Horses naturally infected by Trypanosoma vivax in southern Brazil

Detection of anti-Trypanosoma spp. antibodies in cattle from southern Brazil

Bovine trypanosomosis, caused by Trypanosoma vivax, is a disease that originated in Africa and currently affects cattle in several South American countries, including almost all Brazilian states. Despite the reports on T. vivax infection in southern Brazil, data on its circulation status is currently unavailable. In this study, we aimed to detect anti-Trypanosoma spp. IgG antibodies in cattle from Rio Grande do Sul and suggest areas with T. vivax transmission risk. A total of 691 serum samples from cattle in the intermediate regions of Rio Grande do Sul were analyzed using indirect immunofluorescence assay (IFA). The overall seroprevalence of anti-Trypanosoma antibodies in cattle was 24.6% (170/691). The detection rate ranged from 0-37.3%, with a high prevalence in the intermediate regions of Ijuí (37.3%), Uruguaiana (30.7%), and Passo Fundo (28.9%). Thus, these regions were suggested as possible bovine trypanosomosis risk areas due to the high seroprevalence. This is the first serological study to determine Trypanosoma spp. infection status in cattle from Rio Grande do Sul, providing data on the epidemiology of trypanosomosis in the state.

Clinical and epidemiological aspects of the infection by Babesia, Theileria and Trypanosoma species in horses from northeastern Colombia

Piroplasmosis and trypanosomiasis are debilitating diseases of great economic impact on the equine industry of Latin America. Considering the lack of studies in the northeastern part of Colombia, this study aimed to determine the epidemiological, clinical and genetic features associated with infection of the Babesia, Theileria, and Trypanosoma species in horses from this geographical area. Two hundred and eighty horses from the Arauca, Meta, and Santander departments were molecularly analyzed for infection with Babesia caballi, Theileria equi, Trypanosoma evansi, and Trypanosoma vivax. Furthermore, clinical, epidemiological and entomological analyses were performed on the data sets. Molecular analysis showed 25.7% and 3.9% prevalence for T. equi and T. evansi, respectively, without positive animals for B. caballi and T. vivax. There were no differences in the prevalence of T. equi between departments, whereas T. evansi was detected exclusively in Santander. A total of 633 ticks were collected from 72 horses across the three departments, with 84.7% corresponding to Dermacentor nitens, 10.9% to Amblyomma cajennense (sensu lato) (s.l). and 4.4% to Rhipicephalus microplus. For T. equi, genetic analyses showed that Colombian isolates belong to genotype C of species, along with sequences of Brazil and Mexico. Epidemiological analysis revealed a significant association between tick infestation and lack of vector control with molecular infection of T. equi, whereas clinical analysis revealed a significant reduction in packed cell volume, red blood cells, and mean corpuscular volume in positive animals to this pathogen. Furthermore, molecular infection by T. evansi was associated with epidemiological characteristics in the Santander department. In conclusion, our analysis revealed a moderate infection rate by T. equi of genotype C in horses from northeastern Colombia, which affects their clinical conditions. Control of ticks and treatment of symptomatic animals should be considered to reduce the economic impact associated with these infections in the equine industry.

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.

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.

Global distribution, host range and prevalence of Trypanosoma vivax: a systematic review and meta-analysis

BACKGROUND

Trypanosomosis caused by Trypanosoma vivax is one of the diseases threatening the health and productivity of livestock in Africa and Latin America. Trypanosoma vivax is mainly transmitted by tsetse flies; however, the parasite has also acquired the ability to be transmitted mechanically by hematophagous dipterans. Understanding its distribution, host range and prevalence is a key step in local and global efforts to control the disease.

METHODS

The study was conducted according to the methodological recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. A systematic literature search was conducted on three search engines, namely PubMed, Scopus and CAB Direct, to identify all publications reporting natural infection of T. vivax across the world. All the three search engines were screened using the search term Trypanosoma vivax without time and language restrictions. Publications on T. vivax that met our inclusion criteria were considered for systematic review and meta-analysis.

