Bovine paratuberculosis I. A herd study using complement fixation and intradermal tests.

A dairy herd (102 cattle) which had been enrolled under a paratuberculosis control program for two years utilizing a complement fixation test (carbohydrate antigen) and intradermal skin test (johnin PPD) was subjected to two further herd tests and followed to slaughter to determine infection status by culture and histology. Mycobacterium paratuberculosis infection was demonstrated in 37 of the animals of which only five were considered reactors on the basis of the last two herd tests applied. Cultural and histopathological evaluation indicated the testing procedures had eliminated heavily infected animals. The limitations of these testing procedures under free stall housing conditions are discussed.