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Respiratory disease was identified in 90 cattle postmortem submissions between January and March 2011. The most common pathogens identified included Mannheimia haemolytica (17 cases), Pasteurella multocida (11 cases), Mycoplasma bovis (10 cases), infectious bovine rhinotracheitis virus (IBRV) (seven cases), Arcanobacterium pyogenes (six cases) and Histophilus somni (four cases).
Pneumonia due to combined IBRV, M haemolytica and M bovis infection was diagnosed in a five-month-old suckler calf with lesions of fibrinonecrotic bronchopneumonia and tracheal congestion. M haemolytica type A1 was recovered in large numbers from lung cultures and the lung tissue was positive for M bovis antigen. IBRV was isolated from tracheal tissue.
Bovine viral diarrhoea/mucosal disease
Of 4141 blood samples that were tested for bovine viral diarrhoea virus (BVDV) by virus isolation or antigen capture ELISA, 246 (5.9 per cent) were positive. In addition, nine of 232 (3.9 per cent) submitted tissue and nasal mucus samples were positive by immunofluorescence. Three cases of mucosal disease were confirmed at postmortem examination during the quarter.
Rotavirus and coronavirus
Rotavirus and coronavirus infection were diagnosed in a nine-day-old suckler calf submitted with a history of diarrhoea and dehydration. Escherichia coli K99 antigen detection results were negative. Histological lesions of focal hepatoparenchymal necrosis caused a suspicion of salmonellosis, but no significant organisms were recovered from intestinal and systemic cultures, possibly due to antimicrobial therapy.
Three 10-day-old calves were submitted from the same farm with a history of diarrhoea and dehydration. Intensive antimicrobial therapy had been undertaken before submission. One calf was found to have rotavirus and coronavirus infection and an untypeable (K99-negative) extended-spectrum β-lactamase-positive E coli was recovered from the caecum of …