Serological study against respiratory viruses in calves in a semi-intensive system and its relationship to respiratory symptoms

Abstract

Respiratory diseases are a major health problem due to the high morbidity and mortality rates, with great economic losses. The aim of this study was to determine the frequency of antibodies against the main viral etiological agents related to bronchopneumonia in cattle (bovine viral diarrhea virus, bovine herpesvirus type-1 and bovine respiratory syncytial virus), searching for associations between these agents and the clinical signs observed. We studied 63 calves from two herds from São Paulo, Brazil. After physical examination, the calves were divided into healthy calves and calves with respiratory disease. Serum was obtained for subsequent detection of antibodies by viral neutralization. The association between clinical signs and serological findings was studied. Antibodies against bovine viral diarrhea virus, bovine herpesvirus type-1 and bovine respiratory syncytial virus were detected in 57.10%, 66.70% and 93.70% of the samples. A higher frequency of antibodies against bovine viral diarrhea virus was observed in animals with serous / mucous nasal discharge (P = 0.01). The dehydrated animals (P = 0.008) and those with a rectal temperature above 39.5 ºC (P = 0.03) presented a higher frequency of antibodies against the bovine respiratory syncytial virus. The present work presented results superior to those found in studies in farms with extensive system, confirming the importance of management in the transmission of microorganisms.