Presence of Mycobacterium avium subspecies paratuberculosis in suspensionsof ovine trichostrongylid larvae produced in faecal cultures artificially contaminated with the bacterium

A reference strain of Mycobacterium avium subspecies paratuberculosis was a dded to faecal larval cultures of Haemonchus contortus, Ostertagia circumci ncta and Trichostrongylus colubriformis. Samples of the larvae produced wer e cultured for the presence of the bacterium in modified BACTEC 12B medium, both before and after exposure to gamma irradiation. The water used to was h the larvae off the faecal cultures was also tested for the presence of th e bacterium. Positive growth was confirmed as M avium subspecies paratuberc ulosis by IS900 polymerase chain reaction and restriction endonuclease anal ysis of the product. At avium subspecies paratuberculosis was detected in t he unirradiated larval suspensions and wash waters of all three nematode sp ecies, and in the irradiated H contortus larval suspension.