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 . 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. == As vectors of disease ==