Molecular detection of trypanosomes in cattle in South America and genetic diversity of Trypanosoma evansi based on expression-site-associated gene 6

Seroprevalence of trypanosomosis and associated risk factors in cattle from coast and amazonian provinces of Ecuador

Trypanosomosis is a tropical disease caused by various protozoan haemoparasites, which affects wild and domestic animals, the latter ones related to worldwide livestock production systems. Species such as Trypanosoma vivax and Trypanosoma evansi have been described using serological and molecular tools in several countries from South and Central America. However, Ecuador presents a relevant knowledge gap in the associated general epidemiology and risk factors of the disease. Therefore, the objective of this study was to determine the seroprevalence of trypanosomosis in cattle from different regions of Ecuador. 745 serum samples from 7 Coastal and 3 Amazon provinces were screened for IgG anti-Trypanosoma spp. antibodies, using an in-house indirect ELISA. The seropositivity was explored and associated with several variables such as sex, age, breed, region, management, and province, using statistical tools. The general seroprevalence of trypanosomosis was 19.1% (95% CI: 16.30-22.1%). The Amazonian provinces of Sucumbíos and Napo and the Coastal province of Esmeraldas presented the highest seroprevalence values of 36.7% (95% CI: 27.67-46.47%), 23.64% (95% CI: 16.06-32.68%) and 25% (95% CI: 15.99-35.94%), respectively. Statistical significance was found for the region, province, and management variables, indicating as relevant risk factors the extensive management and Amazon location of the cattle analyzed. Specific actions should be taken to identify the exact species on reservoirs and susceptible hosts, evaluate the implication of farm management and cattle movement as risk factors, and implement surveillance and treatment plans for affected herds.

Improved serodiagnosis of Trypanosoma vivax infections in cattle reveals high infection rates in the livestock regions of Argentina

Bovine trypanosomosis, caused by Trypanosoma vivax, currently affects cattle and has a significant economic impact in sub-Saharan Africa and South America. The development of new diagnostic antigens is essential to improve and refine existing methods. Our study evaluated the efficacy of two recombinant antigens in detecting specific antibodies in cattle. These antigens are derivatives of an invariant surface glycoprotein (ISG) from T. vivax. A fraction of a previously described antigen (TvY486_0045500), designated TvISGAf, from an African strain was evaluated, and a new ISG antigen from an American isolate, TvISGAm, was identified. The two antigens were expressed as fusion proteins in Escherichia coli: TvISGAf was fused to the MBP-His-tag, and TvISGAm was obtained as a His-tag fused protein. An ELISA evaluation was conducted using these antigens on 149 positive and 63 negative bovine samples. The diagnostic performance was enhanced by the use of a combination of both antigens (referred to as TvISG-based ELISA), achieving a sensitivity of 89.6% and specificity of 93.8%. Following the validation of the TvISG-based ELISA, the seroprevalence of T. vivax infection in 892 field samples from cattle in the central region of Argentina was determined. The mean seroprevalence of T. vivax was 53%, with variation ranging from 21% to 69% among the six departments studied. These results support the use of the TvISG ELISA as a valuable serological tool for the detection and monitoring of T. vivax infection in cattle. Furthermore, we report for the first time the seroprevalence of T. vivax in Argentina, which highlights the widespread endemic nature of the disease in the region. In order to effectively manage the increasing spread of T. vivax in the vast livestock production areas of South America, it is essential to implement consistent surveillance programs and to adopt preventive strategies.

Molecular detection and internal transcribed spacer-1 sequence diversity of Trypanosoma evansi in goats from Cavite, Philippines

Goat production is an important source of livelihood and food. Goats may serve as reservoir of surra affecting livestock production. Here, forty-two free-roaming goats from Cavite, Philippines were screened using two primer sets, Trypanosoma brucei minisatellite chromosome for initial detection and the internal transcribed spacer 1 (ITS-1) to determine phylogeny. Initial PCR detection showed that 19/42 (45%) goats were positive, much higher than the rate previously reported in goats from Cebu (34%). The infectivity rate was higher in male (56%) than in female (42%) and the rate was higher in young ≤1 year old (100%) than in adult >1 year old (43%). Phylogenetic analysis of the ITS-1 sequences between T. evansi goat samples and other isolates indicate potential interspecies transmission.

