Horse Deworming: Welfare and Resistance Management

Strategic deworming of horses based on faecal egg counts replaces blanket treatment, improving welfare by targeting those who need treatment while slowing anthelmintic resistance.

Key Facts

Cyathostomins (small strongyles) are the primary internal parasite welfare threat to horses in temperate climates
Blanket deworming programmes have accelerated anthelmintic resistance — resistance is now widespread
Only 20% of horses typically carry 80% of the parasite burden (aggregated distribution)
Faecal egg count (FEC) testing identifies which horses actually need treatment, enabling targeted deworming
Larval cyathostomiasis — mass emergence of encysted larvae — causes severe colitis and can be fatal

Welfare Considerations

Parasite welfare impacts range from subclinical production loss to fatal larval cyathostomiasis. The shift to targeted selective treatment based on faecal egg counts is both a welfare improvement and a resistance management strategy. Horses with consistently low egg counts may not need routine deworming, reducing unnecessary drug exposure while ensuring treatment is concentrated where it is most needed. Post-treatment FEC checks confirm efficacy — resistance reduces effectiveness of commonly used drugs and alternatives must be identified promptly. Pasture management (rotating grazing, picking up droppings) reduces environmental challenge. Every horse owner should work with their vet to establish an evidence-based, individualised deworming programme.

What You Can Do

Establish a targeted deworming programme using faecal egg counts in consultation with your vet
Pick up droppings from horse paddocks regularly to reduce pasture contamination
Conduct post-treatment FEC checks to confirm anthelmintic efficacy in your horses