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

Reproductive, productive and financial consequences of chronic Trypanosoma vivax infection in a dairy cattle herd in a region without a cyclic vector

This study evaluated the reproductive, productive and financial consequences of chronic Trypanosoma vivax infection in a dairy cattle herd located in a region without the cyclic vector during two years. Animals were categorized as either positive (chronically infected) or negative for T. vivax antibodies using a commercial rapid test. Additionally, serum samples from cows were analyzed for the presence of anti-Neospora caninum antibodies. Pregnancy diagnoses were performed through rectal palpation and ultrasonography after 30, 60 and every 21 days until the 144th day of pregnancy. If an abortion occurred in the final trimester, serology and cPCR were performed on calves for T. vivax and N. caninum. The breeding period, calving interval and pregnancy losses were recorded. The milk production of each animal during the 305 days of lactation was measured, and the annual financial impact of milk production was calculated using a revenue minus feed cost (RMFC) indicator. Out of 177 cows, 71.75 % were chronically infected, and 13.50 % were T. vivax-negative. No correlation (p = 0.8854) of co-infection between T. vivax and N. caninum was observed. Negative cows required fewer (p≤0.05) artificial inseminations than chronically infected ones. T. vivax was not significantly associated (p = 0.7893) with pregnancy loss up to 81 days of pregnancy. Cows chronically infected by T. vivax had 4-fold greater chance (p = 0.0280) of experiencing pregnancy loss between 82 and 144 days of gestation. Eighteen cows aborted, two were positive for T. vivax antibodies, and one for N. caninum antibodies. The calves were negative for T. vivax and N. caninum. Chronically infected cows and negative cows for T. vivax that experienced pregnancy loss (82-144 days of pregnancy) had a longer (p≤0.05) breeding period to become pregnant, and consequently a longer calving interval compared to cows that maintained pregnancy. The difference (p≤0.05) in milk production was evident when pregnancy loss occurred between 82 and 144 days of gestation in cows chronically infected by T. vivax. The RMFC indicated a negative impact of 38.2 % on the farm's annual milk revenue due to the presence of chronically infected cows.

Pathogenicity and virulence of African trypanosomes: From laboratory models to clinically relevant hosts

African trypanosomes are vector-borne protozoa, which cause significant human and animal disease across sub-Saharan Africa, and animal disease across Asia and South America. In humans, infection is caused by variants of Trypanosoma brucei, and is characterized by varying rate of progression to neurological disease, caused by parasites exiting the vasculature and entering the brain. Animal disease is caused by multiple species of trypanosome, primarily T. congolense, T. vivax, and T. brucei. These trypanosomes also infect multiple species of mammalian host, and this complexity of trypanosome and host diversity is reflected in the spectrum of severity of disease in animal trypanosomiasis, ranging from hyperacute infections associated with mortality to long-term chronic infections, and is also a main reason why designing interventions for animal trypanosomiasis is so challenging. In this review, we will provide an overview of the current understanding of trypanosome determinants of infection progression and severity, covering laboratory models of disease, as well as human and livestock disease. We will also highlight gaps in knowledge and capabilities, which represent opportunities to both further our fundamental understanding of how trypanosomes cause disease, as well as facilitating the development of the novel interventions that are so badly needed to reduce the burden of disease caused by these important pathogens.

Nucleoside analogues for the treatment of animal trypanosomiasis

Animal trypanosomiasis (AT) is a parasitic disease with high socio-economic impact. Given the limited therapeutic options and problems of toxicity and drug resistance, this study assessed redirecting our previously identified antitrypanosomal nucleosides for the treatment of AT. Promising hits were identified with excellent in vitro activity across all important animal trypanosome species. Compound 7, an inosine analogue, and our previously described lead compound, 3'-deoxytubercidin (8), showed broad spectrum anti-AT activity, metabolic stability in the target host species and absence of toxicity, but with variable efficacy ranging from limited activity to full cure in mouse models of Trypanosoma congolense and T. vivax infection. Several compounds show promise against T. evansi (surra) and T. equiperdum (dourine). Given the preferred target product profile for a broad-spectrum compound against AT, this study emphasizes the need to include T. vivax in the screening cascade given its divergent susceptibility profile and provides a basis for lead optimization towards such broad spectrum anti-AT compound.

