Bites, Arthopod

• • Some arthropod bites can result in death by direct toxicity or by causing hypersensitivity reactions

  • Venom of bees and wasps contains histamine, basic protein components of high molecular weight, free amino acids, hyaluronidase, and acetylcholine

  • Only a few spider venoms are harmful to humans

• • Bite of the Latrodectus species of spiders, including the black widow (Latrodectus mactans) and the red-backed spider (Latrodectus hasseltii), has primarily systemic neurotoxic effects

  • Female black widow spider can be identified by its characteristic black body with a red hourglass-like pattern on the abdomen (male of the species does not bite and is smaller)

  • -Black widow venom: Neuromuscular toxic effects occur by presynaptic motor end plate neurotransmitter release, with release of norepinephrine and acetylcholine causing excessive stimulation and eventual fatigue of the motor end plate and muscle

  • The brown recluse spider (Loxosceles reclusa) is dark tan and has a violin-shaped mark on the back of the main body

• • Envenomation can have significant and prolonged local dermonecrotic effects, with development of deep necrotic wounds at the bite site that are very slow to heal

• • Because of their prevalence and numbers, bees and wasps kill more people than any other venomous animal, including snakes

  • Very young, the elderly, and patients with comorbid medical conditions are at greatest risk for adverse outcomes

Symptoms and Signs

Wasp and Bee Stings

• • Symptoms may vary from minimal erythema to a marked local reaction of severe systemic toxicity

  • Moderately severe reactions will present as generalized syncope or urticarial reactions

Latrodectism

• • Symptoms of envenomation begin with pain at the bite location followed by later development of abdominal wall muscle rigidity, abdominal pain and cramping, respiratory difficulty with potential paralysis, and lower extremity weakness

  • Massive hemolysis, severe hypotension, and cardiovascular collapse can occur

  • Local skin changes are often minimal and can make identification of the bite difficult

Loxoscelism

• • Bite may have local signs of erythema and edema but usually minimal associated pain

  • Hemorrhagic bullae surrounded by localized ischemia develop over the next 24-48 hours

  • Lesion usually progresses to a very slowly healing ulcer

  • Symptoms may include fever, urticaria, lymphangitis, nausea

Laboratory Findings

• • Hemolysis and disseminated intravascular coagulation are rare

Rule Out

• • Concomitant animal/insect bite

  • Multiples bites or stings from multiple different animals or insects

  • Associated injuries

• • Determine type of insect bite or sting

  • Physical exam to determine number of bites or stings

  • Determine tetanus prophylaxis status

When to Admit

• • Systemic signs or complications from bites or stings

• • After being stung by a bee, the exuded ...