Giardia in Dogs

Giardia is a protozoal parasite found worldwide. It infects many mammals, including dogs, cats, and even humans. In dogs, it commonly causes diarrhea, although many infected dogs are asymptomatic. Treating this common parasite can be difficult and dogs are prone to re-infection without careful attention to sanitation and prevention.

Understanding the Giardia Life Cycle

To understand how your pet became infected with giardia, it helps to know a little about the life cycle of this parasite.

Giardia exists in two forms: a trophozoite, which is the growing stage of the parasite, and a cyst. Both forms of giardia are infective. Trophozoites are fragile and cannot live very long outside a host, but cysts are very hardy and can live in the environment for months under the right conditions.

Giardia is found in soil, water, and food that has been contaminated with infected feces. Pets are exposed via the fecal-oral route, meaning they must ingest contaminated feces to become infected. This usually happens by drinking contaminated water, eating contaminated food, or even licking contaminated soil off of the paws. It only takes a few giardia cysts to cause an infection, so even a small amount of contamination can cause your dog to become infected.

After being ingested, giardia cysts travel along the digestive tract to your pet’s small intestine. When they reach the small intestine, trophozoites emerge from the cysts. Some trophozoites attach to the cells lining the walls of the small intestine, causing damage to the cells that leads to malabsorption and diarrhea. Other trophozoites remain free-floating in the small intestine. The trophozoites multiply,
creating new trophozoites and cysts which are shed in the feces beginning 5-12 days after the initial infection.

How Did My Dog Get Infected With Giardia?

Your dog could have encountered giardia anywhere that an infected animal may have defecated. An infected dog begins shedding giardia cysts and trophozoites in their feces about 5-12 days after they are initially infected. These infective parasites are left behind anywhere the dog defecates – including dog parks, sidewalks, water sources, and other areas. Some studies have shown an increased prevalence of giardia among dogs that visit dog parks. Giardia is also common in overcrowded or unsanitary conditions and can spread rapidly in kennels or other environments where dogs are housed together.

Can I Get Giardia From My Dog?

In a healthy adult, it’s highly unlikely that you will get giardia from your dog. Giardia strains tend to be species-specific, which means that dog strains of giardia only infected dogs, cat strains infect cats, and human strains infect humans. However, you should still be careful and practice good hygiene. Wear gloves when picking up your pet’s feces and wash your hands thoroughly with soap and water immediately after handling feces. Young children, elderly adults, and immunocompromised individuals may be more susceptible to giardia infection and should limit their exposure to a giardia-infected pet.

Giardia Symptoms in Dogs

Many dogs with giardia are asymptomatic and their infection is identified only on a routine fecal examination. In animals that do develop clinical signs, symptoms are often self-limiting and may resolve on their own. Severely infected animals often have significant clinical signs. Animals with other concurrent gastrointestinal parasites or illnesses may be more prone to severe giardia infection.

Signs of giardia in dogs can include:

• Diarrhea
• Increased frequency of defecation
• Pale, mucoid stools
• Abdominal pain
• Lethargy
• Loss of appetite
• Weight loss
• Vomiting
• Dehydration

Diagnosing Giardia in Dogs

To diagnose giardia in your dog, your veterinarian will start by taking a thorough history of your dog’s symptoms and exposure risk. Your veterinarian will also perform a full head-to-tail physical examination on your dog and may recommend some or all of the following diagnostic tests:

• Fecal floatation with centrifugation. This is the most commonly used test for the diagnosis of giardia in dogs. In this test, a sample of your dog’s feces is mixed with a solution that makes giardia cysts float to the surface of the solution. The surface layer of the solution is then examined under a microscope, where giardia cysts can be identified. However, because giardia cysts are only shed in the feces intermittently, false negatives can occur with this test.
• Fecal enzyme-linked absorbent immunoassay (ELISA). This test uses a sample of your dog’s feces to detect a giardia-specific antigen from trophozoites. This eliminates the problem of intermittent shedding of giardia cysts and false negatives are rare. However, a negative test does not rule out giardia in an animal with compatible clinical signs.
• Fecal direct smear. Also called a fecal wet mount. In this test, a small amount of your dog’s feces is mixed with two to three drops of saline and then examined under a microscope. This test looks for giardia trophozoites and is usually best performed on soft or liquid feces.

Giardia can be difficult to diagnose and a negative test result does not necessarily rule out giardia as a diagnosis. If giardia is suspected, your veterinarian may recommend repeating the test(s) to increase the chances of diagnosing giardia.

Giardia Treatment for Dogs

There are two goals of giardia treatment. The primary goal is to stop the symptoms of giardia infection, such as diarrhea and abdominal pain. The secondary goal is to eliminate the infection, which can be difficult to achieve due to the resistance of some strains of giardia to treatment. In order to successfully treat a giardia infection, you must both administer medication as prescribed by your veterinarian and ensure proper sanitation of the environment to reduce the risk of re-infection.

Giardia Medication for Dogs

Medications used to treat giardia in dogs include Metronidazole (Flagyl), Fenbendazole (Panacur), and a combination of febantel, pyrantel pamoate, and praziquantel (DrontalPlus). The type of medication used, the dosage, and the duration of treatment will depend on the severity of your dog’s infection and your dog’s body weight. Your veterinarian will prescribe an appropriate treatment protocol based on your dog’s individual needs. Be sure to follow your veterinarian’s instructions and complete the entire course of medication, even if your dog’s symptoms resolve before the course is finished.

Sanitation for Giardia in Dogs

An infected dog sheds infective giardia cysts in its feces. These infective cysts not only pose a risk to other animals but can also re-infect the original host. To reduce your dog’s risk of re-infection, it is essential to practice good sanitation throughout the course of treatment.

Feces should be picked up immediately and disposed of in an appropriate receptacle. Surfaces should be disinfected by steam cleaning or with commercial disinfectants, particularly any surfaces that may have been contaminated by fecal matter, such as kennel floors or crates. On the final day of treatment, bathe your dog with warm water and shampoo to remove fecal debris and infective cysts from the hair coat.

Following completion of treatment, it is recommended that you submit a fecal sample for a fecal floatation with centrifugation. This follow-up testing ensures that the infection has been cleared.

Preventing Giardia in Dogs

There are several steps you can take to reduce your dog’s risk of becoming infected with giardia.

• Practice good sanitation. Clean up feces as soon as your dog defecates to ensure giardia cysts from the feces are not left to contaminate the environment. This will prevent re-infection and transmission to other animals. Feces should be disposed of properly in municipal waste. Be sure to wear gloves and wash your hands with soap and water after handling feces.
• Avoid contact with contaminated water sources. Do not allow your dog to swim in or drink from water where wildlife or infected dogs may have defecated. Carry clean, fresh water with you so that your dog does not need to drink from contaminated water sources.
• Disinfect contaminated areas. Giardia cysts can persist in the environment for a long time under the right conditions. Disinfection or steam cleaning will destroy the cysts and reduce the risk of transmission or re-infection. Most household disinfectants are effective against giardia.
• Bathe your pet to remove cysts and fecal debris. An infected dog intermittently sheds giardia cysts when it defecates. These cysts get caught in the haircoat, serving as a source of reinfection the next time the dog grooms itself. Bathing your dog can remove these cysts, thus removing the source of re-infection. It is recommended that you bathe your dog on the last day of treatment to prevent re-infection.

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