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==Description==

==Description==

[[Image:Giardia Cyst.jpg|thumb|right|150px| Giardia cyst from a dog. Source: Wikimedia Commons; Author: Joel Mills (2006)]]

[[Image:Giardia Cyst.jpg|thumb|right|150px| Giardia cyst from a dog. Source: Wikimedia Commons; Author: Joel Mills (2006)]]

''[[Giardia]]'' is a binucleate, flagellate protozoa that causes enteric infection giardiasis in dogs and occasionally cats. Transmission is via cysts that are shed in the faeces, and may be direct or indirect. Indirect water-borne transmission is the most common modality and is favoured by cool, moist conditions that prolong cyst survival. Once cysts are ingested, motile trophozoites are released and attach to the cells of the lower small intestinal mucosa via an adhesive disc. Multiplication by binary fission can then occur, and trophozoites encyst to a stage adapted for survival in the external environment. Cysts are seen in the faeces from day 3 post-infection, and can survive in the environment for several months. Animals that mount an immune response to ''[[Giardia]]'' can eliminate infection; however, the immunity acquired does not necessarily prevent re-infection after a short period.

''[[Giardia]]'' is a binucleate, flagellate protozoa that causes enteric infection giardiasis in dogs and occasionally cats. Transmission is via cysts that are shed in the faeces, and may be direct or indirect. Indirect water-borne transmission is the most common modality and is favoured by cool, moist conditions that prolong cyst survival. Once cysts are ingested, motile trophozoites are released and attach to the cells of the small intestinal mucosa via an adhesive disc. Predilection sites in the dog are the duodenum and jejunum, where as only the duodenum is favoured in cats. Multiplication by binary fission can then occur, and trophozoites encyst to a stage adapted for survival in the external environment. Cysts are seen in the faeces from day 3 post-infection in dogs (5-16 in cats), and can survive in the environment for several months. Animals that mount an immune response to ''[[Giardia]]'' can eliminate infection; however, the immunity acquired does not necessarily prevent re-infection after a short period.

Giardiasis is a condition of significant zoonotic concern. Although the cat protozoa ''G. felis'' seems to be species-specific, dogs can host both the canine-specific ''G. canis'' and ''G. lamblia'', which has zoonotic genotypes. It is not known how important dogs are as a reservoir for human ''[[Giardia]]'' infection, or how frequently zoonotic transmission occurs. In man, ''[[Giardia]]'' may cause acute diarrhoea, particualrly in immunocompromised individuals. Subclinical infections also occur.

Giardiasis is a condition of significant zoonotic concern. Although the cat protozoa ''G. felis'' seems to be species-specific, dogs can host both the canine-specific ''G. canis'' and ''G. lamblia'', which has zoonotic genotypes. It is not known how important dogs are as a reservoir for human ''[[Giardia]]'' infection, or how frequently zoonotic transmission occurs. In man, ''[[Giardia]]'' may cause acute diarrhoea, particualrly in immunocompromised individuals. Subclinical infections also occur.