Evaluation of highly sensitive indigenous milk ELISA kit with fecal culture, milk culture and fecal-PCR for the diagnosis of bovine Johne's disease (BJD) in India.

Country lacks indigenous diagnostic kits against Johne's disease in animals. Indigenous ELISA and IS 900 PCR kits, originally developed for goats and sheep, have been adapted for screening of lactating cows. Multiple diagnostic tests were used to screen 26 lactating dairy cows against Johne's disease. Milk ELISA was evaluated with fecal culture, milk culture and fecal PCR. Of the 26 samples from lactating cows, 84.6, 96.1, 88.4 and 23.0% were positive in fecal culture, milk culture, m-ELISA and m-PCR, respectively. Comparatively milk sediment and milk fat culture detected 84.6 and 76.9% cows positive, respectively. Comparatively fecal culture and milk culture detected 84.6 and 96.1% cows positive, respectively. M-ELISA detected 11.5, 0.0, 11.5, 61.0 and 15.3%, cows as negative, suspected, low positive, positive and strong positive, respectively. There was good correlation between milk and fecal culture with m-ELISA. Three negative cows in m-ELISA were also detected in milk and fecal culture. Of the 26 decontaminated fecal samples, 23.0% cows were positive using specific IS 900 f-PCR. Comparative evaluation of m-ELISA with fecal and milk culture showed agreement in 80.7 and 84.6% cows, respectively. Sensitivity of m-ELISA with respect to fecal and culture was 90.9 and 95.6%, respectively. Comparative evaluation of four tests (milk culture, fecal culture, m-ELISA and f-PCR) showed that only 15.3% cows were detected in all the four tests. In three tests (fecal and milk culture and m-ELISA), 57.6% cows were detected positive. None of the cow was exclusively detected in f-PCR. Of the four diagnostic tests used milk culture was most sensitive (96.15%), followed by fecal culture (86.6%), m-ELISA (76.9%) and IS 900 PCR (23.0%) for the diagnosis of bovine Johne's disease (BJD). Milk ELISA detected only one cow extra, which was negative in milk culture. In view of the simplicity, rapidity and efficacy present milk ELISA kit employing soluble protoplasmic antigen from native Map 'Bison type' genotype of goat origin can be reliable for screening of bovine population against Johne's disease in India.