Guide to Giardia in Dogs

How to Identify & Treat Dog Giardia
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Common Causes of Giardia in Dogs

The  causes of giardia in dogs are always due to feces contaminated by infected dogs. The feces comes in contact with dogs on surfaces or dirt, food, objects or water (e.g.; lakes, streams or swimming pools). Giardia cysts can also be found in areas where dog feces have contaminated the area such as parks, dog walks and kennels that have not been properly disinfected. Any area or object can become contaminated.  The cysts protect the giardia in the environment, allowing it to survive for several months without a host.

When a dog comes in contact with a contaminated area, and then ingests a giardia cyst, the giardia protozoa emerges from the protective cyst, allowing it to colonize in the dog’s small intestine.  When a dog drinks contaminated water, the cysts enter the intestines, where they begin to multiply as they feed. The giardia protozoa is referred to as a trophozoite, which means that it is a type of protozoa that feeds off its host.

giardia in dogs protzoa

Magnified picture of Protozoa that Causes Giardia in Dogs
Source: CAPC

The giardia spreads from the host to other dogs, when some of the giardia protozoa create protective cysts around themselves, which allows them to pass through the dog in the feces.  This perpetuates the life cycle of the protozoa, contaminating the environment until ingested by the next host.

Most dogs that have giardia are asymptomatic, meaning that they do not show clinical symptoms. This means that they are spreading the cysts into the environment without any of the ill effects of giardia such as persistent mucous containing diarrhea. Other dog giardia symptoms can include vomiting, weight loss, and lethargy.  The only way most owners find out a dog is shedding giardia is during a routine checkup. When a asymptomatic dog is found to have giardia, it is up to the owner in consultation with a veterinarian as to whether or not treatment is required.

Dog Giardia Control and Prevention

After treating your dog, it is recommended that a dog be bathed to eliminate any feces that may have gotten caught in the coat.  This will remove any cysts as well.  There is a high risk of reinfection in dogs that have been treated.

To prevent reinfection, try and eliminate or avoid as many of the causes of giardia in dogs as possible. For example, if feces is left on areas such as concrete patios, consider cleaning with steam heat or an outdoor disinfectant.  Be sure to pick up after your dog using a hygienic plastic baggie.  When handling feces, keep it away from your bare hands.

Dog Giardia and Human Health

Giardia for the most part are host specific. There are no documented cases of canine giardia infecting a human host.  However, there are rare document cases of the reverse, where the strain of giardia and infects humans is found in a dog.  Since human giardia is one of the potential causes of giardia in dogs, it is theoretically possible that a dog infected with human giardia could pass it back to the human host.  The chance of this happening is remote and therefore it is not considered to be a health risk.


Giardia in Dogs, Dog Health Guide


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