Experimental Haemophilus somnus pneumonia in calves

Area of Science:

• Veterinary Pathology
• Bovine Respiratory Disease
• Bacteriology

Background:

• Haemophilus somnus is a significant pathogen causing pneumonia in cattle.
• Understanding the pathogenesis of H. somnus pneumonia is critical for effective disease management.
• Existing models may not fully replicate the naturally occurring disease.

Purpose of the Study:

• To establish and characterize a calf model of purulent bronchopneumonia induced by Haemophilus somnus.
• To investigate the effect of dexamethasone pretreatment on the severity of H. somnus-induced pneumonia.
• To evaluate the pathological and microbiological features of this experimental model.

Main Methods:

• Twelve young calves were inoculated endotracheally with Haemophilus somnus.
• Six calves received dexamethasone pretreatment prior to bacterial inoculation.
• Lung tissues were examined macroscopically and microscopically; bacterial isolation and serological tests were performed.

Main Results:

• All calves developed cranial-ventral lung consolidations with abscesses.
• Dexamethasone-treated calves exhibited more extensive lung changes, including severe alveolar filling and abscessation.
• Two of six dexamethasone-treated calves died, while none of the controls died; H. somnus was isolated from all calves.

Conclusions:

• The experimental model closely mimics naturally occurring Haemophilus somnus pneumonia in calves.
• Dexamethasone pretreatment exacerbates the severity of H. somnus-induced pneumonia.
• This model is valuable for studying the pathogenesis and potential treatments of H. somnus pneumonia.