Trypanosoma evansi and surra: a review and perspectives on origin, history, distribution, taxonomy, morphology, hosts, and pathogenic effects

Seroprevalence of Trypanosoma evansi in cattle and analysis of associated climatic risk factors in Mizoram, India

Surra, a haemoprotozoan parasitic disease even in subclinical form poses a challenge in terms of diagnosis and management to animal health practitioners and policy makers as well; eventually imparting financial loss to the livestock holders. A systematic study was designed to assess the seroprevalence of surra in cattle and associated climatic risk factors, by collecting 480 serum samples across the eight districts of Mizoram during 2017-2019. The apparent and true seroprevalence detected by card agglutination test was 37.08% (CI at 95%: 32.88-41.49) and 36.59% (CI at 95%: 32.4-40.99) whereas by recombinant Variable Surface Glycoprotein based indirect ELISA was 41.88% (CI at 95%: 37.5-46.3) and 40.35% (CI at 95%: 36.02-44.76) respectively. Climate parameters which influence vector population were extracted from their respective database and were correlated with seroprevalence data. Linear discriminant analysis revealed that air temperature, relative humidity and diurnal temperature range, leaf area index and soil moisture as significant risk factors discriminating seropositive and seronegative data sets classified by indirect ELISA. This study is the first report on seroprevalence of surra in cattle of Mizoram and the situation demands deployment of intervention strategies in order to assess the endemicity of the disease and thereby preventing the economic losses.

Efficacy of diminazene diaceturate and isometamidium chloride hydrochloride for the treatment of Trypanosoma evansi in mice model

Diminazene diaceturate (DIM) and isometamidium chloride hydrochloride (ISMM) have been widely used for the treatment of animal trypanosomosis. We evaluated the efficacy of standard doses of DIM and ISMM followed by their double doses for the treatment of Trypanosoma evansi in experimentally infected mice. A T. evansi strain obtained from a naturally infected camel in Afar was used. 25 swiss white mice randomly divided in to five groups were inoculated with 0.2 mL of blood containing 10³ trypanosomes. At the peak of parasitemia (≈ 2 weeks post infection), groups A and B were treated with the standard dose (3.5 mg/kg body weight [BWT]) of DIM; groups C and D were treated with the standard dose (0.5 mg/kg BWT) of ISMM; and group E served as infected control. In the DIM standard dose groups, relapses and peak parasitemia were observed 20- and 25-days post treatment respectively. Similarly, relapses and peak parasitemia were observed 21- and 27-days post treatment in the ISMM standard dose groups. All mice in the control group died within two weeks post infection. Following relapses, mice were treated with the double doses of DIM (7 mg/kg BWT) or ISMM (1 mg/kg BWT). Parasitemia was not detected for 3 months following the double dose treatments. Following dexamethasone administration for 7 days, all but one mouse in the DIM group remained negative for another month. In general, although the T. evansi strain was resistant to the standard doses of DIM and ISMM their double doses completely cleared the infection.

New records and DNA barcoding of deer flies, Chrysops (Diptera: Tabanidae) in Thailand

Chrysops spp. or deer flies (Diptera: Tabanidae) are hematophagous flies of medical and veterinary importance and some species are important vectors of Trypanosoma evansi, the causative agent of surra in Thailand. However, data regarding deer fly species and their molecular identification are limited. Accurate species identification will indicate the appropriate control measures. In this study, an entomological survey of deer flies from different sites in Thailand between May 2018 and June 2019 were conducted. In addition, mitochondrial cytochrome oxidase subunit I (COI) barcoding region was used for species identification. A total of 82 females were collected and 6 species were identified. Of these, three species are new records for Thailand: C. designatus, C. fuscomarginalis and C. vanderwulpi bringing the species total found in Thailand to nine. The COI sequences revealed an intraspecific divergence of 0.0%-2.65% and an interspecific divergence of 7.03%-13.47%. Phylogenetic analysis showed that all deer fly species were clearly separated into distinct clusters according to morphologically identified species. These results indicated that COI barcodes were capable in discriminating between deer fly species on the basis of the barcoding gap and phylogenetic analysis. Therefore, DNA barcoding is a valuable tool for species identification of deer flies in Thailand.

Native and Introduced Trypanosome Parasites in Endemic and Introduced Murine Rodents of Sulawesi

The Indonesian island of Sulawesi is a globally significant biodiversity hotspot with substantial undescribed biota, particularly blood-borne parasites of endemic wildlife. Documenting the blood parasites of Sulawesi's murine rodents is the first fundamental step towards the discovery of pathogens likely to be of concern for the health and conservation of Sulawesi's endemic murines. We screened liver samples from 441 specimens belonging to 20 different species of murine rodents from 2 mountain ranges on Sulawesi, using polymerase chin reaction (PCR) primers targeting the conserved 18S rDNA region across the protozoan class Kinetoplastea. We detected infections in 156 specimens (10 host species) with a mean prevalence of 35.4% (95% confidence interval [CI] = 30.9-39.8%). Sequences from these samples identified 4 infections to the genus Parabodo, 1 to Blechomonas, and the remaining 151 to the genus Trypanosoma. Within Trypanosoma, we recovered 17 haplotypes nested within the Trypanosoma theileri clade infecting 117 specimens (8 host species) and 4 haplotypes nested within the Trypanosoma lewisi clade infecting 34 specimens (6 host species). Haplotypes within the T. theileri clade were related to regional Indo-Australian endemic trypanosomes, displayed geographic structuring but with evidence of long-term connectivity between mountains, and had substantial phylogenetic diversity. These results suggest T. theileri clade parasites are native to Sulawesi. Conversely, T. lewisi clade haplotypes were recovered from both endemic and introduced rodents, demonstrated complete geographic separation between clades, and had low genetic diversity. These results suggest that the T. lewisi clade parasites invaded Sulawesi recently and likely in 2 separate invasion events. Our results provide the first records of metakinetoplastids in Sulawesi's rodents and highlight the need for more extensive sampling for pathogens in this biodiversity hotspot.

A case of Trypanosoma evansi in a German Shepherd dog in Vietnam

A 2.5-year-old male German Shepherd was presented to a private veterinary clinic in Hanoi, Vietnam showing anorexia, weakness, lethargy, reluctant to go for walks with a recent history of intermittent fever. Clinical examination of the dog showed pale mucous membrane, impaired eyesight, edema of the back legs. Complete blood count revealed severe anemia; red blood cell 3.8 × 10¹²/l, hemoglobin 8.7 g/dl, hematocrit 26.4%, associated with thrombocytopenia 145 × 10⁹/l. Biochemical analysis showed a moderate increase of alanine transaminase (150.7 UI/l) and alkaline phosphatase activities (266 UI/I) with mild hypoglycemia (71.46 mg/dl). Trypanosoma evansi was observed in Giemsa-stained blood smears under microscopic observation which was confirmed by PCR. This is the first report of canine trypanosomiasis caused by T. evansi in Vietnam.

Humoral immune response and delayed-type hypersensitivity in rabbits infected with Trypanosoma equiperdum

Trypanosoma equiperdum is the causative agent of dourine, a parasitic venereal disease of equids. In this work, rabbits were infected with T. equiperdum strain OVI; serological tests (complement fixation test, ELISA and immunoblotting), used for the diagnosis of dourine in horses, were applied to study rabbit humoral immune response and to characterise T. equiperdum antigen pattern recognised by antibodies from infected rabbits. Moreover a protein extract of T. equiperdum strain OVI was produced and tested in skin tests on infected rabbits to detect the cell-mediated response induced by T. equiperdum, in order to evaluate its use in the field diagnosis of dourine. Sera of infected rabbits recognized in immunoblotting Trypanosoma protein bands with molecular weight below 37 kDa, providing a serological response comparable with that already observed in dourine infected horses. Moreover the trypanosome protein extract was capable to produce in vivo delayed-type hypersensitivity (DHT Type IV) in rabbits and proved itself to be non-toxic and non-sensitizing.

