Giardia - Parasitic Diarrhea

August 9, 2017


What is Giardia?

Giardia is a one-celled organism that is found in the small intestine of dogs and cats.

There's not too much known about the Giardia parasite.

What we do know is that exposure to Giardia is common, however acquiring the disease from the parasite is less common. It is also found all over the world; in rivers, ponds, puddles, in wild animals, and in humans.


Giardia is zoonotic meaning that if your pet has Giardia then chances are, the whole family has been infected.


How Giardia Occurs

A dog or cat can acquire Giardia by eating or licking an infected cyst contained in another animal's faeces.

The most common route of transmission is through faeces and contaminated water. Giardia parasites prefer cool, moist environments, as this is where they thrive.

Once inside a dog or cat's small intestine, the cyst opens and releases the active form of the parasite. These forms are able to move around and attach themselves to the walls of the intestine, where they reproduce by dividing in two.

In due time, the active forms of Giardia build cysts around themselves and are passed from the animal's body in faeces. Those faeces then contaminate water sources, grass, soil, and other surfaces.

Also, if a dog is Giardia-positive, licks his backside, and then licks another dog, cat or human, there's potential for transmission to occur.


Giardia Symptoms

The majority of Giardia infections are asymptomatic and idiopathic, meaning there are no obvious signs or cause that the pet is infected.

When symptoms arise the most common is diarrhea, which can be acute, chronic or fluctuant. If Giardia is left untreated then the pet can experience an acute bout of bloody, dehydrating diarrhea. Most dogs with diarrhea will not lose their appetite with Giardia, but they may lose a lot of body weight.

This is because a Giardia infection interferes with digestion and inhibits absorption of nutrients from the diet. It can also damage the lining of the intestine.

In fact, this particular parasite is at the root of many cases of chronic GI inflammation in dogs and cats.


Diagnosing Giardia

Diagnosing Giardia is done using a faecal test snap test. It is preferred that this test is completed at a laboratory and not the vet clinic for the following reasons:

In-house parasite testing – which means stool tests that are analyzed at vet clinics rather than being sent out to laboratories – have been recorded up to 30 percent false-negative results. This means vets are assuming certain pets are parasite-free, when they actually aren't.

Parasites detected in Giardia, aren't consistently shed in every stool sample. So if a cyst-free stool sample is collected for analysis, it might not show any evidence of Giardia infection, even though the animal is actually infected.

This is why it is recommend that pets with a history of bowel problems be tested for Giardia with a snap test rather than a faecal flotation test in that it checks for Giardia antigens present in the pets body. A faecal float test only checks for evidence of Giardia cysts in a stool sample.



How Long Does A Giardia Infection Last

Unfortunately, Giardia is growing resistant to many common anti-protozoal medications – with the result that increasing numbers of pets can become persistent carriers.

Monthly faecal float tests for the first 4 months after treatment is encouraged, followed by another snap test to make sure the infection has cleared. It can take approximately 6 months for the antigens to leave the pets body; so multiple faecal float tests are necessary to insure the infection is completely resolved.



To treat a pet that has giardia, a broad spectrum wormer will be needed like fenbendazole (Panacur®) which is given daily for 3 days then repeated after a week or Metronidazole (Flagyl®) which is given daily for 7 days.



How do you prevent a Giardia infection? Pick up your own pet's faeces outside and avoid walking the pet near other pet’s stools. Use fresh water and avoid outdoor water sources altogether – you don’t know what’s lurking in the water.


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