis in Kenya, has been subject to intense control measures with only limited success. The population dynamics and dispersal patterns that underlie limited success in vector control campaigns remain unresolved, and knowledge on genetic connectivity can provide insights, and thereby improve control and monitoring efforts. We therefore investigated the population structure and estimated migration and demographic parameters in using genotypic data from 11 microsatellite loci scored in 250 tsetse flies collected from eight localities in Kenya. Clustering analysis identified two genetically distinct eastern and western clusters (mean between-cluster = 0.202) separated by the Great Rift Valley. We also found evidence of admixture and migration between the eastern and western clusters, isolation by distance, and a widespread signal of inbreeding. We detected differences in population dynamics and dispersal patterns between the western and eastern clusters. These included lower genetic diversity (allelic richness; 7.48 versus 10.99), higher relatedness (percent related individuals; 21.4% versus 9.1%), and greater genetic differentiation (mean within-cluster ; 0.183 versus 0.018) in the western than the eastern cluster. Findings are consistent with the presence of smaller, less well-connected populations in Western relative to eastern Kenya. These data suggest that recent anthropogenic influences such as land use changes and vector control programs have influenced population dynamics in in Kenya, and that vector control efforts should include some region-specific strategies to effectively control this disease vector.
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http://dx.doi.org/10.4269/ajtmh.18-0154DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6159567PMC
October 2018

Investigation of Wolbachia spp. and Spiroplasma spp. in Phlebotomus species by molecular methods.

Sci Rep 2018 Jul 13;8(1):10616. Epub 2018 Jul 13.

Niğde Ömer Halisdemir University, Bor Vocational School, Bor-Niğde, Turkey.

The aim of this study was to determine the presence of Wolbachia spp. and Spiroplasma spp. in natural populations of sand flies in Turkey by molecular methods. A total of 40 Phlebotomus specimens (19 female and 21 male) were used in this study. Genomic DNA from whole sand flies was isolated and Wolbachia spp. infection prevalence was investigated by using Wolbachia gene specific primer sets (wsp and GroEL). In addition, the DNA were analyzed for the presence of Spiroplasma infections utilizing bacterium specific 16 S rDNA PCR-amplification primers. Results of this analysis showed a Wolbachia infection prevalence of 70% (28/40). There was no sex-bias in infection prevalence, being 76% (16/21) and 63% (12/19) in males and females, respectively. Analysis of Spiroplasma infections indicated that 26% (5/19) of female sand flies were positive for infection, while none of the screened males (0/21) were positive. Of the 40 sand fly samples, only 2 were found to be positive for both Wolbachia spp. and Spiroplasma spp. The present study demonstrates the presence of Wolbachia and Spiroplasma infections in the natural sand fly populations in Turkey. This is the first report on Spiroplasma infection in the sand flies from Turkey.
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http://dx.doi.org/10.1038/s41598-018-29031-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045589PMC
July 2018

Expression profiling of Trypanosoma congolense genes during development in the tsetse fly vector Glossina morsitans morsitans.

Parasit Vectors 2018 Jul 3;11(1):380. Epub 2018 Jul 3.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, USA.

Background: The tsetse transmitted parasitic flagellate Trypanosoma congolense causes animal African trypanosomosis (AAT) across sub-Saharan Africa. AAT negatively impacts agricultural, economic, nutritional and subsequently, health status of the affected populace. The molecular mechanisms that underlie T. congolense's developmental program within tsetse are largely unknown due to considerable challenges with obtaining sufficient parasite cells to perform molecular studies.

Methods: In this study, we used RNA-seq to profile T. congolense gene expression during development in two distinct tsetse tissues, the cardia and proboscis. Indirect immunofluorescent antibody test (IFA) and confocal laser scanning microscope was used to localize the expression of a putative protein encoded by the hypothetical protein (TcIL3000_0_02370).

