Neoplasia-Associated Wasting Diseases with Economic Relevance in the Sheep Industry

Abstract

We review three neoplastic wasting diseases affecting sheep generally recorded under common production cycles and with epidemiological and economic relevance in sheep-rearing countries: small intestinal adenocarcinoma (SIA), ovine pulmonary adenocarcinoma (OPA) and enzootic nasal adenocarcinoma (ENA). SIA is prevalent in Australia and New Zealand but present elsewhere in the world. This neoplasia is a tubular or signet-ring adenocarcinoma mainly located in the middle or distal term of the small intestine. Predisposing factors and aetiology are not known, but genetic factors or environmental carcinogens may be involved. OPA is a contagious lung cancer caused by jaagsiekte sheep retrovirus (JSRV) and has been reported in most sheep-rearing countries, resulting in significant economic losses. The disease is clinically characterized by a chronic respiratory process as a consequence of the development of lung adenocarcinoma. Diagnosis is based on the detection of JSRV in the tumour lesion by immunohistochemistry and PCR. In vivo diagnosis may be difficult, mainly in preclinical cases. ENA is a neoplasia of glands of the nasal mucosa and is associated with enzootic nasal tumour virus 1 (ENTV-1), which is similar to JSRV. ENA enzootically occurs in many countries of the world with the exception of Australia and New Zealand. The pathology associated with this neoplasia corresponds with a space occupying lesion histologically characterized as a low-grade adenocarcinoma. The combination of PCR and immunohistochemistry for diagnosis is advised.

The Diagnostic Challenges of Ovine Pulmonary Adenocarcinoma

“…Breathing develops with no apparent clinical signs for extended periods. Clinical signs are observed only becomes deeper and more frequent, associated with abdominal wall motions, orthopneic posture, dilated nostrils and open mouth [3,10,33]. Other signs are due to a build-up of fluid, produced by tumour cells, in the airways.…”

“…OPA can progress without fever, particularly in acute cases, but secondary bacterial complications occur almost always, shortening the duration and changing the course of the disease. The most frequently involved agent is Mannheimia haemolytica, which has a tendency to worsen clinical signs, triggering a febrile reaction in animals [10,34].…”

“…In Portugal, several sporadic cases have been reported, although the prevalence is not known [9]. It is not reported in Australia and New Zealand, the Falkland Islands and Iceland [10].…”

Research Progress on Emerging Viral Pathogens of Small Ruminants in China during the Last Decade

“…Two types of ENTV have been identified: ENTV-1 in sheep and ENTV-2 in goats [116,117]. Genome sequence studies indicated that ENTV-1, ENTV-2, and JSRV are very similar but distinct from each other [118,119]. To date, 26 full-length sequences are available for ENTV-2; among them, 24 sequences have been obtained from Chinese strains.…”

Radiography, CT, and MRI Diagnosis of Enzootic Nasal Tumor in Goats Infected With Enzootic Nasal Tumor Virus

“…ENTV-2 shares an oncogenic mechanism with enzootic nasal tumor virus type 1, and its oncogenic proprieties are associated with env gene products ( 5 ). These tumors have been classified histologically as low grade adenocarcinoma, and their target tissues are secretory epithelial and mesenchymal cells of the ethmoid bone in the nasal cavity ( 6 ). Electron microscopic and histochemical studies have shown that the tumors may originate either in olfactory or respiratory mucosal glands ( 7 ).…”