Atividade viral do vírus respiratório sincicial bovino (brsv) em bezerros leiteiros

Bovine respiratory syncytial virus (BRSV) is one of the major pathogens affecting the respiratory system of young cattle, causing serious economic losses. Data on its epidemiology and occurrence in animals under one-year of age are still scarce in the literature. This study aimed to determine the occurrence of viral activity in three of BRSV seropositive dairy herds (A, B, and C), by serological monitoring of calves from the first day of life until the age of one year, by virus neutralization test. Results showed that in animals from farms A and B, antibody titers increased in the first month, characterizing passive transfer of immunity through colostrums. Over time, the titers decreased till total absence in the sixth and eighth months respectively and then antibodies titration increased in the final months of the study, probably due to natural infection. On property C, although there was a similar antibodies’ dynamics to the others, a period of total absence did not occurred, suggesting that animals may have been infected in the first months of life, despite the presence of colostral antibodies. This study demonstrated fluent BRSV activity amongst animals in all properties. KEYWORDS: antibody titer; bovine respiratory syncytial virus; screening; viral activity; virus neutralization.