The spreading of parasites by human migratory activities

The global spread of parasites is unquestionably linked with human activities. Migration in all its different forms played a major role in the introduction of parasites into new areas. In ancient times, mass migrations were the main causes for the spread of parasites while in the recent past and present, emigration, immigration, displacement, external and internal migration, and labor migration were the reasons for the dispersal of parasites. With the advent of seagoing ships, long-distance trading became another important mode of spreading parasites. This review summarizes the spread of parasites using notable examples. In addition, the different hypotheses explaining the arrival of Plasmodium vivax and soil-transmitted helminths in pre-Columbian America are also discussed.

Prevalence and Associated Risk Factors of Trypanosoma evansi in Camels in Ethiopia Based on Parasitological Examinations

Camel trypanosomosis (surra), caused by Trypanosoma evansi , is a life-threatening disease with negative impacts on health, production, and working efficiency of camels in different camel-rearing areas of the world, including Ethiopia. A cross-sectional study was carried out from November 2016 to May 2017 to determine the prevalence of camel trypanosomosis (surra) and assess the associated potential risk factors in Dubti and Asayita districts of Afar region, Ethiopia. Blood samples were collected from 200 camels. Wet film and Giemsa-stained blood smears were used for the detection of trypanosomes. Out of 200 examined, 9(4.5%) were positive for Trypanosoma evansi. The higher prevalence of the disease was observed in Dubti (6.97%) than in Asayita (2.63%) districts. Highest infection was observed in the age group >4 years old camels (7.47%), followed by <4 years old camels (1.07%). Previously aborted camels were found at higher risk (P=0.03; OR = 5.11, 95% CI = 1.174-22.317) than camels without an abortion history. There was no statistically significant difference in between body condition categories and herd size of camels with the occurrence of the disease (X 2 = 3.839; P=0.147 and X 2 = 0.718; P=0.698), respectively. The result of the current study revealed that camel trypanosomosis is substantially prevalent in the study area, indicating the need for designing control and prevention strategies.

Investigation of Trypanosoma evansi infection in bullfighting cattle in Southern Thailand

Background and Aim

Trypanosoma evansi infection has been reported in Thai livestock such as beef and dairy cattle. However, there is little information on T. evansi infection in bullfighting cattle in Southern Thailand. The aim of this study was to investigate the infection of T. evansi in bullfighting cattle presented for health checks at the Animal Hospital, Faculty of Veterinary Science, Prince of Songkla University, Thailand.

Materials and Methods

Blood and serum samples were collected from 177 bullfighting cattle from April 2016 to February 2017 after bullfighting matches. Animal inspected showed signs of fever, weight loss, or exercise intolerance. Investigation of T. evansi infection was tested using polymerase chain reaction (PCR) with TBR primers and using indirect enzyme-linked immunosorbent assay with T. evansi crude antigen.

Results

The seroprevalence of T. evansi in bullfighting cattle was 22.60% (40/177). The PCR results detected no parasite DNA in this study. However, bullfighting cattle may serve as T. evansi reservoirs.

Conclusion

Health checking procedures for T. evansi should be promoted for bullfighting events so that infected animals can be quarantined in the preparatory stages of such events.

An Unbiased Immunization Strategy Results in the Identification of Enolase as a Potential Marker for Nanobody-Based Detection of Trypanosoma evansi

Trypanosoma evansi is a widely spread parasite that causes the debilitating disease “surra” in several types of ungulates. This severely challenges livestock rearing and heavily weighs on the socio-economic development in the affected areas, which include countries on five continents. Active case finding requires a sensitive and specific diagnostic test. In this paper, we describe the application of an unbiased immunization strategy to identify potential biomarkers for Nanobody (Nb)-based detection of T. evansi infections. Alpaca immunization with soluble lysates from different T. evansi strains followed by panning against T. evansi secretome resulted in the selection of a single Nb (Nb11). By combining Nb11-mediated immuno-capturing with mass spectrometry, the T. evansi target antigen was identified as the glycolytic enzyme enolase. Four additional anti-enolase binders were subsequently generated by immunizing another alpaca with the recombinant target enzyme. Together with Nb11, these binders were evaluated for their potential use in a heterologous sandwich detection format. Three Nb pairs were identified as candidates for the further development of an antigen-based assay for Nb-mediated diagnosis of T. evansi infection.

Dominant IgM synthesis against the soluble form of the prevailing variant surface glycoprotein from TeAp-N/D1 Trypanosoma equiperdum throughout the experimental acute infections of horses with non-tsetse transmitted Trypanozoon parasites

Two horses were infected with distinct non-tsetse transmitted Trypanozoon Venezuelan stocks, namely TeAp-N/D1 Trypanosoma equiperdum and TeAp-El Frio01 Trypanosoma evansi. Preceding reports have revealed that a 64-kDa antigenic glycopolypeptide (p64), which is the soluble form of the predominant variant surface glycoprotein from TeAp-N/D1 T. equiperdum, can be used as a good antigen for immunodiagnosis of animal trypanosomosis. Here, the course of the experimental acute infection in both horses was monitored by evaluating total anti-p64 IgG and particular anti-p64 γ-specific IgG and μ-specific IgM isotypes in sera using indirect enzyme-linked immunosorbent assays. Both equines showed a maximum of whole anti-p64 antibody generation, which dropped to readings below the maximum but always above the positive cutoff point. Levels of specific IgG and IgM isotypes oscillated throughout the course of the experiments. Essentially, the γ-specific IgG response remained very close to the cutoff point, whereas the μ-specific IgM response displayed values that were mostly above the positive cutoff point, showing a major peak that coincided with the maximum of complete anti-p64 IgG production. These results showed that horses infected with non-tsetse transmitted Trypanozoon parasites developed an immune reaction characterized by a dominant IgM generation against the p64 antigen.

First outbreak of autochthonous "surra" in horses in Santa Catarina State, Brazil: Parasitological, hematological and biochemical characteristics

This study reports the first autochthonous "surra" outbreak in horses in the State of Santa Catarina, southern Brazil. Six horses with clinical suspicion of trypanosomosis had the natural infection by T. evansi confirmed by PCR and rapid serum agglutination test. Clinical, parasitological, and hematology evaluations were performed at initial observation (T0) and 90 days after (T1). At T0, all animals that tested positive for T. evansi in PCR presented with severe clinical signs and out of normal range hematological hematological (hematocrit, leukocytes, platelets, hemoglobin) and serum biochemical parameters (alanine aminotransferase (ALT), creatinine phosphokinase (CPK), lactate dehydrogenase (LDH), creatinine, bilirubin, and glucose). At T1, the progressive clinical recovery of animals, normalization of hemato-biochemical parameters, and negative PCR results for T. evansi were observed. It was not possible to identify the vector/mechanism of transmission through which animals were infected; therefore, the implementation of surveillance and control measures is essential to prevent the spread of this disease in horse herds, as well as to other animal species.

Tissue tropism in parasitic diseases

Parasitic diseases, such as sleeping sickness, Chagas disease and malaria, remain a major cause of morbidity and mortality worldwide, but particularly in tropical, developing countries. Controlling these diseases requires a better understanding of host-parasite interactions, including a deep appreciation of parasite distribution in the host. The preferred accumulation of parasites in some tissues of the host has been known for many years, but recent technical advances have allowed a more systematic analysis and quantifications of such tissue tropisms. The functional consequences of tissue tropism remain poorly studied, although it has been associated with important aspects of disease, including transmission enhancement, treatment failure, relapse and clinical outcome. Here, we discuss current knowledge of tissue tropism in Trypanosoma infections in mammals, describe potential mechanisms of tissue entry, comparatively discuss relevant findings from other parasitology fields where tissue tropism has been extensively investigated, and reflect on new questions raised by recent discoveries and their potential impact on clinical treatment and disease control strategies.

