Evaluation of Formol Gel Slide Test With Reference to Blood Microscopy and Enzyme Linked Immunosorbant Assay for Diagnosis of Surra in Cattle

Abstract

The objective of the present study was to evaluate the conventional Formol Gel Slide Test (FGST) vis-avis Enzyme Linked Immunosorbant Assay (ELISA) in diagnosis of Trypanosoma evansi infection in cattle. In all, 51 adult Holstein-Friesian cattle were categorised in three groups i.e T. evansi positive symptomatic, parasite negative symptomatic and apparently healthy from 12 animal sheds at Guwahati, Assam. The FGST was performed with some modifications and results obtained were compared with blood smear findings and ELISA. The serum samples obtained from symptomatic cattle with or without detectable parasite in blood were found positive in the FGST as evidenced by immediate gellification and opacity development akin to white of a boiled egg. When compared to ELISA, the sera from clinical cases with high antibody titre (OD value >0.736) were found positive in FGST, while those from asymptomatic cattle with lower antibody titre, (OD value < 0.736) were all negative in the test. Thus the detection performance of blood microscopy, FGST and ELISA were found to be 3.92%, 5.88% and 17.64 % respectively. The study also suggests that ELISA as usual is more sensitive and suitable for screening of cattle herds during epidemiological investigation. However, the study revealed FGST to be a suitable, simple to perform and low cost screening test for field diagnosis of surra in clinically suspected cattle.