Case 4 - 180316-4

Goat; a one-year-old Alpine doe.)

This animal had a three to four week history of respiratory distress, coughing, and losing weight. Coughing in herd started 5 months ago. The rDVM treated with antibiotics, but there were still chronically coughing individuals. The immediate presentation of this doe at the referral hospital was for respiratory distress. Radiographs revealed a nearly complete alveolar pattern and possible bullae or abscesses.

The lungs were pale, firm, wet and heavy with a diffuse cobblestone appearance. The cranioventral lung lobes were more affected, but no lobe was entirely spared. On cut section the lungs are meaty (hepatized) and do not float in formalin. There were multiple prominent, firm, enlarged lymph nodes in the dorsal thorax (periaortic, hilar) that on section were pale and wet.

Three sections of similarly affected lung are examined. The alveoli in broad regions are flooded with dense eosinophilic material, small amounts of fibrin, proliferative type-II epithelium, and scattered neutrophils and macrophages. Occasionally, macrophages phagocytizing eosinophilic fluid are evident. In addition to the type II hyperplasia, septae are thickened by infiltrates of lymphocytes. Epithelial linings of bronchioles are segmentally, especially terminally, disrupted and a few medium-sized vessels are multifocally surrounded by large aggregates of lymphocytes, plasma cells, and histiocytes.

The bronchiolar lumen in a subset of these affected airways contain large numbers of neutrophils admixed with basophilic material (mucin).

Immunohistochemistry for caprine arthritis encephalitis virus (CAEV) indicates abundant antigen within the cytoplasm of intra-alveolar macrophages.

Severe, diffuse, chronic lymphoplasmacytic, histiocytic, and neutrophilic bronchointerstitial pneumonia with marked alveolar proteinosis and type-2 pneumocyte hyperplasia

This lung was described as having a typical histologic appearance of caprine arthritis encephalitis (and other lentiviruses affecting sheep and goats) from veterinarians outside of California, however Dr. Brian Murphy, who is a retrovirus expert commented that this presentation is very unusual for California goats. The lesions in joints and brain are more typical in CA. The copious proteinaceous fluid filling the alveoli is visually distinct and very characteristic of this disease. This fluid contains surfactant, which correlates with the type II pneumocyte hyperplasia. Molecular and immunology research on the disease shows that as the diffusion capacity of the lung decreases (from the increased wall thickness), cells release hypoxia-induced factor-1α, which activates the transcription of vascular endothelial growth factor, increasing vascular permeability and the leakage of high protein plasma fluid.

The virus was visible by IHC within intraalveolar macrophages, presumably because it was in such high copy number in those cells. However target cells of infection are also type I pneumocytes and type II pneumocytes. Infected macrophages expressing IL-8, which recruits additional inflammatory cells, are thought to perpetuate the inflammatory cycle.

Caswell JL and Williams KJ: Lentiviral pneumonia: maedi-visna (ovine progressive pneumonia) and caprine arthritis-encephalitis viral pneumonia. In: Pathology of domestic animals, ed. Maxie MG, 5th eds., vol. 2, pp. 618- 620. Saunders, Edinburgh, UK, 2007

Case contributor: This case was contributed by Dr. Patricia Pesavento, UC Davis, School of Veterinary Medicine.