Thursday, June 3, 2010

The itchies, habronemas and allergies (or, Welcome to Florida!)

Tucker's face looking beautiful and clear, June 1, 2010
Another shot of his face

The habronema is just a bare spot..hopefully, it stays that way!

Tucker ready to battle the elements in his nightly turnout.

The habronema at its worst. Notice the granulation tissue.

Typical summer face

Sheath and midline

Tail rubbing

Part One, Habronemas!
Florida, with all its miserable, hot, humid seasons of spring/summer/fall (which kind of just flow into one another, with no real discernable fall or spring), and mild winters (usually..thank goodness this past winter it was COLD!), mean that all kinds of funky, icky things like to grow, mutate and generally make the lives of humans and animals miserable. I have always said that Florida is not fit for anything living. I work for a Veterinary Dermatologist, and the large amount of animals we see with allergies and skin issues, and the 2-3 week waiting period for new patients, just proves this. And it seems that everyone I know, suffers allergies once they move to Florida.
I have spent the last 4 years dealing with allergies in horses, and combined with my job, feel that I have learned a thing or two.
Tucker arrived in November of 2003 but his skin issues did not begin until the spring of 2006, when he scraped the bridge of his nose. It didn't appear to be anything abnormal, it certainly wasn't deep, but its inability to heal was our first clue that something was amiss. Using all kinds of medications, both OTC and vet prescribed, nothing worked. Either right from the get-go, there was simply no healing noted, or it would start to heal, and then once a scab developed, Tucker would rub it open and we would be back to square one. Four months passed, and finally a combination of Preparation H and Lidocaine solved the problem and healing finally was achieved, although to this day, there is a slight indentation from where the sore was.
The following spring of 2007, Tucker became itchy. Very itchy! Let me tell you, a 1400 pound draft cross that is itchy is not a good thing for fencing. Lets just say, hot wire became my best friend that year! Tucker was suffering hair loss and was just plain miserable. Medicated shampoos, and anti-fungals were of no help. Eventually, I allergy tested him.
Now one thing I have learned working at the Vet Derm Center is, if you are going to spend the money for allergy testing, which costs hundreds of dollars, if your animal is not on steroids, then do the more reliable intra-dermal skin testing, where a patch of hair is shaved and the animal is injected with possible allergens. It is much more reliable than blood testing. Also, you cannot test for food allergies, only food elimination trials will reveal true food allergies.
I ended up blood testing Tucker, and he tested positive for 26 of 72 allergens. Unfortunately for him, one of the positives was grass. Boy, does this suck for a horse or what? Because I blood allergy tested him, I am not positive that he is truely allergic to all of those 26 items, but I can definitely say he is allergic to culicoides, mosquitoes, no-see-ums and grass!
Changes were made, including the use of a fly sheet and fly boots, but fly boots do not always stay on Tucker. He often came in from the pasture with tiny, crusty sores on his ankles and pasterns, which usually healed in just a few days.
In the fall of 2007 however, one sore would not heal. It became the size of a peach, was oozing and bloody and smelled. Nothing we tried would heal it. My vet speculated it was a habronema, but a biopsy indicated it was an auto-immune issue. Shortly there after, the weather got cooler and it started to shrink and heal and we weren't too concerned about it.
It was well on its way to healing, until the spring of 2008. The first warm day and suddenly the sore, which had shrunk to the size of a nickle, was oozing and bleeding and growing at an alarming rate. It was soon the size of an apple and the smell was horrendous at times. A second biopsy was performed and the culture was sent to the lab we utilize at work. This time, the results showed a habronema.
What is a habronema? If you are eating, you may wish to stop doing so for a few moments.
An open sore attracts flies. Even being diligent with SWAT and fly boots doesn't guarantee 100% protection. Flies land on the sores as well as in the moisture of the genitals or eyes, and lay their larvae. When the larvae emerge, they can migrate into the tissue and this causes a granulomatous reaction.
It can be just bad luck but it can also be attributed to an increased fly population, poor manure management or moist patches of long grass. The condition is seasonal, with remission in cooler weather. Affected horses are often repeatedly infected in succeeding years, which may indicate genetic factors having an influence.
There are 2 kinds: Ophthalmic and Cutaneous. Tucker suffered the Cutaneous. His was a classical case, with the parasite causing a rapidly enlarged superficial and granulating skin ulcer. Irritation results in rubbing, chewing and biting and can cause scarring. Wounds infested with the parasite may fail to heal and can expand with the production of unhealthy tissue.
It is possible to misdiagnose habromenas, as happened with Tucker. Initially we thought it could be cancer, and at one point I was afraid it was pythiosis. Seasonal appearance is really the best clue. Smears and biopsies are not always conclusive and as we learned, 2 different labs came back with different results.
Once we had a diagnosis for Tucker, we began treatment of a mixture of Ivermectin, DMSO and Fura Ointment. Within a week, the sore had healed and shrunk by 90%! Unfortunately however, we hit a wall after the first week, with no more improvement, but no regression either. Then, our farm was flooded with Tropical Storm Fay in August of 2008. Weeks of flooding was the worst possible thing to have to subject Tucker's leg too. The sore began to grow again. It was impossible to keep dry and we just had to deal with Mother Nature. Thankfully, fall came, we dried out, the weather got cooler, and once again we were in a healing pattern.
Again, winter provided a lull in the growth. Once again, it shrunk and healed. But come the spring of 2009, the first warm day and once again, literally overnight, the habronema was growing and now it was bloody and oozing. Again, we spent another summer fighting the habronema: daily regiments of medicating and protecting the leg.
Last winter was probably the best thing to happen to Tucker. With day after day of record lows and multiple freezes, the habronema had disappeared to its smallest size yet. We have now survived 2 months of warm and hot weather with no oozing, bloody mess. It is still there, there is a bald spot about the size of a quarter. But I am diligent about managing his allergies and the habronema. Beginning in March, he started wearing a fly sheet. His leg with the habronema always wears a fly boot. Tucker seems to understand that the left front leg needs to stay covered, and that is the only leg wrap that he does not try to lose! We try to keep a fly mask on, but Tucker and I have different opinions about these and rare is the morning that he comes in with it still on. So instead, I just wipe his face and ears with the EquiDerm mixture before going out. I have learned that all it takes is just one itchy moment for him to rub the leg open, and one small bite on any part of his body can quickly escalate into a big itchy sore by morning. By keeping to these measures, I am hoping that this will be the first summer we do not have an issue.