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

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

A Preliminary Study on the Relationship between Parasitaemia and Cytokine Expression of Peripheral Blood Cells in Trypanosoma vivax-Experimentally Infected Cattle

Simple Summary

Infections by Trypanosoma vivax in livestock have been reported with increasing frequency worldwide. Nevertheless, information regarding the immune response during the infection is scarce. Regarding that, cytokines play an important role as inflammation modulators, influencing the outcome of trypanosomosis. This study aimed to evaluate host cytokine production during T. vivax infection, in order to assess the increase or decrease of selected cytokines with the cattle’s ability to control the infection. While animals that showed an increase in IL-6 and IFNγ managed T. vivax parasitaemia satisfactorily, cattle that showed reduction of IL-1β, IL-2 and TNFα did not control the parasite multiplication. The presented results are preliminary and shed some light on the role of cytokines during T. vivax-infection.

Abstract

Trypanosoma vivax outbreaks have been reported with increasing frequency worldwide, causing significant economic losses in livestock. Though several studies have suggested that cytokine responses may influence infection caused by Trypanosoma sp., their exact role remains unclear and may vary according to the animal species and parasite strain. The present study aimed to evaluate cytokine expression of peripheral blood cells from three Girolando dairy cows experimentally infected with T. vivax. For this purpose, blood samples were collected prior to the inoculation on the day of inoculation (D0), the day after inoculation (D1), and then every seven days up to 119 days after infection (DAI). Each animal presented a unique pattern of cytokine expression. While a tendency of a Th1 cytokine response was observed during the patent phase (presence of circulating parasites), an increase of Th2 cytokine expression was found at the beginning of the sub-patent phase (low parasitaemia or aparasitaemic periods). In animals that presented a better control of parasitaemia, IL-6 and IFNγ increased during most of the trial period. On the other hand, the cow that presented reduction of IL-1β, IL-2, and TNFα during the entire period did not control parasitaemia properly. A balance between the Th1 and Th2 profile is beneficial for parasite control and animal health. The results found in the present study are a first step towards elucidating the dynamics of cattle’s inflammatory response against T. vivax, requiring future studies focusing on the role of key cytokines on the controlling of parasitaemia in different stages of bovine trypanosomosis.

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.

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.

High Trypanosoma vivax infection rates in water buffalo and cattle in the Brazilian Lower Amazon

Highly sensitive and accurate molecular diagnostic methods have not yet been employed for livestock trypanosomosis in the Brazilian Lower Amazon although the first reports of Trypanosoma vivax and Trypanosoma evansi in Brazil were in water buffalo (Bubalus bubalis) in this region. The present study assessed trypanosomosis in buffalo and cattle raised in communal and seasonally flooding pastures in the state of Pará using the fluorescent fragment length barcoding (FFLB) method. T. evansi was not detected, but high infection rates of T. vivax and T. theileri were revealed by a simplified FFLB standardized in the present study that discriminates all trypanosome species infective to livestock in South America. T. vivax infection rates detected by TviCATL-PCR were 24.6% for cattle (n = 61) and 28.1% for buffalo (n = 89). Using the FFLB method, overall T. vivax infection rates increased to 59.6% and 44.3% for buffalo and cattle, respectively. Furthermore, the predominance of a single microsatellite-based genotype of T. vivax was reinforced in the Lower Amazon. Relevant T. vivax infection rates detected in clinically healthy buffalo and cattle through the sampled years (2008-2017) highlight the need for systematic studies to demonstrate the endemic steady state of T. vivax in this region. Our findings provide baseline information for livestock management, including control of T. vivax dispersal, and the introduction of naïve animals. The growing international trade of live livestock from this very important livestock breeding region represents a serious risk for T. vivax spreading outside Amazonia and Brazil.

Comparison of conventional and molecular techniques for Trypanosoma vivax diagnosis in experimentally infected cattle

Livestock infections by Trypanosoma vivax have been occurring with increasing frequency, mainly due to the presence of animals with subclinical infections and without apparent parasitaemia, making diagnosis challenging. The aim of the present study was to evaluate several techniques used for T. vivax diagnosis in order to assess the best way of using them during the course of the disease. Molecular methods demonstrated higher rates of detection than parasitological methods, detecting 33 of the 54 (61.1%) known positive samples, while the hematocrit centrifugation technique (best parasitological test) detected only 44.4%. The serological methods, IFAT and ELISA, detected seropositivity in 51 of the 54 (94.4%) and 49 of the 54 (90.7%) known positive samples, respectively. Despite being highly sensitive, the latter only demonstrates exposure to the infectious agent and does not indicate whether the infection is active. The present study was the first to use the qPCR for a South American isolate, improving disease detection and quantification. Furthermore, the analyses revealed that the patent phase of the disease may extend up to 42 days, longer than previously reported. The combination of several diagnostic techniques can lower the frequency of false negative results and contributes toward better disease control.

