Bovine respiratory syncytial virus infections in young dairy cattle: clinical and haematological findings

Abstract

Clinical signs and haematological findings during the acute and convalescent phases of an infection with bovine respiratory syncytial virus (RSV) were studied under field conditions. The study was carried out in 139 cattle less than 16 months of age in 16 herds with serologically proven bovine RSV infections. Blood was collected for serological and haematological examination. Repeated clinical examinations were carried out until 35 days after appearance of disease. Signs of general disease such as reduced appetite and a body temperature of 40 degrees C or higher lasted less than three days in most cases. Signs of upper respiratory disease, such as coughing, nasal discharge and conjunctivitis were predominant and persisted in 10 to 30 per cent of the animals till the end of the observation period. Signs of lower respiratory disease such as abdominal breathing, bronchial and bronchovesicular sounds on auscultation and a high respiration rate were valuable in diagnosing the disease. These symptoms were present in about 50 per cent of the animals in the early stages of the disease. They lasted for about six days and disappeared in most animals after about 10 days. On haematological examination statistically significant blood changes were observed. A rise in zinc and iron between day 0 and day 10 and a reduction in copper content between day 10 and day 21 were found.

Bovine respiratory syncytial virus reinfections and decreased milk yield in dairy cattle

“…However, the highest percentage of reinfections was observed in cows during their first lactation. Older animals may have a better immunity against BRSV infections because of previous exposure and re-exposure to BRSV (11,13). Some animals in this study already had such a high antibody titre that they may not have been able to develop a significant increase in antibody titre upon reinfection.…”

“…Throughout the world, Bovine Respiratory Syncytial Virus (BRSV) has a significant role in the pathogenesis of respiratory tract disease in cattle (2,11,13). In Western Europe, the outbreaks of BRSV infections show a seasonal pattern, with a peak in autumn and winter (8,11).…”

Bovine respiratory syncytial virus infection

“…In more severe infections, there is slight depression and anorexia, a decrease in milk yield in lactating cows, hyperthermia, polypnea (respiratory rate ≥ 60 movements per min) and an abdominal dyspnea. On auscultation of the lung abnormal breathing sounds caused by bronchopneumonia or bonchiolitis might be detected [159]. Animals may develop severe respiratory distress with a grunting expiration and breathing through an open mouth with the neck stretched and the head down, with saliva poring on the floor and with the tongue out.…”

Age-dependent differences in the pathogenesis of bovine respiratory syncytial virus infections related to the development of natural immunocompetence

“…Clinical signs are characterized by general illness (pyrexia, anorexia and depression), upper respiratory tract disease (URTD; nasal and ocular discharge and cough) and lower respiratory tract disease (LRTD; tachypnoea and, in severe cases, dyspnoea). Although in many cases the lower respiratory tract is involved in infection, the clinical signs may remain limited to the upper respiratory tract (Verhoeff et al, 1984). Age has always been identified as an important risk factor for development of the more severe (lower) respiratory tract disease.…”