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==Introduction==

==Introduction==

[[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|200px| 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 and reptiles. ''[[Giardia]]''  species have been reported to be found in 1-39% of faecal samples from dogs and cats, with a higher rate of infection in younger animals. 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, whereas 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.

''[[Giardia]]'' is a binucleate, flagellate protozoa that causes enteric infection giardiasis in dogs and occasionally cats and reptiles. ''[[Giardia]]''  species have been reported to be found in 1-39% of faecal samples from dogs and cats, with a higher rate of infection in younger animals. 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, whereas 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.

==Signalment==

==Signalment==

[[Image:Giardia lamblia.jpg|thumb|right|150px| ''Giardia lamblia''. Source: Wikimedia Commons; Author: Janice Carr (2006)]]

[[Image:Giardia lamblia.jpg|thumb|right|200px| ''Giardia lamblia''. Source: Wikimedia Commons; Author: Janice Carr (2006)]]

Dogs are more commonly affected than cats. There are no age, breed or sex predispositions for ''[[Giardia]]'' infection, but puppies and kittens are more likely to contract clinical disease than adult animals. Disease may also be seen in immunocompromised or stressed individuals.

Dogs are more commonly affected than cats. There are no age, breed or sex predispositions for ''[[Giardia]]'' infection, but puppies and kittens are more likely to contract clinical disease than adult animals. Disease may also be seen in immunocompromised or stressed individuals.

===Laboratory Tests===

===Laboratory Tests===

[[Image:Giardiasis duodenum high power.jpg|thumb|right|150px|Giardia trophozoites in the duodenum. Source: Wikimedia Commons; Author: Nephron (2009)]]

[[Image:Giardiasis duodenum high power.jpg|thumb|right|200px|Giardia trophozoites in the duodenum. Source: Wikimedia Commons; Author: Nephron (2009)]]

Diagnosis is confirmed by demonstrating ''[[Giardia]]'' antigen, trophozoites or cysts in the faeces. The simplest method is to examine fresh faecal smears for cysts (and occasional trophozoites), but sensitivity is improved by using concentration techniques. Centrifugal flotation in zinc sulphate solution or sugar flotation solution are both appropriate, but zinc sulphate solution is preferred as it causes minimal distortion to cysts. In this technique, faecal material is centrifuged and saturated with zinc sulphate mixture before the fluid from the top of the tube is placed on a microscope slide. Diff-Quik or Lugol's iodine are used to stain cysts and trophozoites, a coverslip is applied, and the slide is examined under the microscope. Although infrequently detected, ''[[Giardia]]'' trophozoites are approximately 8 x 15 micron tear-drop shaped organisms which contain two nuclei. They can sometimes be seen to move in a "falling leaf" pattern.  Cysts are around 12 microns long and, if not distorted, oval in shape. When looking for cysts, three samples collected at two to three day intervals should be examined as shedding is intermittent.

Diagnosis is confirmed by demonstrating ''[[Giardia]]'' antigen, trophozoites or cysts in the faeces. The simplest method is to examine fresh faecal smears for cysts (and occasional trophozoites), but sensitivity is improved by using concentration techniques. Centrifugal flotation in zinc sulphate solution or sugar flotation solution are both appropriate, but zinc sulphate solution is preferred as it causes minimal distortion to cysts. In this technique, faecal material is centrifuged and saturated with zinc sulphate mixture before the fluid from the top of the tube is placed on a microscope slide. Diff-Quik or Lugol's iodine are used to stain cysts and trophozoites, a coverslip is applied, and the slide is examined under the microscope. Although infrequently detected, ''[[Giardia]]'' trophozoites are approximately 8 x 15 micron tear-drop shaped organisms which contain two nuclei. They can sometimes be seen to move in a "falling leaf" pattern.  Cysts are around 12 microns long and, if not distorted, oval in shape. When looking for cysts, three samples collected at two to three day intervals should be examined as shedding is intermittent.