Evaluation of an Indirect-ELISA Test forTrypanosoma evansiInfection (Surra) in Buffaloes and Its Application to a Serological Survey in Thailand

Abstract

Surra, caused by Trypanosoma evansi, is a neglected disease due to frequent subclinical evolution, especially in bovines in Asia. However, acute and chronic signs are regularly observed, with significant sanitary and economic impacts. In this study, we evaluated and applied an indirect-ELISA test for the detection of anti-T. evansi immunoglobulin G in buffaloes using antibovine conjugate. Based on buffalo reference sera from the Philippines, a two-graph receiver operating characteristics analysis (TG-ROC) was conducted to define an optimal cut-off value; sensitivity and specificity were estimated at 92.5% and 94.2%, respectively. A cross-sectional serological survey was carried out in the major buffalo breeding areas of Thailand; 892 buffaloes from 8 provinces were sampled in North, Northeastern, and Southern Thailand. Seropositive buffaloes were found in all 8 provinces, on 20.3% of farms for an overall prevalence of 12.2% (95% CI 10.2–14.5%). Nearly one-third of the sampled population was exposed to infection. Broader sampling would be necessary but is not possible in the southern half-wild breeding systems. According to our results, buffaloes may constitute a large and robust reservoir for T. evansi, which is a permanent threat to other livestock such as cattle and horses as well as wild animals such as elephants in Southest Asia.

Investigation of Trypanosoma evansi infection in bullfighting cattle in Southern Thailand

“…The current study reported for the first time on the seroprevalence of T. evansi infection in bullfighting cattle. In general, the sensitivity and specificity of indirect-ELISA for trypanosomes are higher than 90% [ 9 ]. Previously, indirect ELISA using crude T. evansi antigen was performed.…”

“…In experimentally infected cattle, indirect ELISA showed satisfactory sensitivity and specificity [ 24 ]. Using the same indirect ELISA protocol, the seroprevalence levels of T. evansi infection in dairy cattle and buffaloes were 11.9% and 12.12%, respectively [ 8 , 9 ]. In comparison, seroprevalence in the current study was higher than in the previous studies, indicating that bullfighting cattle may be exposed to infection.…”

The Indirect ELISA Trypanosoma evansi in Equids: Optimisation and Application to a Serological Survey including Racing Horses, in Thailand

“…The indirect ELISA T. evansi , as described by the OIE [17], has been used in several host species and was already validated for camels, cattle, buffaloes, and elephants in Thailand [12, 14, 15, 18]. The test used in this study was derived from previously published protocols with slight modifications and adaptation to horse samples.…”

“…Therefore, knowledge on the prevalence of T. evansi infection in its various host species is needed to better understand the relative roles of those different hosts in the epidemiology of surra . In recent times, epidemiological surveys of surra have been conducted in Thailand, in cattle, buffaloes and elephants [14, 15, 16]. However, equines have not yet been covered by these studies.…”

“…Based on these considerations, in the present paper, we optimized and applied the antibody ELISA T. evansi to equids in Thailand. This test is an OIE-recommended diagnostic method [17] that has already been used and validated for the detection of surra in camels, cattle, buffaloes, and elephants [12, 14, 15, 18]. We then conducted a nationwide seroprevalence survey in Thai equids, including a large group of racing horses and a group of military donkeys and mules working at the border with Myanmar.…”