Molecular epidemiological survey of pathogenic trypanosomes in naturally infected cattle in northern Côte d'ivoire.

Bovine trypanosomiasis is a significant health concern for livestock intensification in Côte d'Ivoire. This study aimed to determine the prevalence and distribution of pathogenic trypanosomes and identify the most infected cattle breed in northern Côte d'Ivoire. We examined 700 cattle and found that polymerase chain reaction (PCR) was more sensitive (12.3%) than microscopic observation (5.6%). Among the trypanosome species detected in naturally infected cattle, Trypanosoma vivax was 7.3%, Trypanosoma simiae tsavo was 6.7%, and Trypanosoma congolense was 0.4%. The overall prevalence of trypanosome infection in all cattle breeds was 12.3%, while the prevalence in individual breeds was 14.8%, 7.3%, 10.6%, and 12.3% for N'Dama, Baoule, Zebu, and Mere breed, respectively. The infected animals had low packed cell volume, influencing the prevalence. Our findings indicate that bovine trypanosomes are prevalent in Côte d'Ivoire, and their prevalence varies by region and breed. These pathogens include T. vivax, T. simiae tsavo, and T. congolense.

Vivaxin genes encode highly immunogenic, non-variant antigens on the Trypanosoma vivax cell-surface.

Trypanosoma vivax is a unicellular hemoparasite, and a principal cause of animal African trypanosomiasis (AAT), a vector-borne and potentially fatal livestock disease across sub-Saharan Africa. Previously, we identified diverse T. vivax-specific genes that were predicted to encode cell surface proteins. Here, we examine the immune responses of naturally and experimentally infected hosts to these unique parasite antigens, to identify immunogens that could become vaccine candidates. Immunoprofiling of host serum shows that one particular family (Fam34) elicits a consistent IgG antibody response. This gene family, which we now call Vivaxin, encodes at least 124 transmembrane glycoproteins that display quite distinct expression profiles and patterns of genetic variation. We focused on one gene (viv-ß8) that encodes one particularly immunogenic vivaxin protein and which is highly expressed during infections but displays minimal polymorphism across the parasite population. Vaccination of mice with VIVß8 adjuvanted with Quil-A elicits a strong, balanced immune response and delays parasite proliferation in some animals but, ultimately, it does not prevent disease. Although VIVß8 is localized across the cell body and flagellar membrane, live immunostaining indicates that VIVß8 is largely inaccessible to antibody in vivo. However, our phylogenetic analysis shows that vivaxin includes other antigens shown recently to induce immunity against T. vivax. Thus, the introduction of vivaxin represents an important advance in our understanding of the T. vivax cell surface. Besides being a source of proven and promising vaccine antigens, the gene family is clearly an important component of the parasite glycocalyx, with potential to influence host-parasite interactions.

Molecular epidemiology of Animal African Trypanosomosis in southwest Burkina Faso.

BACKGROUND: Animal African Trypanosomosis (AAT) is a parasitic disease of livestock that has a major socio-economic impact in the affected areas. It is caused by several species of uniflagellate extracellular protists of the genus Trypanosoma mainly transmitted by tsetse flies: T. congolense, T. vivax and T. brucei brucei. In Burkina Faso, AAT hampers the proper economic development of the southwestern part of the country, which is yet the best watered area particularly conducive to agriculture and animal production. It was therefore important to investigate the extent of the infection in order to better control the disease. The objective of the present study was to assess the prevalence of trypanosome infections and collect data on the presence of tsetse flies. METHODS: Buffy coat, Trypanosoma species-specific PCR, Indirect ELISA Trypanosoma sp and trypanolysis techniques were used on 1898 samples collected. An entomological survey was also carried out. RESULTS: The parasitological prevalence of AAT was 1.1%, and all observed parasites were T. vivax. In contrast, the molecular prevalence was 23%, of which T. vivax was predominant (89%) followed by T. congolense (12.3%) and T. brucei s.l. (7.3%) with a sizable proportion as mixed infections (9.1%). T. brucei gambiense, responsible of sleeping sickness in humans, was not detected. The serological prevalence reached 49.7%. Once again T. vivax predominated (77.2%), but followed by T. brucei (14.7%) and T. congolense (8.1%). Seven samples, from six cattle and one pig, were found positive by trypanolysis. The density per trap of Glossina tachinoides and G. palpalis gambiensis was 1.2 flies. CONCLUSIONS/SIGNIFICANCE: Overall, our study showed a high prevalence of trypanosome infection in the area, pointing out an ongoing inadequacy of control measures.

