Does your horse appear to have a summer cold or summer sores or something else? If so, the cause may be a parasite infestation of either ascarids, also known as large roundworms, or stomach worms, also known as habronema.
Infected summer sores on a horse's leg just above the hoof.
What appears to be a summer cold or summer sores in your horse may be an infestation of worms.
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Ascarids, also called large roundworms, are often found in young horses. They can grow to be twelve inches long and can be found in the hundreds in the small intestine, leading to poor nutrition and causing coughing, colic, and diarrhea. If they reach the lungs, they may cause pneumonia.
Large roundworms can cause stunted growth, digestive problems, ruptured gut, and death.
What appears to be a summer cold can be caused by larval stages in the lungs. Usually, foals and young horses are affected by large roundworms, and immunity to these worms develops at about 18 months.
Stomach worms or habronema live in colonies in the wall of the horse's stomach. Eggs that pass in the feces are picked up by flies, which serve as intermediate hosts. When the fly feeds on the wounds or around moist areas of the horse's body, the larvae escape from the mouth parts of the flies and may be swallowed by the horse.
Symptoms
- Ulceration of moist areas around eyes, mouth, nostrils, foreskin, and wounds
- Intense itching
- Open sores that are messy and moist with pus
- An open wound that enlarges, ulcerates, and becomes covered with reddish-yellow tissue that bleeds easily
- Growth-like (granulomatous) appearance resembling a sacroid or squamous cell carcinoma
A large number of habronema can produce severe gastritis. Tumor-like enlargements may occur in the wall of the stomach and, if these tumor-like enlargements rupture, peritonitis usually ensues.
In addition to internal problems, habronema cause summer sores and conjunctiva or inflamed, sore eyelids.
Diagnosis of both large roundworms and stomach worms is usually by a fecal egg count.
Prevention
Fly control is the best prevention . Keeping stable and pasture areas clean and free of manure will discourage the fly population. Using misting systems in stalls and barns, spraying barn and stable areas with appropriate fly killers, and using fly repellents specifically made for horses in the form of sprays or skin products that are dabbed on and spread around the eyes, will minimize exposure to the larvae which is carried by flies.
In some cases, face masks and other protective coverings will help keep the horse comfortable and limit exposure.
An on-going parasite control program is recommended to keep equines from suffering the consequences of parasite infestations. If you don't already have a scheduled program, your veterinarian can help you establish one that will work best for your horse.