Profiling of Mycobacterium avium subspecies paratuberculosis in the milk of lactating goats using antigen-antibody based assays

Abstract

Johne's disease, caused by Mycobacterium avium subspecies paratuberculosis is endemic in the domestic livestock population, still it is not priority for control in the country. First time we used 'multiple assays’ for screening raw milk of 465 goats (farm/farmer's herds) to estimate bio-load and bio-type profile of bacilli. Each sample was screened by six tests and compared their sensitivity and specificity. Of 465 raw milk samples screened, bio-load of bacilli was 65.3% by six assays. Assay-wise bio-load was 49.4 and 62.7% in antigen and antibody detection tests, respectively. Bio-load was 48.8, 46.6, and 13.9% in Indirect Fluorescent Antibody Test (i_FAT), microscopy and IS900 PCR and 39.1, 57.4 and 55.6% in Indirect Enzyme Linked Immuno Sorbant Assay (i_ELISA), Dot Enzyme Linked Immuno Sorbant Assay (d_ELISA) and Latex Agglutination Test (LAT), respectively. Dot-ELISA was most sensitive followed by LAT, i_FAT, microscopy and i_ELISA. Milk DNA samples positive in IS900 PCR on bio-typing using IS1311 PCR_ Restriction Enzyme Analysis (IS1311 PCR_REA) revealed, 72.3% (47/65) were 'Indian Bison Type'. Milk was easy to collect sample and first time we used 'whole milk' as 'test sample' without centrifugation. High bio-load of MAP in milk underlined need for urgent control of disease in lactating goatherds. Bacilli was important 'Milk born' infection and on the basis of sensitivity, specificity, resources and requirements, of the ‘six assays’ most appropriate assay/s (single or in combination) can be chosen for the screening and diagnosis of Johne’s disease in lactating goatherds using whole milk as sample.