Small redworms can spell big problems for horses

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As winter takes hold in the Northern Hemisphere, an animal health company is urging horse owners to understand the risk of encysted small redworms, which can survive in the horse in low temperatures.

Zoetis UK has unveiled a video showing why encysted small redworms are a serious health risk to horses. It is encouraging all horse owners to speak to their vet or suitably qualified person now to make sure they understand the risk this winter.

The new animated video uses engaging illustrations to explain the complicated life cycle of the small redworms and the life-threatening damage they can cause to horses.

Encysted small redworm. © Zoetis

In the autumn and winter as the temperature drops, small redworm larvae have a unique way of surviving in the horse. They are ingested when a horse is grazing and then they bury themselves in the intestinal wall where they form cysts and stop their development, to hibernate during the colder weather. Up to 90% of small redworms in a horse may be these hidden ‘encysted’ small redworms.

In the spring the larvae can erupt from their hibernation in large numbers, breaking and damaging the lining of the intestinal wall, which can cause diarrhoea, weight loss and colic.  This potentially fatal condition is known as larval cyathostominosis, which has a mortality rate of up to 50%. Any age of horse can be affected and young horses (under 6 years old) are particularly at risk.

A faecal worm egg count will not detect encysted small redworms because the larvae do not produce eggs. In fact a horse may have a burden of several million encysted small redworm larvae yet show a negative or low egg count.

Life cycle of the small redworm.
Life cycle of the small redworm. © Zoetis

“Many horse owners may believe they know all they need to about worming but research shows a lack of understanding about the danger posed by encysted small redworm,” Zoetis vet Wendy Talbot said.

“Unfortunately, once the horse shows symptoms of larval cyathostominosis it is a very difficult condition to treat effectively. The intention of our new video is to help owners get to grips with why encysted small redworm can cause serious harm to their horses and how important it is to take steps to prevent it.”

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This image of a horse's caecum - the first portion of the large bowel - shows the damage that can be caused by encysted strongyles, also known as cyathostomins. Encysted strongyles are very resilient. ©
This image of a horse’s caecum – the first portion of the large bowel – shows the damage that can be caused by encysted strongyles, also known as cyathostomins. Encysted strongyles are very resilient. © Martin Krarup Nielsen

One thought on “Small redworms can spell big problems for horses

  • August 21, 2019 at 10:48 pm
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    Hello my name is Michael have a standardbred that seemed to get worm infestation can cause him to colic and loss of appetite

    Reply

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