Evaluation of the Immunoprotective Potential of Recombinant Paraflagellar Rod Proteins of Trypanosoma evansi in Mice

Trypanosomosis, caused by Trypanosoma evansi, is an economically significant disease of livestock. Systematic antigenic variation by the parasite has undermined prospects for the development of a protective vaccine that targets the immunodominant surface antigens, encouraging exploration of alternatives. The paraflagellar rod (PFR), constituent proteins of the flagellum, are prominent non-variable vaccine candidates for T. evansi owing to their strategic location. Two major PFR constituent proteins, PFR1 (1770bp) and PFR2 (1800bp), were expressed using Escherichia coli. Swiss albino mice were immunized with the purified recombinant TePFR1 (89KDa) and TePFR2 (88KDa) proteins, as well as with the mix of the combined proteins at equimolar concentrations, and subsequently challenged with virulent T. evansi. The PFR-specific humoral response was assessed by ELISA. Cytometric bead-based assay was used to measure the cytokine response and flow cytometry for quantification of the cytokines. The recombinant TePFR proteins induced specific humoral responses in mice, including IgG1 followed by IgG2a and IgG2b. A balanced cytokine response induced by rTePFR 1 and 2 protein vaccination associated with extended survival and improved control of parasitemia following lethal challenge. The observation confirms the immunoprophylactic potential of the covert antigens of T. evansi.

Development of a recombinase polymerase amplification lateral flow assay for the detection of active Trypanosoma evansi infections

BACKGROUND

Animal trypanosomosis caused by Trypanosoma evansi is known as "surra" and is a widespread neglected tropical disease affecting wild and domestic animals mainly in South America, the Middle East, North Africa and Asia. An essential necessity for T. evansi infection control is the availability of reliable and sensitive diagnostic tools. While DNA-based PCR detection techniques meet these criteria, most of them require well-trained and experienced users as well as a laboratory environment allowing correct protocol execution. As an alternative, we developed a recombinase polymerase amplification (RPA) test for Type A T. evansi. The technology uses an isothermal nucleic acid amplification approach that is simple, fast, cost-effective and is suitable for use in minimally equipped laboratories and even field settings.

METHODOLOGY/PRINCIPLE FINDINGS

An RPA assay targeting the T. evansi RoTat1.2 VSG gene was designed for the DNA-based detection of T. evansi. Comparing post-amplification visualization by agarose gel electrophoresis and a lateral flow (LF) format reveals that the latter displays a higher sensitivity. The RPA-LF assay is specific for RoTat1.2-expressing strains of T. evansi as it does not detect the genomic DNA of other trypanosomatids. Finally, experimental mouse infection trials demonstrate that the T. evansi specific RPA-LF can be employed as a test-of-cure tool.

CONCLUSIONS/SIGNIFICANCE

Compared to other DNA-based parasite detection methods (such as PCR and LAMP), the T. evansi RPA-LF (TevRPA-LF) described in this paper is an interesting alternative because of its simple read-out (user-friendly), short execution time (15 minutes), experimental sensitivity of 100 fg purified genomic T. evansi DNA, and ability to be carried out at a moderate, constant temperature (39°C). Therefore, the TevRPA-LF is an interesting tool for the detection of active T. evansi infections.

Prevalence of Trypanosoma evansi in livestock in Palestine

Background

Trypanosoma evansi is the causative agent of surra, a disease that occurs in many animal species. The disease is responsible for substantial losses in global production and can be fatal if not diagnosed early. This study aims to determine the prevalence of T. evansi in livestock, equids and dromedary camels in Palestine.

Methods

Blood samples were collected during 2015–2017 from domesticated animals (n = 259 animals; 77% females and 23% males) including camels (n = 87), horses (n = 46), donkeys (n = 28), mules (n = 2), sheep (n = 49) and goats (n = 48) from eight districts: Ariha (Jericho), Nablus, Bethlehem, Deir Al Balah, Jenin, Rafah, Tubas, and Khan Yunis. Parasite prevalence was determined using PCR and blood smear microscopy. PCR-positive samples were further phylogenetically analyzed using DNA sequences of the 18S ribosomal RNA gene.

Results

The overall infection prevalence was 18% (46/259). The positivity rates according to PCR and microscopy examination were 17% (45/259) and 2.7% (7/259), respectively. The infection rates were as follows: camels, 26/61 (30%); horses, 8/46 (17%); donkeys, 3/28 (11%); mules, 1/2 (50%); sheep, 2/42 (4%); and goats, 6/42 (13%). Phylogenetic analyses of the 18S rRNA gene showed that 24 positive T. evansi samples from Palestine formed a monophyletic cluster with seven T. evansi sequences from Africa, Asia and South America, and three T. brucei sequences from Africa retrieved from GenBank. The spatial analysis showed three statistically significant foci of T. evansi infection in Jenin, Tubas (P = 0.02) and Ariha (Jericho) (P = 0.04). No statistically significant foci were detected in the Gaza Strip.

Conclusions

To the best of our knowledge, this is the first confirmation of high levels of infection with T. evansi as a causative agent of surra in Palestine. Our study emphasizes the need for a stringent surveillance system and risk assessment studies as prerequisites for control measures. Further investigations focusing on vectors and evaluation of risk factors are needed.

Zoonotic parasites of dromedary camels: so important, so ignored

With a global population of about 35 million in 47 countries, dromedary camels play a crucial role in the economy of many marginal, desert areas of the world where they survive under harsh conditions. Nonetheless, there is scarce knowledge regarding camels' parasite fauna which can reduce their milk and meat productions. In addition, only scattered information is available about zoonotic parasites transmitted to humans via contamination (e.g. Cryptosporidium spp., Giardia duodenalis, Balantidium coli, Blastocystis spp. and Enterocytozoon bieneusi), as foodborne infections (e.g. Toxoplasma gondii, Trichinella spp. and Linguatula serrata) or by arthropod vectors (Trypanosoma spp.). Herein, we draw attention of the scientific community and health policy-making organizations to the role camels play in the epidemiology of parasitic zoonotic diseases also in the view of an increase in their farming in desert areas worldwide.

Inhibition of Trypanosoma evansi Protein-Tyrosine Phosphatase by Myristic Acid Analogues Isolated from Khaya senegalensis and Tamarindus indica

BACKGROUND

Trypanosome infections still pose severe health and economic consequences, especially in the endemic regions of Sub-Saharan Africa. Trypanosome differentiation to the procyclic forms which lack the immune evasion mechanisms for survival in the bloodstream is prevented by tyrosine dephosphorylation which is catalyzed by protein-tyrosine phosphatase; thereby promoting survival of the parasites in the host. Inhibition of Protein-tyrosine phosphatase is a strategic therapeutic target that could attenuate trypanosomiasis. This study investigated the in vitro inhibitory effect of stem bark extracts of Khaya senegalensis and Tamarindus indica on the enzymatic activity of protein-tyrosine phosphatase.

METHODS

All determinations were carried out following standard procedures for analytical experiments. The analogues of myristic acid that inhibited the enzymatic activity of protein-tyrosine phosphatase were isolated by bioassay-guided fractionation of stem bark extracts of Khaya senegalensis and Tamarindus indica.

RESULTS

Analogues of myristic acid proved to be potent inhibitors of protein-tyrosine phosphatase. Double reciprocal (Lineweaver-Burk) plots of the initial velocity data indicated non-competitive inhibition with Ki of 0.67 mg/mL for Khaya senegalensis and 2.17 mg/mL for Tamarindus indica. The kinetic parameters for the cleavage of para-nitrophenylphosphate by the enzyme showed a KM of 3.44 mM and Vmax of 0.19 µmol/min. Sodium orthovanadate, the enzymes' specific inhibitor, inhibited the enzyme competitively with Ki of 0.20 mg/mL. Gas chromatography-mass spectrometry analysis of the stem bark bioactive fractions of Khaya senegalensis and Tamarindus indica revealed the presence of myristic acid analogues.

CONCLUSION

Analogues of myristic acid are potent inhibitors of protein-tyrosine phosphatase that could be developed as trypanocide to inhibit the enzymatic activity of protein-tyrosine phosphatase in order to prevent transmission of trypanosomes.

