Detection and excretion pattern of Mycobacterium avium subspecies paratuberculosis in milk of asymptomatic sheep and goats by Nested-PCR

IS900 Nested-PCR was applied to milk from asymptomatic sheep and goats known to have a history of Johne's disease in order to detect the presence of Mycobacterium avium subsp. paratuberculosis (MAP). Experimental animals were from two MAP seropositive flocks (90 heads) in Piedmont, North-western Italy. During a 6-month period, milk samples were collected from 29 lambing and kidding animals (20 sheep and 9 goats, five milk collections per animal). MAP DNA was intermittently recovered in milk samples from 13 out of 29 animals (44.8% prevalence). MAP was particularly found in 9 out of 15 seropositive animals, and in 4 out of 14 seronegative. Sensitivity of Nested-PCR was assessed by analyzing a serial dilution of MAP DNA. Results suggest that sheep and goats’ raw milk may represent a potential vehicle for transmitting MAP to off-springs. Control measures could be usefully applied to small ruminants as already used for cattle. Taking into account the possible link between MAP, Crohn's disease and consumption of raw milk products, it is suggested that there should be more careful collaboration in veterinary and public health services, livestock breeders and dairy producers, as well as improved diagnostic tools for routine tests.