WORMING: Why is it still so important?
Horses are host to many types of internal parasites and virtually ALL horses that graze pasture, will at some get worms!
Most horses tolerate low worm burdens well but high worm burdens can lead to clinical disease.
Clinical signs include:
- Illthrift (poor doer)
- Weight loss
WHAT IS RESISTANCE?
Resistance is when a parasite is no longer affected by an anti-worming drug (anthelmintic). There are only THREE types of anthelmintics available in the UK although there are many different brand names. Alarming research has revealed that cyathostomes are already showing some resistance to two of these drug types and there are no new anthelmintics currently under development for use in horses in the UK.
Resistance is caused by:
- Using the wrong wormer at the wrong time – Inappropriate or no veterinary advice (Eg. Internet sales)
- Incorrect dosage of wormer, namely under dosing. Accurate weight of horse is required.
- Frequent and unnecessary worming (Research shows 20% of an equine herd carry 80% of the worm burden)
How can we reduce the risk of resistance in our horses?
- Seek appropriate veterinary advice so the correct drug is used at the correct time
- Use the correct dose of drug – Weigh your horse / pony prior to worming
- Identify the animals that require worming using worm egg counts +/- tapeworm tests. Worm ONLY the horses that have a significant worm burden.
What factors increase the risk of high worm burdens?
- High stocking density
- Heavily grazed pasture
- Presence of horses with high worm burdens
- Presence of youngstock
- Warm, damp weather