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Common Conditions - Articles of Interest - Giardia


What is Giardia?

Giardia is a tiny microscopic protozoan parasite that is infectious to both humans and pets all over the world.  Giardia have  whip-like structures called “flagella” which enable them to move. The trophozoite forms live in the intestine where they cause diarrhoea and pass out in the faeces. After a short period of time outside, trophozoites form cysts enabling them to survive in the environment. If it is cold and wet, the cyst can live for months with two forming trophozoites waiting inside to infect a new host.  They are then swallowed, the cyst shell digested away, freeing trophozoites to attach to the intestinal lining. Contaminated water is the usual source of infection.

After infection, it takes 5 to 12 days in dogs or 5 to 16 days in cats for Giardia to be found in the stool. Diarrhoea can precede the shedding of the Giardia.  Infection is more common in kennel situations where animals are housed in groups.

How is Giardia diagnosed?

Giardia shed organisms intermittently and may be difficult to detect. Sometimes pets must be retested in order to find an infection.

  • Examine  faecal sample with zinc sulphate flotation and direct smears
  • ELISA test - A faecal sample is tested immunologically for Giardia proteins

Can it be treated? T

A broad spectrum  wormer called fenbendazole (Panacur®) given daily for 3 days then repeated after a week or  Metronidazole (Flagyl®) daily for  7 days are common treatments Giardia.  For some resistant cases, both medications are used concurrently.   Drontal® may also be used in some cases. Your vet will prescribe the most appropriate treatment for your pet. The ELISA test for Giardia should be negative within 2 weeks of treatment indicating success.

Because cysts can stick to the fur of the infected patient and be a source for reinfection, the positive animal should receive a bath at least once in the course of treatment.

Environmental Decontamination

The most readily available effective disinfectant is bleach diluted 1:32 in water. Organic matter such as dirt or stool is protective to the cyst, so basic cleaning should be done prior to disinfection. Animals should be thoroughly bathed before being reintroduced into a “clean” area. A properly chlorinated swimming pool should not become contaminated.
If you have any further questions or concerns regarding your pet’s health, please feel free to contact your local Greencross Vets. 

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