A comparative in silico linear B-cell epitope prediction and characterization for South American and African Trypanosoma vivax strains

Trypanosoma vivax is a parasite widespread across Africa and South America. Immunological methods using recombinant antigens have been developed aiming at specific and sensitive detection of infections caused by T. vivax. Here, we sequenced for the first time the transcriptome of a virulent T. vivax strain (Lins), isolated from an outbreak of severe disease in South America (Brazil) and performed a computational integrated analysis of genome, transcriptome and in silico predictions to identify and characterize putative linear B-cell epitopes from African and South American T. vivax. A total of 2278, 3936 and 4062 linear B-cell epitopes were respectively characterized for the transcriptomes of T. vivax LIEM-176 (Venezuela), T. vivax IL1392 (Nigeria) and T. vivax Lins (Brazil) and 4684 for the genome of T. vivax Y486 (Nigeria). The results presented are a valuable theoretical source that may pave the way for highly sensitive and specific diagnostic tools.

Spatial-temporal and phylogeographic characterization of Trypanosoma spp. in cattle (Bos taurus) and buffaloes (Bubalus bubalis) reveals transmission dynamics of these parasites in Colombia

Animal Trypanosomiasis (AT) is one of the most important problems in the Colombian livestock industry reducing its production around 30%. Caribbean and Orinoquia regions play a significant role in the development of this industry, having about 6.9 million cattle and 113,000 buffaloes. Considering the paucity in studies to understand the epidemiological features and control of AT in Colombia, the present study reports the seasonal transmission patterns and phylogeographic traits of the causal agents of AT in cattle and buffaloes from these regions. Between 2014 and 2016, a three-point longitudinal survey was designed to evaluate the mentioned characteristics. Molecular analysis in cattle showed an AT prevalence of 39.2% (T. theileri 38.6%, T. evansi 6.7% and T. vivax 0.2%), with higher values during wet and late wet seasons, while in buffaloes the prevalence was 28.2% (T. theileri 28.2% and T. evansi 1.3%), with higher values during the dry season. Additionally, variables such as tabanid abundance, vector control, breeding system, age and anemia signs were significantly associated with AT prevalence (P<0.05). Only T. theileri infection was higher in cattle with anemia signs than those with normal packed cell volume. Finally, phylogeographic analysis revealed that Colombian T. theileri isolates were associated to specific host genotypes IA and IIB, described worldwide; T. vivax isolates were related to the genotype from West Africa; while T. evansi isolates are related to the South American genotypes and to new genotypes. This is the first longitudinal survey that evaluates through molecular methods, the infection of Trypanosoma spp. in two important livestock regions from Colombia, showing that the clinical effects and prevalence of these trypanosomes in cattle and buffaloes are modulated by seasonal variations, host factors, and parasite traits. The results suggest that these factors have to be taken into account to successfully control AT in these regions.

New insights from Gorongosa National Park and Niassa National Reserve of Mozambique increasing the genetic diversity of Trypanosoma vivax and Trypanosoma vivax-like in tsetse flies, wild ungulates and livestock from East Africa

BACKGROUND

Trypanosoma (Duttonella) vivax is a major pathogen of livestock in Africa and South America (SA), and genetic studies limited to small sampling suggest greater diversity in East Africa (EA) compared to both West Africa (WA) and SA.

METHODS

Multidimensional scaling and phylogenetic analyses of 112 sequences of the glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) gene and 263 sequences of the internal transcribed spacer of rDNA (ITS rDNA) were performed to compare trypanosomes from tsetse flies from Gorongosa National Park and Niassa National Reserve of Mozambique (MZ), wild ungulates and livestock from EA, and livestock isolates from WA and SA.

RESULTS

Multidimensional scaling (MDS) supported Tvv (T. vivax) and TvL (T. vivax-like) evolutionary lineages: 1) Tvv comprises two main groups, TvvA/B (all SA and WA isolates plus some isolates from EA) and TvvC/D (exclusively from EA). The network revealed five ITS-genotypes within Tvv: Tvv1 (WA/EA isolates), Tvv2 (SA) and Tvv3-5 (EA). EA genotypes of Tvv ranged from highly related to largely different from WA/SA genotypes. 2) TvL comprises two gGAPDH-groups formed exclusively by EA sequences, TvLA (Tanzania/Kenya) and TvLB-D (MZ). This lineage contains more than 11 ITS-genotypes, seven forming the lineage TvL-Gorongosa that diverged from T. vivax Y486 enough to be identified as another species of the subgenus Duttonella. While gGAPDH sequences were fundamental for classification at the subgenus, major evolutionary lineages and species levels, ITS rDNA sequences permitted identification of known and novel genotypes.

