Pathology and Aetiology of Pneumonia in Nigerian Sheep: Evidence of Viral–Bacterial Co-infections and Breed Susceptibility

Background:

Current vaccination and therapeutic strategies have not effectively controlled pneumonic cases in sheep. A better understanding of the nature, pathology, and etiological factors of ovine pneumonia is essential for improved prevention and management, particularly in Nigeria.

Methods:

A total of 828 sheep from different regions of Nigeria were evaluated ante- and post-mortem for pulmonary consolidation in relation to breed, age, sex, clinical signs, and body condition. Lung samples were examined using histopathology, bacterial culture, and bronchoalveolar lavage fluid (BALf) cytopathology. Paraffin-embedded tissues were analyzed immunohistochemically for viral antigens—Peste des petits ruminants virus (PPRV), Parainfluenza-3 virus (PI3V), Respiratory syncytial virus (RSV)—and bacterial antigens—Mannheimia haemolytica (Mh), Pasteurella multocida (Pm), and Mycoplasma mycoides var. capri (Mmvc). Data were analyzed using descriptive statistics and ANOVA at α = 0.05.

Results:

Pneumonia occurred in 56% of sheep, with higher susceptibility in Yankasa breed (38%) and females (39.5%). Histopathological patterns included interstitial (24%), bronchointerstitial (18%), bronchopneumonia (12%), and granulomatous pneumonia (2%). BALf showed elevated neutrophils, lymphocytes, and macrophages in pneumonic lungs. The predominant bacterial isolates were E. coli, Mh, and Pm. Immunohistochemistry revealed strong viral antigen staining in bronchointerstitial pneumonia and bacterial antigen in bronchopneumonia. Co-infections were frequent, particularly PPRV with Mh (63%).

Conclusion:

Pneumonia is common among young and Yankasa sheep in Nigeria, with PPRV and RSV as key viral agents, often complicated by M. haemolytica. Effective control may require a multivalent vaccine incorporating these pathogens.