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What is Midge Bite Allergy?

Not only does the midge bite cause itching and swelling, it can also transfer viruses from other animals such as West Nile (flavivirus) and Vesicular stomatitis (vesiculovirus) so it is best to get veterinary advice if you believe your horse has a midge bite allergy. Also, if your horse continues to bite and scratch at the skin, infection can set in and make him extremely ill. Lesions that resemble welts, papules, or ulcers can be found on the ears, face, mane, and tail mostly. You will see your horse constantly try to itch the area in any way possible to get at the bites.

One of the most common causes of itchiness in horses is insect bite hypersensitivity (IBH), and midges (Culicoides spp) are very intense biters. This itchy condition may not be serious, but for your horse it can be incredibly irritating and uncomfortable. These little insects can create a severe dermatitis on the ears, face, and belly. The bites are painful and can last up to five minutes, with each insect biting several times. The saliva is what causes the allergic reaction in your horse and the skin can be seriously inflamed and itchy within minutes of the bite.

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Symptoms of Midge Bite Allergy in Horses

The main symptoms of midge bite allergy are intense scratching and areas of injury on your horse from repeated skin biting. Your horse will do whatever he can to scratch the itch including rubbing his face or head on buildings and fences. Some of the other most reported signs of midge bite allergy include:

  • Biting at areas of skin
  • Thickened skin on ears, mane, tail, face, and belly from biting
  • Scaling rash at bite sites
  • Redness and inflammation
  • Hair loss in affected areas

Causes of Midge Bite Allergy in Horses

The saliva from the bite of the midge (culicoides) is what causes the hypersensitivity. There is something in the saliva that, when mixed with the horse’s skin tissues, causes an allergic reaction of itching and inflammation.

Diagnosis of Midge Bite Allergy in Horses

The veterinarian will do a complete and thorough physical examination of your horse, paying special attention to the areas of skin affected by the midge bites. Skin scrapings will be taken for cultures and biopsy. These are necessary to rule out bacterial infections, fungal conditions, and parasites. If all of these tests are negative, allergy tests are needed. Veterinary professionals are now able to isolate an Immunoglobulin E (IgE) mediated response to the proteins in the saliva of the culicoides which gives them an easier way to confirm the diagnosis of midge bite allergy.

Treatment of Midge Bite Allergy in Horses

Treatments include insecticides, environmental cleanup, and bug repellents as well as drugs to calm the itching and prevent infection.

Insecticides

Methoprene can stop the larvae from turning into adults. Teknar or Vectobac are some biological insecticides that may work as well.

Environmental Cleanup

Cleaning up the area where your horse is stabled and spends most of his time is important in getting rid of the midge infestation. Even with insecticide and repellents, midges have to be removed to control the population due to the number of eggs they lay in humid areas. Be sure to get rid of any standing water and replace your horse’s water daily to prevent hatching. Clean up any compost and manure piles you may have as they are likely already infested.

Repellents

There are repellents that contain DEET (N,N-diethyl-meta-toluamide) which are used to successfully get rid of midges, but not for long. This is a drug you have to use constantly to be effective. Be sure to use as directed and speak to the veterinarian first to be sure it is safe to use on your horse.

Medications

An antihistamine such as pyrilamine or hydroxyzine will be administered to give immediate relief for itching. Steroids such as prednisolone and dexamethasone; oral glucocorticoids; and topical cortisone cream or ointment may be prescribed for continued use at home in order to relieve the itching and inflammation. Antibiotics such as amoxicillin or cephalexin are usually given by injection to prevent infection from scratching. Ivermectin is a good drug for this type of infestation as well. It kills parasites and can keep midges from biting in some cases.

Recovery of Midge Bite Allergy in Horses

Recovery is excellent as long as your horse does not get a serious skin infection from biting himself or scratching. Many horses actually harm themselves badly from biting on themselves so it is important to treat them right away. Be sure to get approval from the veterinarian for whichever repellents or insecticides you use beforehand so you do not harm the environment or other wildlife.