Estimated financial impact of Trypanosoma vivax on the Brazilian pantanal and Bolivian lowlands

Drug resistance in animal trypanosomiases: Epidemiology, mechanisms and control strategies

Animal trypanosomiasis (AT) is a complex of veterinary diseases known under various names such as nagana, surra, dourine and mal de caderas, depending on the country, the infecting trypanosome species and the host. AT is caused by parasites of the genus Trypanosoma, and the main species infecting domesticated animals are T. brucei brucei, T. b. rhodesiense, T. congolense, T. simiae, T. vivax, T. evansi and T. equiperdum. AT transmission, again depending on species, is through tsetse flies or common Stomoxys and tabanid flies or through copulation. Therefore, the geographical spread of all forms of AT together is not restricted to the habitat of a single vector like the tsetse fly and currently includes almost all of Africa, and most of South America and Asia. The disease is a threat to millions of companion and farm animals in these regions, creating a financial burden in the billions of dollars to developing economies as well as serious impacts on livestock rearing and food production. Despite the scale of these impacts, control of AT is neglected and under-resourced, with diagnosis and treatments being woefully inadequate and not improving for decades. As a result, neither the incidence of the disease, nor the effectiveness of treatment is documented in most endemic countries, although it is clear that there are serious issues of resistance to the few old drugs that are available. In this review we particularly look at the drugs, their application to the various forms of AT, and their mechanisms of action and resistance. We also discuss the spread of veterinary trypanocide resistance and its drivers, and highlight current and future strategies to combat it.

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.

First molecular survey of animal trypanosomes in Paraguayan horses

Despite the epidemic situation of animal trypanosomosis caused by Trypanosoma evansi, Trypanosoma equiperdum and Trypanosoma vivax in South American countries, there are no reports for the prevalence of animal trypanosomes in Paraguay. In this study, 408 blood samples were obtained from apparently healthy horses from sixteen departments of Paraguay, for routine medical check-up from August to September 2019, and a polymerase chain reaction (PCR)-based cross-sectional study was carried out to identify trypanosome prevalence. The prevalence of Trypanozoon (T. evansi and T. equiperdum) and T. vivax was 7.11% (29/408) and 26.23% (107/408), respectively. Mixed infections were detected in 4.90% (20/408) of the samples. Some of the selected trypanosome positive samples were confirmed as T. vivax and T. evansi Type A by sequence analysis of the internal transcribe spacer region and RoTat1.2 variant surface glycoprotein gene, respectively. In conclusion, we found higher prevalence of T. vivax than Trypanozoon in Paraguayan horses. However, the genotypic variation should be verified in further studies.

Detection of Trypanosoma vivax in tissues of experimentally infected goats: what is the role of adipose tissue in the life cycle of this protozoon?

Trypanosomiasis, caused by Trypanosoma vivax, is responsible for great economic losses among livestock in Africa and South America. During the life cycle of these parasites, they may present different morphological, metabolic and physiological characteristics depending on the interactions that are encountered at each point of their life cycle. Although T. vivax is frequently reported in the circulation of its mammalian hosts, it has the ability to migrate to the tissues of these individuals. However, this characteristic is poorly understood. In this context, we aimed to investigate the presence of T. vivax and the changes caused in different tissues of experimentally infected goats. Despite the animals were not perfused before tissues collection, using different approaches, we demonstrated its presence in different samples, including in the adipose tissue and skin of infected animals. In addition, a mononuclear inflammatory reaction, mostly characterized by an infiltrate of lymphocytes, plasma cells and macrophages were observed. The results highlight the possibility that, like other trypanosomatids, T. vivax may use these tissues during its life cycle. Future studies aiming to elucidate the length of time for which T. vivax remains active in these sites, and whether it uses these sites as a refuge from trypanocidal drugs, and whether it is capable of recolonizing the blood circulation, are much needed.

