Bovine brucellosis: An investigation of latency in progeny of culture-positive cows

Abstract

Calves (n = 150) born to cows infected with field strains of Brucella abortus were weaned within 24 hours after birth or allowed to nurse until weaned (age at weaning ranged from 10 to 43 weeks). After weaning, female calves were placed in small groups in special pens constructed to prevent further direct and environmental exposure to brucellae. At weaning, male calves were moved to an isolated pasture and were kept as a single group. Later, first-generation heifers were bred and placed in individual isolation pens until termination of pregnancy. Two of the first-generation heifers (that were culture-negative) developed persistent serologic responses (to B abortus) of unexplained origin. Brucellae were not isolated from progeny of infected cows (105) or from progeny offspring (95 fetuses and neonates), indicating that latency may be infrequent.