Equine Worm Management: Welfare and Resistance Challenges

Internal parasites cause significant welfare harm in horses while anthelmintic resistance is growing rapidly, requiring strategic targeted treatment approaches to protect welfare and preserve drug efficacy.

Key Facts

Small redworm (cyathostomins) are now the most significant equine worm welfare threat
Anthelmintic resistance is widespread with ivermectin resistance emerging in some areas
Larval cyathostominosis from mass emergence of arrested larvae can be fatal
Worm egg count testing enables targeted treatment rather than blanket treatment
Around 80% of worm burdens are carried by 20% of horses requiring priority treatment
Strategic anthelmintic treatment based on worm egg counts reduces resistance development

Welfare Considerations

Horses with heavy worm burdens experience weight loss, colic, diarrhoea, and in severe cases death from larval cyathostominosis when arrested larvae simultaneously emerge. Blanket regular treatment that ignores individual worm burden levels is driving resistance that will eventually compromise the ability to treat heavily infected horses. Strategic targeted treatment based on monitoring protects welfare by treating when needed while preserving drug efficacy for the future.

What You Can Do

Implement worm egg count testing as the basis for treatment decisions
Consult your vet or equine nutritionist for a strategic anthelmintic programme
Test all horses in a group before any treatment decisions
Avoid unnecessary treatment of horses with consistently low worm burdens
Conduct annual dose confirmation testing to check anthelmintic effectiveness
Support research into alternative worm control methods including biological approaches