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

Diagnosis of animal trypanosomoses: proper use of current tools and future prospects

Reliable diagnostic tools are needed to choose the appropriate treatment and proper control measures for animal trypanosomoses, some of which are pathogenic. Trypanosoma cruzi, for example, is responsible for Chagas disease in Latin America. Similarly, pathogenic animal trypanosomoses of African origin (ATAO), including a variety of Trypanosoma species and subspecies, are currently found in Africa, Latin America and Asia. ATAO limit global livestock productivity and impact food security and the welfare of domestic animals. This review focusses on implementing previously reviewed diagnostic methods, in a complex epizootiological scenario, by critically assessing diagnostic results at the individual or herd level. In most cases, a single diagnostic method applied at a given time does not unequivocally identify the various parasitological and disease statuses of a host. These include “non-infected”, “asymptomatic carrier”, “sick infected”, “cured/not cured” and/or “multi-infected”. The diversity of hosts affected by these animal trypanosomoses and their vectors (or other routes of transmission) is such that integrative, diachronic approaches are needed that combine: (i) parasite detection, (ii) DNA, RNA or antigen detection and (iii) antibody detection, along with epizootiological information. The specificity of antibody detection tests is restricted to the genus or subgenus due to cross-reactivity with other Trypanosoma spp. and Trypanosomatidae, but sensitivity is high. The DNA-based methods implemented over the last three decades have yielded higher specificity and sensitivity for active infection detection in hosts and vectors. However, no single diagnostic method can detect all active infections and/or trypanosome species or subspecies. The proposed integrative approach will improve the prevention, surveillance and monitoring of animal trypanosomoses with the available diagnostic tools. However, further developments are required to address specific gaps in diagnostic methods and the sustainable control or elimination of these diseases.

Isolation and in vitro cultivation of Trypanosoma evansi Thai strains

Trypanosoma evansi is a flagellate protozoan parasite responsible for "surra." To generate T. evansi antigens for serodiagnosis, parasites are generally propagated in laboratory animals before isolation. The alternation of animal models using axenic cultivation systems to produce trypomastigotes of various Trypanosoma species is currently available but has never been applied in Thailand. The isolation protocol for separation of live T. evansi trypomastigotes from animal blood components before in vitro cultivation has not been clearly documented. This study focused on validation of trypomastigote isolation method, in vitro cultivation of T. evansi Thai strains, and its virulence ability in vivo. In this study, two strains of T. evansi collected from Thailand were used. Trypanosoma evansi trypomastigotes were propagated in mice, and three different isolation methods, including: low-speed centrifugation, high-speed centrifugation, and ion exchange chromatography using diethylaminoethyl (DEAE) cellulose (or DE52), were compared. Four solutions of in vitro cultivation media, two different in vitro cultivation containers, and different trypomastigote densities for initiation of in vitro culture were compared. Virulence test using in vitro-adapted parasite for 100 days was conducted in vivo. The results showed that the DE52 isolation method was suitable for separation of live T. evansi trypomastigotes from animal blood components before conducting in vitro cultivation. Trypanosoma evansi Thai strains were successfully cultivated and multiplied in HMI-9 Solution I using 25 cm² flasks and 12-well plates. The parasite was growing slowly at the initiation of in vitro culture for 15-16 days, and then rapidly increased to 10, 20, 50, 100, and 200 folds, approximately. The doubling times were varied from 11.95 ± 8 h to 41.18 ± 4.29 h in vitro. The maximum densities have reached from 0.14 × 10⁶ to 4.63 × 10⁶ trypomastigotes/ml. Virulence test showed that the in vitro-cultivated T. evansi was virulent in mice. In conclusion, T. evansi Thai strains were successfully isolated and cultivated in vitro for the first time. The isolation and in vitro cultivation protocols were clearly provided. The benefit of using the in vitro cultivation system helps in the production of T. evansi antigen, and replacing the use of experimental animals. It is also useful for the development of diagnostic tests in the future.

Molecular surveillance of Trypanosoma spp. reveals different clinical and epidemiological characteristics associated with the infection in three creole cattle breeds from Colombia

In South America, Colombia is the third-largest livestock producer with approximately 28.8 million cattle, of which Colombian Creole cattle represent around 1% of the livestock population. Animal Trypanosomiasis (AT) is one of the most critical problems in the livestock industry, reducing its production by about 30 %. Considering the paucity of information to understand the epidemiological features of AT in Colombian Creole cattle, the present study reports the molecular prevalence and clinical traits associated with the infection of Trypanosoma spp. in three Colombian Creole breeds. From 2019 to 2020, cross-sectional surveillance in farms of central and west of Colombia was designed to evaluate the mentioned characteristics in Casanareño, Chino Santandereano, and Sanmartinero Creole breeds. Molecular analysis showed an AT prevalence of 60.2 % (95 % CI = 54.2 % - 66.2 %). The Chino Santandereano population presented the highest value (Trypanosoma spp., 75.2 %, T. theileri 59.6 % and T. evansi 15.6 %), followed by Casanareño (Trypanosoma spp., 65.3 %, T. theileri 38.6 %, T. evansi 24.0 %, and T. vivax 5.3 %) and Sanmartinero (Trypanosoma spp., 33.3 %, T. theileri 24.0 % and T. evansi 9.3 %). Features such as breeds, age, and feeding system were significantly associated with AT prevalence (P <  0.05). Additionally, a low level of serum total proteins was observed during T. evansi infection in Sanmartinero (P <  0.05). To our knowledge, this is the first cross-sectional survey that evaluates using molecular methods the infection of Trypanosoma spp. in Colombian Creole breeds, showing significant variations in the prevalence and clinical signs associated with the infection. These results suggest different degrees of trypanotolerance in these breeds, as well as a possible effect of environmental variables on the prevalence and clinical characteristics associated with the infection. The epidemiological and economic implications of these findings are discussed here.

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.