Pinworms (Oxyuris equi) are not a formidable foe like strongyles.
Mature pinworms, sometimes called itchworms, have a long, tapering tail and hang out in the large intestine, where the females lay eggs in masses that they deposit around the horse’s anus.
The eggs develop into an infective stage in just four to five days – sometime as quickly as two days – and the sticky agent the females use to stick them there in the first place begins to break up, causing the horse some irritation.
The larvae drop into the paddock, or stable floor, and are capable of re-infecting another horse for up to four months.
Your typical infected horse will go in search of a suitable fence or post to rub their bottom in an effort to relieve the itching.
A pinworm infection can also result in mild diarrhoea.
This itching may well be a sign that your worming programme needs adjusting, as pinworms usually fall victim to just about any drench. That said, recent research has shown signs of pinworms developing drench resistance.
Basically, if you have an effective worming programme in place to deal with the bigger equine threats, pinworms should not be a problem.
Thankfully, we have moved on from the days of 120 years ago when a small plug of tobacco up the bottom was recommended as a means of dealing with pinworms.
Interestingly, a close relative of the pinworm is not uncommon in children.
» Next: What about lungworms?
First published on Horsetalk.co.nz in February, 2009