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Arthropod bites and stings

Medical condition

  • 7 min read
  • 6 chapters

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Signs and symptoms

Most arthropod bites and stings cause self-limited redness, itchiness and/or pain around the site. Less commonly (around 10% of Hymenoptera sting reactions), a large local reaction occurs when the area of swelling is greater than 10 centimetres (4 in). Rarely (1-3% of Hymenoptera sting reactions), systemic reactions can affect multiple organs and pose a medical emergency, as in the case of anaphylactic shock.

Defensive and predatory bites and stings

Many arthropods bite or sting in order to immobilize their prey or deter potential predators as a defense mechanism. Stings containing venom are more likely to be painful. Less frequently, venomous spider bites are also associated with morbidity and mortality in humans.

Most arthropod stings involve Hymenoptera (ants, wasps, and bees). While the majority of Hymenoptera stings are locally painful, their associated venom rarely cause toxic reactions unless victims receive many stings at once. The low mortality (around 60 deaths per year in the US out of unreported millions of stings nationwide) associated with Hymenoptera is mostly due to anaphylaxis from venom hypersensitivity.

Most scorpion stings also cause self-limited pain or paresthesias. Only certain species (from family Buthidae) inject neurotoxic venom, responsible for most morbidity and mortality. Severe toxic reactions can occur resulting in progressive hemodynamic instability, neuromuscular dysfunction, cardiogenic shock, pulmonary edema, multi-organ failure, and death. Although robust epidemiological data is unavailable, global estimates of scorpion stings exceed 1.2 million resulting in more than 3000 deaths annually.

Spider bites most often cause minor symptoms and resolve without intervention. Medically significant spider bites involve substantial envenomation from only certain species such as widow spiders and recluse spiders. Symptoms of latrodectism (from widow spiders) may include pain at the bite or involve the chest and abdomen, sweating, muscle cramps and vomiting among others. By comparison, loxoscelism (from recluse spiders) can present with local necrosis of the surrounding skin and widespread breakdown of red blood cells. Headaches, vomiting and a mild fever may also occur.

Feeding bites

Feeding bites have characteristic patterns and symptoms that reflect feeding habits of the offending pest and the chemistry of its saliva. Feeding bites are less likely to be felt at the time of the bite, although there are some exceptions. Since feeding requires longer attachment to prey than envenomation, feeding bites are more often associated with vector transmission of disease.

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