Spider bites come in various shapes and sizes, just like the arachnid that does the deed. A bite without venom usually appears as a hard bump that resolves on its own, just like a mosquito bite. You may not even know the horse was bitten unless complications arise.
However, if the spider injects venom when it bites, the initial reaction is redness and inflammation, virtually invisible through a horse’s coat. This will be followed in a few hours by a hard bump. The bite may resolve at this stage or progress over the next day or two to blistering.
During this time, systemic flu-like reactions and fever are common. The open, ulcer-like bite area can be fairly small or up to several inches in diameter. The ulcer forms because the injected venom destroys the skin and underlying tissues, including muscle and fat if enough venom is injected.
Tissue death may continue slowly for the next few weeks and the surface of the bite develops a leathery-like black covering, which is a natural bandage. Once that falls off, the open bed of granulation tissue gradually heals. In rare instances, new swellings and ulcerations may appear for months after the initial bite. Bites may carry bacteria in with them, so secondary infections may develop and complicate the treatment.
Your veterinarian will need to scrape away the dead, infected tissue so it can heal. Some veterinarians leave the wound open, rather than stitch it closed, to produce optimum drainage. In two to four weeks skin and hair will grow back.
Mosquitoes and biting flies can cause painful bites, which then either swell and/or scab or may enlarge on hypersensitive horses. Tiny black flies can cause blood loss, toxemia, anphylactic shock and, in rare instances, death when they attack in large swarms.
Culicoides — better known as midgies, no-see-ums, sandflies, biting gnats and a myriad of other nicknames — are the most common cause of midline dermatitis.
Bee, wasp and hornet stings are generally not life-threatening, unless the horse has an allergic reaction. Ice may help ease the sting, but otherwise chances are your horse will be fine. However, watch carefully for severe, increasing swelling, an increase in temperature, or rapid breathing. These can be signs of the onset of anaphylactic shock, requiring immediate veterinary care.
Check your horse daily for ticks, as early removal reduces the chance of illness. Ticks transmit diseases, including Lyme, Babesia and Ehrlichia. Tick-related irritations and infections in the mane and tail can go unnoticed until they ooze and itch. They can damage skin and cause anemia.
Ticks often prefer to attach in secluded areas, such as under the tail, in the mane and tail, behind the elbow, under fetlock hair, even under saddles or girths if picked up when riding.
Permethrin sprays have good repellent action. Saturate the hair of the lower legs, mane and tail down to the skin. Apply to face/ears with a rag.
If you find an attached tick, use tweezers to grasp its head close to the skin and pull it straight out. Deep ear ticks can be treated by your veterinarian with Lindane or ivermectin solution into the ear and administration of ivermectin orally.
Also With This Article
”Basic Care For Bites And Stings”