Toxoplasmosis in Dogs

Causes, Treatment, and Prevention

Sad brown dog lying down on floor
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Toxoplasmosis is a parasitic disease most often associated with cats, which are the only known hosts of the parasite. But, dogs can contract the disease, too. Healthy adult dogs generally remain asymptomatic, but puppies are particularly at risk for developing a fever, diarrhea, respiratory distress, and other concerning symptoms.

What is Toxoplasmosis?

Toxoplasmosis is a disease process caused by a protozoal (single-celled) parasite called Toxoplasmosis gondii. This parasite can infect any warm-blooded animal, including dogs, cats, and people. Although dogs can become infected by this parasite, the T. gondii organism cannot complete its life cycle in the dog as it can in the cat (the only definitive host).

Symptoms of Toxoplasmosis in Dogs

The T. gondii organism can spread and encyst itself anywhere in the body, so the symptoms of infection are varied and depend on where the parasites are located.


  • Fever
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Cough/difficulty breathing
  • Jaundice
  • Seizures/tremors/uncoordinated gait/other neurological symptoms
  • Depression
  • Lethargy
  • Muscle weakness
  • Partial or complete paralysis
  • Loss of appetite/weight loss
  • Eye infections/inflammation

One or more of these symptoms may appear with a toxoplasmosis infection, depending on where the parasites migrate and settle in the body tissues. Symptoms are mostly seen in puppies or severely immunocompromised dogs. Healthy adult dogs rarely show signs of infection.

Causes of Toxoplasmosis

Dogs contract toxoplasmosis by ingesting one of the following items infected with T. gondii eggs:

  • Feces from outdoor cats or cat litter boxes
  • Raw or under-cooked meat
  • A wild animal such as a rodent or rabbit

The disease replicates by cloning, then it migrates from the GI system and spreads throughout a dog's body. The replicated clones cluster together, forming cysts that lodge various tissues and organs.

An infected dog cannot spread the parasite through its stool.

Diagnosing Toxoplasmosis in Dogs

A diagnosis of toxoplamosis cannot be made from symptoms alone because so many of the effects of the T. Gondii parasite are similar to signs of other illnesses.

Instead, a veterinarian will arrive at a definitive diagnosis based on a variety of lab work, including urinalysis, blood and serological tests, and possibly a spinal tap to determine a dog's level of toxoplasma antigens.

Blood work may show abnormally low numbers of white blood cells (including neutrophils and/or lymphocytes), abnormally high levels of the liver enzymes ALT and/or AST, and in some cases, abnormally low levels of albumin.

A urinalysis may show abnormally high proteins as well as the presence of bilirubin. Serological testing can also determine if an infection is acute or chronic and whether an infection is active or dormant.


Although toxoplasmosis can cause clinical disease, most dogs have a robust enough immune system to prevent the cysts from causing any harm. In these instances, treatment isn't necessary.

If a dog does start to exhibit symptoms, antibiotics are the primary treatment along with supportive measures and anticonvulsants if a dog experiences seizures.

Prognosis for Dogs with Toxoplasmosis

If a dog is asymptomatic, then it can live with a latent or chronic toxoplasmosis infection without any sign of illness or discomfort. Symptomatic puppies and dogs usually respond well to antibiotic treatment, but severe cases can be fatal in young puppies or dogs with compromised immunity.

How to Prevent Toxoplasmosis

Preventing your dog from eating raw meat, wild animals. and other animals' feces (including that of a pet cat in the household litter box), Cleaning the litter box on a daily basis can protect your dog from ingesting infectious stool.

If you are interested in feeding your dog a raw diet, there are commercial freeze-dried brands and varieties that undergo a process called high-pressure pasteurization. This is a process that kills any potential pathogens within the food without actually cooking it.

Article Sources
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  1. Toxoplasmosis in Dogs. Merck Veterinary Manual.