The short version, because I’m a very busy cat and I haven’t got all day. Summer sores, technically termed Habronemiasis, happen when insect larvae end up in the wrong place: namely either in a wound or in your horse’s mucous membranes such as eyes, lips, or genitalia.

      Habronema is actually the horse stomach worm, and rarely causes any problems when it stays in the digestive tract where it belongs. However, when the larval stage is deposited in a wound or elsewhere on the skin, instead of being ingested by the horse, it causes a major inflammatory reaction.

       I guess it’s kind of a bummer if you’re a habronema larva…it would be like getting dropped off at the wrong house by your Uber driver. (The Uber driver in this scenario would be a house fly, face fly, or stable fly; and your pick-up location would be a steaming pile of manure.)

      Summer sores that develop in wounds are actually the easiest to prevent. Here’s the secret: cover them up!! For wounds on the legs, this means bandaging. For the face, it means a fly mask. For elsewhere on the body…time to get creative! Summer sores are definitely one of those places where an ounce of prevention is worth a pound of cure.

     Even the tiniest break in the skin can offer an opportunity for habronema larvae to be deposited and set up shop. Be wary of summer sores anytime you are dealing with Scratches on the back of the pasterns, nicks from walking or riding through thick brush, and of course any time you have a wound big enough to require stitches.

    In fact, preventing summer sores is one of the best reasons to have those borderline lacerations stitched up. The less space flies have to land, the less opportunity they have to drop a little habronema larva in there too. And believe me, flies LOVE wounds! Yummy, weeping serum, blood droplets, maybe some pus…it’s a fly dreamland! For those wounds on the lower limbs, we love Sox for Horses Silver Whinnys. They provide a good combination of skin coverage and breathability, while the silver-impregnated threads help the wound to heal.

    If I were a fly, the choice between landing in a weepy eye or a bleeding wound would be a real toss-up. Decisions, decisions. I guess I’d have to say the eyes have it, because horses always (well, usually) have 2 of those, whereas the wounds are more of a hit-or-miss thing.

    I guess what I’m really trying to say here is, keep a fly mask on your horse. Especially in the summer. And especially during the day. If your horse has allergies, uveitis, or otherwise tends to have runny eyes, then he probably should have a fly mask on 24/7/365. No, it doesn’t hurt to do that, as long as you are peeking under the fly mask at least once a day to make sure there are no  hidden injuries. Yes, they can see through a fly mask, even at night.

    Ocular habronemiasis, or habronema in the eye, is probably the most common location where my docs find these parasites. The larvae are deposited and then migrate into the conjunctiva, the third eyelid, or the nasolacrimal duct which runs from the inside corner of the eye to the nose.

    Once these larvae realize they are in the wrong place (i.e. not the stomach), they die. But THEN their little bodies calcify into this hard, yellow granular material, the consistency of which is not unlike concrete. Imagine several of these rock-hard dead larvae carcasses imbedded in your horse’s eyelid and I bet you can guess what comes next: a corneal ulcer.

    Now, you know from reading my blog and coming to my seminars that corneal ulcers are always an emergency, and often a bad deal because they can become infected so easily. With corneal ulcers caused by habronema, you have the added disadvantage of a jagged calcified granule rubbing up against the cornea and not allowing it to heal. So, not surprisingly, my vets will do their best to remove these dead larvae before they can cause any more damage. This involves squeezing them out like a pimple, pulling them out with tweezers, or flushing them out through the nose with saline. Spoiler alert: this is not a fun procedure for your horse. So, again, FLY MASK!

    The tough summer sores to treat are the ones that occur somewhere that is impossible to wrap and too deep to dig out. Common locations for these include the corners of the mouth and the sheath on males. These summer sores usually need to be treated aggressively and repeatedly by a veterinarian. My docs have a special cocktail of a dewormer, a steroid, and DMSO that they will inject directly into the summer sore. This combination is aimed at killing the larvae while also treating the severe secondary inflammation associated with habronemiasis.

    In addition to local injection, my docs will also instruct you to deworm your horse with Quest. Why Quest, you ask? Because Quest contains Moxidectin. Similar to Ivermectin, the active ingredient in most dewormer, Moxidectin is the strongest drug in its class. This is probably the ONLY time you will hear me recommend Quest, as we try to reserve it for treating summer sores and not use it on deworming for internal parasites.

    The silver lining, if there is one, is that summer sores are not life-threatening, and they will heal eventually. As the name implies, summer sores are almost exclusively seen during periods of warm weather. As such, winter in itself cures most summer sores.

    So, now you know all the secrets. If you would like to pick an expert’s brain on Ocular  habronemiasis as well as all other eye things, don’t miss my next seminar, All About Eyes, on May 2nd at 6:30pm, featuring Dr. Dennis Brooks!

   Until next Tuesday,

           -Tony