The Indirect ELISA Trypanosoma evansi in Equids: Optimisation and Application to a Serological Survey including Racing Horses, in Thailand

Surra, caused by Trypanosoma evansi, is a widely distributed animal trypanosomosis; it affects both domestic and wild mammals with high economic impact. Clinical picture is moderate in bovines but severe in equids. Surra is also an important constraint for international animal trade and movements. Despite its impact, surra remains poorly diagnosed because of low sensitivity tests. To improve epidemiological knowledge of the disease and to secure international movement, efficient diagnosis tools are required. Here, we optimized and applied to equids the OIE-recommended indirect ELISA T. evansi that was validated in other species. Based on 96 positive and 1,382 negative horse reference samples from Thailand, a TG-ROC analysis was conducted to define the cutoff value. ELISA's sensitivity and specificity were estimated at 97.5% and 100%, respectively, qualifying the test to provide a reliable immune status of equids. The test was then applied on 1,961 horse samples from 18 Thai Provinces; the only scarce positives suggested that horses do not constitute a reservoir of T. evansi in Thailand. All samples from racing horses were negative. Conversely, two outbreaks of surra reported to our laboratory, originating from a bovine reservoir, exhibited high morbidity and lethality rates in horses. Finally, posttreatment follow-ups of infected animals allowed us to provide outbreak management guidelines.

Evolutionary Insight into the Trypanosomatidae Using Alignment-Free Phylogenomics of the Kinetoplast

Advancements in next-generation sequencing techniques have led to a substantial increase in the genomic information available for analyses in evolutionary biology. As such, this data requires the exponential growth in bioinformatic methods and expertise required to understand such vast quantities of genomic data. Alignment-free phylogenomics offer an alternative approach for large-scale analyses that may have the potential to address these challenges. The evolutionary relationships between various species within the trypanosomatid family, specifically members belonging to the genera Leishmania and Trypanosoma have been extensively studies over the last 30 years. However, there is a need for a more exhaustive analysis of the Trypanosomatidae, summarising the evolutionary patterns amongst the entire family of these important protists. The mitochondrial DNA of the trypanosomatids, better known as the kinetoplast, represents a valuable taxonomic marker given its unique presence across all kinetoplastid protozoans. The aim of this study was to validate the reliability and robustness of alignment-free approaches for phylogenomic analyses and its applicability to reconstruct the evolutionary relationships between the trypanosomatid family. In the present study, alignment-free analyses demonstrated the strength of these methods, particularly when dealing with large datasets compared to the traditional phylogenetic approaches. We present a maxicircle genome phylogeny of 46 species spanning the trypanosomatid family, demonstrating the superiority of the maxicircle for the analysis and taxonomic resolution of the Trypanosomatidae.

Zoonotic Trypanosomes in Rats and Fleas of Venezuelan Slums

Rattus spp. are reservoirs of many human zoonoses, but their role in domestic transmission cycles of human trypanosomiasis is underestimated. In this study, we report trypanosome-infected Rattus norvegicus and Rattus rattus in human dwellings in slums neighboring Maracay, a large city near Caracas, the capital of Venezuela. Blood samples of R. norvegicus and R. rattus examined by PCR and FFLB (fluorescent fragment length barcoding) revealed a prevalence of 6.3% / 31.1% for Trypanosoma lewisi (agent of rat- and flea-borne human emergent zoonosis), and 10.5% / 24.6% for Trypanosoma cruzi (agent of Chagas disease). Detection in flea guts of T. lewisi (76%) and, unexpectedly, T. cruzi (21.3%) highlighted the role of fleas as carriers and vectors of these trypanosomes. A high prevalence of rats infected with T. lewisi and T. cruzi and respective flea and triatomine vectors poses a serious risk of human trypanosomiasis in Venezuelan slums. Anthropogenic activities responsible for growing rat and triatomine populations within human dwellings drastically increased human exposure to trypanosomes. This scenario has allowed for the reemergence of Chagas disease as an urban zoonosis in Venezuela and can propitiate the emergence of atypical T. lewisi infection in humans.

Sustainable Elimination (Zero Cases) of Sleeping Sickness: How Far Are We from Achieving This Goal?

The recent massive reduction in the numbers of fresh Human African Trypanosomiasis (HAT) infection has presented an opportunity for the global elimination of this disease. To prevent a possible resurgence, as was the case after the reduced transmission of the 1960s, surveillance needs to be sustained and the necessary tools for detection and treatment of cases need to be made available at the points of care. In this review, we examine the available resources and make recommendations for improvement to ensure the sustenance of the already achieved gains to keep the trend moving towards elimination.

Molecular diagnosis of acute and chronic infection of Trypanosoma evansi in experimental male and female mice

Trypanosoma evansi is enzootic in camels in Egypt, and water buffaloes act as a reservoir for camel infection. Molecular techniques have contributed towards understanding the epidemiology of T. evansi. Trypanosoma evansi was detected in acute and chronic stages of the disease in male and female mice by polymerase chain reaction (PCR) using two primers. Two experiments were conducted. In experiment I, two groups consisting of 26 female and 26 male mice received 10⁴ trypanosome by I/P inoculation for each mouse. In experiment II, 42 female and 42 male mice were inoculated I/P with 10² trypanosome/mouse. In addition, five mice were kept as uninfected control for each group. Mice were monitored daily for parasitaemia level during the pre-patent period using the micro-haematocrit centrifugation technique (MHCT) and conventional PCR. The primer pairs, (Trypanosoma brucei) TBR1/2 and TeRoTat1.2 (T. evansi Rode Trypanozoon antigen type [RoTat] 1.2), detected the infection after 24 hours earlier than MHCT in both experiments. The course of infection that was detected by MHCT revealed three waves of parasitaemia in female mice and two waves in male mice in the chronic stage of infection. In addition, PCR was able to detect T. evansi in different organs in the chronic stage (i.e. disappearance of parasite from blood). Application of the two primer sets on blood samples from camels showed that all samples were positive by TBR1/2 primers and only 32 of 44 were positive by TeRoTat1.2 primers. Acutely and chronically Trypanosoma-infected mice were detected by PCR in blood and organs. TBR1/2 primers were more sensitive than TeRoTat1.2 primers in detecting Trypanosoma-infected mice, and more reliable in detecting field-infected camels and excluding carrier animals.

Epidemiological investigations on Trypanosoma evansi infection in dromedary camels in the South of Algeria

An epidemiological study of Trypanosoma evansi (T. evansi) infection in dromedaries was conducted in four wilayate (localities) of Southern Algeria: Béchar, El Bayadh, Ouargla, Tamanrasset. Between February 2014 and April 2016, 1056 camels of different ages and both sexes from 84 herds were sampled. The prevalence was determined through parasitological examination (Giemsa stained thin smear, GST), serological tests (CATT/T. evansi, ELISA/VSG RoTat 1.2, immune trypanolysis), and molecular tests (T. evansi type A specific RoTat 1.2 PCR and T. evansi type B specific EVAB PCR). The overall prevalence was 2.4 % with GST, 32.4% with CATT/T. evansi, 23.1% with ELISA/VSG RoTat 1.2, 21.0% with immune trypanolysis (TL), 11.2 % with RoTat 1.2 PCR and 0% with EVAB PCR. El Bayadh was the most affected wilaya with 11.8% positives in GST, 74.9% in CATT/T. evansi, 70.1% in ELISA/VSG RoTat 1.2 and 62.2% in immune trypanolysis. Only in Béchar, a non-significantly higher prevalence (13.6%) was observed with RoTat1.2 PCR than in El Bayadh (13.0%). We didn't find any evidence of the presence of T. evansi type B in the study area.

