The indirect haemolysis test (IHLT) for bovine brucellosis - comparisons with the complement fixation test (CFT) in vaccinated and experimentally infected cattle.

Cattle were vaccinated with Brucella abortus strain 19 subcutaneously in doses ranging from the normal (2.0 ml) dose of standard vaccine down to 1/400 of the normal dose, and via the conjunctival sac with 1/2 of 1/20 of the normal dose. Under all vaccination regimes serum antibody titres in the complement fixation test (CFT) rose more rapidly, reached higher levels, declined more slowly and involved a greater proportion of animals, than titres in the indirect haemolysis test (IHLT). The interval between the first positive serological test and parturition was determined for 54 pregnant cows infected with a virulent field strain (VRI 3) of B. abortus. On average the CFT titre rose to 1/4 43 days, and 1/8 33 days, before parturition, while the IHLT reached a 2/8 reaction 31 days before parturition.