Giardiasis in Dogs: Why Your Dog Has Smelly, Greasy Diarrhea

Introduction

It is one of the more common forms of intestinal parasites caused by the microscopic parasite Giardia. Unlike worms which live freely in the intestines, Giardia is a single-celled organism that attaches itself to the intestines, preventing the dog from digesting and absorbing nutrients.

Life Cycle of Giardia

To prevent re-infection, an understanding of how Giardia works is important. The Giardia has two life stages:

1. Trophozoite (The "Motile" Life Stage)

Once ingested, the cyst travels to the small intestine of the dog.

Two trophozoites develop from the cyst and attach themselves to the villi inside the intestine.

This leads to inflammation of the villi and prevents the uptake of nutrients.

This organism undergoes binary fission and is responsible for causing diarrhea.

2. Cyst (The "Infective" Life Stage)

After migrating in the intestine, the trophozoite moves deeper down.

As they travel close to the large intestine, they cover themselves in a layer of "cyst".

These cysts are expelled from the dog's body when it defecates and remain dormant in soil or cold water until ingested.

Method of Transmission in Dogs

​The transmission happens through the fecal-oral pathway whereby the dog will ingest the "Cyst" stage of the organism:

​From Water Sources: 

Any puddle, lake or even communal water source.

​Through the Environment: 

Sniffing and licking areas where there are infected feces present.

​Self-Infection: 

Licking of their own paws after walking on feces containing Giardia.

​Signs of Infection to Look Out For

​Adult dogs are asymptomatic, but puppies will exhibit symptoms such as:

​Steatorrhea: 

Foul-smelling greasy stools.

​Stool with Mucus: 

Stools with mucus lining or appearing like soft serve ice-cream.

​Weight Loss: 

Normal appetite but failure to gain weight.

​Dehydration: 

Due to persistent intermittent diarrhea.

​Occasional vomiting is observed but rare compared to diarrhea.

​Diagnosis in Laboratory Settings

​Diagnosing Giardia can be difficult since the organisms are not shed consistently:

​Fecal Zinc Sulfate Flotation: 

Visualizing the organisms under the microscope.

​Fecal Smear/Saline Mount: 

Visualizing the active and mobile "Trophozoite" form ("dancing" appearance).

​ELISA/Snap test: 

Most reliable way of identifying Giardia antigens in the feces.

Protocol for Treatment

Metronidazole: 

An antibiotic/antiprotozoal drug that is frequently used for 5-7 days.

Fenbendazole: 

Used either alone or in conjunction with Metronidazole for more effective results.

Bathing: 

It is essential to bath your dog on the final day of the medication to ensure removal of all cysts attached to the fur.

Conclusion

​​One thing about Giardia that makes it quite irritating is its resistance as well as the challenge in diagnosing. It is impossible to diagnose the disease without finding the presence of antigens in the body through the ELISA process since normal fecal flotation tests tend to produce false negatives.

​​In treating the dog, there is need to follow two approaches. The first approach is to give prescribed medicine such as Metronidazole while the second approach involves effective environmental treatment through proper disposal of feces, bathing to clear any cysts on the dog’s hair, as well as disinfection of common bowls.

The Giardia parasite has a simple life cycle but requires specific intervention to stop reinfection.