The pathology of bronchointerstitial pneumonia in young foals associated with the first outbreak of equine influenza in Australia.
Authors: Patterson-Kane J C, Carrick J B, Axon J E, Wilkie I, Begg A P
Journal: Equine veterinary journal
Summary
# Editorial Summary: Equine Influenza and Fatal Pneumonia in Neonatal Foals During Australia's first equine influenza outbreak in 2007, a cluster of neonatal foals (aged 2–12 days) presented with bronchointerstitial pneumonia, a disease pattern rarely documented in such young animals. Post mortem examination of 11 EIV-positive foals revealed diffuse pulmonary consolidation with characteristic histological findings including bronchiolar and alveolar necrosis, neutrophilic infiltration, hyaline membrane formation, and airway epithelial hyperplasia; equine influenza virus nucleic acid was confirmed in tissues from 10 of these animals. These pathological changes—whilst consistent with previous reports of bronchointerstitial pneumonia from other causes—represent the first definitive documentation of EIV-associated disease in this age group with consistent viral detection across a case series. For equine practitioners, this outbreak underscores the vulnerability of immunologically naive neonates to severe viral respiratory disease and highlights the critical importance of obtaining tissue samples (nasal swabs, lung tissue, or both) for virological and bacteriological analysis in all cases of pneumonia affecting young foals, particularly during periods of unknown aetiology. Given that similar outbreaks have occurred previously (UK, 1965), clinicians should maintain a high index of suspicion for emerging infectious agents in neonatal pneumonia presentations.
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Practical Takeaways
- •EIV can cause fatal bronchointerstitial pneumonia in very young foals lacking maternal immunity; remain alert during outbreaks in naive populations
- •Submit tissue specimens from pneumonia cases in young foals for virological and bacteriological testing, as histological lesions alone cannot distinguish EIV from other causes
- •Recognize that bronchointerstitial pneumonia in neonatal foals represents a stereotypical response to various insults and requires diagnostic confirmation rather than clinical assumption
Key Findings
- •11 young foals (age 2-12 days) died with bronchointerstitial pneumonia during the first Australian EIV outbreak in 2007
- •10 of 11 foals tested positive for EIV nucleic acid; remaining foal had positive nasal swab
- •Histological lesions included bronchiolar and alveolar necrosis, neutrophilic infiltration, hyaline membrane formation, and airway epithelial hyperplasia with squamous metaplasia
- •This is the first detailed pathological description of bronchointerstitial pneumonia associated with EIV in young foals and the first series where a causative agent was consistently detected