Abortion and congenital transmission of Trypanosoma vivax in goats and ewes in semiarid northeastern Brazil.

The main effects of trypanosomosis in Brazil are related to reproductive alterations. In this context, the present study aimed to report the occurrence of abortions in goats and sheeps in the semiarid region of Northeastern Brazil, associated with Trypanosoma vivax. Trypomastigotes forms visualized by Buffy coat technique (BCT) method in 68.7% of the goats and 50.0% of the ewes that aborted. PCR identified that 100% of the goats and ewes that aborted were infected with T. vivax. The goats and ewes that aborted showed high parasitemia and developed clinical signs of trypanosomosis. The presence of T. vivax DNA was identified in the blood of fetuses by the PCR technique, proving infection by T. vivax in aborted fetuses, as well as confirming the congenital transmission of the parasite.

Presence of Trypanosoma vivax DNA in cattle semen and reproductive tissues and related changes in sperm parameters.

The present work investigated the presence of Trypanosoma vivax in semen and reproductive tissues of experimentally infected cattle and evaluated changes in seminal parameters. Two groups of cattle were established: T01 - experimentally infected with T. vivax (n = 8) and T02 - not experimentally infected with T. vivax (n = 8). After infection, blood (every seven days until 182 days post-infection - DPI), semen (7, 14, 35, 56, 70, 120 and 182 DPI) and reproductive tissue (after euthanasia, 182 DPI) were collected to search for T. vivax using different techniques, including PCR, Woo and Brener. Seminal parameters, including turbulence, motility, concentration, and vigor, were also analyzed. Packed cell volume (PCV) of the animals was determined weekly and weight gain was calculated. The PCR revealed T. vivax DNA in 7/56 semen samples of post-infection T01 cattle. Trypanosoma vivax DNA was detected in the semen of 5/8 animals at 7, 14, 56, 70 and 120 DPI, in the testis of four, and in the epididymis and fat located around the testis of two others. Trypomastigote forms of T. vivax were not found in any semen sample. Sperm of T01 cattle had lower turbulence (p ≤ 0.05) at 7, 14, 35, 56, 120 and 182 DPI, lower vigor (p ≤ 0.05) at 120 DPI and more sperm abnormalities (p ≤ 0.05) than T02. Digital dermatitis was observed among T01 cattle. Animals of T01 had lower PCV values than did those of T02 for most of the evaluations performed and T02 animals gained more weight during the experiment. The results highlight the presence of T. vivax DNA in semen of infected cattle and the importance of this disease for male breeding cattle. Further research is needed to determine whether T. vivax can be sexually transmitted in cattle.

Genetic connectivity of trypanosomes between tsetse-infested and tsetse-free areas of Kenya.

