ISOLATION OF MYCOBACTERIUM-PARATUBERCULOSIS FROM MONONUCLEAR-CELLS INTISSUES, BLOOD, AND MAMMARY-GLANDS OF COWS WITH ADVANCED PARATUBERCULOSIS

Seven mature dairy cows from 6 herds were obtained with history, clini cal signs of disease, and laboratory findings suggestive of advanced p aratuberculosis. A surgically implanted collection chamber was used to obtain peripheral tissue fluid. Blood, mammary gland flush fluid, and collection chamber flush fluid (CCFF) samples were obtained 6 times o ver a 2-week period from each cow. Mononuclear cell-rich portions of t hese fluids obtained by gradient centrifugation were submitted for bac teriologic culture of Mycobacterium paratuberculosis and for total and differential cell counts. Bacteriologic culture of feces for M paratu berculosis and complete necropsy performed on each cow at the conclusi on of the study confirmed the diagnosis of paratuberculosis. Numbers o f tissue macrophages obtained from CCFF samples were lower than expect ed. Mean (+/- SD) differential count of tissue macrophages collected f rom CCFF was 65.57 (+/- 23.39). Mean calculated tissue macrophages (to tal cell count x differential count) collected from CCFF samples was 6 23.1 (+/- 784.55) cells/mul. Mycobacterium paratuberculosis was isolat ed from 1 of 42 (2.4%) collections of mononuclear cell-rich portions o f plasma and from 2 of 42 (4.8%) CCFF samples. Mycobacterium paratuber culosis was not isolated from any collections of mammary gland flush f luid. The collection and processing techniques used in this study did not enhance detection of M paratuberculosis infection in cows with adv anced paratuberculosis, beyond that of ileocecal lymph node biopsy or fecal culture.