- Arthropod bites and stings:
- Cause a wide spectrum of reactions
- Transmit local and systemic infections
- Superficial infestations:
- Epidermal: Pediculosis, scabies, tungiasis
- Dermal: Larva migrans, myiasis
- Terrestrial arthropods that bite/sting humans: arachnids, centipedes, millipedes, insects.
- Cutaneous reactions to arthropod bites (CRAB) are inflammatory and/or allergic reactions.
- Characterized by an intensely pruritic eruption at the bite sites immediately to minutes to hours to days after the bite, persisting for days to weeks, manifested by solitary or grouped:
- Urticarial papules
- Patients are often unaware of having been bitten.
- In some cases, systemic symptoms may occur, ranging from mild to severe, with death occurring from anaphylactic shock.
- Arthropods are vectors of many systemic infections.
Summer in temperate climates.
5 of 9 classes of arthropods cause local and systemic reactions associated with their bites: Arachnida, Chilopoda, Diplopoda, Crustacea, Insecta.
Arthropods that Bite, Sting, or Infest
- Arachnida (four pairs of legs): mites, ticks, spiders, scorpions
- Mites: Sarcoptes scabiei causes scabies; Demodex folliculorum, human hair follicle mite; many others including food, fowl, grain, straw, harvest, animal, and house dust mites.
- Araneae: spiders
- Chilopoda and Diplopoda: centipedes, millipedes
- Insecta (three pairs of legs)
- Anoplura: lice (Phthirius and Pediculus)
- Coleoptera: beetles
- Diptera: mosquitoes, black flies, midges (punkies, no seeums, sand flies), Tabandae (horseflies, deerflies, clegs, breeze flies, greenheads, mango flies); botflies, Callitroga americana, Dermatobia hominis, phlebotomid sand flies, tsetse flies
- Hemiptera: bedbugs, kissing bugs
- Hymenoptera: ants, bees, wasps, hornets
- Lepidoptera: caterpillars, butterflies, moths
- Siphonaptera: fleas, chigoe or sand flea
- Lyme borreliosis, tularemia, bubonic plague.
- Scrub typhus, endemic (murine) typhus, spotted fever groups, Q fever
- Human granulocytic anaplasmosis,
- Tick-borne meningoencephalitis
- Leishmaniasis, trypanosomiasis (sleeping sickness, Chagas disease).
- Malaria, babesiosis.
- Filariasis, onchocerciasis (river blindness), loiasis
- Produce pruritus and/or allergic reactions through salivary proteins deposited during feeding.
- Harvest mites (chiggers) may present as intense pruritus on the ankles, legs, belt line; mites usually fall off after feeding or may be scratched off.
- In nonsensitized individuals, 1- to 2-mm pruritic papules are seen.
- In sensitized individuals, CRAB may be papular urticaria, vesiculation, or granulomatous reaction with fever and lymphadenopathy.
Reactions include foreign body reactions, reactions to salivary secretions, reactions to injected toxins, and hypersensitivity reactions. Tick paralysis is caused by a toxin secreted in the saliva of the tick.
- Loxosceles reclusa: Brown recluse spider bite causes reactions ranging from mild urticaria to full-thickness necrosis (loxoscelism).
- Latrodectus: “Widow” spiders inject a venom that contains a neurotoxin (α-latrotoxin) producing reactions at the bite site ...