Evaluation of an alternative indirect-ELISA test using in vitro-propagated Trypanosoma brucei brucei whole cell lysate as antigen for the detection of anti-Trypanosoma evansi IgG in Colombian livestock

Surra is a zoonotic disease caused by Trypanosoma evansi, affecting the health and production of the livestock significantly. There are several methods to diagnose this disease, which have different principles, sensitivity, and specificity. Among them, the serological techniques using T. evansi as antigen are powerful tools for its epidemiological surveillance. However, they are poorly used due to inefficient in vitro propagation of T. evansi, which requires the use of laboratory animals for antigen production. In the present study, whole cell lysate of T. brucei brucei propagated in vitro was used as an antigen for the detection of anti-T. evansi immunoglobulin G in cattle through an indirect-ELISA. Based on a total of 45 samples from non-infected and 45 samples from T. evansi infected cattle, the sensitivity and specificity were estimated as 100% and 97.7%, respectively. After the validation, serological and molecular surveys were carried out in 710 cattle samples from two endemic Colombian regions (Antioquia and Arauca departments) for T. evansi where molecular prevalences of ˜7.0% were detected through the year and sporadic outbreaks of T. vivax infections have been associated to low prevalence of this species (<1%). A total of 424 (59.7%) samples were positive by indirect-ELISA T. b. brucei, while PCR test for T. evansi and T. vivax, showed 49 (6.9%) and no positive samples, respectively. Interestingly, categories of animals aged>1 year, Bos taurus breed, and those raised under intensive farming system exhibited a higher seroprevalence to T. evansi (P < 0.05). The results displayed a new alternative for antibody detection anti-T. evansi in livestock, using parasites propagated in vitro as antigen, which presents the advantage of higher standardization potential, and avoid the use of live animal for antigen production. A larger availability of this ELISA will generate useful information for a better understanding of the epidemiologic aspects, as well as for the management and control of these diseases in Colombia. However, the ability of the test to detect and/or cross react with T. vivax infections remains to be investigated.

Equine trypanosomosis: enigmas and diagnostic challenges

Equine trypanosomosis is a complex of infectious diseases called dourine, nagana and surra. It is caused by several species of the genus Trypanosoma that are transmitted cyclically by tsetse flies, mechanically by other haematophagous flies, or sexually. Trypanosoma congolense (subgenus Nannomonas) and T. vivax (subgenus Dutonella) are genetically and morphologically distinct from T. brucei, T. equiperdum and T. evansi (subgenus Trypanozoon). It remains controversial whether the three latter taxa should be considered distinct species. Recent outbreaks of surra and dourine in Europe illustrate the risk and consequences of importation of equine trypanosomosis with infected animals into non-endemic countries. Knowledge on the epidemiological situation is fragmentary since many endemic countries do not report the diseases to the World Organisation for Animal Health, OIE. Other major obstacles to the control of equine trypanosomosis are the lack of vaccines, the inability of drugs to cure the neurological stage of the disease, the inconsistent case definition and the limitations of current diagnostics. Especially in view of the ever-increasing movement of horses around the globe, there is not only the obvious need for reliable curative and prophylactic drugs but also for accurate diagnostic tests and algorithms. Unfortunately, clinical signs are not pathognomonic, parasitological tests are not sufficiently sensitive, serological tests miss sensitivity or specificity, and molecular tests cannot distinguish the taxa within the Trypanozoon subgenus. To address the limitations of the current diagnostics for equine trypanosomosis, we recommend studies into improved molecular and serological tests with the highest possible sensitivity and specificity. We realise that this is an ambitious goal, but it is dictated by needs at the point of care. However, depending on available treatment options, it may not always be necessary to identify which trypanosome taxon is responsible for a given infection.

The prevalence of horse trypanosomiasis in Sumba Island, Indonesia and its detection using card agglutination tests

Background and Aim:

Horses have a strategic and vital role to play in the lives of the people of Sumba Island, East Nusa Tenggara Province. They act as social animals that are involved in death ceremonies, horse races, and during pasola, thereby supporting tourism, and are given away as dowry in wedding ceremonies. This study aimed to investigate the prevalence of trypanosomiasis among horses in four districts of Sumba Island by examining clinical symptoms and detecting parasites, antibodies, and other factors that are related to Trypanosoma evansi infection in horses.

Materials and Methods:

We studied a total of 211 horses that belonged to 88 clinical hobby breeders. Giemsa-colored smears and serum were examined in order to detect antibodies using card-agglutination tests (CATT). The study was conducted during the rainy season that lasted from January to March 2017. Potential risk factors such as the species, sex, origin of the livestock, how the livestock were maintained, and the farmers’ knowledge concerning trypanosomiasis were recorded using questionnaires. Data were collected annually for three years from 2010-2012 and repeatedly analyzed by a Chi-square test.

Results:

Clinical signs of trypanosomiasis were found in 34 horses; blood smears were examined using Giemsa staining and negative preparations were obtained at a frequency of 0.0% (0/211). The CATT results generally showed that 13.3% (28/211) of the samples were seropositive for antibodies to T. evansi; the highest percentage, 16.67% (8/48), of seropositivity was found in the West Sumba District, and the lowest, 12.0% (5/50), was found in Southwest Sumba. The incidence of trypanosomiasis was higher (75% [21/28]) among female hip horses; horses with 1-5 years of experience were more susceptible to a T. evansi infection (46.4% [13/28]). In general, farmers on Sumba Island knew of trypanosomiasis (89.8% [79/88]), and 69.3% (61/88) of the farmers reported that their livestock was sick. This study was the first serological study conducted on trypanosomiasis in horses of Sumba Island after the surra outbreak in 2010-2012. There were 3% of farmers who were willing to provide the government with information on implementing a prevention program and controlling the spread of surra on the island.

Conclusion:

The diagnoses of surra disease were made based on clinical symptoms and parasitological examinations. CATTs could be used to diagnose T. evansi infection in horses.

Epidemiological survey of hemoprotozoan parasites in cattle from low-country wet zone in Sri Lanka

The diseases caused by hemoprotozoan parasites in cattle often result in economic losses. In Sri Lanka, previous studies found that the up-country wet zone, which is located in central Sri Lanka, was characterized by a high rate of Theileria orientalis and a low rate of Theileria annulata compared with the dry zone. In this study, DNA samples were prepared from the blood of 121 cattle in Galle, a coastal district located in low-country wet zone in Sri Lanka, and were PCR-screened for Babesia bovis, Babesia bigemina, T. annulata, T. orientalis, and Trypanosoma theileri. All the parasite species, except B. bovis, were detected among the surveyed cattle. The animals had a high rate of T. orientalis (100%) and a low rate of T. annulata (1.6%), as in the up-country wet zone. Babesia bigemina and Tr. theileri were detected in 19.0% and 20.6% of the animals, respectively, and their infection rates were higher in the animals reared in extensive management systems (32.8% and 27.9%, respectively) than in those managed in intensive/semi-intensive systems (5.0% and 13.3%, respectively). Genotypic analyses found that the T. orientalis mpsp type 5 was predominant similar to up-country wet zone, and that Tr. theileri consisted of seven catl genotypes, including two new genotypes (IL and IM) and four previously detected genotypes (IA, IB, II, and IK). These findings suggest that the hemoprotozoan infection profiles are largely conserved within the wet zone, despite differences in the geography, cattle breeds, and management practices between the up-country and low-country wet zones.

Utilization of crude and recombinant ELISAs for serodiagnosis of camel trypanosomosis in Sudan

This study was carried out to evaluate the application of CATT/T. evansi, crude and recombinant (TeGM6-4r) antigen ELISAs in the diagnosis of camel trypanosomosis caused by two trypanosome species, T. evansi and T. vivax, in Sudan. Concurrently, the current situation of camel trypanosomosis was investigated based on the results of a serological analysis. The recombinant tandem repeat antigen TeGM6-4r is conserved among salivarian trypanosome species and was highly sensitive in the detection Trypanozoon, and T. vivax. It has been validated in the diagnosis of surra in cattle and water buffalo but not in camels. A comparative evaluation of a crude antigen ELISA and a recombinant antigen GM6 (rTeGM6-4r) ELISA was performed using 189 blood samples, which included 148 samples obtained from different camel herds in Eastern Sudan and 41 samples from camels that had been brought from Western Sudan to local markets. The results showed that the rTeGM6-4r ELISA detected the greatest number of positive samples (n = 118, 62%), while CATT/T. evansi and the crude antigen ELISA detected the lowest number of positive samples (n = 73, 39%). The kappa value of rTeGM6-4r as compared to TeCA ELISA was 0.5515, which indicated moderate agreement. We concluded that the rTeGM6-4r ELISA is the test of choice for use in screening camel for trypanosomosis caused by T. evansi and T. vivax in Sudan.

