Pneumonia in Sheep

Moredun-logoSummary 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.


The full news sheet for any of the disease summaries can be ordered from the Moredun Foundation by using the following request form. The first news sheet title requested is free*, further news sheet titles are charged at £5.00 per copy (including postage).

*offer limited to one news sheet title per postal address in any one year. After that each news sheet will be charged at the standard price of £5.00 (including postage).


Click here for more information about Moredun Foundation News Sheets


  Moredun Membership Scheme

Moredun runs a membership scheme which aims to keep farmers and their vets up to date with the latest developments in animal health research. If you are interested in becoming a member of the Moredun Foundation, please click here.