The prevalence rates of trypanosomes, including those that require cyclical transmission by tsetse flies, are widely distributed in Africa. Trypanosoma brucei and Trypanosoma congolense are actively maintained in regions where there are no tsetse flies although at low frequencies. Whether this could be due to an independent evolutionary origin or multiple introduction of trypanosomes due to continuous movement of livestock between tsetse-free and -infested areas is not known. Thus, the aim of the study was to carry out microsatellite genotyping to explore intra-specific genetic diversity between T. (Trypanozoon), T. congolense and Trypanosoma vivax from the two regions: tsetse infested and tsetse free. Microsatellite genotyping showed geographical origin-based structuring among T. (Trypanozoon) isolates. There was a clear separation between isolates from the two regions signalling the potential of microsatellite markers as diagnostic markers for T. brucei and Trypanosoma evansi isolates. Trypanosoma vivax isolates also clustered largely based on the sampling location with a significant differentiation between the two locations. However, our results revealed that T. congolense isolates from Northern Kenya are not genetically separated from those from Coastal Kenya. Therefore, these isolates are likely introduced in the region through animal movement. Our results demonstrate the occurrence of both genetic connectivity as well as independent evolutionary origin, depending on the trypanosome species between the two ecologies.

A review on the diagnosis of animal trypanosomoses.

This review focuses on the most reliable and up-to-date methods for diagnosing trypanosomoses, a group of diseases of wild and domestic mammals, caused by trypanosomes, parasitic zooflagellate protozoans mainly transmitted by insects. In Africa, the Americas and Asia, these diseases, which in some cases affect humans, result in significant illness in animals and cause major economic losses in livestock. A number of pathogens are described in this review, including several Salivarian trypanosomes, such as Trypanosoma brucei sspp. (among which are the agents of sleeping sickness, the human African trypanosomiasis [HAT]), Trypanosoma congolense and Trypanosoma vivax (causing "Nagana" or animal African trypanosomosis [AAT]), Trypanosoma evansi ("Surra") and Trypanosoma equiperdum ("Dourine"), and Trypanosoma cruzi, a Stercorarian trypanosome, etiological agent of the American trypanosomiasis (Chagas disease). Diagnostic methods for detecting zoonotic trypanosomes causing Chagas disease and HAT in animals, as well as a diagnostic method for detecting animal trypanosomes in humans (the so-called "atypical human infections by animal trypanosomes" [a-HT]), including T. evansi and Trypanosoma lewisi (a rat parasite), are also reviewed. Our goal is to present an integrated view of the various diagnostic methods and techniques, including those for: (i) parasite detection; (ii) DNA detection; and (iii) antibody detection. The discussion covers various other factors that need to be considered, such as the sensitivity and specificity of the various diagnostic methods, critical cross-reactions that may be expected among Trypanosomatidae, additional complementary information, such as clinical observations and epizootiological context, scale of study and logistic and cost constraints. The suitability of examining multiple specimens and samples using several techniques is discussed, as well as risks to technicians, in the context of specific geographical regions and settings. This overview also addresses the challenge of diagnosing mixed infections with different Trypanosoma species and/or kinetoplastid parasites. Improving and strengthening procedures for diagnosing animal trypanosomoses throughout the world will result in a better control of infections and will significantly impact on "One Health," by advancing and preserving animal, human and environmental health.

Molecular epidemiological insights into Trypanosoma vivax in Argentina: From the endemic Gran Chaco to outbreaks in the Pampas.

Argentina is a home to millions of beef and dairy cattle and is one of the world's major exporters of meat. In the present study, Trypanosoma vivax was prevalent (2016-2018) in two major livestock farming regions, the Gran Chaco and the Pampas. In the Gran Chaco, 29% and 51% of animals (n = 72, taurine x zebuine crossbreed) were, respectively, positive by TviCATL-PCR and the more sensitive fluorescent fragment length barcoding (FFLB) method. While 18.4/38.8% of breeding cows (n = 49) tested positive by PCR/FFLB, infection increased to 52.2/78.3% in an outbreak of acute infection in steers (n = 23, taurine breed) brought from a non-endemic area. In the Pampas, overall infection rates in dairy cows (n = 54, taurine breed) were comparable (p > .01) between PCR (66.7%) and FFLB (62.9%) and showed a remarkable increase (PCR / FFLB) from 48.3/44.8% in 2017 to 88/84% in 2018. Infected dairy cattle exhibited anaemia, fever, anorexia, enlarged lymph nodes, emaciation and neurological signs. In contrast, beef cows (taurine x zebuine crossbreed) from the Pampas (n = 30) were asymptomatic despite exhibiting 16.7% (PCR) and 53.3% (FFLB) infection rates. Microsatellite genotyping revealed a remarkable microheterogeneity, seven genotypes in the Gran Chaco, nine in the Pampas and five shared between both regions, consistent with regular movement of T. vivax infected livestock. Data gathered in our study support the Gran Chaco being an endemic area for T. vivax, whereas the Pampas emerged as an outbreak area of acute infection in dairy cattle with critical negative impact in milk production. To the best of our knowledge, this is the first molecular study of T. vivax in Argentina, and results indicated the need for preventive measures to control T. vivax spread from the Gran Chaco to vast livestock farming areas across Argentina.

