April 29, 2009 | | Comments 0

Ascarids in Horses

Parascaris equorum or ascarids are among the parasites that can seriously compromise a horse’s health. This particular species of roundworms can lead to serious complications that may even lead to death.

Ascarid Life Cycle

Like other parasites, ascarids can infect horses through contaminated food or water. Adult roundworms typically lay eggs that are passed out into fecal matter. Eggs and larvae of this parasite type are quite hardy. Unlike other parasites, ascarids can be in an infectious state for a long time.

Picture of an Ascarid

Picture of an Ascarid

Swallowed eggs hatch in the intestine and penetrate intestinal walls. They then move to the liver and lungs. At this stage, an infected horse may begin to cough and larvae are discharged into the mouth, only to be swallowed again. Upon their second entry into the horse’s system, larvae mature into large adults that can grow up to 15 inches.

Foals are the ones that are usually infected. This is because adults are often immune to roundworm infections.

Symptoms of Ascarids in Horses

Signs and symptoms of an infection are often observed across a period of time. If you don’t pay close attention to an infected horse, you may even miss the signs. Often, ascarids can lead to nutrient deficiency which in turn can result in poor growth, bad coat quality and a large belly. In its advanced stage, coughing that is accompanied by discharges may also indicate an infection.


If left untreated, an infection can lead to serious complications. An infected horse may begin to suffer from diarrhea as well as lung and liver damage. The infection may progress to internal bleeding and pneumonia. As adults, roundworms can create even more problems. Because they are large, they can be the cause of a significant blockage which can progress to colic, intestinal ruptures and eventually death.

Treatment of Ascarids

Fortunately, ascarids can be treated with dewormers. Different products however may have to be used depending on the stage of infection. A slow acting treatment may be advisable if the parasites are already in their adult form. If your horse is already at an advanced stage of infection, it is always best to consult a veterinarian first before any kind of treatment is attempted. Improper treatment administration may lead to severe intestinal blockage.


Foals, like adult horses should undergo regular or scheduled deworming. This is a guaranteed preventive measure that can stop infections before they progress to life threatening conditions. For foals, deworming is often recommended two months after it is born. A different schedule may have to be followed after it passes its first year.

Of course, prevention also encompasses stable and feeding management. Foals ingest ascarids through contaminated food and water. Hence, it always makes sense to ensure that feeding and water trays are always kept clean. Stables should also be kept free of fecal matter as often as possible.

Ascarids may be easier to deal with than other parasites like strongyles. Even so, this is not a reason for horse owners to be complacent. A roundworm infection that is not promptly addressed may be life threatening.

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Filed Under: Horse Health

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