Giardia is a single-celled parasitic microorganism that lives in the intestines of infected animals and people. Giardia in cats and dogs can cause a plethora of health problems. Thankfully, Giardia is easy to diagnose and treat, and it is usually not life-threatening.

Causes of Giardia

Giardia is not visible to the naked eye and has two life stages. The first life stage is the cyst — or egg — stage. Once cysts are produced in the small intestine, they are eventually shed in the host's feces and can remain in the environment for up to 7 months. 

Ways dogs and cats can become infected with Giardia include:

• Eating infected feces

• Drinking water from a contaminated water source, such as outdoor puddles.

• Eating or chewing on contaminated grass, leaves, sticks, or dirt.

Once the pet has ingested a Giardia cyst, the organism begins its second life stage — trophozoite — in the small intestines of the host. A trophozoite is the mature form of the parasite and can begin reproducing cysts. 

The cysts will move to the large intestines and evacuate the host’s body when the host defecates. The process begins again as the cysts wait to be ingested by a new host.

Giardia is transmittable, but usually between dogs and other dogs. It is not likely for a dog to give Giardia to a cat or human, although humans can become infected, in which the condition is known as "beaver fever."

Signs of Giardia

The small and large intestines are responsible for absorbing nutrients and water. When a dog or cat is infected with Giardia, the parasite can disrupt the absorption of nutrients and water. Diarrhea is the primary indicator that a pet could be infected with Giardia. 

Giardia symptoms in cats and giardia symptoms in dogs are the same and include:

• Lethargy

• Weight loss

• Vomiting

• Dehydration

• Poor coat and skin appearance

Unfortunately, these clinical signs are the same for many dog and cat conditions and diseases. Pet parents should contact their vet if they have cat health questions or dog health questions. 

A fecal test is the fastest way to diagnose Giardia. Most vet clinics will perform two types of fecal tests — a smear and a float. To perform these tests, a vet technician or assistant will need a sample of feces from the dog or cat. 

Giardia Treatment

If the dog or cat is dehydrated, they will need to get intravenous or subcutaneous fluids administered. However, fluids will only help the dehydration and won't kill the Giardia. 

Curing a pet of Giardia will require medication and a universal de-wormer won’t work. The two most common medications used to treat Giardia are fenbendazole and metronidazole.  A vet will prescribe the correct dosage needed based on the pet’s size. Usually, the pet parent will have to administer the medication for five to seven days. 

These medications are bitter so it can be difficult for pet parents to administer them. Usually, the medication comes in pill form and is coated to mask the bitterness. It is usually easier to give the medication to dogs. 

Pet parents can place the tablet in treats, such as a piece of hot dog, and give it to their dog. The pet parent should watch and make sure their dog eats all of the medication. Sometimes, if the dog bites into the pill, they will spit it out. 

Cats can be much more challenging to medicate — especially since the tablet usually needs to be broken to give the cat the correct dosage. Pet parents can discuss various medication options to determine the easiest and least stressful way to medicate the infected cat.

There is also an option to administer medication in liquid form. This doesn't taste good so it it recommended that pet parents work closely with a veterinarian for instructions on administering. 

After initially treating an animal, retesting is required at 2 to 4 weeks. 

Additional Giardia Information

Giardia is not usually life-threatening in a healthy adult dog or cat. However, the parasite can be life-threatening if left untreated, especially in kittens, puppies, senior pets, and immunocompromised pets. 

Pet parents can disinfect their homes with diluted bleach to kill any possible Giardia cysts. They should also clean and scoop litter boxes daily to remove any potentially infected feces. Finally, all pet feces should be removed from the yard. It is recommended to let areas dry out for a week before letting animals back into the space.