Lacto-prevalence, genotyping of Mycobacterium avium subspecies paratuberculosis and evaluation of three diagnostic tests in milk of naturally infected goatherds

Three diagnostic tests (milk culture, Milk-ELISA and Milk-PCR) were evaluated for the diagnosis of Johne's disease in naturally infected (endemic) lactating goats. Indigenous antigen from Map ‘Bison type’ of goat origin was used in Milk-ELISA (m-ELISA). Sensitivity and specificity of m-ELISA was 56.7 and 50.0% in comparison to the milk culture. M-ELISA was used as ‘herd screening test’ and 70.1% milk samples were positive in organized herds (Central Institute for Research on Goats) and 58.2% in farmer's herds (villagers around CIRG). Prevalence of JD was high in few important breeds of goats of UP and Rajasthan. Lacto-prevalence of Map in organized herds was 69.8% by milk culture (43.3 and 45.2% in fat and sediment, respectively) and 57.4% cultures were pauci-bacillary. Maximum colonies appeared from 60 to 105 days post-inoculation. In Milk-PCR (m-PCR), 37.7% milk samples were positive (fat, 9.4%; sediment, 28.3%). Mycobacterium avium subspecies paratuberculosis, isolated from milk were characterized and genotyped as ‘Bison type’ using IS 900 PCR and IS 1311 PCR–REA. Of the three tests, milk culture was most sensitive. Culture and PCR together detected, 79.2% goats’ positive. Screening of both fat and sediment in culture and m-PCR improved the detection of Map. M-ELISA was quick and economical ‘herd screening test’. This is the first report of genotyping of Map (‘Bison type’), from the milk samples of Indian goats. Lacto-prevalence of Map was high in organized and farmer's goatherds. Milk was good clinical material for the diagnosis of Johne's disease in lactating goatherds.