Enzootic nasal adenocarcinoma of sheep in Canada.

A survey of veterinary diagnostic laboratories revealed that intranasal tumors occur in sheep in most provinces of Canada. Tumors were diagnosed in 44 sheep of several breeds including Polled Dorset, Suffolk, Cheviot, Rambouillet and various crossbreeds. Twenty-seven percent of tumors occurred in sheep that were less than two years old. Most tumors were sporadic but 33% of cases occurred in six related flocks, indicating that this disease can be an enzootic problem. The clinical signs were persistent serous, mucous or mucopurulent nasal discharge and stridor. Affected sheep progressively developed anorexia, dyspnea and mouth breathing and most died from effects of asphyxia and inanition within 90 days of the onset of clinical signs. Tumors originated unilaterally or occasionally bilaterally in the olfactory mucosa of the ethmoid turbinates. They were expansive and sometimes locally invasive but metastases were not found. Histologically, the tumors were classified as adenomas or, more frequently, adenocarcinomas. The etiology was not established but retrovirus like particles were observed in tumor tissue from one affected sheep.