Morphopathological Investigation of Incidence, Prevalence, and Different Forms of Ovine Pulmonary Adenocarcinoma, Garmsar County; An Abattoir-Based Study

BACKGROUND: Ovine pulmonary adenocarcinoma, also known as jaagsiekte, is a chronic, contagious, and transmissible lung cancer. It is prevalent in ovine spp while rarely occurring in caprine with long incubation period. The disease is mostly observed in older animals (over 2 years old).OBJECTIVES: The present study aims to determine the prevalence of the disease based on histopathological diagnosis and investigate its correlation with age and sex in the slaughtered local sheep in Garmsar (Semnan province).METHODS: Herein, the lungs of 9030 slaughtered sheep are morphopatthologically examined for the presence of ovine pulmonary adenocarcinoma.RESULTS: Based on the morphopathological examination, ovine pulmonary adenocarcinoma was observed in the lungs of 438  (4.87 %) out of 9030 sheep. That said, 250 indicated the classical form, as firm, white to grayish coalescing masses mostly in the cranio-ventral lobes; this form is associated with wet cut surface and frothy fluid in the airways. The remaining 188 sheep showed the atypical form, as small, clear demarcated nodules mostly in diaphragmatic lobes associated with dry cut surface and minor fluid in the airways. Almost similar histopathological changes were seen in the two forms. An acinar or papillary growth of neoplastic cells in the alveoli and polypoid proliferation of bronchiolar epithelium were observed in both forms. However, there were variable amounts of connective tissue, and infiltration of lymphocytes and plasma cells in the interstitial tissue of the affected alveoli and no metastatic lesion in the lymph nodes. The peribronchial and peribronchiolar lymphoid aggregates were consistent features in most of the cases studied.CONCLUSIONS: The findings of the present study, as the first report of ovine pulmonary adenocarcinoma in sheep from Garmsa county, revealed the higher prevalence of this disease compared to that reported in previous reports in the country. Moreover, according to the obtained results, atypical and classical forms represented different stages of a single disease spectrum.