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Key takeaways

Toxoplasmosis is a parasitic infection that can affect dogs and other mammals, including humans.

  • It is caused by the protozoan parasite Toxoplasma gondii
  • The parasite can be found in raw meat, contaminated soil, and cat feces
  • Dogs may become infected by consuming infected meat or by exposure to contaminated feces
  • Symptoms of toxoplasmosis can range from mild to severe and can include fever, lethargy, loss of appetite, and neurological symptoms
  • Definitive diagnosis is obtained through specialized bloodwork
  • Most cases of toxoplasmosis do not require medical treatment; when treatment is needed, options include antiparasitics, seizure medication, and supportive care
  • Prognosis depends on the severity of symptoms and overall health of the affected dog
  • Due to the zoonotic nature of the condition, prevention and general health measures are paramount in reducing the chances of human infection
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A closer look: Toxoplasmosis in Dogs

In most cases, toxoplasmosis is not considered a medical emergency as adult and healthy dogs tend not to develop symptomatic infections and do not require medical attention. Puppies and immunosuppressed animals require prompt medical attention as they can develop severe symptoms such as seizures and difficulty breathing.

Medical attention is essential as toxoplasmosis is a zoonotic condition, meaning it can pass from animals to humans.

Toxoplasmosis is a common condition in humans. Pregnant women must avoid any contact with infected animals and potentially contaminated material, as toxoplasmosis can cause birth defects and miscarriage.

Most cases of toxoplasmosis occur as the result of ingestion of contaminated food; on occasion, it can be caused by the ingestion of trace amounts of feline fecal matter.

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Risk factors

Toxoplasmosis is uncommon in dogs as they are not the primary host of the parasite. Dogs do not shed T. gondii in their feces, and a diagnosis of toxoplasmosis, especially in multi pet households (with cats), indicates transmission through cat feces within the home.

Immunosuppressed dogs and those suffering from pre-existing underlying conditions are more likely to develop severe symptoms.

Dogs living in multi-pet households (with cats), outdoor, hunting dogs, and those living in rural areas are more likely to become infected.

Rarely, toxoplasmosis can cause neurologic symptoms.

Possible causes

Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii. Dogs can become infected by consuming infected or contaminated:

  • Raw and undercooked meat
  • Animals carcasses
  • Soil
  • Cat feces

Rarely, transmission can occur from mother to puppies in the womb or through infected milk.

Main symptoms

The majority of cases of toxoplasmosis infection do not develop noteworthy symptoms.

Testing and diagnosis

Diagnosis of toxoplasmosis can be challenging, as the symptoms are nonspecific and common to a number of other conditions. Dogs presenting symptoms of toxoplasmosis generally undergo the following diagnostics:

  • Physical examination
  • Bloodwork
  • Serology test
  • Fecal analysis
  • Diagnostic imaging

Steps to Recovery

Dogs rarely require treatment for toxoplasmosis. When treatment is required, options include:

  • Intravenous fluids
  • Anti-parasitic medications
  • Anti-seizure medication

Frequent monitoring is warranted to assess the effectiveness of treatment.

The majority of dogs diagnosed with toxoplasmosis carry a good prognosis as they do not develop symptoms of the condition.

Immunosuppressed dogs and those suffering from underlying conditions carry a fair to guarded prognosis, with the majority of symptomatic patients able to improve 24 to 48 hours after initiating therapy.


Toxoplasmosis is contagious. The best way to prevent toxoplasmosis in dogs is to minimize their exposure to the parasite.

Strategies include:

  • Feeding only high-quality food
  • Fully cooking homemade pet food
  • Frequent washing of the dog’s bedding, crate, and other belongings, especially in multi-pet households
  • Keeping infected cats isolated from other pets
  • Preventing dogs from coming into contact with cat feces (e.g., sandboxes, litter boxes, and gardens)
  • Keeping dogs on a leash when walking in unknown rural areas

Is Toxoplasmosis in Dogs common?

Clinical infections in dogs are rare.

Typical Treatment

  • Often not necessary
  • Antiparasitic medications
  • Anti-seizure medication
  • IV fluid therapy


J. P. Dubey, MVSc, PhD - Writing for Merck Veterinary Manual
Gastón A. Moré, DVM, PhD - Writing for Merck Veterinary Manual
J.P. Dubey - Writing for Veterinary Partner
Stephen Barr BVSc MVS PhD DipACVIM; Bryn Tennant DVSc PhD CertVR MRCVS - Writing for Vetlexicon
No Author - Writing for Vetlexicon
No Author - Writing for Centers for Disease Control and Prevention
No Author - Writing for BC Centre for Disease Control
No Author - Writing for Canadian Centre for Occupational Health and Safety

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