Pathology and bronchoalveolar lavage fluid cellular and oxidative stress changes in canine pneumonia in Nigeria

Studies on canine respiratory diseases are scant in the literature especially in Africa, unlike the situation on ruminants. This study is on the pathology and bronchoalveolar cellular and oxidative stress changes in naturally occurring canine pneumonia in Nigeria. The dogs used were collected from cases submitted for necropsy in the institutional Department of Veterinary Pathology. Gross examination, bronchoalveolar lavage (BAL) cytology, oxidative biochemical assay of BAL fluid (BALf) supernatant and histology of sections from all the lung lobes were done using standard procedures. Grossly, 22 (31%) were normal while 48 (69%) were congested, haemorrhagic and/or pneumonic out of the 70 canine lungs examined. Microscopically, there were pulmonary congestion (4%), pulmonary oedema (20%), pulmonary haemorrhages (7%), atelectasis (4%), interstitial pneumonia (10%), bronchointerstitial pneumonia (14%) and bronchopneumonia (9%). The BALf cytology of pneumonic lungs showed increases in neutrophils, alveolar macrophages, lymphocytes and haemosiderophages including free and phagocytosed bacteria, and fungal hyphae. Glutathione peroxidase (GPx) and glutathione transferase (GST) activities increased in congested and bronchointerstitial pneumonic lungs but were reduced in other pneumonic lungs. The superoxide dismutase (SOD) activity was significantly reduced in the pneumonic canine lungs. Hydrogen peroxide generation increased in congestion and oedema, bronchopneumonia and bronchointerstitial pneumonia. Malondialdehyde (MDA) level increased in other congested and pneumonic lungs. There was also significant positive correlation of BALf pro-oxidant assay to the type and severity of pneumonia (+ 0.75, P < 0.05). Pneumonias account for 57.2% of the respiratory conditions of which bronchointerstitial and interstitial pneumonias are the prevalent types. The study also showed that oxidative stress markers in BALf may serve as predictors of pneumonia especially in the early stages. Since treatment recommendations for pneumonia often centre primarily on supportive care and anti-oxidant and antibiotic administration, further studies on causal agents, treatment and prevention strategies for canine pneumonia in Nigeria are warranted.