Giardia spp

From Dog
Giardia spp parasite[1]

Giardia are a zoonotic diplomonad protozoan parasite of dogs which causes intermittent diarrhoea.

Prevalence rates in dogs varies but it is commonly reported in 5 - 15% of dogs in routine epidemiological surveys[2][3][4][5][6]. Seasonal increases in prevalence are usual during the winter and summer months[7].

Species which are pathogenic to dogs include:

  • Giardia duodenalis assemblage A & B - mainly human-to-human, but also seen in dogs and cats[8]
  • Giardia duodenalis assemblage C - mainly dogs
  • Giardia duodenalis assemblage D - mainly dogs[9]
  • Giardia duodenalis assemblage D - mainly ungulates (cattle, sheep, horses, pigs, goats)

Other species such as G. lamblia, G. intestinalis, and G. enterica primarily infect humans[10].

The distinction of assemblages is usually determined by analysis of the glutamate dehydrogenase locus, a distinction which has importance since assemblages A & B are usually zoonotic and have been commonly detected in dogs and cats living in households[11].

The life cycle is relatively direct, with dogs ingesting cysts in soil contaminated with feces from other dogs, cats or humans.

Under proteolytic activation by gastric acids, cysts release the flagellate protozoa (trophozoites), which eventually reside in the mucosal surfaces of the small intestine, attaching to the brush border. They multiply by binary fission and trophozoites consequently encyst in the small or large intestine and pass in the feces. Transmission occurs by the fecal-oral route. Prepatent period is usually 1 - 2 weeks. Infections are usually associated with kenneled dogs[12].

Clinical signs are usually mild acute diarrhea. As is observed in cats, chronic, intermitten diarrhea can be observed in kennels, and steatorrhea is not uncommon.

Diagnosis is based on light microscopic visualization of cysts, or ELISA detection of Giardia antigens. Speciation requires PCR assays.

Concurrent infections with other endoparasites such as Cryptosporidium spp are common[13].

A differential diagnosis must include other endoparasites and exocrine pancreatic insufficiency.

Treatment is relatively effective with fenbendazole, albendazole, ronidazole, metronidazole or secnidazole[14]. However, elimination of the organism is usually unsuccessful in large kennels and sporadic outbreaks are regularly observed.

Drug treatment combined with the disinfection of the environment and shampooing of the dogs is often effective at reducing Giardia cyst excretion[15].


  1. Scoop on Pets
  2. Dado D et al (2012) Prevalence and genotypes of Giardia duodenalis from dogs in Spain: possible zoonotic transmission and public health importance. Parasitol Res Sep 15
  3. Schurer JM et al (2012) Sentinel surveillance for zoonotic parasites in companion animals in indigenous communities of Saskatchewan. Am J Trop Med Hyg 87(3):495-498
  4. Joffe D et al (2011) The prevalence of intestinal parasites in dogs and cats in Calgary, Alberta. Can Vet J 52(12):1323-1328
  5. Li J et al (2012) Genotype identification and prevalence of Giardia duodenalis in pet dogs of Guangzhou, Southern China. Vet Parasitol 188(3-4):368-371
  6. Mircean V et al (2012) Prevalence and risk factors of Giardia duodenalis in dogs from Romania. Vet Parasitol 184(2-4):325-329
  7. Mohamed AS et al (2013) Prevalence and risk factors for Giardia spp. infection in a large national sample of pet dogs visiting veterinary hospitals in the United States (2003-2009). Vet Parasitol Jan 3
  8. Mark-Carew MP et al (2013) Characterization of Giardia duodenalis infections in dogs in Trinidad and Tobago. Vet Parasitol Feb 4
  9. Scorza AV et al (2011) Prevalence of selected zoonotic and vector-borne agents in dogs and cats in Costa Rica. Vet Parasitol 183(1-2):178-183
  10. Bowman, DD (2009) Georgis' parasitology for veterinarians. Saunders Elsevier, St. Louis, Missouri. pp:89
  11. Sotiriadou I et al (2013) Molecular identification of Giardia and Cryptosporidium from dogs and cats. Parasite 20:8
  12. Merck Veterinary Manual
  13. Berrilli F et al (2012) Giardia duodenalis genotypes and Cryptosporidium species in humans and domestic animals in Côte d'Ivoire: occurrence and evidence for environmental contamination. Trans R Soc Trop Med Hyg 106(3):191-195
  14. Da Silva AS et al (2011) Secnidazole for the treatment of giardiasis in naturally infected cats. Parasitol Int 60(4):429-432
  15. Fiechter R et al (2012) Control of Giardia infections with ronidazole and intensive hygiene management in a dog kennel. Vet Parasitol 187(1-2):93-98