EFFECTIVENESS OF MILK AS A TRANSMISSION ROUTE OF Mycobacterium avium subsp. paratuberculosis IN DAIRY CALVES

Abstract

Paratuberculosis is an infectious disease that affects mainly cattle; its long period of incubation and rapid dissemination at individual and herd level makes it difficult to control; for these reasons, it has been difficult to measure the extent of this infection in dairy herds of southern Chile. The aim of the present study was to know how effective is the transmission via the milk of Mycobacterium avium subsp. paratuberculosis (MAP) to calves in the first 90 days of life. Ten calves from MAP free herds were fed with milk from infected nurse cows confirmed by fecal culture and serology that were previously analyzed in the laboratory; the calves were separated into two groups, the first "A" received milk with a load known bacterium (106 / mL) and group "B" (control group) received milk replacer. From the first month of life, samples of fecal matter were analyzed, and blood serum in the two groups of calves and weekly the milk was studied to confirm the presence of the bacteria in the corresponding group. As a result, at the third and fourth month after the start of the study, one of the individuals in group A was detected as positive to the fecal culture in a consecutive manner, PCR confirmed the presence of MAP, one of the calves of the same group was positive to ELISA in the fourth and fifth month of the study. It was concluded that the calves exposed to a high load of MAP in milk, the transmission of the infection via milk were 100% effective, and the progress of this was faster than reported in the literature. The present study confirms that calves subjected to a high infection pressure could become infected at an early age and become a source of infection of other calves.