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What is Spider Bite?

While spider and insect bites are relatively common in horses, it is important to be aware of the possible danger from a severe reaction. Because conditions like abscesses can mimic a spider bite, evaluation by a veterinarian is advised if the bite develops beyond a mild irritation or if you suspect the spider bite could present a danger to your horse.

There are 4 types of spiders that tend to be the most dangerous if they bite your horse. The brown recluse, black widow, red widow, and tarantula can all inflict wounds that will need attention. If your horse is experiencing labored breathing, pain, tissue damage or swelling do not delay in calling in the veterinarian to take a look.

Spider bites in your horse can result from contact with any type of spider. The bite is not necessarily the problem, the possibility for a severe reaction is the larger concern.

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Symptoms of Spider Bite in Horses

  • Swollen limb – The limb may become swollen and painful to the touch when you attempt to examine it
  • Warmth at the site of the swelling
  • Elevated heart rate – Your horse’s heart rate may be very fast, presenting a danger 
  • Labored breathing 
  • Physical pain – When you try to touch the area, your horse may recoil due to the pain; he may also present with difficulty putting weight on the limb 
  • Red spot – If you can spot a wound on the swollen limb, you may have a very specific indicator of what is causing your horse’s symptoms 
  • Yellow or green discharge from around the bite area
  • Fever
  • Hair loss 

Types

There are multiple types of spiders that can bite your horse and cause a severe reaction. 

Brown Recluse Spider

  • Their bites are typically warm and painful
  • If left untreated can develop into severe wounds within 3 to 7 days
  • These spiders hide during the day in dark areas 

Black Widow Spider

  • Found in barns, wood and brush piles
  • Underneath water troughs
  • Are present in North America 
  • Responsible for most of the severe horse bites
  • Can cause severe pain and itching
  • Can kill tissue
  • Not aggressive spiders, but will bite when threatened

Red Widow Spider

  • Found in barns, wood and brush piles
  • Underneath water troughs
  • Live in North America 

Tarantulas

  • Can cause tissue to die quickly
  • If left untreated, can create a deep wound within 3 to 7 days
  • Damage can be permanent

Causes of Spider Bite in Horses

  • Time of year – Spider bites tend to be frequent in the fall season as insects begin moving indoors 
  • Environment – Spiders will build nests in dark, quiet areas

Diagnosis of Spider Bite in Horses

Depending on the type of spider, the veterinarian may be able to form a diagnosis quickly by evaluating the wound where the spider penetrated the skin. He will assess the degree of pain your horse is experiencing and whether there is swelling, heat, or discharge. Having the veterinarian examine any type of wound that looks like more than a superficial scratch or insect bite is essential as secondary infection is a possibility with a spider bite.

If you saw the spider in question, a photo of the culprit will assist the veterinarian in the diagnosis. In the case of a black widow spider for example, antivenin may need to be administered, making identification crucial.

Treatment of Spider Bite in Horses

Treatment of your horse’s injury will focus on when the bite is found and in what condition your horse is in at that time. There should be limited concern with any relapse unless your horse is bitten again. 

Immediate Identification

  • Your veterinarian can provide antivenin if the spider has been identified
  • Your horse can be given medication for pain management and immediate treatment of the bite area

Late Identification

  • If there is damage to the tissue at the bite site, such as blackened skin around the wound, your veterinary caregiver may need to treat and possibly remove any dead tissue
  • Treating any open wounds or secondary infections will also be a priority if the bite wound is found later
  • Antibiotics may be necessary
  • NSAIDs will provide pain and inflammatory relief

A horse with respiratory distress or additional symptoms may be given oxygen and fluids.

Recovery of Spider Bite in Horses

Follow up appointments may be necessary to ensure full healing of the bite wound. Your veterinarian will discuss this will you if deemed essential. Ensuring your horse’s area in the barn is kept clean and regularly brushed free of webs will decrease the odds of spiders creating homes there.

Keeping outdoor areas clean and tidied up such as troughs, wood piles, or standing brush will help to discourage spiders from nesting.  If necessary treating the areas where your horse is out to pasture with insecticide can be an option.