CONCLUSIONS

Our results corroborate a remarkable diversity of Duttonella trypanosomes in EA, especially in wildlife conservation areas, compared to the moderate diversity in WA. Surveys in wilderness areas in WA may reveal greater diversity. Biogeographical and phylogenetic data point to EA as the place of origin, diversification and spread of Duttonella trypanosomes across Africa, providing relevant insights towards the understanding of T. vivax evolutionary history.

Remarkable richness of trypanosomes in tsetse flies (Glossina morsitans morsitans and Glossina pallidipes) from the Gorongosa National Park and Niassa National Reserve of Mozambique revealed by fluorescent fragment length barcoding (FFLB)

Trypanosomes of African wild ungulates transmitted by tsetse flies can cause human and livestock diseases. However, trypanosome diversity in wild tsetse flies remains greatly underestimated. We employed FFLB (fluorescent fragment length barcoding) for surveys of trypanosomes in tsetse flies (3086) from the Gorongosa National Park (GNP) and Niassa National Reserve (NNR) in Mozambique (MZ), identified as Glossina morsitans morsitans (GNP/NNR=77.6%/90.5%) and Glossina pallidipes (22.4%/9.5%). Trypanosomes were microscopically detected in 8.3% of tsetse guts. FFLB of gut samples revealed (GNP/NNR): Trypanosoma congolense of Savannah (27%/63%), Kilifi (16.7%/29.7%) and Forest (1.0%/0.3%) genetic groups; T. simiae Tsavo (36.5%/6.1%); T. simiae (22.2%/17.7%); T. godfreyi (18.2%/7.0%); subgenus Trypanozoon (20.2%/25.7%); T. vivax/T. vivax-like (1.5%/5.2%); T. suis/T. suis-like (9.4%/11.9%). Tsetse proboscises exhibited similar species composition, but most prevalent species were (GNP/NNR): T. simiae (21.9%/28%), T. b. brucei (19.2%/31.7%), and T. vivax/T. vivax-like (19.2%/28.6%). Flies harboring mixtures of trypanosomes were common (~ 64%), and combinations of more than four trypanosomes were especially abundant in the pristine NNR. The non-pathogenic T. theileri was found in 2.5% while FFLB profiles of unknown species were detected in 19% of flies examined. This is the first report on molecular diversity of tsetse flies and their trypanosomes in MZ; all trypanosomes pathogenic for ungulates were detected, but no human pathogens were detected. Overall, two species of tsetse flies harbor 12 species/genotypes of trypanosomes. This notable species richness was likely uncovered because flies were captured in wildlife reserves and surveyed using the method of FFLB able to identify, with high sensitivity and accuracy, known and novel trypanosomes. Our findings importantly improve the knowledge on trypanosome diversity in tsetse flies, revealed the greatest species richness so far reported in tsetse fly of any African country, and indicate the existence of a hidden trypanosome diversity to be discovered in African wildlife protected areas.

Genetic diversity among Trypanosoma vivax strains detected in naturally infected cattle in Nigeria based on ITS1 of rDNA and diagnostic antigen gene sequences

Trypanosoma vivax (sub-genus Duttonella) is largely responsible for non profitable livestock production in sub-Sahara Africa. In Nigeria, no study has addressed the molecular characteristic of T. vivax except Y486. Hence, we characterized and assessed the genetic diversity among T. vivax detected in naturally infected cattle in Nigeria using internal transcribed spacer 1 (ITS1) of ribosoma DNA (rDNA) and diagnostic antigen gene (DAG) sequences. The length of ITS1 and DAG sequences range from 215-220 to 257-338 bp, respectively and the mean G-C contents were 60 and 61.5 %. Homology search revealed 93-99 and 95-100 % homologies to T. vivax DAG and ITS1 sequences from GenBank. Aligned sequences revealed both ITS1 rDNA and DAG to be less polymorphic but DAG sequences of the Y486 strain and its clone showed marked variation from autochthonous strains. Phylogenetic analysis yielded tree that grouped T. vivax ITS1rDNA gene and DAG sequences into two main clades each. Considering the ITI1 rDNA sequences, clade A contained autochthonous T. vivax within which the South American sequences clustered, clade B contained the sequences of T. vivax from East Africa. Analysis of DAG revealed that the clade A contains autochthonous T. vivax sequences but clade B contained the Y486 and its clones. In conclusion, the diagnostic antigen gene sequences of the T. vivax detected in this study may have undergone considerable gene recombination through time and suggests that more than one strain of T. vivax exist among cattle population in Nigeria.

