An indirect-ELISA for the diagnosis of mixed gastrointestinal (GI) nematode infection comprising Oesophagostomum, Haemonchus and Trichuris species was standardized using crude somatic antigen of Oesophagostomum columbianum (CSAg-Oc) and sera of slaughtered goats with known parasitological status including Oesophagostomum, Haemonchus, and Trichuris (strong positive), Haemonchus and Trichuris (weak positive) and parasite free goats (negative). Two cut-off points, i.e. higher and lower cut-off were determined using the strong positive, weak positive and the negative control sera of goats. Thus the test sera having optical density (OD) values greater than the higher cut-off were considered positive for mixed infection with all the three nematode species, intermediate between the higher and the lower cut-off values were considered positive for mixed infection of Haemonchus and Trichuris, and less than the lower cut-off value were considered negative for any of these three nematode species. The sensitivity, specificity and accuracy of the ELISA for diagnosis of mixed GI nematodoses were 81.25, 93.18% and 90.00%, respectively, while it was 92.86% sensitive, 75.00% specific and 91.67% accurate for the diagnosis of mixed infection with Haemonchus and Trichuris. The ELISA, so standardized, detected 27.78% sero-prevalence of Oesophagostomum plus Haemonchus and Trichuris infection and 38.89% percent of Haemonchus and Trichuris infection in the field goats. The standardized assay might be exploited as a diagnostic tool and also for sero-epidemiological study of two important GI nematodes of goats.
Keywords: Diagnosis; Goat; Haemonchus; Indirect-ELISA; Oesophagostomum.