Prevalence and risk factors for trypanosome infection in cattle from communities surrounding the Murchison Falls National Park, Uganda.

BACKGROUND: Bovine trypanosomosis transmitted by tsetse flies is a major constraint to cattle health and productivity in all sub-Saharan countries, including Uganda. The objectives of this study were to determine the prevalence of bovine trypanosomosis and identify its associated risk factors and the species of trypanosomes associated with the disease. METHODOLOGY: A cross-sectional study was conducted around Murchison Falls National Park, Uganda from January 2020 to April 2020. Trypanosomes were detected in blood samples by PCR analysis targeting the internal transcribed spacer 1 (ITS-PCR assays), and trypanosomes in positive blood samples were sequenced. RESULTS: Of 460 blood samples collected and tested, 136 (29.6%) were positive for trypanosome infections and 324 (70.4%) were negative. The overall trypanosome prevalence was 29.6% (95% confidence interval 25.4-33.8%), attributed to three trypanosome species. Of these three species, Trypanosoma vivax was the most prevalent (n = 130, 28.3%) while the others were detected as mixed infections: T. vivax + Trypanosoma congolense (n = 2, 0.4%) and T. vivax + Trypanosoma evansi (n = 1, 0.2%). There were significant differences in trypanosome prevalence according to sex (χ2 = 62, df = 1, P < 0.05), age (χ2 = 6.28, df = 2, P = 0.0043) and cattle breed (χ2 = 10.61, df = 1, P = 0.001). CONCLUSIONS: Trypanosomosis remains a major limitation to cattle production around Murchison Falls National Park and interventions are urgently needed. In our study, the prevalence of trypanosome infections was high, with T. vivax identified as the most prevalent species. Age, sex and breed of cattle were risk factors for trypanosome infection.

Evaluation of five primer sets for molecular detection of Trypanosoma vivax by polymerase chain reaction (PCR) and their implementation for diagnosis in naturally infected ruminants from Venezuela.

Trypanosoma vivax is a protozoan parasite that causes trypanosomosis in ruminants and is widely distributed in tropical areas in the world. The control of this disease depends on the sensitivity and specificity of the diagnostic tests implemented for naturally infected samples, where parasitaemias are usually low. This study aimed to evaluate the analytical sensitivity and specificity of several primers for T. vivax detection in experimental infections and their implementation for the diagnosis of trypanosomosis in naturally infected bovine and ovine samples. Using a T. vivax Venezuelan isolate, five sets of primers were evaluated: TviSL1/2, ITS1CF/BR, TVMF/R, ILO1264/1265, TVWA/B. Additionally, we tested the PCR protocols using different DNA quantities. The best set of primers (ILO1264/1265) was used to detect T. vivax DNA from whole blood and buffy coat samples of 12 sheep (ovine) and 45 cattle (bovine) of small farms from Venezuela, and compared to the micro-haematocrite centrifugation technique (MHCT). The highest sensitivity was 0.0001 ng for ILO1264/1265 and TVWA/B primers. Using 100 ng of DNA extracted from the buffy coat and the ILO1264/1265 primers for trypanosomosis diagnosis from naturally infected samples, yielded 66.7% (8/12) and 35.7% (16/45) positives in ovine and bovine respectively. The percentage of positives samples increased to 83.3% (10/12) and 64.4% (29/45), with 300 ng in the assays. Contrary, using 300 ng of DNA extracted from the whole blood yielded only 50% (6/12) and 28.9% (13/45) of positives samples for T. vivax respectively. MHCT only detected the parasite in bovine samples with 17.8% (8/45) of positives. Based on our results, we recommend the use of the ILO1264/1265 primers and 300 ng of DNA extracted from the buffy coat for epidemiological studies of naturally infected animals. Moreover, detection of the parasite in ovine herds highlights a possible role of this host in the epidemiology of trypanosomosis in Venezuela.