In vitro and in vivo effectiveness of disinfectants against Trypanosoma vivax

Trypanosoma vivax causes bovine trypanosomosis in cattle and resulting in economic losses to farmers. In Brazil, shared contaminated materials is the main transmission pathway. To evaluate the effectiveness of different disinfectants for T. vivax, in vitro and in vivo analyses were performed. At the laboratory, 21 disinfectants were tested. The disinfectants were placed in microtubes containing blood with approximately 1.0 × 10⁶ trypomastigotes of T. vivax. The viability and motile of trypomastigotes after 30 s, one, 10, 15 and 30 min was evaluated by the thick drop method and the efficacy calculated. Disinfectants that showed 100% effectiveness were used in in vivo tests. Thirty calves negative for T. vivax were divided into six groups and were inoculated with disinfectant solutions (46% alcohol, 70% alcohol, or 0.5% iodine) + 1 × 10⁶ trypomastigotes of the protozoa. Blood from each animal was collected at seven, 14 and 21 days after inoculation to verify the viability and presence of the protozoan by Woo, Brener, PCR, and LAMP methods. In the in vitro step, 13 of the 21 disinfected solutions exhibited 100% effectiveness against T. vivax at all evaluation times. In contrast, 70% alcohol and 0.5% iodine solutions exhibited 100% effectiveness in the in vivo tests and can be used to disinfect needles and syringes. The use of disinfectants is a rapid and efficient procedure to disinfect materials utilized in the field and concomitantly could help to reduce the dissemination of T. vivax in the cattle herd in cases of iatrogenic transmission.

Follow-up of dairy cattle naturally infected by Trypanosoma vivax after treatment with isometamidium chloride

Trypanosoma vivax infections cause nonspecific clinical signs in cattle associated with aparasitemic intervals, making disease diagnosis a challenge. In Brazil, diminazene aceturate and isometamidium chloride (ISM) are available to treat bovine trypanosomosis. The objective of this study was to follow-up, by molecular and serological techniques, dairy cattle naturally infected by T. vivax after ISM treatment. Thirty cattle naturally infected with T. vivax received two applications of ISM, at a dosage of 1.0 mg/kg intramuscularly, on days 0 and 150. For T. vivax diagnosis, EDTA-blood and serum samples were evaluated on 0, 7, 15, 30, 60, 90, 120, 150, 180, 210, and 240 days after treatment PCR, Loop-mediated isothermal amplification (LAMP) and ELISA. Animals with persistent detection of T. vivax DNA by both PCR and LAMP were found and continuous detection of anti-T. vivax IgG antibodies by ELISA, suggesting the presence of T. vivax resistance to ISM. The combination of LAMP and ELISA tests can prevent misdiagnosis of the parasite clearance in treated cattle, contributing to better disease control. This is the first experiment that demonstrates the persistence infection of T. vivax under ISM treatment in a natural infected herd and evidence of ISM chemotherapy-resistant T. vivax in Brazil.

Spermatic profile of captive giant anteaters (Myrmecophaga tridactyla): Knowing more to preserve better

The giant anteater (Myrmecophaga tridactyla) is being threatened by natural habitat destruction and fragmentation, illegal hunting and road kills. In this context, the generation of basic information on the reproductive parameters of this species is vital, aiming to improve reproductive management via, amongst others, assisted reproductive technologies. This study aimed to describe the morphological and functional features of semen collected from captive giant anteaters. Electroejaculation was performed in 13 animals housed in zoos located in São Paulo state, Brazil. Semen samples were collected from 13 animals in 16 procedures. Samples were evaluated for volume, motility, vigor, pH, concentration, sperm morphology, and functional tests. The following mean values were obtained: volume 1.28 ± 0.27 mL; motility 28.3 ± 6.2%; vigor 2.4 ± 0.25; concentration 129.4 ± 36.1 × 10⁶ sperm/mL; pH 7.4 ± 0.2. Total acrosome, head, midpiece, and tail sperm abnormalities were 3.2 ± 0.8%, 25.4 ± 3.6%, 20.7 ± 3.2%, and 14.7 ± 2.6%, respectively. Intact acrosome was found in 83.7 ± 3.1% and intact membrane in 81.1 ± 4.0% of all samples collected. Mitochondrial activity was 66.4 ± 6.0% (Class I), 18.7 ± 2.9% (Class II), 8.0 ± 2.0% (Class III), 3.9 ± 1.0% (Class IV), and 3.0 ± 0.9% (Class V). Sperm DNA fragmentation rate was 13.2 ± 3.7%. These results indicated that electroejaculation is a feasible method for semen collection in giant anteaters, allowing a more detailed description of the semen in this species.

