Chilomastix spp

From Dog
Trophozoite of C. mesnili[1]

Chilomastix are a cosmopolitan non-parasitic microaerophilic retortamonad (Mastigophoran) flagellate protist[2] occasionally found in the large intestine of dogs.

Species which have been reported include:

  • Chilomastix mesnili

These protists have a commensal life cycle similar to Giardia lamblia and are not thought to be primary parasites or initiators of disease in dogs.

Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites). The cyst stage is resistant to environmental pressures and is responsible for transmission of this organism.

Chilomastix normally reside in the microaerophilic epithelium of the colon and are commonly found during routine coprological surveys, with up to 10% of urban dogs commonly harboring them in their intestinal microflora[3][4].

This parasite appears to cycle between humans who live in close association with domestic animals and rodents[5]. They are commonly reported in indigenous populations[6].

Both cysts and trophozoites can be found in the feces (diagnostic stages).

No disease has been reported in dogs associated with Chilomastix, although they should be considered in dogs with chronic diarrhea.


  1. Funscrape
  2. Takishita K et al (2012) Multigene phylogenies of diverse Carpediemonas-like organisms identify the closest relatives of 'amitochondriate' diplomonads and retortamonads. Protist 163(3):344-355
  3. López J et al (2006) Intestinal parasites in dogs and cats with gastrointestinal symptoms in Santiago, Chile. Rev Med Chil 134(2):193-200
  4. Hopkins RM et al (1993) A field and laboratory evaluation of a commercial ELISA for the detection of Giardia coproantigens in humans and dogs. Trans R Soc Trop Med Hyg 87(1):39-41
  5. McInnes EF et al (2011) Prevalence of viral, bacterial and parasitological diseases in rats and mice used in research environments in Australasia over a 5-y period. Lab Anim (NY) 40(11):341-350
  6. Meloni BP et al (1993) The prevalence of Giardia and other intestinal parasites in children, dogs and cats from aboriginal communities in the Kimberley. Med J Aust 158(3):157-159