First report of Trypanosoma vivax infection in sheep from Nicaragua.

In Central America, outbreaks of trypanosomiasis by Trypanosoma vivax have been recorded only in cattle. This is the first report of an outbreak of trypanosomiasis by T. vivax in 30 Pelibuey sheep (2 to 7 years old, male and female) from Nicaragua, which occurred in 2009. Clinical signs included fever, apathy, pale mucous membranes, weakness, progressive weight loss, and sudden death. Infection by T. vivax was detected in 22 (73.3%) sheep by blood smear analysis and/or PCR. Trypanosomes were morphologically identified in 11 (36.7%) blood smear samples, whereas 17 (85%) of the 20 samples subjected to PCR were positive for T. vivax. Eighteen (81.8%) of the 22 infected sheep presented a packed red cell volume (PCV) lower than 25%. Upon diagnosis, the treated animals were clinically recovered and no parasites could be observed in subsequent examinations. Tabanids were potential mechanical vectors of T. vivax in the farm. This is the first report of T. vivax in Nicaragua and for the first time this haemoparasite is recorded in sheep in Central America.

Diversity of tsetse flies and trypanosome species circulating in the area of Lake Iro in southeastern Chad.

BACKGROUND: African trypanosomiases are vector-borne diseases that affect humans and livestock in sub-Saharan Africa. Although data have been collected on tsetse fauna as well as trypanosome infections in tsetse flies and mammals in foci of sleeping sickness in Chad, the situation of tsetse fly-transmitted trypanosomes remains unknown in several tsetse-infested areas of Chad. This study was designed to fill this epidemiological knowledge gap by determining the tsetse fauna as well as the trypanosomes infecting tsetse flies in the area of Lake Iro in southeastern Chad. METHODS: Tsetse flies were trapped along the Salamat River using biconical traps. The proboscis and tsetse body were removed from each fly. DNA was extracted from the proboscis using proteinase K and phosphate buffer and from the tsetse body using Chelex 5%. Tsetse flies were identified by amplifying and sequencing the cytochrome c oxydase I gene of each tsetse fly. Trypanosome species were detected by amplifying and sequencing the internal transcribed spacer 1 of infecting trypanosomes. RESULTS: A total of 617 tsetse flies were trapped; the apparent density of flies per trap per day was 2. 6. Of the trapped flies, 359 were randomly selected for the molecular identification and for the detection of infecting trypanosomes. Glossina morsitans submorsitans (96.1%) was the dominant tsetse fly species followed by G. fuscipes fuscipes (3.1%) and G. tachinoides (0.8%). Four trypanosome species, including Trypanosoma vivax, T. simiae, T. godfreyi and T. congolense savannah, were detected. Both single infection (56.7%) and mixed infections of trypanosomes (4.6%) were detected in G. m. submorsitans. The single infection included T. simiae (20.5%), T. congolense savannah (16.43%), T. vivax (11.7%) and T. godfreyi (9.8%). The trypanosome infection rate was 61.4% in G. m. submorsitans, 72.7% in G. f. fuscipes and 66.6% in G. tachinoides. Trypanosome infections were more prevalent in tsetse bodies (40.6%) than in the proboscis (16.3%). CONCLUSION: This study revealed the presence of different tsetse species and a diversity of trypanosomes pathogenic to livestock in the area of Lake Iro. The results highlight the risks and constraints that animal African trypanosomiasis pose to livestock breeding and the importance of assessing trypanosome infections in livestock in this area.