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

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

Achilles heel of a powerful invader: restrictions on distribution and disappearance of feral pigs from a protected area in Northern Pantanal, Western Brazil

This paper focuses on a rare case of natural disappearance of feral pigs (Sus scrofa) in an extensive area without using traditional methods of eradication programs. The study was conducted both in the Private Reserve of Natural Heritage (PRNH) Sesc Pantanal and in an adjacent traditional private cattle ranch. In 1998, feral pigs were abundant and widely distributed in the PRNH. However, the feral pigs gradually disappeared from the area and currently, the absence of pigs in the PRNH contrasts with the adjacent cattle ranch where the species is abundant. To understand the current distribution of the species in the region we partitioned the effects of variation of feral pigs' presence considering the habitat structure (local), landscape composition and the occurrence of potential predators. Additionally, we modeled the distributions of the species in Northern Pantanal, projecting into the past using the classes of vegetation cover before the PRNH implementation (year 1988). Our results show areas with more suitability for feral pigs in regions where the landscape is dominated by pastures and permeated by patches of Seasonal Dry Forest. The species tends to avoid predominantly forested areas. Additionally, we recorded that the environmental suitability decreases exponentially as the distance from water bodies increases. The disappearance of feral pigs in the PRNH area seems to be associated with changes in the landscape and vegetation structure after the removal of the cattle. In the Brazilian Pantanal, the feral pigs' occurrence seems strongly conditioned to environmental changes associated to livestock activity.

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.

Acute phase proteins: a potential approach for diagnosing chronic infection by Trypanosoma vivax

The present study aimed to assess potential changes in acute phase proteins in sheep experimentally infected with Trypanosoma vivax. There were studied eight male sheep, four used as controls and four infected with 10(5) T. vivax trypomastigotes. Blood samples were collected at two points times before infection and then at 5,7, 9, 11, 13, 15, 20, 30, 45, 60, 75, 90, 105 and 120 days post-infection (dpi). Blood samples were centrifuged and allotted, and acute phase proteins were then separated by electrophoresis on acrylamide gel containing sodium dodecyl sulfate. Protein concentrations were determined by computer-assisted densitometry. Total protein was determined by colorimetric biuret method. Trypanosomes were counted daily using a 5 mL aliquot of blood smear on a glass slide under a 22 × 22 mm coverslip. Parasites were counted in 100 microscopic fields (40× magnification), and then multiplied by a correction factor. The results were expressed as parasites per mL of blood. For statistical analyses, we used the Wilcoxon test at 5% significance level. There was found a reduction in several acute phase proteins and increase in antitrypsin and transferrin. This finding can be used for the diagnosis of T. vivax infection, especially in chronic infection.

Trypanosoma (Duttonella) vivax: its biology, epidemiology, pathogenesis, and introduction in the New World--a review

The biology, epidemiology, pathogenesis, diagnostic techniques, and history of the introduction of Trypanosoma (Duttonella) vivax in the New World are reviewed. The two main immunological responses of trypanosome-infected animals - antibody production and immunodepression - are discussed in the context of how these responses play a role in disease tolerance or susceptibility. Isolation and purification of T. vivax are briefly discussed. The recent reports of bovine trypanosomiasis diagnosed in cattle on farms located in the Pantanal region of the states of Mato Grosso do Sul and Mato Grosso, Brazil, are also discussed.

