Felis ISSN 2398-2950

Neotrombicula autumnalis

Synonym(s): N. autumnalis, Harvest mite, Trombicula autumnalis, Chiggers

Contributor(s): Dwight Bowman, David Scarff




  • Family: Trombiculidae.
  • Genus: Neotrombicula/Trombicula.

Active Forms

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Clinical Effects



  • Damp, but drained, usually chalky soil with only the larva becoming parasitic.
  • The natural hosts are usually small rodents, eg field-mice, but larvae will attach themselves to any grazing animals, humans working in the fields, eg harvest time, or humans, dogs, cats, etc walking over the often low-lying fields.


  • See lifecycle diagram Lifecycle: Neotrombicula autumnalis - diagram .
  • Only the larvae are parasitic.


  • The mites are acquired from the chalky soils that they favor.
  • Larvae will climb up to 8 cm on grass, harvested corn stalks, etc to locate and attach to a host.

Pathological effects

  • A hypersensitivity reaction (presumably in response to antigens in saliva and feeding tunnel) that persists for days to weeks after the mite has been removed or fallen off.
  • The proteolytic enzymes and hypersensitivity reaction lead to severe pruritis and irritation.
  • The pet persistently licks or scratches.
  • Marked hyperemia at site(s) of attachment with formation of red nodules and wheals often up to 2 cm, with exudation of tissue fluid to form a yellow crust over very reddened skin.
  • If the yellow exudate crust is lifted, the mites are attached underneath.
  • The 'feeding tunnel' in the dermis becomes surrounded with inflammatory cells.
  • Secondary infection can lead to pustule formation.

Other Host Effects

  • Larva attaches to host for up to 4-5 days and feeds on host's tissue fluids.
  • Attachment and feeding is aided by cytolytic enzymes that dissolve tissues.
  • A 'feeding tunnel' is formed of a hardened hyaline material secreted by the mite and this penetrates through the epidermis.


Control via animal


  • Remove any visible mites.
  • Treat with acaricide.
  • Anti-inflammatory therapy is useful as the hypersensitivity reaction persists after the mites have been removed.
  • Antibacterial therapy Therapeutics: antimicrobial drug may be useful if secondary infection present.


  • Restrict access to known infested areas in late summer/autumn.
  • Apply repellents if animal is known to frequent known infested soils in the autumn (efficacy seems variable and also will depend on the animal not licking off the repellent).

Control via chemotherapies


  • Amitraz Amitraz.
  • Dichlorvos/fenithrothion (not available in US).
  • Phosmet.
  • Fipronil Fipronil.


  • Benzyl benzoate (unlicensed use in cat).
  • DEET (NN-diethyl-m-toluamide) (not available in UK).
  • Can also apply long-acting collars (amitraz, diazonin, chlopyirifos) (not available in UK).


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Further Reading


Refereed papers