Molecular characterization of Trypanosoma vivax in tsetse flies confirms the presence of the virulent Tvv4 genotype in Kenya: Potential implications for the control of trypanosomiasis in Shimba Hills.

Trypanosoma vivax is a vector-borne protozoan parasite of livestock endemic to Africa and South America. To date, fifteen genotypes of the parasite have been described in vertebrate and insect hosts in East Africa. However, information regarding T. vivax diversity remains limited in many endemic countries in the sub-region, including Kenya. Such information could deepen insight into the local epidemiology of animal trypanosomiasis in Shimba Hills, a wildlife area in southeast Kenya where T. vivax is endemic and infects livestock. We employed two-gene conventional-PCR-sequencing and phylogenetic analysis to characterize T. vivax genotypes in tsetse flies collected between November 2018 and September 2019 in the wildlife-livestock interface of the Shimba Hills National Reserve. Phylogenetic analysis of Internal Transcribed Spacer-1 (ITS-1) sequences of T. vivax isolates confirmed the presence of two T. vivax genotypes in Shimba Hills of which >80% of T. vivax isolates from tsetse flies clustered within the virulent Tvv4-genotype clade. Tsetse infections with the Tvv4 genotype were also confirmed based on 18S rRNA gene sequencing. Expanded gene characterization identified three closely related haplotypes within the Tvv4-clade. The Tvv4-isolates were detected in male and female Glossina pallidipes tsetse flies, most of which were collected from grasslands and within two kilometres of the Shimba Hills National Reserve boundary. Considering that T. vivax is the most common trypanosome in the Shimba Hills area and causes severe clinical conditions in livestock, the Tvv4 genotype reported here for the first time in Kenya contributes to our understanding of these pathologies. The effectiveness of trypanocidal drugs in the management of Tvv4 is presently not clearly understood. Therefore, the parasite management in Shimba Hills should focus on vector control to reduce the density of G. pallidipes, especially in grasslands near the wildlife protectorate.

Different kinetoplast degradation patterns in American Trypanosoma vivax strains: Multiple independent origins or fast evolution?

We analyzed the kinetoplast (mitochondrial genome) of Trypanosoma vivax strains from America and Africa to determine their precise architecture and to understand their adaptive response to mechanical transmission. The use of long-read based assemblies that retain individuality of tandem repeats, without erasing inter-copy variability, allowed us to investigate the evolutionary dynamics of repetitive kinetoplast-DNA. This analysis revealed that repeat elements located in edges of repeat clusters are less active in terms of renewal, whereas internal copies appear to undergo a permanent process of birth-and-death. Comparing different American strains with the African Y486 strain, we found that in the former, protein coding genes from the maxicircle contain several function disrupting mutations that with very few exceptions are present in one or the other American strain but not in both, suggesting the absence of common ancestry for most of the genomic changes that led to their loss of oxidative phosphorylation capacity. Analysis of another component of kinetoplast, the minicircles, revealed great loss of diversity, and loss of their encoded guideRNAs. Both groups of American strains retain minimal sets required to edit the still functional A6-APTase and RPS12 genes. The extensive maxi- and minicircle divergence suggests a history of multiple introduction events in America of strains that probably started to degrade their kinetoplast in Africa. The notion that kinetoplast degradation began after incursion in America would imply a pace of accumulation of genetic changes considerably faster than other trypanosomatids.

First report and molecular identification of Trypanosoma (Duttonella) vivax outbreak in cattle population from Ecuador.

