Outbreak of fibrinous pneumonia in recently weaned beef calves in southern Queensland.

OBJECTIVE: To describe an outbreak of fibrinous pneumonia in 331 recently weaned beef calves on two properties in the Miles district in southern Queensland. DESCRIPTION OF THE HERD: The affected calves came from three groups: 88 recently weaned calves purchased at Casino NSW saleyards on 29 April 1994, 91 recently weaned calves purchased at Inverell NSW saleyards on 11 May 1994 and 152 homebred calves weaned on 18 May 1994 off the owner's cows. All calves were Hereford and Hereford cross.

INVESTIGATION: The two groups of purchased calves (the Casino-Inverell weaners) were mixed together and moved to another recently purchased property on May 19 after handling on May 18. The homebred weaners were not mixed with the Casino-Inverell weaners, but had nose-to-nose contact for one night via a 3 m gateway while yarded on May 18. By May 25, an outbreak of acute undifferentiated bovine respiratory disease was evident among all 331 calves and two were dead. The morbidity risk in all three groups was 90%, suggesting the three groups of calves were equally susceptible. Five calves died during the outbreak, giving a crude mortality rate of 1.5% (5/331), with necropsy of three calves showing they died of fibrinous pneumonia. Treatment of all calves with a single injection of 20 mg/kg of long acting oxytetracycline lead to rapid clinical improvement in affected calves, and appeared to prevent further mortality. Mortality clustered, with three of the four dead purchased calves coming from one vendor of the Inverell sale.

CONCLUSIONS: Fibrinous pneumonia can occur after weaning in beef calves in Australia. It is highly contagious among groups of recently weaned calves.