Sero-diagnosis of surra exploiting recombinant VSG antigen based ELISA for surveillance

- A recombinant VSG of T. evansi (buffalo isolate) was developed.
- The immunoreactivity of the recombinant protein showed that it can be effectively used successfully in the sero-diagnosis and seroprevalence study in control programme of surra.
- The sensitivity and specificity of ELISA using the VSG antigen was determined with a panel of field serum samples.
- Seroprevalence of surra was also carried out in some states of India.

Trypanosoma evansi, a haemoflagellate, causes “surra” an important chronic wasting disease of a wide range of wild and domestic herbivorous and carnivorous animals including cattle, buffaloes, camels, horses, etc. The untreated recovered animal can act as a carrier without exhibiting the disease symptoms and can be a source of infection to healthy animals. The diagnosis and subsequent treatment of the carrier animals is helpful to curb the disease. As the parasitaemia in carrier animals is very scanty, the conventional blood smear examination, which is widely practiced in the field, cannot detect such condition. For this purpose improved diagnostics are very much useful for mass sero-screening test such as ELISA. In the present study, the VSG of T. evansi was expressed in prokaryotic system (E. coli) and thereafter its immunoreactivity has been evaluated in immuno blot and enzyme immuno assay. The expressed protein showed 95.6% sensitivity, 98.0% specificity and 0.93 Cohen's kappa value, when compared with standard antigens. The developed antigen has also been validated with field serum samples from bovine, camel and horse collected from different states of India. The data showed that the developed recombinant antigen can be a diagnostic tool to detect carrier animals as well as control of the disease.