Parasitological, Hematological, and Immunological Response of Experimentally Infected Sheep with Venezuelan Isolates of Trypanosoma evansi, Trypanosoma equiperdum, and Trypanosoma vivax

There are three trypanosoma species of veterinary importance in South America: (1) Trypanosoma evansi, the causative agent of derrengadera mechanically transmitted by bloodsucking insects such as tabanids, (2) Trypanosoma vivax, also mechanically transmitted by some dipteras hematophages as tabanids and/or Stomoxys, and (3) T. equiperdum, a tissue parasite adapted to sexual transmission and the causative agent of dourine, a distinctive disease that affects only Equidae. In order to evaluate the parasitological, hematological, and serological response of sheep infected with T. vivax, T. evansi, and T. equiperdum, four female sheep were experimentally infected with Venezuelan trypanosome field isolates: two T. evansi of differing virulences, one T. equiperdum; one T. vivax. Parasitemia and clinical parameters such as hematocrit, red blood cell count, hemoglobin, and body temperature were measured. T. evansi caused a chronic disease with undulant parasitemia alternating with some cryptic periods of at least 54 days, with no clinical signs. T. equiperdum, never described as infectious to ruminants, also caused a chronic disease with low undulant parasitemia. T. vivax caused an acute infection with severe anemia showing a drop of more than 70% of the hematocrit value, high fever, and rapid deterioration of physical condition, for 36 days of infection. Indirect ELISAs using crude extracts of the three species of trypanosomes as antigens were performed for detection of anti-trypanosome antibodies in sheep sera. Cross-reaction was observed between the three parasite species. These results show that sheep are susceptible to the three-trypanosome species and suggest they can act as a reservoir when sheep are raised and managed with other important livestock such as cattle, horses, buffalos, or goats. These findings are especially interesting for T. equiperdum, a species that has not been reported as infective to sheep.

A single test approach for accurate and sensitive detection and taxonomic characterization of Trypanosomes by comprehensive analysis of internal transcribed spacer 1 amplicons

To improve our knowledge on the epidemiological status of African trypanosomiasis, better tools are required to monitor Trypanosome genotypes circulating in both mammalian hosts and tsetse fly vectors. This is important in determining the diversity of Trypanosomes and understanding how environmental factors and control efforts affect Trypanosome evolution. We present a single test approach for molecular detection of different Trypanosome species and subspecies using newly designed primers to amplify the Internal Transcribed Spacer 1 region of ribosomal RNA genes, coupled to Illumina sequencing of the amplicons. The protocol is based on Illumina's widely used 16s bacterial metagenomic analysis procedure that makes use of multiplex PCR and dual indexing. Results from analysis of wild tsetse flies collected from Zambia and Zimbabwe show that conventional methods for Trypanosome species detection based on band size comparisons on gels is not always able to accurately distinguish between T. vivax and T. godfreyi. Additionally, this approach shows increased sensitivity in the detection of Trypanosomes at species level with the exception of the Trypanozoon subgenus. We identified subspecies of T. congolense, T. simiae, T. vivax, and T. godfreyi without the need for additional tests. Results show T. congolense Kilifi subspecies is more closely related to T. simiae than to other T. congolense subspecies. This agrees with previous studies using satellite DNA and 18s RNA analysis. While current classification does not list any subspecies for T. godfreyi, we observed two distinct clusters for these species. Interestingly, sequences matching T. congolense Tsavo (now classified as T. simiae Tsavo) clusters distinctly from other T. simiae Tsavo sequences suggesting the Nannomonas group is more divergent than currently thought thus the need for better classification criteria. This method presents a simple but comprehensive way of identification of Trypanosome species and subspecies-specific using one PCR assay for molecular epidemiology of trypanosomes.

Natural Trypanosoma (Trypanozoon) evansi (Steel, 1885) infection among mammals from Brazilian Amazon

Trypanosoma evansi (Kinetoplastea Trypanosomatidae) is the Trypanosoma species that infects the greatest variety of mammals worldwide. In 2014, a dog from Rio Branco/AC, in the Brazilian Amazon region, presented flagellates without evident kinetoplasts in blood and symptoms of T. evansi infection. Our aim was to investigate the occurrence of T. evansi in dogs, bats and capybaras from Rio Branco. Blood was collected from 78 dogs from residential areas near the Zoobotanical Park (PZ). The serological diagnosis by IFAT detected the presence of anti-T. evansi antibodies in 21.9% of the evaluated dogs. T. evansi DNA was detected in one dog using a higly specific target of a repeated monomer of the satellite DNA of Trypanosoma (Trypanozoon) sp. Molecular diagnosis was also performed on 182 bat spleen samples collected inside PZ, and one Carollia perspicillata was positive. The DNA sequences obtained from these two samples showed similarities with T. brucei satellite DNA. Anti-T. evansi IFAT was carried out in 46 capybaras from rural and urban areas and the infection detected in 17.4% of them. We confirmed for the first time the presence of T. evansi in Acre State and describe three putative host species involved in the parasite transmission in that Amazon region. Moreover, this is the first study that confirms the infection by T. evansi through DNA sequence analysis in the Brazilian Amazon Region.

Systematic review and meta-analysis on the global distribution, host range, and prevalence of Trypanosoma evansi

BACKGROUND

Surra is an animal trypanosomosis, caused by infection with Trypanosoma evansi and leading to severe economic loss due to mortality and morbidity. Compared to tsetse-transmitted animal trypanosomoses, little attention is given to the epidemiology and control of surra. Understanding its epidemiology is a first step in local and global efforts to control the disease. We conducted a systematic review and meta-analysis of published studies on distribution, host ranges and prevalence of T. evansi infection.

METHODS

Four electronic databases were searched for publications on T. evansi that met our inclusion criteria for the systematic review. Subsets of publications were subjected to meta-analysis for the pooled prevalence of T. evansi in various hosts as determined by multiple detection methods.

RESULTS

A total of 272 references published between 1906-2017 were included. Trypanosoma evansi was reported from 48 countries; largely confined to Africa and Asia with publications on natural T. evansi infections from 77% (n = 48) of countries, contrasting with seven countries in South America, and four in Europe where T. evansi is not endemic but was imported with infected animals. Although surra is a notifiable disease, many countries do not report surra cases to OIE. Trypanosoma evansi was mainly reported from dromedary camels in Africa and the Middle East, water buffaloes, cattle, dogs and horses in East and Southeast Asia. In South America, the acute form of the disease was reported in horses and dogs. Surra was also reported in a wide range of wild animals. Some rare human cases occurred in India and Vietnam. Meta-analysis on a subset of 165 publications indicated pooled prevalence of T. evansi in domestic animals ranging from 14-31%, 6-28% and 2-9% using respectively antibody detection, molecular and parasitological tests, with camels as the most affected, followed by buffalo and cattle.

CONCLUSIONS

This study illustrates that T. evansi affects a wide range of domestic and wild animals in Africa, Asia and South America with highest prevalence observed in dromedary camels. For successful control of T. evansi, both locally and globally, the role of wild animals in the epidemiology of surra needs further investigation.

Trypanosoma evansi and "Candidatus Mycoplasma haemolamae" Co-Infection in One-Humped Camel (Camelus dromedarius) from the Northwest of Iran: A Case Report

A 4-year-old male one-humped camel (Camelus dromedarius) was referred to Veterinary Teaching Hospital of Urmia University, Iran in 2017 with anorexia, weakness, depression and pale mucosa. Decreased red blood cell count, packed cell volume and hemoglobin concentration were detected by complete blood cell count. In Giemsa-stained peripheral blood smears Trypanosoma spp. trypomastigotes scattered between erythrocytic spaces and Mycoplasma-like organisms were observed attached to the surface of erythrocytes. Species-specific PCR assay confirmed T. evansi and Candidatus Mycoplasma haemolamae (CMhl) co-infection. Administration of diminazene aceturate, oxytetracycline 20%, flunixin meglumine and phosphorus-vitamin B₁₂ were not effective in treatment. Hemoplasmosis should be considered as an important differential diagnosis of conditions associated with hemolytic anemia in camel.

