Enzootic pneumonia-pleurisy complex in sheep and lambs.

Seventy-nine to ninety-three percent of 49 young lambs less than 3 months old, which were too small to go to the meat works at the time of the first draft, showed sub-clinical lesions of enzootic pneumonia when examined post-mortem. Later samples from the same population showedthat some, but not all, lambs developed pleurisy. During the months that the lambs were growing and fattening, the prevalence of enzootic pneumonia diminshed while that of pleurisy increased. The increase in the prevalence of pleurisy was greater during the latter 5 months of the lamb-kill period and reached 11% of all lambs killed during July 1974. A higher prevalence of pleurisy was observed in sheep over l-year-old killed at the meat works, indicating that the prevalence of pleurisy continued to rise beyond the first year of the lamb’s life.