Potential Emergency Situation: Need to go to vet
  • SYSTEM(S) EFFECTED:
    		•  Nervous
  • CAUSE(S):
    		• Envenomation by spider
  • DIAGNOSTICS:
    		• None
  • TREATMENT:
    		• Supportive care

GENERAL DESCRIPTION

Black Widow Spiders are a venomous spider that is common throughout eastern North America, focused mainly in the southern part of it’s geographic range. These spiders are usually found outdoors or in garages and sheds, frequently near buildings. The dangerous females are easily recognized by their bulbous black abdomen with bright red hourglass shape on the underside. The juveniles and males very rarely ever bite.

Death can occur from a Black Widow bite when the muscles and nerves associated with respiration become damaged. Envenomation can cause abnormally high blood pressure in cats, which makes them particularly susceptible to death. Dogs that receive prompt veterinary care tend to do well after a Black Widow bite.

SOURCE & CAUSE(S)

The toxin found in the venom of the Black Widow Spider is a protein called α-latrotoxin which acts on the nerve endings, causing gradual pain and involuntary muscle contractions.

Black Widow Spiders belong to the genus Latrodectus. There are a number of other species in the genus, all of which have potent neurotoxic venom. Black Widow Spiders (Latrodectus mactans) just happen to be the most widespread and most likely to come in contact with people and their pets.

SIGNS & SYMPTOMS

The bite may initially go unnoticed by your pet or it could cause a sharp, burning pain. Immediately after bite, pain spreads to regional lymph nodes nearest bite site. Initially, there is little to no swelling at the site of the bite. 1 to 3 hours after the bite, pain reaches maximum intensity. After which pain may be continuous or intermittent, sometimes lasting up to 48 hours.Your pet may show increased activity for the first 10-20 hours after the bite, after which paralysis may set in.

Symptoms of a Black Widow Spider bite include:

Black Widow Spider

  • Numbness surrounding bite site
  • Restlessness
  • Muscle pain
  • Muscle rigidity, particularly the abdominal muscles 
  • Seizures
  • Increased heart rate
  • Labored breathing, usually rapid and shallow
  • Weakness of the limbs
  • Paralysis
Cats who have been bitten by a Black Widow Spider may show these additional symptoms:
  • Severe pain
  • Drooling
  • Early paralysis
  • Death 
Variety in the number and severity of the symptoms may occur due to the location of the bite, the amount of venom injected, and your pet’s individual sensitivity to the venom.

TREATMENT & MANAGEMENT

If you suspect your cat has been bitten by a Black Widow Spider, take your pet to the veterinarian IMMEDIATELY! This is an emergency situation, as Black Widow bites in cats can be very severe and fatal.

If you suspect your dog has been bitten by a Black Widow Spider, contact your veterinarian IMMEDIATELY.  They may recommend administering Benadryl or an ice pack at home to prevent inflammation. They will likely not be able to determine the severity of the bite in a dog without seeing your pet, so a visit to the veterinarian is usually recommended. There, they will likely treat your pet for the symptoms it is displaying.

An antivenin is available, but is usually not given to pets because it is extremely expensive. Veterinarians do not typically keep antivenin at their clinics and would likely have to retrieve it from a human hospital.

    PREVENTION & HELPFUL TIPS

    The best way to prevent a Black Widow Spider bite is to limit your pet’s exposure to the spider. If you know that you live within the Black Widow’s geographic distribution, or if you have seen one in your area before, keep an eye on your pets when they are outside if possible. Exclusion may also be possible by sealing storage boxes tight and keeping sheds and attics clean and free of spider webs.


    Written by: PetsMD Veterinary Editorial Staff