Giardiasis in Dogs

While some dogs show no symptoms, others may experience malabsorption, foul-smelling feces, and weight loss says Yung-Tsun Lo D.V.M, Ph.Dfrom Bioguard Corporation.

Giardiasis is a common parasitic infection in dogs, caused by the intestinal parasite Giardia. Puppies, young dogs, and those with weakened immune systems are particularly susceptible. While some dogs show no symptoms, others may experience malabsorption, foul-smelling feces, chronic diarrhea, and weight loss. The infection can be difficult to eliminate due to the risk of reinfection, requiring antiparasitic treatment and thorough environmental cleaning. Adult dogs may carry the parasite without symptoms, shedding cysts and unknowingly spreading the infection.

Transmission

Infected dogs shed cysts in their feces, which can immediately infect other animals. The cycle from ingestion to shedding in feces takes 5 to 12 days in dogs. Giardiasis is common in crowded environments like kennels or shelters due to high levels of fecal contamination. While cysts found in healthy adult dogs may be insignificant, they are more concerning in vulnerable dogs. Controlling environmental contamination is challenging because the cysts are robust and infectious immediately upon shedding in contaminated soil, food and water.

Clinical signs

Dogs with giardiasis can show a range of symptoms, from no signs at all to severe illness. Some dogs remain asymptomatic with normal appetite and energy levels, while others develop acute, intermittent, or chronic diarrhea. The parasite damages the intestinal lining, leading to malabsorptive diarrhea, often with mucus, a foul odor, and sometimes a greenish tinge or blood. Other symptoms may include abdominal discomfort, lethargy, decreased appetite, weight loss, and vomiting. While most dogs don’t have a fever, they may be less active. The disease can persist for weeks, with younger or immunocompromised dogs more likely to show symptoms. Many dogs remain asymptomatic carriers without developing illness.

Diagnosis

Diagnosing giardiasis in dogs can be challenging because Giardia cysts are not consistently present in the stool. Standard fecal flotation tests may not always detect these cysts, so a special zinc sulfate solution is often used. Additionally, parasites can be identified through a direct smear of the feces. If giardiasis is suspected, stool samples can be tested for Giardia-specific antigens using methods like direct smears, centrifugal fecal flotation, or antigen detection tests, including rapid tests. PCR detection of Giardia in feces is also becoming more common. It may be necessary to conduct multiple tests over several days to confirm the infection.

Treatment

The goal of treatment of giardia in dogs is to resolve an affected dog’s diarrhea and abdominal discomfort. The primary drugs used to treat giardiasis in dogs are fenbendazole and metronidazole, typically administered for three to ten days. In cases of refractory diarrhea, both drugs may be used in combination. Supportive treatments, such as fluid therapy for dehydration may also be necessary. Follow-up testing is recommended two to four weeks after treatment. To prevent reinfection, promptly remove and dispose of feces, bathe the dog regularly to eliminate cysts from the coat, and disinfect bedding and resting areas.

Prognosis

With proper treatment, most dogs recover fully from giardiasis. However, debilitated, geriatric dogs or those with compromised immune systems are at a higher risk for complications, including potentially fatal outcomes. It’s important to re-test all pets diagnosed with Giardia two to four weeks after completing treatment. Dogs can become reinfected if their environment is not adequately managed. Additionally, refractory infections may occur if the Giardia is resistant to the medication or if the treatment was not properly dosed.

Prevention

Preventing and controlling giardiasis is challenging due to the persistence of cysts in the environment and on a dog’s coat. To reduce the risk of reinfection or transmission, bathe dogs to remove cysts, dispose of faces daily, and clean surfaces with boiling water or chlorine bleach at a 1:32. Since Giardia cysts are susceptible to drying, keep the environment as dry as possible. Thoroughly clean and dry the pet’s living areas before reintroducing them.