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centipedes

centipede bites

Introduction

  • centipedes are widespread around the world and Australia is home to many species, some of which are native to Australia
  • centipedes are solitary, nocturnal fast moving predators, usually around 10cm in length but some Australian species such as Ethmostigmus rubripes reach 20cm and these larger ones are capable of subduing small vertebrates although most largely feed on insects, spiders, slaters, snails, worms and even other centipedes 1)
  • the largest centipede in the world, Scolopendra gigantea, is a 30 cm centipede from South America that is able to eat mice and lizards
  • they grasp prey with their last pair of legs and immobilise it by biting with their fangs and venom
  • the larger centipedes are capable of biting humans with their strong venom-wielding front fangs, the larger the centipede the more toxin is likely to be released and the greater the pain which can be severe and prolonged lasting a day or so
  • serious adverse effects in human are rare, including potential anaphylaxis, although one young girl has died after a bite from a Scolopendra subspinipes, and a 21 yr old died in Thailand presumably from anaphylaxis
  • the most common ones in Australian urban centres are Scolopendrid Centipedes (there are 40 named species in 9 genera in Australia but the most common genera are Scolopendra, Cormocephalus and Ethmostigmus ), and these are the main order of centipedes worldwide which cause painful human bites
  • humans generally encounter them when they are gardening and lift up bricks or rocks under which the centipede is sleeping and avoiding birds and other predators and bites are usually to the hands or feet, although over 50% of bites occur indoors and at night, and most bites occur in Summer
  • they also like to rest between the bark of trees and in leaf litter2)
  • infants are sometimes found chewing on centipedes but usually to no ill effect - if they don't get bitten themselves - there is one report of a young child ingesting a Scutigeromorpha centipede in Australia resulting in the child appearing pale, floppy, and lethargic
  • contact with the legs which are known to secrete various chemicals such as hydrogen cyanide may cause local skin reactions

Toxins

  • there are a mix of toxins designed to rapidly immobilise invertebrates and even small vertebrates
  • Scolopendrids are unique amongst centipedes for having complex venom glands with many venom-producing structures3)
  • the physically stronger scolopendromorphs can have up to 100 times as many venom-secreting cells as the weaker scutigeromorphs
  • toxins include:
    • histamine
    • neurotoxins such as:
      • Spooky Toxin (SsTx) in the Scolopendra subspinipes mutilans4)

Clinical features

  • most cause minor effects
  • severe pain occurs more likely with larger species and in Australia that is5):
    • Ethmostigmus - 100% develop severe pain
    • Scolopendra - 60% develop severe pain
    • Cormocephalus - < 20% develop severe pain
  • usually two puncture marks (or multiples of these if it has had a few goes) with local erythema, itching and wheal reaction
  • the pain may radiate proximally and generally lasts a few hours
  • nausea, vomiting, diaphoresis and hypertension may occur
  • erythema and local swelling can last days
  • there has been one report of Wells Syndrome, also known as eosinophilic cellulitis, which is an acute dermatitis resembling cellulitis, which evolves into plaques that resolve spontaneously
  • Rhabdomyolysis and acute renal failure have been reported after a desert giant centipede bite (S. heros))
  • and rarely, anaphylaxis and myocardial ischaemia in those at risk
  • a 4-yr-old bull-terrier following a bite by E. rubripes

First aid management

  • it seems that immersion in hot water may resolve the pain6)
  • ice packs can also help with the pain
  • oral analgesia may be needed
  • cleanse the wound to reduce infection
centipedes.txt · Last modified: 2020/05/12 23:18 by gary1