Molecular identification and prevalence of trypanosomes in cattle distributed within the Jebba axis of the River Niger, Kwara state, Nigeria

Background

Trypanosomiasis is a fatal disease that threatens the economy of at least 37 countries in sub-Saharan Africa, particularly with regard to livestock farming. In this study, we investigated the prevalence of trypanosome infection in cattle, and molecularly identified the species of trypanosomes in infected cattle and the spatial distribution of trypanosome-infected herds along the Jebba axis of the River Niger.

Methods

A randomized cross-sectional study was conducted along the Jebba axis of the River Niger by screening cattle from 36 herd clusters by nested PCR using ITS-1 generic primers. Data generated were analysed using the Chi-square test at a 95% confidence interval.

Results

Microscopic examination revealed three infected cattle out of 398 examined, representing 0.8% prevalence. Twelve animals (3.0%) were positive by PCR. Our results showed a decline in the packed cell volume of infected animals (24.7%). The infection rates were categorized as single infection in 11/12 (91.7%) and mixed infection in 1/12 (8.3%). Animals were most frequently infected by Trypanosoma congolense (50.0%), with T. congolense Savannah being the most prevalent subspecies (71.4%). Aside from the infection rate by age (10.0%) and relative distance of animals from the River Niger (56.2%), statistical differences in every other parameter tested were based on mere probabilistic chance. Spatial data showed that the disease was prevalent among herds located less than 3 km from the River Niger.

Conclusions

Six species of trypanosomes were identified in cattle herds along the Jebba axis of the River Niger, with T. congolense being the most prevalent. Age and relative distance of herds from the River Niger may be risk factors for trypanosome infection in cattle herds in this area.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05054-0.

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.

Prevalence of Trypanosoma evansi in livestock in Palestine

Background

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

Methods

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

Results

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

Conclusions

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

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Trypanosoma brucei Plimmer & Bradford, 1899 is a synonym of T. evansi (Steel, 1885) according to current knowledge and by application of nomenclature rules

Proper application of the principles of biological nomenclature is fundamental for scientific and technical communication about organisms. As other scientific disciplines, taxonomy inherently is open to change, thus species names cannot be final and immutable. Nevertheless, altering the names of organisms of high economical, medical, or veterinary importance can become a complex challenge between the scientific need to have correct classifications, and the practical ideal of having fixed classifications. Trypanosoma evansi (Steel, 1885), T. brucei Plimmer & Bradford, 1899 and T. equiperdum Doflein, 1901 are important parasites of mammals. According to current knowledge, the three names are synonyms of a single trypanosome species, the valid name of which should be T. evansi by the mandatory application of the Principle of Priority of zoological nomenclature. Subspecies known as T. brucei brucei Plimmer & Bradford, 1899, T. b. gambiense Dutton, 1902 and T. b. rhodesiense Stephens & Fantham, 1910 should be referred to respectively as T. evansi evansi (Steel, 1885), T. e. gambiense and T. e. rhodesiense. The polyphyletic groupings so far known as T. evansi and T. equiperdum should be referred respectively to as surra- and dourine-causing strains of T. e. evansi. Likewise, trypanosomes so far known as T. b. brucei should be referred to as nagana-causing strains of T. e. evansi. Though it modifies the scientific names of flagship human and animal parasites, the amended nomenclature proposed herein should be adopted because it reflects phylogenetic and biological advancements, fixes errors, and is simpler than the existing classificatory system.

