Microbiology & parasitology

Parasites-cutaneous / subcutaneous / soft tissue

Myiasis



Topic Completed: 1 July 2018

Minor changes: 1 October 2021

Copyright: 2018-2021, PathologyOutlines.com, Inc.

PubMed Search: Myiasis[TI] pathology full text[sb]

See Also: Botfly

Jaya Ruth Asirvatham, M.B.B.S.
Julie M. Jorns, M.D.
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Cite this page: Asirvatham JR, Jorns J, Pernick N. Myiasis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/parasitologymyiasis.html. Accessed October 15th, 2021.
Definition / general
Terminology
  • Most common: human botfly (Dermatobia hominis)
  • Others: Cochliomyia hominovaroxiz, Chrysomya bezziana, Cordylobia anthrophaga
Epidemiology
Pathophysiology
  • Adult flies are usually attracted to host orifices and unattended open wounds where they lay eggs
  • Some species infect living tissue (e.g. botfly)
  • May lay eggs on soiled clothes, larvae may develop and can penetrate intact skin (e.g. green bottle fly)
  • Botfly larvae creates a cavity with an opening (like a long neck bottle) after penetrating the skin and grow into a mature fusiform shape up to 3 cm in diameter
  • A firm red subcutaneous nodule / furuncle is formed in 2 - 3 weeks
Clinical features
  • May cause fever, local inflammation and bleeding and superimposed bacterial infection
  • Cause abscess and rarely granulomatous response to dead larvae
  • May be a secondary infection in fungating breast carcinoma
  • Can mimic breast carcinoma (East Afr Med J 1999;76:115)
  • Often multiple infestations in breast
  • Also affects lips of breast fed infants (Int J Dermatol 2006;45:1069)
  • Can be misdiagnosed as cellulitis, mosquito bites, herpes etc.
Laboratory
  • Genus / species identification: comparing certain morphological structures on the larvae (spiracles, mouthparts, cephalopharyngeal skeleton, cuticular spines)
  • Travel history helpful
Radiology description
  • May form an ill defined mass with calcification (Radiology 2001;218:517)
  • US may show a hyperechoic mass representing the larva surrounded by a hypoechoic halo representing the cavity
  • Larval movement may be noted
Radiology images

Images hosted on other servers:

Various images

Case reports
Treatment
Clinical images

Contributed by Bobbi Pritt, M.D. and Lars Westblade, Ph.D.

Furuncular myiasis



Images hosted on other servers:

Breast lesion with tumbu fly larvae

Sinuses after extraction of the larva

Extracted tumbu fly larvae

One week after extraction

Gross images

Contributed by Bobbi Pritt, M.D.

Cordylobia anthropophaga removed from elderly woman

Posterior end of Cordylobia anthropophaga

Posterior spiracles
with sinuous slits


Sheep with wound infected with blow fly larvae (Phormyia regina or Cochliomyia macellaria)



Images hosted on other servers:

Extracted from dog

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Bobbi Pritt, M.D. and Lars Westblade, Ph.D.

Representative sections of skin biopsy show botfly larva

Videos

Creepy Dreadful Wonderful Parasites Case

Differential diagnosis
  • Auchmeromyia (Congo floor maggot):
    • Doesn't form furuncles (boil-like lesions with a live dipteran maggot within) but stays on the host only for feeding, similar to a bedbug
    • It has 3 spiracular slits per side, straight, lying horizontally
  • Cordylobia rodhani (Lund fly):
    • Has 3 posterior spiracular slits on each side but its slits are more sinuous than Cordylobia anthropophaga
  • Ticks:
    • Have legs and mouth and don't burrow deeply into skin
  • Tunga penetrans:
    • Flea with legs, almost always involves feet, has cuticle > 20 microns, lacks a spine
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