Trypanosoma vivax in water buffalo of the Venezuelan Llanos: An unusual outbreak of wasting disease in an endemic area of typically asymptomatic infections

Trypanosoma vivax has been associated with asymptomatic infections in African and South American buffalo. In this study, T. vivax was analyzed in water buffalo (Bubalus bubalis) from Venezuela in a molecular survey involving 293 blood samples collected from 2006 to 2015 across the Llanos region. Results demonstrated constant infections (average 23%) during the years analyzed. In general, animals were healthy carriers of T. vivax with low levels of parasitemia and were diagnosed exclusively by TviCATL-PCR. However, an outbreak of severe acute infections mostly in dairy animals was reported during a prolonged drought affecting 30.4% of a buffalo herd (115 animals examined). During the outbreak, animals exhibiting anemia and neurological disorders developed fatal infections, and 7% of the herd died within nine months before treatment against trypanosomosis. Microsatellite locus genotyping (MLG) of T. vivax samples before and during the outbreak revealed similar genotypes, but outbreak isolates exhibited the most divergent MLG. Venezuelan samples from symptomless and sick buffalo did not share the MLGs previously detected in asymptomatic Brazilian buffalo. Trypanosoma evansi was not detected in the herd examined during the outbreak. However, as expected Babesia sp. (62.6%) and Anaplasma sp. (55.6%) infections were highly prevalent in asymptomatic buffalo in the studied areas. This is the first South American outbreak of highly lethal acute T. vivax infections in water buffalo. Our results suggest that chronically infected and asymptomatic buffalo living in areas of enzootic equilibrium can develop symptomatic/lethal disease triggered by stressful scarcity of green forage and water during long droughts, inappropriate management of herds and likely concomitant anaplasmosis and babesiosis. Altogether, these factors weaken buffalo immune defenses, allowing T. vivax to proliferate and, consequently, allowing for progression to wasting disease.

Evaluation of clinical signs, parasitemia, hematologic and biochemical changes in cattle experimentally infected with Trypanosoma vivax

Abstract Infections by Trypanosoma vivax cause great losses to livestock in Africa and Central and South Americas. Outbreaks due this parasite have been occurred with increasing frequency in Brazil. Knowledge of changes caused byT. vivax during the course of this disease can be of great diagnostic value. Thus, clinical signs, parasitemia, hematologic and biochemical changes of cattle experimentally infected by this hemoparasite were evaluated. Two distinct phases were verified during the infection – an acute phase where circulating parasites were seen and then a chronic phase where fluctuations in parasitemia were detected including aparasitemic periods. A constant reduction in erythrocytes, hemoglobin and packed cell volume (PVC) were observed. White blood cells (WBC) showed pronounced changes such as severe neutropenia and lymphopenia during the acute phase of the illness. Decreases in cholesterol, albumin, aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and increases in glucose, globulin, protein, and alkaline phosphatase (ALP) were observed. The “Lins” isolate of T. vivax showed pathogenicity for cattle, and intense parasitemia was detected in the early stages of infection. Circulating parasites were detected for about two months. The most evident laboratory abnormalities were found in WBC parameters, including thrombocytopenia.

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.

Population Genetics and Reproductive Strategies of African Trypanosomes: Revisiting Available Published Data

Trypanosomatidae are a dangerous family of Euglenobionta parasites that threaten the health and economy of millions of people around the world. More precisely describing the population biology and reproductive mode of such pests is not only a matter of pure science, but can also be useful for understanding parasite adaptation, as well as how parasitism, specialization (parasite specificity), and complex life cycles evolve over time. Studying this parasite’s reproductive strategies and population structure can also contribute key information to the understanding of the epidemiology of associated diseases; it can also provide clues for elaborating control programs and predicting the probability of success for control campaigns (such as vaccines and drug therapies), along with emergence or re-emergence risks. Population genetics tools, if appropriately used, can provide precise and useful information in these investigations. In this paper, we revisit recent data collected during population genetics surveys of different Trypanosoma species in sub-Saharan Africa. Reproductive modes and population structure depend not only on the taxon but also on the geographical location and data quality (absence or presence of DNA amplification failures). We conclude on issues regarding future directions of research, in particular vis-à-vis genotyping and sampling strategies, which are still relevant yet, too often, neglected issues.