The bovine trypanosomosis is responsible for economic losses from tropical and subtropical areas of Africa and Latin America. This disease is characterized by fever, anaemia, loss of production and even death. Few studies have been carried out in Ecuador regarding Trypanosoma spp. presence but the species has not been determined in cattle and those have only determined the presence of genus, but not the species. The aim of this study was to identify and characterize the trypanosome species involved in the suspected bovine trypanosomosis outbreak reported in Convento Village in Manabí Province located in the coastal region of Ecuador. Twenty cattle from three farms were sampled. Three samples were positive for T. vivax, using an end-point polymerase chain reaction (PCR) to amplify a fragment of the cathepsin L-like cysteine protease (CatL-like) gene. A phylogenetic tree analysis of these three Ecuadorian isolates showed a close relationship with isolates from South America (Colombia, Brazil and Venezuela) and West Africa (Nigeria). This is the first report of T. vivax in Ecuadorian cattle.

Epidemiological and molecular identification of Trypanosoma vivax diagnosed in cattle during outbreaks in central Brazil.

Bovine trypanosomosis has been spreading in Brazil. In the present study, we evaluated the spatial distribution, prevalence and risk factors of this disease in the state of Goiás, Brazil, and performed both molecular and phylogenetical analyses of Trypanosoma vivax. A total of 4049 blood samples were collected from cattle for a period of 2 years. The parasitological diagnosis was performed using the Woo method and a questionnaire was administered to the farmers to document risk factors associated with the disease in the herd. Positive samples were DNA sequenced and compared to GenBank codes. The prevalence of T. vivax was 8.84%, occurring on 24 ranches only in dairy cattle and mainly in the central and southern portions of the state. The acquisition of new animals infected with T. vivax and the administration of exogenous oxytocin to cows using the same syringe and needle were the main associated factors (P ≤ 0.05). After an outbreak, milk production decreased by 39.62%. The presence of biting flies (tabanids, Haematobia irritans and Stomoxys calcitrans) was not a risk factor (P > 0.05) for the occurrence of T. vivax. The epidemiological data demonstrate the importance of restricting the practice of auctions as well as eliminating the use of exogenous oxytocin in animals during milking. The samples tested by polymerase chain reaction were positive for T. vivax and were genetically homologous with T. vivax found in different states of Brazil and west Africa based on the 18S rRNA gene.

Variant antigen diversity in Trypanosoma vivax is not driven by recombination.

African trypanosomes (Trypanosoma) are vector-borne haemoparasites that survive in the vertebrate bloodstream through antigenic variation of their Variant Surface Glycoprotein (VSG). Recombination, or rather segmented gene conversion, is fundamental in Trypanosoma brucei for both VSG gene switching and for generating antigenic diversity during infections. Trypanosoma vivax is a related, livestock pathogen whose VSG lack structures that facilitate gene conversion in T. brucei and mechanisms underlying its antigenic diversity are poorly understood. Here we show that species-wide VSG repertoire is broadly conserved across diverse T. vivax clinical strains and has limited antigenic repertoire. We use variant antigen profiling, coalescent approaches and experimental infections to show that recombination plays little role in diversifying T. vivax VSG sequences. These results have immediate consequences for both the current mechanistic model of antigenic variation in African trypanosomes and species differences in virulence and transmission, requiring reconsideration of the wider epidemiology of animal African trypanosomiasis.

Genetic diversity of trypanosome species in tsetse flies (Glossina spp.) in Nigeria.

