HORSE INTERNAL WORM PARASITES

Like most animals, horses suffer from internal worms. Roundworms and Tapeworms are the most common and should be treated otherwise they can cause the horse severe discomfort.

The roundworms are the most troublesome and there are three groups of roundworm: large and small strongyles and ascarids.
 
Roundworms

Parascaris equorum is the main roundworm of the ascarid group, which affects the horse.

It is usually only a problem with foals because an older horse would have developed an immunity and this immunity stops more worms developing. The foal contracts the worm larvae from the grass it grazes and the larvae migrate to the lungs and trachea and on to the larynx. They are then swallowed again and the larvae become adult worms in the intestines. While in the intestines the roundworms lay eggs which are able to survive in the grass until they hatch to infect next year's foals. 

 
  Strongylus vulgaris is the main roundworm of the large stronglye group and has a six month life cycle.

The larvae which are ingested during grazing migrate up the blood vessels until they reach the main blood supply. They can stay there for several months causing significantly less blood supply to the intestine as the larvae reduces the diameter of the intestine allowing less blood to flow through. This causes the horse digestive problems and when the larvae are fully grown they suck blood from the bowl wall cause the horse anaemia problems.

There are good worming treatments such as ivermectins available which are able to kill the migrating worm larvae and also stamping out the colic problem these larvae could cause for the horse some years ago.

Cyathostome or small strongyle roundworm has many different types but they all cause the horse same type of problem. Their life cycle is only 3-4 weeks so they they can infect more than one horse each season as they emerge as adult worms after only a short time in the gut wall.

Because of the damage these roundworm do to the intestines they can cause weight loss in the horse and respiratory problems. The coughing, nasal discharges and high temperatures symptoms these worms cause can sometimes be misdiagnosed as respiratory viral infections. The worm tablets from your vet should control this problem if they are given to the horse every 6-8 weeks.

 

If you are looking for information about internal worm parasites in horses, the following links may also be of interest to you: See also: horse external worm parasites

 

Tapeworms

Anoplocephela is the most common tapeworm contracted by horses. It's tiny mites cling to the grass and are eaten by the horse. It is not clear whether they cause the horse any problems but the sensible precaution is to give the horse the pyrantel medication every year or so.

Speak to your vet about drug resistance to worm problems in horses because it might be better to change the wormer type every year, he will be able to advise you.

 

 
 
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