Pneumonia in Sheep
Summary written Dr Peter Nettleton and Professor Willie Donachie
Taken from Moredun Foundation Newsheet Volume 4 No. 11 (2006)
- Pneumonia is an inflammation of the lungs caused by infection with one or more of a number of microorganisms or parasites.
- The cause is complex but adverse weather conditions and physiological stress may act as ‘trigger factors’ to allow infectious microorganisms to cause pneumonia.
- Pneumonia in lambs can be caused by bacteria, mycoplasma and viruses.
- The most important form of acute pneumonia in Britain is pasteurellosis caused by two very closely related bacteria, Mannheimia haemolytica (formerly Pasteurella haemolytica) and Pasteurella trehalosi.
- Pasteurellosis can be prevented by vaccines which protect against pasteurellosis alone or against pasteurellosis and clostridial diseases.
- Pasteurella are susceptible to antibiotics as is Mycoplasma ovipneumoniae, another microorganism which can cause a chronic non-progressive atypical pneumonia in young lambs, especially if they are housed.
- Five viruses can cause pneumonia in sheep. Three of them, parainfluenza type 3 (PI3), adenoviruses and respiratory syncytial virus (RSV) are usually associated with lamb pneumonia in which pasteurellosis is also involved.
- The other two viruses cause two distinct diseases usually in older sheep:- maedi visna (MV) and ovine pulmonary adenocarcinoma (OPA). Both these chronic forms of pneumonia develop slowly with affected sheep remaining bright but gradually losing condition.
- There are effective blood tests for diagnosing sheep with MV but OPA can only be diagnosed by the ‘wheelbarrow test’ or at post mortem.
- Lungworms cause parasitic bronchitis and occasionally pneumonia in young sheep during the summer and autumn. There is no vaccine but Dictyocaulus filaria, the causal roundworm, is killed by anthelmintics commonly used to kill gut roundworms.
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