Retroviral coinfection (Jaagsiekte and Maedi-Visna viruses) in sheep with pulmonary tumors in Transylvania (Romania): retrospective study on 82 cases

Abstract

Ovine pulmonary adenocarcinoma (OPA) is an important viral-induced neoplasia in sheep caused by exogenous Jaagsiekte sheep retrovirus (exJSRV). Coinfection of exJSRV and Maedi-Visna virus (MVV) is reported in OPA cases, but its worldwide distribution and significance on lung pathology is not yet completely understood. This study aimed to investigate the MVV coinfection rate in 82 exJSRV-related OPA cases, and their pathological effects on lung parenchyma in slaughtered sheep in Transylvania (Romania). On gross examination, classical form of OPA was identified in 92.7%; no changes consisting with MVV interstitial pneumonia were identified in the included cases. The most common histological type of OPA was acinar (58.5%) and the myxoid growths were found in 18 cases. The exJSRV and MMV coinfection rate in examined sheep was 47.6% (39/82). The assessment of perineoplastic areas from coinfected animals, revealed interstitial lymphoplasmacytic infiltrates in all cases, lymphoid hyperplasia in 60.6% cases (20/33) and fibromuscular hyperplasia in 63.7% (21/33). This is the first report providing new data on distribution of OPA coexisting with MVV infection in slaughtered sheep in Romania. We consider that the OPA and MVV coinfection may play an important role on the severity of ovine chronic pulmonary diseases and further studies are needed to confirm this hypothesis.

Keywords: Maedi-Visna; Romania; coinfection; interstitial pneumonia; ovine pulmonary adenocarcinoma.

Figure 1

Gross features of pulmonary tumors. (A) Classical form of OPA - approximately 40% of the right lung parenchyma is replaced by a large, dense neoplastic mass (outlined with white dashes). (B) Atypical form of OPA - a single nodular mass of approximately 1.5–2 cm is present on the surface of the right diaphragmatic lobe.

Figure 2

Histological features of OPA. (A) Acinar type (H&E, bar = 50μm). (B) Papillary type (H&E, bar = 50μm). (C) Acinar type with a myxoid growth nodule (H&E, bar = 50μm). (D) A detail of a myxoid growth nodule (H&E, bar = 20μm).

Figure 3

Photomicrographs of peritumoral area. (A, B) At the periphery of the neoplastic lesions (T), the alveolar septa are moderately thickened due to the presence of inflammatory infiltrates with lymphocytes and plasma cells (I) (H&E, bar = 50μm, 20μm). (C) Interstitial lymphoid hyperplasia (black arrow) without germinative center (H&E, bar = 100μm). (D) Fibromuscular proliferation (black arrows), characterized by irregular bundles of fibrous connective tissue and smooth muscle cells (H&E, bar = 20μm).