The development of an enzyme-linked immunosorbent assay for Trypanosoma vivax antibodies and its use in epidemiological surveys

There are data indicating that the distribution of Trypanosoma vivax in the Brazilian territory is expanding with potential to reach other areas, where the vectors are present. The detection of anti-trypanosomal antibodies in serum provides important information of the trypanosomal status in cattle herds. For this reason, an enzyme-linked immunosorbent assay (Tv-ELISA-Ab) with crude antigen from one Brazilian isolate of T. vivax was developed and evaluated. The sensitivity and specificity were respectively 97.6 and 96.9%. In the evaluation of cross-reactions, three calves inoculated with T. evansi trypimastigotes blood forms showed optical densities (OD) under the cut-off during the whole experimental period, except one at 45 days post-inoculation. With relation to Babesia bovis, B. bigemina, and Anaplasma marginale, which are endemic hemoparasites in the studied area, the cross-reactions were shown to be 5.7, 5.3, and 1.1%, respectively. The first serological survey of Pantanal and state of Pará showed that T. vivax is widespread, although regions within both areas had significantly different prevalences. Therefore, this Tv-ELISA-Ab may be a more appropriate test for epidemiological studies in developing countries because the diagnostic laboratories in most countries may be able to perform an ELISA, which is not true for polymerase chain reaction.

Trypanosoma vivax: A novel method for purification from experimentally infected sheep blood

Trypanosoma vivax is the principal etiological agent of bovine trypanosomosis, a widely disseminated disease in tropical and subtropical regions. Here, we present a simple and reproducible method for the purification of T. vivax from experimentally infected and immunosuppressed sheep, using an isopycnic Percoll gradient, followed by DEAE-cellulose chromatography, with an estimated yield of 11-15%. This method could be used for the purification of T. vivax geographical isolates from various locations and from different natural hosts.

Exploring the Genome of Trypanosoma vivax through GSS and In Silico Comparative Analysis

A survey of the Trypanosoma vivax genome was carried out by the genome sequence survey (GSS) approach resulting in 1,086 genomic sequences. A total of 455 high-quality GSS sequences were generated, consisting of 331 non-redundant sequences distributed in 264 singlets and 67 clusters in a total of 135.5 Kb of the T. vivax genome. The estimation of the overall G+C content, and the prediction of the presence of ORFs and putative genes were carried out using the Glimmer and Jemboss packages. Analysis of the obtained sequences was carried out by BLAST programs against 12 different databases and also using the Conserved Domain Database, InterProScan, and tRNAscan-SE. Along with the existing 23 T. vivax entries in the GenBank, the 32 putative genes predicted and the 331 non-redundant GSS sequences reported herein represent new potential markers for the development of PCRbased assays for specific diagnosis and typing of Trypanosoma vivax.

Animal trypanosomiasis in South America. Current status, partnership, and information technology

Animal trypanosome species of economical importance in South America include T. vivax and T. evansi. Both species are described in Brazil, Bolivia, Colombia, French Guyana, Peru, Suriname, and Venezuela. In Argentina and Guyana, only T. evansi and T. vivax are found, respectively. Our studies on T. vivax indicated that the parasite was spreading around 1.3 km per day in Bolivia. We found severe leukopenia in bovines from Pantanal (Brazil) and the Department of Santa Cruz (Bolivia). Because it can cause immunosuppression, the importance of trypanosomiasis control in ensuring success of vaccination campaigns against foot and mouth disease (FMD) in the Pantanal and Bolivia should be considered. The use of one needle for several animals during FMD campaigns in Brazil and Bolivia could also contribute to the spread of T. vivax. The anticipated losses due to T. vivax could exceed $160 million, assuming there are 11 million head of cattle in the Brazilian Pantanal and Bolivian lowlands. International collaboration among research institutes is needed to deal with these diseases and parasites. Previous efforts using information technologies resulted in the creation of two discussion lists (Tryplink and Trypan), the edition of the on-line version of Trypnews and Internet conferences.

Trypanosoma vivax--out of Africa

Trypanosoma vivax is a blood parasite of ruminants that was introduced into Latin America in cattle imported from Africa, possibly in the late 19th century. The parasite has now spread to ten of the 13 countries of the South American continent, often resulting in a severe wasting disease and death. Here, we review the current state of knowledge about this parasite and the problems faced by animal health agencies in controlling the disease.