Horses share an outdoor environment inhabited by many types of biting and stinging insects. Inspect your horse carefully if you notice him rubbing or scratching; treating itching bites early can prevent them from becoming infected. If you notice localized swelling, he may have been bitten by a wasp or bee. Applying ice to any bite can give your horse relief and reduce swelling.
Inspect your horse's pasture for obvious nests of ants, wasps and bees, and keep the barn and shelter clean to prevent spider infestations.
Small Flying Insects
Most areas of the country host several types of flies, in addition to mosquitoes and other small insects. Culicoides are those small gnats, no-see-ums, midges and other tiny insects that seem to swarm around horses during warm weather. For most horses, they are an annoyance that you can help them combat by diligently applying fly sprays that contain pyrethrin insecticides and outfitting your horse in fly masks, sheets and leg wraps. Some horses, however, have varying degrees of insect bite hypersensitivity, or IBH, and will be extremely uncomfortable without additional measures.
Treatment for IBH
If your horse suffers from IBH, also referred to as "sweet itch" or Queensland itch, he is allergic to the insect's saliva, leading to excessive itching, scratching and rubbing. You will also notice signs of dermatitis, including hair loss, scaly skin, excoriations -- which are small pieces of skin rubbed off -- and possibly hives. Only your veterinarian can make a definitive diagnosis through allergy tests, but you can try to treat mild cases yourself as long as no open skin is infected. Look for phytogenic, or plant-based ointments for skin conditions; one such type is aloe vera gel. Your veterinarian may also be able to recommend a topical application with essential oils.
If any of the bites become infected lesions, your veterinarian may prescribe an antibiotic, corticosteroids or suggest allergy shots. Prescribed antihistamines may work in some cases.
Consult your veterinarian before applying a topical ointment containing antibiotics or cortisone.
Preventing IBH and Small Insect Discomfort
Any treatment for small insect bites work best in conjunction with ongoing preventive measures. Repelling the annoying insects with fly spray is a basic line of defense; look for one with sunscreen so the pyrethrin doesn't break down in the sunlight. Your fly spray's effectiveness is diminished by high temperature, humidity and your horse's perspiration, despite what the bottle label might indicate, so apply daily. Schedule your horse's turnout during the day, if possible, since the small biting creatures are more active at dawn and at dusk.
In addition to his protective fly wear, keep the barn free of standing water in buckets, tires, or hollow logs that invite mosquitoes to breed. A stall fan can keep insects at bay in a barn with poor ventilation or on calm days. Finally, supplementing your diet with foods or oil high in omega-3 can help reduce inflammation associated with insect bites.
A well-ventilated barn is essential for your horse's overall health, not just for flying insects.
The social stingers aren't as friendly as their label implies; they sting to protect their nests: wasps, hornets, bees and ants. Of these insects, bees are the only ones that leave incriminating evidence: their stingers. Try to remove a stinger with tweezers or by scraping the bite bump with a credit card, but if you can't remove it, contact your veterinarian. In many cases, you won't even notice your horse was bitten or stung by these insects until you groom him and notice a soft swelling.
A sting in a sensitive area, such as the eye or muzzle, can be extremely uncomfortable for your horse, so call your veterinarian.
Most horses recover fine from stinging bites, but you can increase your horse's comfort by applying an ice pack to the swelling. Then, make a paste from baking soda and water to apply to the sting, or apply calamine lotion. You can also apply ichthammol ointment to draw out inflammation. If your horse seems lethargic, depressed or runs a fever, he may be allergic to the insect bite, or you may have misdiagnosed its source. Contact your veterinarian immediately if the bite leads to anything more than minor discomfort at the site.
Scorpions, spiders and centipedes all frequent barns. One way to prepare yourself is to ask your veterinarian what types of spiders are common in your area of the country that can cause problems with your horse; some areas, for example, are home to brown recluse and black widow spiders, whose bites can warrant a veterinarian visit.
Unless you see the spider, you're not likely to know what type caused it, but check your horse's temperature, and contact your veterinarian if he's running a fever, has labored breathing or seems chilled. Most horses typically have an initial painful and localized reaction from centipede and scorpion bites, but otherwise recover well over time.
Keep your horse's vaccinations current, especially his tetanus vaccine, to protect against serious consequences from spider bites.
Treating and Preventing Spider Bites
Treat a spider bite as you would an open wound, with the goal of preventing infection. Keep it clean with tap water; per your veterinarian's instructions, you can wash it with a chlorhexidine or other antibacterial solution. Apply a topical phytogenic or antibiotic ointment.
If you know a black widow bit your horse, your veterinarian may give him an antivenin. Your vet will typically remove any dead tissue from the bite area, give a tetanus booster, and may prescribe antibiotics.
Check your barn, especially dark corners, for signs of spiders and remove webs. Keep the barn free of debris and clean to make it less hospitable for arachnids.
Horses and Fleas
The good news is that fleas are not as common on horses as they are on your household pets, but they can persist if you have several horses in close quarters. Your horse can also get fleas from barn cats and chickens. Your horse will react much as your flea-infested dog and cat will, with excessive scratching and rubbing.
You will also treat your horse in much the same way. Fleas die in water, so give your horse a bath, paying attention to his mane and tail. Apply fly spray to help keep fleas at bay and keep your horse's stall clean. If you have more than one horse, you will have to treat all of them at the same time.
Adding some vinegar to your horse's bath and drinking water may help keep fleas at bay.