The first case report of trypanosomiasis caused by Trypanosoma evansi in Uruguay

Trypanosoma evansi, the causal agent of Surra, is a salivarian African trypanosoma introduced in America during the 15th century. In this study we report the first case of African trypanosomiasis in Uruguay. We describe clinical signs and the evolution of the disease on an Uruguayan Cimarron dog, as well as the isolation and molecular characterization of the Trypanosoma evansi reported strain. This constitutes the first case of Surra in Uruguay, showing the expansion of the parasite to the south of the American continent. Future work is needed to identify the vector and possible reservoirs in order to avoid the spread of the disease. The epidemiological relevance of the findings are discussed.

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.

Intra and inter species genetic variability of transferrin receptor gene regions in Trypanosoma evansi isolates of different livestock and geographical regions of India

Trypanosoma evansi, the aetiological agent of Surra affects a wide range of livestock and wild animals in India. In the present study, we studied intra- and inter species genetic variability in the transferrin receptor encoding gene regions (ESAG6/7 gene region) of T. evansi isolates by cloning, sequencing and phylogenetic study collected from camel, cattle, donkeys and ponies from North-Western and Central India. The nucleotide sequence variation of ESAG6/7 gene region between Indian T. evansi isolates was up to 17.7% and amino acid sequence variation was up to 31%. Twenty nine clones from six T. evansi isolates from geographical regions of India were included into Clade 1, 5, 6, 7 and 9 consisting of ESAG6 variants reported among T. evansi isolates from South-east Asia and South America. The cladogram indicated a relation between the host species and the genetic variability in the hyper-variable region of ESAG6 gene. Analysis of the Indian ESAG6 variants and their respective Clade positions presented a host specific distribution indicating homogenous parasite population in their respective animal hosts.

Molecular diagnosis of cattle trypanosomes in Venezuela: evidences of Trypanosoma evansi and Trypanosoma vivax infections

In South America Trypanosoma evansi has been determined by molecular methods in cattle from Bolivia, Brazil, Colombia and Peru, reason for which the presence of this parasite is not excluded in Venezuelan livestock. Therefore, the aim of this study was to perform parasitological and molecular diagnosis of cattle trypanosomosis in small livestock units from two regions in this country. The parasitological diagnosis was carried out by MHCT and the molecular by PCR using genus-specific ITS1 primers that differentiate T. vivax and T. evansi infections. 47 cattle were evaluated in the "Laguneta de la Montaña" sector, Miranda State, where 3 animals were diagnosed as positive (6.4 %) by MHCT and 14 (30 %) by PCR as Trypanosoma spp., out of which 9 animals resulted positive for T. vivax, 3 for T. evansi and 2 with double infections. Whilst in the "San Casimiro" sector, State of Aragua, out of the 38 cattle evaluated 7 animals were diagnosed as positive (18.4 %) by MHCT and 19 (50 %) by PCR, determining only the presence of T. evansi in this locality. The molecular diagnosis by PCR using ITS1 primers allowed T. evansi detection in cattle field populations, which suggests the possible role of these animals as reservoirs in the epidemiology of the disease caused by T. evansi in Venezuela.

Molecular diagnosis of infections and resistance in veterinary and human parasites

Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal.

Molecular identification and phylogenetic analysis of Trypanosoma evansi from dromedary camels (Camelus dromedarius) in Egypt, a pilot study

Animal trypanosomiasis is one of the major constraints of livestock industry in developing countries. In the present study, prevalence of Trypanosome evansi was assessed in the blood of dromedary camels (Camelus dromedarius) brought to Al Bassatein abattoir, Cairo, Egypt, by mouse inoculation test out of 84 tested camels, 4 animals (4.7%) were infected. Molecular analysis was achieved by PCR amplification and sequence analysis of part of ribosomal RNA gene including 18S, ITS1, 5.8S and ITS2 regions. Despite the conserved nature of 18S region, ITS region showed obvious heterogeneity compared to analogous sequences in database. Analysis of transferrin receptor encoding gene (ESAG6) showed variable repertoire in the studied isolates, which may indicate to a novel structure of T. evansi population from Egypt and/or a difference in host range. Furthermore, analysis of variable surface glycoprotein RoTat 1.2 gene marker revealed some heterogeneity at this gene locus. To our knowledge, this is the first molecular analysis of T. evansi in Egypt.