Part Two, the Itchies!

In addition to the habronema, Tucker is extremely itchy! I read an interesting thread on COTH (Chronicle of the Horse) bulletin board regarding Onchocerciasis or neck threadworms. I will spare you all the details, if you want to read more, I highly suggest going to COTH ( and searching or you can go to
A lot of itching, and the lumps and crusty sores which develop along the midline, which Tucker has, as well as tail rubbing (which Imp was doing) has been proven to be related to neck threadworms. I already grossed you out with the habronemas, so really, go read about these nasty things on the 2 sites I mentioned. A good cure for this is a double dosing of Ivermectin, 2 weeks apart. I did this to all my horses. Interestingly, the lumps disappeared from the midline, and Imp stopped rubbing her tail. I now do a DD of Ivermectin several times a year!
Another cause of rubbing, especially the face, can be ulcers. Jockey Calvin Borel told me about this cure. A tube of UlcerGuard will cure this. I told Calvin that how could Tucker be stressed out enough to have ulcers, he has it pretty easy, but as I thought about it, his skin issues could be pretty stressful enough. And sure enough, a treatment with UlcerGuard did clear up his face. Another handy trick Calvin taught me is to use castille soap and rub the bar good over the legs at bath time. The soap will remove any contact allergens. You can also use this all over the body for that matter.
I have tried alot of different products for Tucker. Toad Juice and Calm Coat are great to use on open, crusty and oozing sores. I add Calm Coat to my fly spray as well. He gets bathed weekly with MicroTek Medicated shampoo. My favorite medication, and he gets coated with this every night during the summer, as both a prevention and a treatment, is a mixture of EquiDerm and Desitin. The first raw spot I see, he gets a good coating of it.
We have about 4 more months of hot, humid, miserable weather. Keeping up with an allergic horse requires a lot of diligence. One slip up, whether its not medicating a sore, or not putting on the fly sheet or leg wraps, can mean we have lost the battle for another season. It really does not take much for him to regress that quickly.


  1. Great Post! I'm going to save this in my favorites because there are some great references/info here. For what it's worth, my best solutions thus far have been Toad Mist fly spray and Schneiders mosquito mesh flysheet for prevention and MTG for cure.

  2. My horse is going through the exact problem! I am so happy to find out hes not the only one! I feel like I had no other solutions to cure him! I'm going to start to do exactly what you have explained.