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Friday, 1 March 2013

Pinworm in horses

Yet again 2013 is proving to be another year when equine Pinworm burden is becoming more widely reported by UK horse owners. Pinworm (Oxyuris equi) is not generally thought to be harmful as they pass through the intestine but more of a nuisance and an irritant when the female pinworm lays her eggs around the horse’s anus. The female can grow up to approximately 10cm in length and are white in colour. They reside in the large intestine and attach themselves to the intestinal wall to ingest the contents for food. Adults produce eggs approximately 5 months after the initial infection. Eggs are laid around the anus and within a few hours of being laid they develop into embryos and are infective in 4-5 days.  On occasion the actual female worms can be seen in the process of egg laying. Eggs find their way onto the pasture, into water and feed supplies, on fences, stables and walls and onto grooming kits
Eggs are ingested by the horse and L3 larvae are released in the small intestine, they then migrate to the large intestine to develop into the mucosa to L4 larvae which then emerge and mature into adults. The female adults then migrate from the large intestine to the anus where they lay eggs in clumps in a sticky substance on the skin causing irritation around the anus leading to tail rubbing.  These can be removed on a daily basis by cleansing the area around the tail, anus and hindquarters with warm diluted disinfectant The pinworm likes to emerge in the night to lay eggs so cleaning first thing in the morning is best. The recent prevalence of pinworm burden which  be in some manner due to the different strategies recently introduced involving worming horses so treating for pinworm needs to be considered when creating a animal health plan..

Active ingredients that treat for adult and pinworm larvae are Moxidectin, Ivermectin, Febendazole and Mebendazole with Pyrantel treating adults only.
Not all brands are licensed so care needs to be taken by checking the brand’s label.

Extra care should be taken in the stable environment to help reduce the risk of re-contamination from buckets, feed bowls, haynets and rugs etc.  A thorough clean with a disinfectant in these areas and most importantly the stable after removing all bedding will help and is always a good idea in areas of animal care and management. Do not share grooming brushes.

SH Wetherald

0844 808 6070