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Community Corner

How to Keep Your Horse Safe from Habronema

I recently learned about summer sores—what they are and how to avoid them.

I received an email from a friend a couple of days ago with the subject line “habronema.” I had no clue what that word meant, except that it had to do with horses, since she is a horsey-friend.

Upon opening the email, I discovered a plea for help. She said habronema is a horrible, ugly thing that she has dealt with for two years during fly season. Her horse has sores all over his face and tummy that seem to get much better after fly season. 

Aha! Flies! The pests, the bane of the horse existence and to those of us living in rural areas. I had to look into this right away.

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Here is what I found out:

Habronema muscae is an internal stomach parasite that is most commonly found in horses. So it’s not a fly, but here’s the connection: The adult worms lay eggs within the horse’s stomach, and later the eggs exit through the feces and then hatch quickly.

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After hatching, the tiny larvae are ingested by the maggots of different types of flies, such as the house fly and the stable fly, which are very common around horses. Flies carry the larvae and land on a horse’s mouth, nostrils, eyes and lips. These little “bugs” can cause ulceration if deposited into open wounds; chronic conjunctivitis if living in the eyes; and can even affect the lungs and cause abscesses.

The parasites get into the horse’s stomach when the horse licks her lips and swallows—down they go.

The most common indication of infection is the presence of summer sores, which, put simply, are bald patches or owies on your pony pal. You’ll most likely see hair loss and even areas of light bleeding or possibly pus. The typical areas it will show, of course, are the face and head, where all the moist mucus membranes are on your horse.

If the infestation is large enough, digestive problems can arise, and if it is substantial, the passing of food can be completely blocked.  

So how do you prevent these little parasites from infecting your horse, and how can you treat them if they are already present? The stages when you can intervene are the egg and larval stages. The eggs can be removed by picking up the manure in and around your horse’s stall, corral or pasture. Since the eggs are found in the feces, get it out and away from your horse.

If you think there is a possibility that you have these guys around, pick up and remove manure as often as possible, at least daily. Properly deworming your horse will help prevent issues at the larval stage of life. Some brand of ivermectin is the most recommended and must be used according to the directions. (Do not use ivermectin on a horse that has been diagnosed with sleeping sickness—a topic for another day.)

If you’ve never tried to deworm a mustang, it is quite an experience, let me tell you. Cricket does not like chemicals around her. She can smell the dewormer chemicals from a mile away and can clamp her mouth shut tighter than any vice I’ve ever used. I have found that jelly or honey on the tip of the applicator can help some, but I haven’t quite figured out how to completely outsmart her with the dewormer. I have to be quick and lucky to get any paste into her system.

Fly control is another important factor in avoiding a habronema infestation. Removing manure helps with fly control, but fly control in a horse environment can be a challenge. Remember the piece I wrote a while ago about ? External repellents do not kill flies, but do help in keeping them from landing on your horse.

Repellents can be very difficult to keep on around the mouth and nose of your horse because she is drinking water, licking her lips and rubbing her face. Fly repellents also do not kill habronema at any stage, but keeping flies off your horse can help ward off an infestation. Keeping a fly mask with a long nose and a fly sheet on your horse will help keep flies off as well.

Like most horse-health issues, cleanliness, hygiene and prevention are key in keeping habronema at bay. I am happy this topic came up and that I am now aware of it. I am also thankful I have never had this happen at my barn and hope it never does.

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