Kinetoplast adaptations in American strains from Trypanosoma vivax

The mitochondrion role changes during the digenetic life cycle of African trypanosomes. Owing to the low abundance of glucose in the insect vector (tsetse flies) the parasites are dependent upon a fully functional mitochondrion, capable of performing oxidative phosphorylation. Nevertheless, inside the mammalian host (bloodstream forms), which is rich in nutrients, parasite proliferation relies on glycolysis, and the mitochondrion is partially redundant. In this work we perform a comparative study of the mitochondrial genome (kinetoplast) in different strains of Trypanosoma vivax. The comparison was conducted between a West African strain that goes through a complete life cycle and two American strains that are mechanically transmitted (by different vectors) and remain as bloodstream forms only. It was found that while the African strain has a complete and apparently fully functional kinetoplast, the American T. vivax strains have undergone a drastic process of mitochondrial genome degradation, in spite of the recent introduction of these parasites in America. Many of their genes exhibit different types of mutations that are disruptive of function such as major deletions, frameshift causing indels and missense mutations. Moreover, all but three genes (A6-ATPase, RPS12 and MURF2) are not edited in the American strains, whereas editing takes place normally in all (editable) genes from the African strain. Two of these genes, A6-ATPase and RPS12, are known to play an essential function during bloodstream stage. Analysis of the minicircle population shows that its diversity has been greatly reduced, remaining mostly those minicircles that carry guide RNAs necessary for the editing of A6-ATPase and RPS12. The fact that these two genes remain functioning normally, as opposed to that reported in Trypanosoma brucei-like trypanosomes that restrict their life cycle to the bloodstream forms, along with other differences, is indicative that the American T. vivax strains are following a novel evolutionary pathway.

Variant surface glycoproteins from Venezuelan trypanosome isolates are recognized by sera from animals infected with either Trypanosoma evansi or Trypanosoma vivax

•

Soluble forms of VSGs from seven Venezuelan animal trypanosomes were purified and characterized.

•

All purified soluble VSGs exhibited cross-reactivity with Trypanosoma vivax.

•

Anti-VSG antibodies behaved as markers of infection for non-tsetse transmitted trypanosomes.

•

All purified soluble VSGs can be used as diagnostic reagents for bovine trypanosomosis.

Salivarian trypanosomes sequentially express only one variant surface glycoprotein (VSG) on their cell surface from a large repertoire of VSG genes. Seven cryopreserved animal trypanosome isolates known as TeAp-ElFrio01, TEVA1 (or TeAp-N/D1), TeGu-N/D1, TeAp-Mantecal01, TeGu-TerecayTrino, TeGu-Terecay03 and TeGu-Terecay323, which had been isolated from different hosts identified in several geographical areas of Venezuela were expanded using adult albino rats. Soluble forms of predominant VSGs expressed during the early infection stages were purified and corresponded to concanavalin A-binding proteins with molecular masses of 48–67 kDa by sodium dodecyl sulfate-polyacrylamide gel electropohoresis, and pI values between 6.1 and 7.5. The biochemical characterization of all purified soluble VSGs revealed that they were dimers in their native form and represented different gene products. Sequencing of some of these proteins yielded peptides homologous to VSGs from Trypanosoma (Trypanozoon) brucei and Trypanosoma (Trypanozoon) evansi and established that they most likely are mosaics generated by homologous recombination. Western blot analysis showed that all purified VSGs were cross-reacting antigens that were recognized by sera from animals infected with either T. evansi or Trypanosoma (Dutonella) vivax. The VSG glycosyl-phosphatidylinositol cross-reacting determinant epitope was only partially responsible for the cross-reactivity of the purified proteins, and antibodies appeared to recognize cross-reacting conformational epitopes from the various soluble VSGs. ELISA experiments were performed using infected bovine sera collected from cattle in a Venezuelan trypanosome-endemic area. In particular, soluble VSGs from two trypanosome isolates, TeGu-N/D1 and TeGu-TeracayTrino, were recognized by 93.38% and 73.55% of naturally T. vivax-infected bovine sera, respectively. However, approximately 70% of the sera samples did not recognize all seven purified proteins. Hence, the use of a combination of various VSGs for the diagnosis of animal trypanosomosis is recommended.