RESULT

The study provides a global database of T. vivax, consisting of 899 records from 245 peer-reviewed articles in 41 countries. A total of 232, 6277 tests were performed on 97 different mammalian hosts, including a wide range of wild animals. Natural infections of T. vivax were recorded in 39 different African and Latin American countries and 47 mammalian host species. All the 245 articles were included into the qualitative analysis, while information from 186 cross-sectional studies was used in the quantitative analysis mainly to estimate the pooled prevalence. Pooled prevalence estimates of T. vivax in domestic buffalo, cattle, dog, dromedary camel, equine, pig, small ruminant and wild animals were 30.6%, 6.4%, 2.6%, 8.4%, 3.7%, 5.5%, 3.8% and 12.9%, respectively. Stratified according to the diagnostic method, the highest pooled prevalences were found with serological techniques in domesticated buffalo (57.6%) followed by equine (50.0%) and wild animals (49.3%).

CONCLUSION

The study provides a comprehensive dataset on the geographical distribution and host range of T. vivax and demonstrates the potential of this parasite to invade other countries out of Africa and Latin America.

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.

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.

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.

The animal trypanosomiases and their chemotherapy: a review

Pathogenic animal trypanosomes affecting livestock have represented a major constraint to agricultural development in Africa for centuries, and their negative economic impact is increasing in South America and Asia. Chemotherapy and chemoprophylaxis represent the main means of control. However, research into new trypanocides has remained inadequate for decades, leading to a situation where the few compounds available are losing efficacy due to the emergence of drug-resistant parasites. In this review, we provide a comprehensive overview of the current options available for the treatment and prophylaxis of the animal trypanosomiases, with a special focus on the problem of resistance. The key issues surrounding the main economically important animal trypanosome species and the diseases they cause are also presented. As new investment becomes available to develop improved tools to control the animal trypanosomiases, we stress that efforts should be directed towards a better understanding of the biology of the relevant parasite species and strains, to identify new drug targets and interrogate resistance mechanisms.

Field and experimental symptomless infections support wandering donkeys as healthy carriers of Trypanosoma vivax in the Brazilian Semiarid, a region of outbreaks of high mortality in cattle and sheep

Background

The Brazilian Semiarid is the home of the largest herd of donkeys in South America and of outbreaks of Trypanosoma vivax infection of high mortality in dairy cattle and sheep. For a comprehensive understanding of the underlying mechanisms of these outbreaks and epidemiological role of donkeys, we surveyed for T. vivax in wandering donkeys and follow the experimental infection of donkeys and sheep with a highly virulent isolate from the Semiarid.

Methods

Blood samples from 180 randomly selected wandering donkeys from the Brazilian Semiarid region were employed for PCV and parasitemia assessments and tested using the T. vivax-specific TviCATL-PCR assay. PCR-amplifed Cathepsin L (CATL) sequences were employed for genotyping and phylogenetic analysis. Four wandering donkeys were experimentally infected with a T. vivax isolate obtained during an outbreak of high mortality in the Semiarid; the control group consisted of two non-inoculated donkeys.

Results

We detected T. vivax in 30 of 180 wandering donkeys (16.6 %) using TviCATL-PCR. The prevalence was higher during the dry (15.5 %) than the wet season (1.1 %) and more females (23.1 %) than males (8.9 %) were infected. All the PCR-positive donkeys lacked patent parasitemia and showed normal values of body condition score (BCS) and packed cell volume (PCV). To evaluate the probable tolerance of donkeys to T. vivax, we inoculated five donkeys with a highly virulent isolate (TviBrRp) from the Semiarid. All inoculated donkeys became PCR-positive, but their parasitemia was always subpatent. A control goat inoculated with TviBrRp showed increasing parasitemia concurrently with fever, declining PCV, tachycardia, mucous membrane pallor, enlarged lymph nodes and anorexia. None of these signs were observed in donkeys. However, T. vivax from wandering donkeys shared identical or highly similar genotypes (identified by Cathepsin L sequences) with isolates from cattle and sheep outbreaks of acute disease in the Semiarid.