Molecular detection of equine trypanosomiasis in the Riyadh Province of Saudi Arabia

We conducted a cross-sectional study to detect trypanosome infections of horses and donkeys in the Riyadh Province of Saudi Arabia. DNA was extracted from blood samples collected from 368 horses and 142 donkeys, and subjected to universal first ribosomal internal transcribed spacer region (ITS1)-PCR followed by Trypanosoma evansi species-specific RoTat1.2-PCR. The universal ITS1-PCR revealed T. evansi infection in horses ( n = 12; 3.3%) and donkeys ( n = 4; 2.8%). There was no significant effect of sex or age on the prevalence of trypanosomiasis in horses or donkeys. Application of the RoTat1.2-PCR revealed that the RoTat1.2 VSG gene was absent from the positive ITS1-PCR samples of 3 horses and 1 donkey. This discrepancy could be explained by the circulation of T. evansi type B in Saudi Arabia; however, this suspicion requires confirmation.

Validation of a new experimental model for assessing drug efficacy against infection with Trypanosoma equiperdum in horses

Trypanosoma equiperdum, the causative agent of dourine, may affect the central nervous system, leading to neurological signs in infected horses. This location protects the parasite from most (if not all) existing chemotherapies. In this context, the OIE terrestrial code considers dourine as a non-treatable disease and imposes a stamping-out policy for affected animals before a country may achieve its dourine-free status. The use of practices as drastic as euthanasia remains controversial, but the lack of a suitable tool for studying a treatment's efficacy against dourine hampers the development of an alternative strategy for dourine infection management. The present study reports on the development of an experimental infection model for assessing drug efficacy against the nervous form of dourine. The model combines the infection of horses by Trypanosoma equiperdum and the search for trypanosomes in the cerebrospinal fluid (CSF) through an ultrasound-guided cervical sampling protocol. After a development phase involving four horses, we established an infection model that consists of inoculating 5 × 10⁴T. equiperdum OVI parasites intravenously into adult Welsh mares (Equus caballus). To evaluate its efficacy, eight horses were infected according to this model. In all these animals, parasites were observed in the blood at 2 days post-inoculation (p.i.) and in CSF (12.5 ± 1.6 days p.i.) and seroconversion was detected (8.25 ± 0.5 days p.i.). All eight animals also developed fever (rectal temperature > 39 °C), low hematocrit (< 27%), and ventral edema (7.9 ± 2.0 days p.i.), together with other inconstant clinical signs such as edema of the vulva (six out of eight horses) or cutaneous plaques (three out of eight horses). This model provides a robust infection protocol that induces an acute trypanosome infection and that allows parasites to be detected in the CSF of infected horses within a period of time compatible with animal experimentation constraints. We conclude that this model constitutes a suitable tool for analyzing the efficacy of anti-Trypanosoma drugs and vaccines.

Salivarian Trypanosomosis: A Review of Parasites Involved, Their Global Distribution and Their Interaction With the Innate and Adaptive Mammalian Host Immune System

Salivarian trypanosomes are single cell extracellular parasites that cause infections in a wide range of hosts. Most pathogenic infections worldwide are caused by one of four major species of trypanosomes including (i) Trypanosoma brucei and the human infective subspecies T. b. gambiense and T. b. rhodesiense, (ii) Trypanosoma evansi and T. equiperdum, (iii) Trypanosoma congolense and (iv) Trypanosoma vivax. Infections with these parasites are marked by excessive immune dysfunction and immunopathology, both related to prolonged inflammatory host immune responses. Here we review the classification and global distribution of these parasites, highlight the adaptation of human infective trypanosomes that allow them to survive innate defense molecules unique to man, gorilla, and baboon serum and refer to the discovery of sexual reproduction of trypanosomes in the tsetse vector. With respect to the immunology of mammalian host-parasite interactions, the review highlights recent findings with respect to the B cell destruction capacity of trypanosomes and the role of T cells in the governance of infection control. Understanding infection-associated dysfunction and regulation of both these immune compartments is crucial to explain the continued failures of anti-trypanosome vaccine developments as well as the lack of any field-applicable vaccine based anti-trypanosomosis intervention strategy. Finally, the link between infection-associated inflammation and trypanosomosis induced anemia is covered in the context of both livestock and human infections.

Isometamidium chloride and homidium chloride fail to cure mice infected with Ethiopian Trypanosoma evansi type A and B

Background

Trypanosoma evansi is mechanically transmitted by biting flies and affects camels, equines, and other domestic and wild animals in which it causes a disease called surra. At least two types of Trypanosoma evansi circulate in Ethiopia: type A, which is present in Africa, Latin America and Asia, and type B, which is prevalent in Eastern Africa. Currently, no information is available about the drug sensitivity of any Ethiopian T. evansi type.

Methodology/principal findings

This study was conducted with the objective of determining the in vivo drug sensitivity of two T. evansi type A and two type B stocks that were isolated from camels from the Tigray and Afar regions of Northern Ethiopia. We investigated the efficacy of four trypanocidal drugs to cure T. evansi infected mice: melarsamine hydrochloride (Cymelarsan), diminazene diaceturate (Veriben and Sequzene), isometamidium chloride (Veridium) and homidium chloride (Bovidium). Per experimental group, 6 mice were inoculated intraperitoneally with trypanosomes, treated at first peak parasitemia by daily drug injections for 4 consecutive days and followed-up for 60 days. Cymelarsan at 2 mg/kg and Veriben at 20 mg/kg cured all mice infected with any T. evansi stock, while Sequzene at 20 mg/kg caused relapses in all T. evansi stocks. In contrast, Veridium and Bovidium at 1 mg/kg failed to cure any T. evansi infection in mice.

Conclusions/significance

We conclude that mice infected with Ethiopian T. evansi can be cured with Cymelarsan and Veriben regardless of T. evansi type. In contrast, Veridium and Bovidium are not efficacious to cure any T. evansi type. Although innate resistance to phenanthridines was previously described for T. evansi type A, this report is the first study to show that this phenomenom also occurs in T. evansi type B infections.

Surra is a vector borne disease in camels, horses, water buffaloes, cattle and other domestic animals caused by Trypanosoma (T.) evansi. This protozoan parasite is transmitted by biting flies such as tabanids and stable flies and is endemic in many countries in Northern and Eastern Africa, Latin America and Asia. Surra is responsible for high economic losses due to mortality and morbidity of draught animals and leads to animal trade restrictions in endemic regions. Control of surra is mainly based on the treatment of sick animals presenting clinical symptoms. In Ethiopia two different types of T. evansi (A and B) have been described, yet no data existed about the drug sensitivity of any T. evansi type. In this study, we show for the first time that T. evansi type B is naturally in vivo resistant to the phenanthridine class of trypanocidal drugs, a phenonomen that was previously described for T. evansi type A. All Ethiopian T. evansi types are sensitive to melarsamine hydrochloride and diminazene diaceturate. Unfortunately, the most efficacious drugs are either not registered in Ethiopia or escape quality control of the active substance in commercial drug formulations. Furthermore, the inefficacious drugs remain accessible on the market despite their toxicity for animals.

The trypanocidal benzoxaborole AN7973 inhibits trypanosome mRNA processing

Kinetoplastid parasites-trypanosomes and leishmanias-infect millions of humans and cause economically devastating diseases of livestock, and the few existing drugs have serious deficiencies. Benzoxaborole-based compounds are very promising potential novel anti-trypanosomal therapies, with candidates already in human and animal clinical trials. We investigated the mechanism of action of several benzoxaboroles, including AN7973, an early candidate for veterinary trypanosomosis. In all kinetoplastids, transcription is polycistronic. Individual mRNA 5'-ends are created by trans splicing of a short leader sequence, with coupled polyadenylation of the preceding mRNA. Treatment of Trypanosoma brucei with AN7973 inhibited trans splicing within 1h, as judged by loss of the Y-structure splicing intermediate, reduced levels of mRNA, and accumulation of peri-nuclear granules. Methylation of the spliced leader precursor RNA was not affected, but more prolonged AN7973 treatment caused an increase in S-adenosyl methionine and methylated lysine. Together, the results indicate that mRNA processing is a primary target of AN7973. Polyadenylation is required for kinetoplastid trans splicing, and the EC50 for AN7973 in T. brucei was increased three-fold by over-expression of the T. brucei cleavage and polyadenylation factor CPSF3, identifying CPSF3 as a potential molecular target. Molecular modeling results suggested that inhibition of CPSF3 by AN7973 is feasible. Our results thus chemically validate mRNA processing as a viable drug target in trypanosomes. Several other benzoxaboroles showed metabolomic and splicing effects that were similar to those of AN7973, identifying splicing inhibition as a common mode of action and suggesting that it might be linked to subsequent changes in methylated metabolites. Granule formation, splicing inhibition and resistance after CPSF3 expression did not, however, always correlate and prolonged selection of trypanosomes in AN7973 resulted in only 1.5-fold resistance. It is therefore possible that the modes of action of oxaboroles that target trypanosome mRNA processing might extend beyond CPSF3 inhibition.

