Mycobacterium
avium subspecies paratuberculosis (MAP) the cause of
Johne's disease in ruminants and Crohn's disease in
human beings escapes pasteurization temperature and liquid milk has
been subject of intense research. India though is the highest milk
producer also has largest population (403.8 million) of dairy
animals in the world, however, status of MAP in un-pasteurized and
pasteurized milk and milk products was not known. This pilot study
was the first attempt to know presence of live cultivable MAP in
branded pasteurized milk and milk products and un-pasteurized milk
marketed in 3 major cities of North India for human consumption,
using 3 sensitive diagnostic assays (culture, ELISA and PCR).
Specific IS900 PCR was used to characterize MAP from positive
cultures. Of the 43 samples screened by 3 tests, culture was most
sensitive (58.1%) followed by PCR (23.2%) and ELISA (4.6%). In
culture, 43.7, 72.2 and 55.5% un-pasteurized milk, pasteurized milk
and milk products were positive. The 44.1, 34.8 and 20.9% were
positive in culture of fat, sediment and both together,
respectively and 12.1 and 87.8% cultures were multi (>10
colonies) and pauci-bacillary, respectively. Colonies first
appeared on 45 DPI and continued to appear up to 120 DPI. PCR was
used for screening of decontaminated pallets (Fat and sediment) of
un-pasteurized and pasteurized milk and milk products, 6.2, 38.8
and 22.2% samples were detected positive, respectively. Specific
IS900 PCR confirmed all the positive cultures as that of MAP. ELISA
detected 12.5% lacto-antibodies in un-pasteurized raw milk samples
only. Pasteurization improved the recovery of MAP in culture and
PCR. Presence of MAP in the un-pasteurized milk indicated that
livestock population was infected and may be cause of low
productivity of the Indian livestock. In view of the increasing
human population the dairy products are in high demand. High
presence of MAP in the pasteurized milk and milk products are
potential threat to human contamination with MAP in India.