Prophylactic administration of ponazuril reduces clinical signs and delays seroconversion in horses challenged with Sarcocystis neurona.

This research illustrates that administering ponazuril, a drug, to horses before they are infected with Sarcocystis neurona (a parasite), can reduce symptoms and slow disease progression associated with equine protozoal myeloencephalitis (EPM), a neurological disease.

Method of Research

• The researchers examined the potential of ponazuril in preventing or limiting the symptoms of EPM post-infection with Sarcocystis neurona (S. neurona).
• To run this experiment, eighteen horses were divided into three groups: one group received no treatment, the second was given 2.5 mg/kg of ponazuril, and the third was given 5.0 mg/kg of the same drug.
• The dosage of ponazuril was administered daily for 35 days – a week before the horses were infected (on trial day 0) and the following four weeks after infection.
• On trial day 0, each horse was deliberately infected with a million S. neurona sporocysts, and transported as a source of stress (since stress can compound disease progression).

Procedure and Results

• Throughout the study, sequential neurological examinations were conducted. Apart from this, the researchers collected serum and cerebrospinal fluid from the horses to assay for antibodies to S. neurona.
• Consequently, all the horses in the group without any treatment showed neurological symptoms. At the same time, only 71% and 40% of horses in the 2.5 and 5.0 mg/kg ponazuril groups respectively displayed neurological abnormalities.
• Significantly, seroconversion (the time period during which a specific antibody develops and becomes detectable in the blood) was lower in the group administered with 5.0 mg/kg ponazuril compared to the untreated horses.
• Horses showing neurological signs were put down, and an autopsy was performed, revealing the subtle to moderate signs of neuroinflammation.

Conclusion

• The results of this study validated that a dosage of ponazuril at 5.0 mg/kg can reduce, but not completely eradicate, infection and clinical symptoms of EPM in horses.