Exotic Parasite Threats to Australia's Biosecurity-Trade, Health, and Conservation

Parasites have threatened Australia’s biosecurity since the early days of European settlement. Tick fever in cattle and liver fluke, along with their invertebrate hosts, and hydatid disease head the list of parasites that are still impacting livestock industries. In addition, there are many parasites that have been introduced that are of significance to public health as well as the conservation of native wildlife. As a consequence of these early arrivals, Australia has become much more aware of its vulnerability should parasites such as Trichinella and Trypanosoma evansi become established in Australia. However, recent discoveries concerning Leishmania and other trypanosomes have demonstrated that Australia must not become complacent and reliant on dogma when considering the potential emergence of new threats to its biosecurity. In this short review, the major parasite threats to Australia’s biosecurity are summarised, some misconceptions are emphasised, and attention is given to the importance of challenging dogma in the face of a dearth of information about Australian native fauna.

Parasitological and Molecular Detection of Canine Trypanosomiasis From Riyadh Province, Saudi Arabia

Trypanosoma evansi is the most widespread of the pathogenic salivarian trypanosomes; it causes a serious disease called surra that affects domestic animals such as camels, horses, and dogs, and often leads to reduced productivity and economic losses. Therefore, the objectives of the present study were to determine the prevalence rates of trypanosomiasis using 3 parasitological tests (wet blood film, Giemsa staining, and microhematocrit centrifugation technique) and polymerase chain reaction (PCR) among stray dogs from Riyadh Province, Saudi Arabia. In the current study, 117 dog blood samples collected from certain districts of Riyadh Province showed that 5 of 117 dogs (4.3%) were positive for the genus Trypanosoma. In addition, the findings indicated no effect of dog gender or age on parasite infection. For a more specific diagnosis, PCR amplification of the RoTat 1.2 VSG gene in 5 internal transcribed spacer1-positive samples diagnosed with Trypanosoma indicated that 2 were positive for RoTat 1.2 T. evansi. The absence of the RoTat 1.2 VSG gene in 3 of the 5 T. evansi-positive samples could be explained by the circulation of T. evansi type B in dogs from Saudi Arabia. Thus, this is the first study demonstrating T. evansi type B outside of Africa.

Mitochondrial DNA is critical for longevity and metabolism of transmission stage Trypanosoma brucei

The sleeping sickness parasite Trypanosoma brucei has a complex life cycle, alternating between a mammalian host and the tsetse fly vector. A tightly controlled developmental programme ensures parasite transmission between hosts as well as survival within them and involves strict regulation of mitochondrial activities. In the glucose-rich bloodstream, the replicative 'slender' stage is thought to produce ATP exclusively via glycolysis and uses the mitochondrial F1FO-ATP synthase as an ATP hydrolysis-driven proton pump to generate the mitochondrial membrane potential (ΔΨm). The 'procyclic' stage in the glucose-poor tsetse midgut depends on mitochondrial catabolism of amino acids for energy production, which involves oxidative phosphorylation with ATP production via the F1FO-ATP synthase. Both modes of the F1FO enzyme critically depend on FO subunit a, which is encoded in the parasite's mitochondrial DNA (kinetoplast or kDNA). Comparatively little is known about mitochondrial function and the role of kDNA in non-replicative 'stumpy' bloodstream forms, a developmental stage essential for disease transmission. Here we show that the L262P mutation in the nuclear-encoded F1 subunit γ that permits survival of 'slender' bloodstream forms lacking kDNA ('akinetoplastic' forms), via FO-independent generation of ΔΨm, also permits their differentiation into stumpy forms. However, these akinetoplastic stumpy cells lack a ΔΨm and have a reduced lifespan in vitro and in mice, which significantly alters the within-host dynamics of the parasite. We further show that generation of ΔΨm in stumpy parasites and their ability to use α-ketoglutarate to sustain viability depend on F1-ATPase activity. Surprisingly, however, loss of ΔΨm does not reduce stumpy life span. We conclude that the L262P γ subunit mutation does not enable FO-independent generation of ΔΨm in stumpy cells, most likely as a consequence of mitochondrial ATP production in these cells. In addition, kDNA-encoded genes other than FO subunit a are important for stumpy form viability.

First Report of Trypanosoma cruzi Infection in Salivary Gland of Bats from the Peruvian Amazon

In the Americas, 8 million people are infected with Chagas disease, and an additional 90 million people are at risk for infection. Little is known about the role bats play in the sylvatic transmission cycle of Trypanosoma cruzi, the parasite causing Chagas disease. Here, we captured bats in the villages of Palmiche, Pachacutec, Nuevo San Martin, and Mayuriaga located in the Datem del Marañon Province in Loreto, Peru. Venous blood samples were collected by cardiac puncture or from the upper extremities, and trypanosomatids were identified by microscopy and molecularly. We collected blood samples from 121 bats on filter paper for molecular studies and 111 slides for microscopic examination of thin and thick blood smears from 16 different bat species. The prevalence of trypanosomatids in all bats species was 34.7% (42/121) and the prevalence of T. cruzi was 4.1% (5/121). In hematophagous bat species, the prevalence of trypanosomatids and T. cruzi was 36.9% (27/73) and 2.7% (2/73), respectively. In non-hematophagous bats, the prevalences of trypanosomatids and T. cruzi were 31.2% (15/48) and 6.2% (3/48), respectively. Also, we confirm the presence of T. cruzi in salivary glands of hematophagous bats Diaemus youngi. These results suggest a sylvatic cycle of trypanosomatid transmission in which bats may harbor infectious T. cruzi parasites that could be transmitted to humans via hematophagous bat bites or salivary contamination by non-hematophagous bats of vegetables consumed by humans.

Molecular Characterization of Trypanosoma evansi Mevalonate Kinase (TeMVK)

The mevalonate pathway is an essential part of isoprenoid biosynthesis leading to production of a diverse class of >30,000 biomolecules including cholesterol, heme, and all steroid hormones. In trypanosomatids, the mevalonate pathway also generates dolichols, which play an essential role in construction of glycosylphosphatidylinositol (GPI) molecules that anchor variable surface proteins (VSGs) to the plasma membrane. Isoprenoid biosynthesis involves one of the most highly regulated enzymes in nature, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), which catalyzes the conversion of HMG-CoA to mevalonic acid. The enzyme mevalonate kinase (MVK) subsequently converts mevalonic acid to 5-phosphomevalonic acid. Trypanosoma evansi is a flagellate protozoan parasite that causes the disease "Surra" in domesticated large mammals, with great economic impact. T. evansi has only a trypomastigote bloodstream form and requires constant modification of the variant surface glycoprotein (VSG) coat for protection against the host immune system. We identified MVK of T. evansi (termed TeMVK) and performed a preliminary characterization at molecular, biochemical, and cellular levels. TeMVK from parasite extract displayed molecular weight ~36 kDa, colocalized with aldolase (a glycosomal marker enzyme) in glycosomes, and is structurally similar to Leishmania major MVK. Interestingly, the active form of TeMVK is the tetrameric oligomer form, in contrast to other MVKs in which the dimeric form is active. Despite lacking organized mitochondria, T. evansi synthesizes both HMGCR transcripts and protein. Both MVK and HMGCR are expressed in T. evansi during the course of infection in animals, and therefore are potential targets for therapeutic drug design.