Conclusions

This is the first report of T. vivax in donkeys in Brazil and, to our knowledge, the first experimental infection of donkeys with T. vivax. The symptomless field and experimental infections corroborated that donkeys are more tolerant to T. vivax than other livestock species as shown in African countries. Therefore, farmers, veterinaries and control programmes should be aware of healthy carrier donkeys as a possible source of T. vivax for susceptible livestock species in the Brazilian Semiarid.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1169-7) contains supplementary material, which is available to authorized users.

Epidemiology of Trypanosoma evansi and Trypanosoma vivax in domestic animals from selected districts of Tigray and Afar regions, Northern Ethiopia

Background

African animal trypanosomosis, transmitted cyclically by tsetse flies or mechanically by other biting flies, causes serious inflictions to livestock health. This study investigates the extent of non-tsetse transmitted animal trypanosomosis (NTTAT) by Trypanosoma (T.) evansi and T. vivax in domestic animals in the tsetse-free regions of Northern Ethiopia, Afar and Tigray.

Methods

A cross sectional study was conducted on 754 dromedary camels, 493 cattle, 264 goats, 181 sheep, 84 donkeys, 25 horses and 10 mules. The microhaematocrit centrifugation technique was used as parasitological test. Plasma was collected for serodiagnosis with CATT/T.evansi and RoTat 1.2 immune trypanolysis (ITL) while buffy coat specimens were collected for molecular diagnosis with T. evansi type A specific RoTat 1.2 PCR, T. evansi type B specific EVAB PCR and T. vivax specific TvPRAC PCR.

Results

The parasitological prevalence was 4.7% in Tigray and 2.7% in Afar and significantly higher (z = 2.53, p = 0.011) in cattle (7.3%) than in the other hosts. Seroprevalence in CATT/T.evansi was 24.6% in Tigray and 13.9% in Afar and was significantly higher (z = 9.39, p < 0.001) in cattle (37.3%) than in the other hosts. On the other hand, seroprevalence assessed by ITL was only 1.9% suggesting cross reaction of CATT/T.evansi with T. vivax or other trypanosome infections. Molecular prevalence of T. evansi type A was 8.0% in Tigray and in Afar and varied from 28.0% in horses to 2.2% in sheep. It was also significantly higher (p < 0.001) in camel (11.7%) than in cattle (6.1%), donkey (6%), goat (3.8%), and sheep (2.2%). Four camels were positive for T. evansi type B. Molecular prevalence of T. vivax was 3.0% and was similar in Tigray and Afar. It didn’t differ significantly among the host species except that it was not detected in horses and mules.

Conclusions

NTTAT caused by T. vivax and T. evansi, is an important threat to animal health in Tigray and Afar. For the first time, we confirm the presence of T. evansi type B in Ethiopian camels. Unexplained results obtained with the current diagnostic tests in bovines warrant particular efforts to isolate and characterise trypanosome strains that circulate in Northern Ethiopia.

Escape mechanisms of African trypanosomes: why trypanosomosis is keeping us awake

African trypanosomes have been around for more than 100 million years, and have adapted to survival in a very wide host range. While various indigenous African mammalian host species display a tolerant phenotype towards this parasitic infection, and hence serve as perpetual reservoirs, many commercially important livestock species are highly disease susceptible. When considering humans, they too display a highly sensitive disease progression phenotype for infections with Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense, while being intrinsically resistant to infections with other trypanosome species. As extracellular trypanosomes proliferate and live freely in the bloodstream and lymphatics, they are constantly exposed to the immune system. Due to co-evolution, this environment however no longer poses a hostile threat, but has become the niche environment where trypanosomes thrive and obligatory await transmission through the bites of tsetse flies or other haematophagic vectors, ideally without causing severe side infection-associated pathology to their host. Hence, African trypanosomes have acquired various mechanisms to manipulate and control the host immune response, evading effective elimination. Despite the extensive research into trypanosomosis over the past 40 years, many aspects of the anti-parasite immune response remain to be solved and no vaccine is currently available. Here we review the recent work on the different escape mechanisms employed by African Trypanosomes to ensure infection chronicity and transmission potential.

