Sarcocystis fayeri in skeletal muscle of horses with neuromuscular disease.

This research investigated the prevalence of Sarcocystis fayeri, a parasite, in horses with neuromuscular diseases, revealing a common occurrence in young mature horses. The study did not establish a direct cause-effect relationship, but found potential associations between S. fayeri infection and myopathic and neurogenic processes.

Context and Motivation

• This study was prompted by recent reports of Sarcocystis fayeri causing toxicity in humans who consumed horse meat.
• Previously, the presence of these parasites in horse muscle was deemed incidental and not associated with disease.
• Given the potential zoonotic and health implications, the researchers aimed to understand the extent and nature of Sarcocystis spp. infection in horses, specifically those suffering from neuromuscular diseases.

Findings and Implications

• The study found a common occurrence of S. fayeri infection in young mature horses with neuromuscular diseases.
• The infected horses had significantly higher numbers of infected muscles and sarcocysts per muscle than the control horses.
• Notably, S. fayeri tended to be present in low oxidative, highly glycolytic myofibers, suggesting that the parasite had a high glycolytic metabolism.
• Clinical signs in the horses included muscle atrophy, weakness, pain, gait deficits, and trouble swallowing (dysphagia), especially if the tongue and esophagus were involved. Horses with myositis (inflammation of muscle tissue) appeared lethargic, painful, stiff, and unwilling to move.
• This study suggests that like in humans, horses can develop sarcocystosis and cardiomyopathy, both serious health conditions.
• While the research did not conclusively prove causality, the findings suggest a potential link between S. fayeri infection and neuromuscular disease in horses. This challenges the commonly held assumption that Sarcocysts spp. are always incidental findings in horses.

Conclusion

• This research has opened the door to further investigations into the role of Sarcocystis fayeri and similar parasites in neuromuscular diseases, by suggesting that infusion might not always be incidental. As the horses are also a major source of meat, apart from their primary role as sports and helper animals, this research can have far-reaching impact on food safety and disease transmission to humans.