Pet Factsheets


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Giardiasis is caused by a parasite which is transmitted to dogs and cats through contact with infected feces or with water, food, or soil that has been contaminated by infected feces. It can cause diarrhea, appetite loss, and vomiting, but pets can often be infected with Giardia without showing outward signs. Avoid high-risk environments and behaviors to reduce the risk of infection.

What is Giardiasis?

Giardiasis is a diarrheal disease that can affect dogs, cats, and humans. It is caused by Giardia, a single-celled parasite that attacks the gastrointestinal tract of infected animals. Among experts, there is some debate about the number of Giardia subtypes that can cause disease in animals and also, the potential of these subtypes to also infect humans. While humans are susceptible to infection with Giardia, infection by the same subtypes prevalent in animals is thought to be exceedingly rare but remains a point of controversy and investigation.

According to the Companion Animal Parasite Council, approximately 16% of symptomatic dogs and approximately 10% of symptomatic cats have been found to be infected with Giardia. The parasite is found worldwide and lives in the intestines of infected animals and humans, and infected individuals pass the parasite in their feces, in the form of cysts, into the environment. These cysts can remain infective for months, especially when conditions are cool and humid/moist. The infection is transmitted when a host ingests water from a contaminated pond, lake, or stream or ingests contaminated food or soil. Outbreaks of giardiasis are more common when animals are housed in crowded kennels or shelters.

What are the signs of Giardiasis?

Clinical signs of giardiasis typically develop within 5 to 16 days after exposure to the parasite. In many cases, infected pets show no or slight signs of disease, but signs can include:

  • Weight loss
  • Inappetence (appetite loss)
  • Diarrhea (sometimes severe and with very smelly!)
  • Flatulence
  • Vomiting
  • Lethargy (tiredness)

However, these signs can also be caused by many other diseases and health problems, and so a complete physical examination and diagnostic testing may be recommended.

How is giardiasis diagnosed and treated?

Several types of fecal tests can be used to diagnose giardiasis. In some cases, tests may need to be repeated more than once to obtain a definitive result.

In most cases, the disease course is mild. Some animals, in particular puppies, kittens, or animals with underlying health conditions, may have more severe diarrhea and vomiting and may require supportive therapy with fluids and anti-nausea medications. In such cases, dehydration can be a serious concern.

Medications for treating giardiasis are available, but the infection can be difficult to cure, so multiple courses of treatment may be necessary. Pets should be bathed throughout treatment to remove infective cysts from the haircoat. Because pets that have been treated have no immunity against future infection, these pets can easily be reinfected. Therefore, living areas should be disinfected - ammonia, dilute bleach solution, or steam cleaning can be effective. If there are other pets in the household, medications may be administered to them as a preventive measure. Contaminated soil can remain infective for months under certain conditions, so the risk of reinfection may be reduced by walking treated dogs in a different area.

How can I prevent my pet getting giardiasis?

Giardia is common in the environment and outdoor dogs and cats, working or hunting dogs, and pets that swim or have contact with potentially contaminated water can be at risk for exposure. Regular removal of feces from the garden or kennel as a preventative measure is recommended and pets should be prevented from drinking from, or swimming in, lakes, streams, and ponds.

Your veterinarian may recommend testing new puppies or kittens or adult pets for Giardia before they are introduced to other pets. In addition, as humans and pets may be infected by the same subtypes of Giardia, it is always a good idea to wash your hands after playing with your pet or disposing of fecal material.

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