Microsatellite analysis supports clonal propagation and reduced divergence of Trypanosoma vivax from asymptomatic to fatally infected livestock in South America compared to West Africa

BACKGROUND

Mechanical transmission of the major livestock pathogen Trypanosoma vivax by other biting flies than tsetse allows its spread from Africa to the New World. Genetic studies are restricted to a small number of isolates and based on molecular markers that evolve too slowly to resolve the relationships between American and West African populations and, thus, unable us to uncover the recent history of T. vivax in the New World.

METHODS

T. vivax genetic diversity, population structure and the source of outbreaks was investigated through the microsatellite multiloci (7 loci) genotype (MLGs) analysis in South America (47isolates from Brazil, Venezuela and French Guiana) and West Africa (12 isolates from The Gambia, Burkina Faso, Ghana, Benin and Nigeria). Relationships among MLGs were explored using phylogenetic, principal component and STRUCTURE analyses.

RESULTS

Although closely phylogenetically related, for the first time, genetic differences were detected between T. vivax isolates from South America (11 genotypes/47 isolates) and West Africa (12 genotypes/12 isolates) with no MLGs in common. Diversity was far greater across West Africa than in South America, where genotypes from Brazil (MLG1-6), Venezuela (MLG7-10) and French Guiana (MLG11) shared similar but not identical allele composition. No MLG was exclusive to asymptomatic (endemic areas) or sick (outbreaks in non-endemic areas) animals, but only MLGs1, 2 and 3 were responsible for severe haematological and neurological disorders.

CONCLUSIONS

Our results revealed closely related genotypes of T. vivax in Brazil and Venezuela, regardless of endemicity and clinical conditions of the infected livestock. The MLGs analysis from T. vivax across SA and WA support clonal propagation, and is consistent with the hypothesis that the SA populations examined here derived from common ancestors recently introduced from West Africa. The molecular markers defined here are valuable to assess the genetic diversity, to track the source and dispersion of outbreaks, and to explore the epidemiological and pathological significance of T. vivax genotypes.

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

Trypanosoma evansi, the agent of "surra," is a salivarian trypanosome, originating from Africa. It is thought to derive from Trypanosoma brucei by deletion of the maxicircle kinetoplastic DNA (genetic material required for cyclical development in tsetse flies). It is mostly mechanically transmitted by tabanids and stomoxes, initially to camels, in sub-Saharan area. The disease spread from North Africa towards the Middle East, Turkey, India, up to 53° North in Russia, across all South-East Asia, down to Indonesia and the Philippines, and it was also introduced by the conquistadores into Latin America. It can affect a very large range of domestic and wild hosts including camelids, equines, cattle, buffaloes, sheep, goats, pigs, dogs and other carnivores, deer, gazelles, and elephants. It found a new large range of wild and domestic hosts in Latin America, including reservoirs (capybaras) and biological vectors (vampire bats). Surra is a major disease in camels, equines, and dogs, in which it can often be fatal in the absence of treatment, and exhibits nonspecific clinical signs (anaemia, loss of weight, abortion, and death), which are variable from one host and one place to another; however, its immunosuppressive effects interfering with intercurrent diseases or vaccination campaigns might be its most significant and questionable aspect.

First report of Trypanosoma vivax outbreak in dairy cattle in São Paulo state, Brazil

This is the first description of a Trypanosoma vivax outbreak in the state of São Paulo (municipality of Lins). Fever, jaundice, decreased milk production, weight loss, profuse diarrhea, abortion, anemia, leukocytosis and hyperfibrinogenemia were observed in the affected animals. Thirty-one cows and calves died out of a total of 1080 in the herd. Three cows showed neurological symptoms like dysmetria, ataxia, muscle weakness, ptyalism, lymph node enlargement and submandibular edema. Flagellated hemoparasites were observed in blood smears. The species was diagnosed as T. vivax by means of PCR. This T.vivax strain showed resistance to diaminazene aceturate and the infection spread quickly at the herd. From the ELISA test, 599 serum samples (98.36%) were positive for anti-T.vivax IgG antibodies. This outbreak occurred during a very dry period, which indicates that other factors were involved in the outbreak, such as absence of tabanids and large populations of Haematobia irritans and Stomoxys calcitrans. The increases in these populations may have been due to the use of biosolid waste from sugar and ethanol plants in the sugarcane plantations surrounding the dairy farm.

