Five herds, each containing 200 to 300 cows, were surveyed for listeriosis. Since listeriosis is predominantly linked to reproductive diseases in the surveyed area, suspected cows were first selected ...according to the records on their previous reproductive disorders such as abortion, endometritis and sterility. By simultaneous serological, bacteriological and skin allergenic testing 40 cows suffering from listeriosis were detected. But, only seven of those cows were occasionally shedding listeriae in milk. The specific agglutinins for Listeria monocytogenes were detected in blood sera of all seven cows and the titre was from 1:20 to 1:160. The difference of skin thickness induced by allergenic test was from 1 to 2 mm. L. monocytogenes was isolated from milk of all seven cows and indirectly through the inoculation in enrichment broth, and directly only from milk of two cows. The results indicate that the positive skin allergenic and serological tests do not necessarily mean the shedding of listeriae in milk. However, the listeria-shedding in milk was always accompanied by a positive skin allergenic test and the presence of agglutinins in blood sera.