BACKGROUND: Trypanosomes cause disease in humans and livestock in sub-Saharan Africa and rely on tsetse flies as their main insect vector. Nigeria is the most populous country in Africa; however, only limited information about the occurrence and diversity of trypanosomes circulating in the country is available. METHODS: Tsetse flies were collected from five different locations in or adjacent to protected areas, i.e. national parks and game reserves, in Nigeria. Proboscis and gut samples were analysed for trypanosome DNA by molecular amplification of the internal transcribed spacer 1 (ITS1) region and part of the trypanosome specific glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) gene. RESULTS: The most abundant Trypanosoma species found in the tsetse gut was T. grayi, a trypanosome infecting crocodiles. It was ubiquitously distributed throughout the country, accounting for over 90% of all cases involving trypanosomes. Trypanosoma congolense was detected in gut samples from all locations except Cross River National Park, but not in the proboscis, while T. brucei (sensu lato) was not detected at all. In proboscis samples, T. vivax was the most prominent. The sequence diversity of gGAPDH suggests that T. vivax and T. grayi represent genetically diverse species clusters. This implies that they are highly dynamic populations. CONCLUSIONS: The prevalence of animal pathogenic trypanosomes throughout Nigeria emphasises the role of protected areas as reservoirs for livestock trypanosomes. The genetic diversity observed within T. vivax and T. grayi populations might be an indication for changing pathogenicity or host range and the origin and consequences of this diversity has to be further investigated.

VAPPER: High-throughput variant antigen profiling in African trypanosomes of livestock.

BACKGROUND: Analysing variant antigen gene families on a population scale is a difficult challenge for conventional methods of read mapping and variant calling due to the great variability in sequence, copy number, and genomic loci. In African trypanosomes, hemoparasites of humans and animals, this is complicated by variant antigen repertoires containing hundreds of genes subject to various degrees of sequence recombination. FINDINGS: We introduce Variant Antigen Profiler (VAPPER), a tool that allows automated analysis of the variant surface glycoprotein repertoires of the most prevalent livestock African trypanosomes. VAPPER produces variant antigen profiles for any isolate of the veterinary pathogens Trypanosoma congolense and Trypanosoma vivax from genomic and transcriptomic sequencing data and delivers publication-ready figures that show how the queried isolate compares with a database of existing strains. VAPPER is implemented in Python. It can be installed to a local Galaxy instance from the ToolShed (https://toolshed.g2.bx.psu.edu/) or locally on a Linux platform via the command line (https://github.com/PGB-LIV/VAPPER). The documentation, requirements, examples, and test data are provided in the Github repository. CONCLUSION: By establishing two different, yet comparable methodologies, our approach is the first to allow large-scale analysis of African trypanosome variant antigens, large multi-copy gene families that are otherwise refractory to high-throughput analysis.

Cardiac involvement in trypanosomiasis in sheep experimentally infected by Trypanosoma vivax (Ziemman, 1905).

The objective of the present study was to evaluate the clinical signs, electrocardiographic signs and evolution of histopathological lesions in the heart of sheep experimentally infected by Trypanosoma vivax during the acute and chronic phases of infection as well as to investigate the presence of parasitic DNA in the heart using polymerase chain reaction (PCR). Twenty-two male sheep were divided into the following four groups: G1, which consisted of six sheep infected by T. vivax that were evaluated until 20 days post-infection (dpi; acute phase); G2, which consisted of six sheep infected by T. vivax that were evaluated until 90 dpi (chronic phase); and G3 and G4 groups, which each consisted of five uninfected sheep. At the end of the experimental period, electrocardiographic evaluations and necroscopic examinations were performed. Fragments of the heart were collected and stained by Hematoxylin-Eosin and Masson's trichrome, and the fragments were also evaluated by PCR for T. vivax. G2 animals presented clinical signs suggestive of heart failure and electrocardiogram alterations characterized by prolonged P, T and QRS complex durations as well as by a cardiac electrical axis shift to the left and increased heart rate. In these animals, mononuclear multifocal myocarditis and interstitial fibrosis were also observed. PCR revealed positivity for T. vivax in two G1 animals and in all G2 animals. Thus, these findings suggested that T. vivax is responsible for the occurrence of cardiac lesions, which are related to heart failure, electrocardiographic alterations and mortality of the infected animals.