Follicular degeneration in the ovaries of goats experimentally infected with Trypanosoma vivax from the Brazilian semi-arid region

Infection by Trypanosoma vivax and other African trypanosomes plays an important role in reproductive disorders in male and female livestock. Outbreaks of T. vivax in the semi-arid region of northeastern Brazil are characterized by wasting disease in cattle, sheep and goats with hematological, cardiac and nervous compromises in addition to reproductive failures. Similar to reports from Africa, we previously observed a reduction in fertility rates and severe testicular degeneration and epididymitis in male sheep infected with T. vivax from this region. Although anestrus is frequently reported in goats and sheep infected with T. vivax, the effects of this infection on the female reproductive organs need clarification. In this study, we addressed this issue through a histopathological evaluation of ovarian follicular morphology and classification in goats experimentally infected with a T. vivax isolate from the Brazilian semi-arid region. The infected animals presented typical clinical signs of trypanosomosis by T. vivax, including anemia, hyperthermia, pallor of the mucous membranes, enlarged lymph nodes, and progressive loss of weight. All the infected goats remained anestrus throughout the experimental period and exhibited important disturbances in the ovaries, evidenced by reduced size and a smooth surface without follicles or corpora lutea, and abnormal follicular development. In addition, through PCR, we detected T. vivax DNA in the ovarian tissues of the infected goats. Our findings contributed to understand the female reproductive failure associated with trypanosomosis caused by T. vivax.

Genetic engineering of Trypanosoma (Dutonella) vivax and in vitro differentiation under axenic conditions

Trypanosoma vivax is one of the most common parasites responsible for animal trypanosomosis, and although this disease is widespread in Africa and Latin America, very few studies have been conducted on the parasite's biology. This is in part due to the fact that no reproducible experimental methods had been developed to maintain the different evolutive forms of this trypanosome under laboratory conditions. Appropriate protocols were developed in the 1990s for the axenic maintenance of three major animal Trypanosoma species: T. b. brucei, T. congolense and T. vivax. These pioneer studies rapidly led to the successful genetic manipulation of T. b. brucei and T. congolense. Advances were made in the understanding of these parasites' biology and virulence, and new drug targets were identified. By contrast, challenging in vitro conditions have been developed for T. vivax in the past, and this per se has contributed to defer both its genetic manipulation and subsequent gene function studies. Here we report on the optimization of non-infective T. vivax epimastigote axenic cultures and on the process of parasite in vitro differentiation into metacyclic infective forms. We have also constructed the first T. vivax specific expression vector that drives constitutive expression of the luciferase reporter gene. This vector was then used to establish and optimize epimastigote transfection. We then developed highly reproducible conditions that can be used to obtain and select stably transfected mutants that continue metacyclogenesis and are infectious in immunocompetent rodents.

Trypanosoma vivax is a major parasite of domestic animals in Africa and Americas. Most studies on this parasite have focused on gathering epidemiological data in the field. Studies on its biology, metabolism and interaction with the host immune system have been hindered by a lack of suitable tools for its maintenance in vitro and its genetic engineering. The work presented herein focused on determining axenic conditions for culturing and growing insect (epimastigote) forms of T. vivax and prompting their differentiation into metacyclic forms that are infectious for the mammalian host. In addition, we describe the development of appropriate vectors for parasite transgenesis and selection in vitro and their use in analyzing genetically modified parasite lines. Finally, we report on the construction of the first T. vivax recombinant strain that stably expresses a foreign gene that maintains its infectivity in immunocompetent mice. Our work is a significant breakthrough in the field as it should lead, in the future, to the identification of parasite genes that are relevant to its biology and fate, and to work that may shed light on the intricacies of T. vivax–host interactions.