Pulmonary adenomatosis is a contagious, viral, neoplastic disease of the lungs of sheep and more rarely of goats. It has been reported from Europe, Asia, Africa, and South and North America.

Etiology

Respiratory exudates from affected sheep are infectious. The causal agent is a type B/D retrovirus, jaagsiekte sheep retrovirus (JSRV). A closely related retrovirus, enzootic nasal tumor virus, induces nasal epithelial neoplasia in sheep and goats (see enzootic adenoma/adenocarcinoma under see Respiratory Diseases of Sheep and Goats: Upper Respiratory Tract). Natural transmission seems to occur generally by the respiratory route. Close contact (eg, at feeding troughs) may spread the virus.

Clinical Findings

The period of incubation after natural infection extends over months so that clinical signs generally become evident when sheep are 2–4 yr old. The tumors produce clinical signs when they become sufficiently large or numerous enough to interfere with respiration. Affected sheep lose weight and show increasing respiratory distress and panting. Moist rales may be heard even without a stethoscope. Coughing is not prominent, and infected animals are usually afebrile unless secondary infection occurs. Forced lowering of the head often causes frothy mucus to run from the nostrils. Clinical disease ends in death after days or weeks, sometimes due to secondary bacterial pneumonia.

Lesions

Tumors are confined to the lungs and, rarely, the associated lymph nodes. They vary from small nodules to extensive solid areas that involve the ventral parts of one or more lobes and that are firm, gray, flat, and sharply demarcated. Copious amounts of white, frothy fluid are present in the air passages. Histologic changes are caused by uncontrolled proliferation of columnar-shaped type II pneumonocytes and similar cells in the bronchioles (Clara cells).

Diagnosis

Chronic weight loss, dyspnea, moist rales, and copious amounts of serous nasal discharge from accumulated lung fluid in an adult sheep that is afebrile are highly suggestive clinical signs of pulmonary adenomatosis. Within a flock, many sheep may be infected, however, only 1 or 2 may show clinical evidence of disease. Currently, histologic examination of affected lung is still the standard used to confirm the disease. Recent advances in the use of PCR show promise in detecting JSRV in blood mononuclear cells in infected sheep before they show clinical signs of disease.

Control

There is no specific treatment or vaccine available. At this time, the best that can be recommended once a diagnosis is confirmed is removal of all animals showing signs suggestive of pulmonary adenomatosis. However, subclinically infected sheep serve as a reservoir for the virus.

Last full review/revision March 2012 by Michelle Kopcha, DVM, MS