Protozoal Infection in Dogs

Protozoal infections are more common in puppies, seniors, canines with suppressed immune systems and in dogs that are in close-quarters (shelters, kennels, and pet stores).

Some protozoal infections are zoonotic, which means an infected dog can transmit the infection to humans.

Protozoal infections in dogs are caused by protozoans. Protozoans are unicellular organism that are transmitted by the bite of infected insect or by the ingestion of the parasite.

Giardiasis is an intestinal infection in dogs, caused by protozoan the Giardia. Long term giardiasis damages the gastrointestinal tract and causes digestion problems and malnutrition.  This protozoa can be transmitted to humans. In the beginning stages the canine may have no symptoms, as the disease progresses signs may include:

• Intermittent diarrhea
• Lethargy
• Vomiting
• Weight loss
• Foul smelling feces
• Flatulence

Babesiosis infection in dogs is caused by protozoan parasite Babesia.  Canine babesiosis infections can occur worldwide but there are more diagnosed cases occurring in the southern United States. During the incubation period there may be no symptoms. Some dogs show mild signs while others show more severe symptoms. Symptoms may include one or more of the following:

• Very dark urine
• Fever
• Depression
• Swollen lymph nodes
• Enlarged spleen
• Distended abdomen
• Pale gums
• Weight loss
• Lack of appetite

Toxoplasmosis infection in dogs is a parasitic disease caused by the protozoan Toxoplasma gondii. This protozoan starts off multiplying in the gastrointestinal tract and then spreads to the bloodstream and the lymphatic system. This infection can be transmitted to humans. Pregnant women that are infected by toxoplasmosis can miscarry or transmit the infection to the fetus. Toxoplasmosis may cause congenital defects to the fetus. Clinical signs of toxoplasmosis usually appear 20 days after the parasite was ingested. Signs may include:

• Lack of appetite
• Anorexia
• Fever
• Breathing difficulties
• Inflammation in the eye
• Jaundice
• Cough
• Seizures
• Sudden death

Giardiasis infection is transmitted by ingesting the cyst stage of the parasite:

• Drinking fecal contaminated water
• Smelling or ingesting contaminated feces 
• Contaminated feces gets on the dogs fur; he then grooms himself ,ingesting the parasite

Babesiosis infection is transmitted by:

• The bite of infected tick
• An infected dog bites another dog
• Infected mother can pass the parasites through the placenta
• Blood transfusion (with infected blood)

Toxoplasmosis infection is transmitted by:

• Ingesting food or water that has contaminated feces of an infected cat
• Infected mother can pass the parasite through the placenta
• Blood transfusion (with infected blood)
• Dog ingests or bites an infected animal
• Eating raw meat, more common in pork
• Flies and roaches may carry the parasite on their bodies

The veterinarian will go over your pet’s medical history.  Let him know what symptoms you have observed and when they started. Also tell the veterinarian if you have seen ticks on your pet, if he has been bitten by another dog, or if your pet has bitten another animal (birds, rodents, cats).

A complete physical exam will be performed on your dog which will include taking his temperature and blood pressure, listening to his heart and lungs with a stethoscope, checking his gums, eyes, reflexes, and palpation of the abdomen and lymph nodes.   Diagnostic tests the veterinarian may suggest are a complete blood count (CBC), serum chemistry profile, urinalysis and a fecal exam.

Giardiasis infection can be diagnosed using a fecal flotation test, which can detect the tiny cysts that are shed in the feces.  The parasites may also be visible doing a direct smear of the feces on a slide and checking it under a microscope.

Babesiosis infection can be diagnosed by doing a blood smear on a slide and looking under the microscope to identify the parasite. Other diagnostic tests that help diagnose babesiosis infection are: 

• FA (fluorescent antibody)
• Polymerases Chain Reaction (PCR) test 
• Enzyme Linked Immunosorbent Assay (ELISA) test
• Immunofluorescence Antibody (IFA) test 

Toxoplasmosis infection can be diagnosed by measuring the antibodies to toxoplasma gondii in the dog’s blood. The parasites may sometimes be visual in a fecal exam.

In critical cases of protozoal infections, your pet may need to be hospitalized in order to monitor his vitals.  Intravenous therapy will be used to administer medications, and fluids to keep him hydrated.

Giardiasis infection is usually treated by a combination of medications such as antibiotic drug metronidazole (Flagyl) and the de-worming drug fenbendazole. In cases of severe diarrhea or nausea your pet will be prescribed medications to help him with digestion problems.

Babesiosis infection patients may need blood transfusion in addition to fluids for hydration. Medications that your veterinarian may suggest are atovaquone, diminazene aceturate or imidocarb diproprionate. Other treatment medications may include anti-inflammatory drugs and corticosteroids.

Toxoplasmosis infection is treated by antibiotics such as Clindamycin or pyrimethamine.  There are immune system canine supplements that may help your dog’s healing progress.

Follow up visits will need to be scheduled to monitor the patient’s progress.  It is important to follow the treatment plan, your veterinarian has given. Bloodwork, urinalysis and fecal test will need to be performed. 

Giardiasis has a good prognoses in most cases. Senior dogs may have more complications. The pet’s bedding and living area must be cleaned.  Diluted bleach solution will help disinfect and kill parasites. Babesiosis infections have a guarded prognosis. Dogs that survive babesiosis may suffer relapses.  Dogs that have had babesiosis should never be a donor for blood transfusions. Toxoplasmosis infection has a guarded prognosis.  It has a better prognosis when the infection is found early on.