Hammondia spp

From Dog
H. heydorni cysts in canine feces, viewed under light microscopy[1]

Hammondia spp are an ampicomplexan cyst-forming protozoan parasite found worldwide[2], with very low prevalence rates as determined by epidemiological surveys in both urban and rural dogs[3][4].

This parasite is closely related genetically to Toxoplasma gondii[5].

Species which are pathogenic to dogs include:

  • Hammondia hammondi
  • Hammondia heydorni[6]

The oocysts of this parasite are physically identical to Neospora caninum and Toxoplasma gondii, and can only be distinguished via PCR assays[7].

Concurrent infections with Toxoplasma gondii, Neospora spp and Sarcocystis spp have been recorded in dogs[8], which can confuse the etiological cause in dogs presenting with protozoan-related neurological disease.

Hammonida spp have a two-host obligatory life cycle, but is similar to Toxoplasma spp that uses dogs, foxes and coyotes as final hosts and ruminants, guinea pigs and dogs as intermediate hosts. Cats remain noninfectious to this parasite[9].

This protozoan is often found incidentally, but can cause diarrhea in immunosuppressed dogs[10]. Its role as a primary initiator of disease in dogs is currently unknown.

Diagnosis is based on presenting clinical signs, fecal examination for oocysts (usually unreliable), ELISA detection of H. hammoni or H. heydorni antibodies in tissue samples, light microscopy identification of tachyzoites in CSF or other tissues and PCR assays[11] for species identification.

A differential diagnosis would include other causes of diarrhea, include protzoan endoparasites[12], Leishmania spp[13], Giardia spp and Brucella spp[14].

The recommended drug of choice in treatment is clindamycin (10 - 50 mg/kg orally for 2 - 4 weeks), with aggressive supportive therapy in acutely ill pups.

Dogs of any age with neurological signs have a more guarded prognosis.

Feeding of raw meat is a potential risk factor for infection of dogs and should be discouraged.


  1. Kansas State Uni
  2. Ellis JT & Pomroy WE (2003) Hammondia heydorni oocysts in the faeces of a greyhound in New Zealand. N Z Vet J 51(1):38-39
  3. Becker AC et al (2012) Prevalence of endoparasites in stray and fostered dogs and cats in Northern Germany. Parasitol Res 111(2):849-857
  4. Schares G et al (2005) Oocysts of Neospora caninum, Hammondia heydorni, Toxoplasma gondii and Hammondia hammondi in faeces collected from dogs in Germany. Int J Parasitol 35(14):1525-1537
  5. Ellis JT et al (1999) The genus Hammondia is paraphyletic. Parasitology 118(4):357-362
  6. Gjerde B & Dahlgren SS (2011) Hammondia triffittae n. comb. of foxes ( Vulpes spp.): biological and molecular characteristics and differentiation from Hammondia heydorni of dogs. Parasitology 138(3):303-321
  7. Hill,m DE et al (2001) Specific detection of Neospora caninum oocysts in fecal samples from experimentally-infected dogs using the polymerase-chain reaction. J Parasitol 87:395
  8. Dubey JP et al (2003) Clinical Toxoplasma gondii, Hammondia heydorni, and Sarcocystis spp. infections in dogs. Parassitologia 45(3-4):141-146
  9. Bowman, DD (2009) Georgis' Parasitology for veterinarians. 9th edn. Elsevier Saunders, Missouri. pp:103-104
  10. Reichel MP et al (2007) Neosporosis and hammondiosis in dogs. J Small Anim Pract 48(6):308-312
  11. Slapeta JR et al (2002) Coprodiagnosis of Hammondia heydorni in dogs by PCR based amplification of ITS 1 rRNA: differentiation from morphologically indistinguishable oocysts of Neospora caninum. Vet J 163(2):147-154
  12. Lopes MG et al (2011) Presence of antibodies against Toxoplasma gondii, Neospora caninum and Leishmania infantum in dogs from Piauí. Rev Bras Parasitol Vet 20(2):111-114
  13. Cabezón O et al (2010) Kennel dogs as sentinels of Leishmania infantum, Toxoplasma gondii, and Neospora caninum in Majorca Island, Spain. Parasitol Res 107(6):1505-1508
  14. Valadas S et al (2010) Occurrence of antibodies anti-Neospora caninum, anti-Toxoplasma gondii, and anti-Leishmania chagasi in serum of dogs from Pará State, Amazon, Brazil. Parasitol Res 107(2):453-457