Equine viral Pneumonia and secondary Bacterial infection

Background: Equine herpesvirus (EHV), primarily types ۱ and ۴, are significant pathogens in horses responsible for respiratory disease, abortion, and occasionally neurological disorders. The respiratory form is characterized by fever, nasal discharge, and interstitial pneumonia with necrotizing bronchiolitis. Histologically, the presence of eosinophilic intranuclear inclusion bodies within epithelial cells is considered pathognomonic. Secondary bacterial infections, particularly with Streptococcus zooepidemicus, are common complications that exacerbate pulmonary lesions and clinical severity. Methods: A ۱۵-year-old horse with a one-month history of nasal discharge, anorexia, and fever was examined postmortem following death despite treatment with multiple antibiotics and anti-inflammatory drugs. Complete necropsy was performed, and tissues from the lungs, liver, spleen, kidney, and lymph nodes were collected for histopathology and bacterial culture. Results: Grossly, the liver exhibited multiple fibrinous foci, the heart showed hydropericardium, and the lungs displayed diffuse fibrosis and purulent exudate. Histopathological findings included necrotizing bronchiolitis, severe interstitial fibrosis, and intranuclear inclusion bodies confirming EHV infection. Lymphoid depletion in the spleen and lymph nodes indicated viral-induced immunosuppression. Bacterial culture of the lungs yielded Streptococcus zooepidemicus. Conclusion: The pathological and microbiological findings in this case confirm equine herpesvirus (EHV) infection as the primary cause of pneumonia, complicated by secondary Streptococcus zooepidemicus infection. The presence of eosinophilic intranuclear inclusion bodies in bronchiolar epithelial cells is pathognomonic for EHV infection. Systemic lymphoid depletion in the spleen and lymph nodes indicates viral-induced immunosuppression, which likely facilitated bacterial superinfection. These results highlight the importance of early diagnosis, vigilant herd monitoring, and strict biosecurity measures to prevent the spread of EHV in equine populations.

کلیدواژه ها:

Equine Herpesvirus ، Streptococcus zooepidemicus ، Pneumonia ، Horse ، Pathology