Main Content Area

Beware of Protozoan Parasites

Image may contain: dog, grass and outdoor

Image Credit: Facebook Fan Kelly from Nova Scotia and “Reno.”


Giardia is a tricky protozoan parasite that does not always cause symptoms when present and it infects multiple vertebrate species. These single-celled microorganisms live in the intestinal tracts of their hosts; infective units are called cysts and they shed in feces. Cysts are durable and survive several months in cool, moist environments. Major symptoms of Giardia infection in dogs include diarrhea, poor body condition, and ill-thrift appearance.

Infection in Canines

Giardia infection (Giardiasis) occurs when a potential host ingests infective giardia cysts. Some dogs are chronic carriers of the parasite and show no symptoms or will only demonstrate intermittent symptoms when stressed. A newly infected dog can begin showing symptoms within a few days up to a few weeks after ingestion of cysts. Giardia lives in the intestines of its host where it disrupts absorption of nutrients; Diarrhea is the main symptom.

Animal crowding facilitates ease of disease transmission and reinfection can occur frequently, even with treatment. Once inside a dog,high speeds of cell division leads to rapid infection, as well as buildup of infectious cysts in the environment. Dogs in group housing or housed in close quarters with infected dogs can easily pass the organism through fecal-contaminated food or water bowls, or through mutual grooming practices. Lakes, ponds, and puddles are easy targets for transmission to dogs-so are toilets!

Risks Factors for Infection:
● High-density or high frequency pet facilities (kennels, daycare, parks, etc.)
● Humid or damp environments
● Ingestion of unclean water sources
● Frequent contact with wildlife
● Poor sanitation/disinfection practices


Giardia infection must be differentiated by laboratory testing from other parasites or diseases that can contribute to poor-weight gain and loose stools. Fresh fecal samples are best for detection of any intestinal parasites. Cysts are not always shed in the feces which can put routine fecal exams at a disadvantage in detecting giardia. Additional testing techniques that allow for giardia antigen (a type of protein) detection in the feces are useful. If the antigen test is not available, feces from several samples over a multiple day period may be recommended by your veterinarian to aid in detection.


A universal treatment protocol is not currently available but a few medications can aid in resolution. Diarrhea appears to improve more readily on a diet specific for gastrointestinal health that your veterinarian can prescribe. Dehydration from severe diarrhea can occur and may require hospitalization. Bathing and proper environmental cleaning can help decrease reinfection. Dogs with symptoms of ill-thrift or intermittent diarrhea should not be taken to dog classes, dog parks, or boarding facilities, or be working as therapy or service dogs until after completing treatment and cleared by a veterinarian to return.

Disease Prevention

Disinfectants like bleach and Lysol work well to kill Giardia cysts when used at appropriate concentration and contact time. All organic material must be physically removed prior to disinfection of surfaces. Steam cleaning or boiling water are also effective methods used to destroy cysts. One of the many reasons to filter or boil water for both people and pets when water source is potentially contaminated.

More ways to prevent disease include:
● Pick up feces from the environment to prevent environmental buildup of cysts.
● Always wash hands after handling pets or pet feces.
● Bathe dogs prior to introducing them into a clean environment.

Responsible pet owners or boarding facilities will not intentionally risk the health of other dogs,  though mistakes can happen. It is also wise to keep all pets up to date on vaccinations and have negative fecal results prior to boarding to limit spread of other infectious diseases.

Note: Giardia parasites can reside in animals who do not display symptoms- these animals are known as carriers. Carrier animals are chronically harboring the parasite and intermittently shed cysts into the environment. Their feces may never appear loose and their body condition may not appear adversely affected.


Amanda Burow, D.V.M. (Dr. B), is a graduate of Iowa State University’s College of Veterinary Medicine. Dr. Burow’s patient list includes hunting dogs of all varieties, as well as several field trial dogs and full time sporting guide dogs. In addition to practicing general veterinary medicine, she has special interest in the areas of preventive care, emergency medicine, and dermatology. In her spare time, she enjoys being outdoors and on the lake, staying active, reading, and spending time with family and friends.

Mud River is proud to share these tips from Dr. B with our customers. Keep in mind it is best to work with your local veterinarian to determine the needs for your animals.

Leave a Reply

Your email address will not be published. Required fields are marked *