Results: Consistent with current knowledge, genes coding several variant surface glycoproteins (including metacyclic specific VSGs), and the surface coat protein, congolense epimastigote specific protein, were upregulated in parasites in the proboscis (PB-parasites). Additionally, our results indicate that parasites in tsetse's cardia (C-parasites) and PB employ oxidative phosphorylation and amino acid metabolism for energy. Several genes upregulated in C-parasites encoded receptor-type adenylate cyclases, surface carboxylate transporter family proteins (or PADs), transport proteins, RNA-binding proteins and procyclin isoforms. Gene ontology analysis of products of genes upregulated in C-parasites showed enrichment of terms broadly associated with nucleotides, microtubules, cell membrane and its components, cell signaling, quorum sensing and several transport activities, suggesting that the parasites colonizing the cardia may monitor their environment and regulate their density and movement in this tissue. Additionally, cell surface protein (CSP) encoding genes associated with the Fam50 'GARP', 'iii' and 'i' subfamilies were also significantly upregulated in C-parasites, suggesting that they are important for the long non-dividing trypomastigotes to colonize tsetse's cardia. The putative products of genes that were upregulated in PB-parasites were linked to nucleosomes, cytoplasm and membrane-bound organelles, which suggest that parasites in this niche undergo cell division in line with prior findings. Most of the CSPs upregulated in PB-parasites were hypothetical, thus requiring further functional characterization. Expression of one such hypothetical protein (TcIL3000_0_02370) was analyzed using immunofluorescence and confocal laser scanning microscopy, which together revealed preferential expression of this protein on the entire surface coat of T. congolense parasite stages that colonize G. m. morsitans' proboscis.

Conclusion: Collectively, our results provide insight into T. congolense gene expression profiles in distinct niches within the tsetse vector. Our results show that the hypothetical protein TcIL3000_0_02370, is expressed on the entire surface of the trypanosomes inhabiting tsetse's proboscis. We discuss our results in terms of their relevance to disease transmission processes.
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http://dx.doi.org/10.1186/s13071-018-2964-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6029126PMC
July 2018

A spatial genetics approach to inform vector control of tsetse flies () in Northern Uganda.

Ecol Evol 2018 Jun 4;8(11):5336-5354. Epub 2018 May 4.

Department of Ecology and Evolutionary Biology Yale University New Haven Connecticut.

Tsetse flies (genus ) are the only vector for the parasitic trypanosomes responsible for sleeping sickness and nagana across sub-Saharan Africa. In Uganda, the tsetse fly is responsible for transmission of the parasite in 90% of sleeping sickness cases, and co-occurrence of both forms of human-infective trypanosomes makes vector control a priority. We use population genetic data from 38 samples from northern Uganda in a novel methodological pipeline that integrates genetic data, remotely sensed environmental data, and hundreds of field-survey observations. This methodological pipeline identifies isolated habitat by first identifying environmental parameters correlated with genetic differentiation, second, predicting spatial connectivity using field-survey observations and the most predictive environmental parameter(s), and third, overlaying the connectivity surface onto a habitat suitability map. Results from this pipeline indicated that net photosynthesis was the strongest predictor of genetic differentiation in s in northern Uganda. The resulting connectivity surface identified a large area of well-connected habitat in northwestern Uganda, and twenty-four isolated patches on the northeastern margin of the distribution. We tested this novel methodological pipeline by completing an ad hoc sample and genetic screen of samples from a model-predicted isolated patch, and evaluated whether the ad hoc sample was in fact as genetically isolated as predicted. Results indicated that genetic isolation of the ad hoc sample was as genetically isolated as predicted, with differentiation well above estimates made in samples from within well-connected habitat separated by similar geographic distances. This work has important practical implications for the control of tsetse and other disease vectors, because it provides a way to identify isolated populations where it will be safer and easier to implement vector control and that should be prioritized as study sites during the development and improvement of vector control methods.
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http://dx.doi.org/10.1002/ece3.4050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6010828PMC
June 2018

Impact of vector biology research on old and emerging neglected tropical diseases.

PLoS Negl Trop Dis 2018 05 31;12(5):e0006365. Epub 2018 May 31.

Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America.

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http://dx.doi.org/10.1371/journal.pntd.0006365DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5978780PMC
May 2018
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