Clinical, molecular, and pathological investigations of ovine pulmonary adenocarcinoma in the middle of Iraq

Abstract

Background: Ovine pulmonary adenocarcinoma (OPA), caused by Jaagsiekte sheep retrovirus (JSRV), is a contagious neoplastic disease in sheep characterized by chronic respiratory signs, inducing the transformation of secretory epithelial cells of the distal respiratory tract.
Aims: To perform clinical, epidemiological, and molecular studies with evaluation of some predisposing factors at the herd level of OPA infection in sheep in Al-Qadisiyah Province, Iraq.
Methods: The first step of the study was undertaken to evaluate the clinical cases of OPA in naturally infected sheep and correlation with observing respiratory signs. Seventy-five sheep with chronic respiratory signs were examined clinically, and by molecular and sequences analysis. The second step was the epidemiological part that was carried out on 195 randomly selected animals from 30 flocks, with the prevalence rate based on PCR; sex, age, and size of flocks were assessed, as well as macroscopic and microscopic features of the neoplastic lung. Deep nasal swabs and nasal secretion were collected from all animals. RNA extraction and RT-PCR were also carried out.
Results: The results showed that 12 (16%) samples were positive for OPA, based on env gene-specific primers. Nucleotide sequences of partial 545 bp of the env gene showed (0.07–0.12) variations from global strains presented in the NCBI database. The prevalence rate of OPA was 21/195 (10.76%) with PCR. The epidemiological factors analysis showed that there was no effect of sex and herd size on the prevalence rates (p ≥ 0.01), whereas age was significantly affected and the age of 2–4 years was more susceptible (p ≥ 0.01). Gross and microscopic examinations were discussed with the confirmation of an OPA infection.
Conclusion: The current study provides useful data about the clinical and epidemiological features of JSRV that is circulating in sheep of Iraq, and concludes that epidemiological studies and disease control may require multidiagnostic assays.