Daily feeding of diclazuril top dress pellets in foals reduces seroconversion to Sarcocystis neurona.
Authors: Pusterla Nicola, Packham Andrea, Mackie Sarah, Kass Philip H, Hunyadi Laszlo, Conrad Patricia A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Diclazuril prophylaxis against Sarcocystis neurona in foals Sarcocystis neurona poses a significant risk to young stock on farms with high environmental contamination, yet practical prevention strategies remain limited. Researchers at UC Davis monitored 33 foals on a high-exposure farm, administering either daily diclazuril top-dress pellets (0.5 mg/kg) or no treatment from one to twelve months of age, with monthly serology using indirect fluorescent antibody testing to detect IgG seroconversion. Both groups initially showed declining seroprevalence as maternally derived antibodies waned through weaning, but from that point onwards, untreated foals experienced a marked increase in new infections whilst the diclazuril-treated cohort remained significantly protected. These findings demonstrate that low-dose prophylactic diclazuril is effective at reducing S. neurona seroconversion during the critical post-weaning period when foals lose colostral protection and face increased exposure risk. For practitioners on farms with documented protozoal myeloencephalitis (EPM) pressure, this approach offers a practical evidence-based tool to mitigate disease burden during the foal's most vulnerable developmental window.
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Practical Takeaways
- •Daily prophylactic diclazuril pellets appear effective for preventing S. neurona infection in foals on farms with high exposure; consider implementation in endemic areas
- •Protection becomes critical post-weaning when colostral antibodies wane; this is when treatment difference becomes apparent
- •Low-dose (0.5 mg/kg) daily dosing appears sufficient for prophylaxis, making this a practical farm management strategy
Key Findings
- •Daily diclazuril at 0.5 mg/kg from 1-12 months of age significantly reduced seroconversion to S. neurona in treated foals compared to untreated controls
- •Untreated foals showed a significant increase in monthly seroprevalence after weaning, while treated foals remained protected
- •Colostral antibodies declined steadily in both groups until weaning age, after which divergence occurred between groups