Toxoplasmosis: Infection Dangerous for Dogs and Humans

Toxoplasmosis is the most common parasitic infection worldwide. The organism that causes toxoplasmosis is Toxoplasma gondii that infects a wide range of warm-blooded vertebrates, including humans. About fifty percent of stray dogs and cats carry T.gondii antibodies, which means that they have been infected and may transmit the parasite. Although rare in dogs, toxoplasmosis does occur in young dogs infected with distemper or other viral infection. In other cases, dogs develop disease without any other present infectious disease. Even though only cats shed the infective organisms, dogs may act as a mechanical factor in transmitting toxoplasmosis to humans by rolling in infective substances and by ingesting fecal material.

Many dogs get infected and become carriers of this parasite, but in most cases only puppies and young dogs develop the disease with clear clinical signs that vary depending on the site of the infection. Infection of the central nervous system and musculature may result in behavioral changes, limb shaking, blindness, circling, muscle pain, progressive paralysis, and death. In other cases, dogs may develop hepatitis, pneumonia, and ulcerative dermatitis. Because the disease resembles many other infections, diagnosis is difficult and requires several tests. Treatment may be effective, however, serious complications affecting nervous system and muscles often result.

To prevent toxoplasmosis:

  • Avoid handling free-roaming dogs or any that show signs of illness.
  • Protect your dogs from infections by avoiding feeding them raw meet or unpasteurized dairy products.
  • Pregnant women should avoid changing cat litter, if possible. If no one else is available to change the cat litter, use gloves, then wash hands thoroughly. Change the litter box daily because Toxoplasma oocysts require several days to become infectious. Pregnant women should be encouraged to keep their cats inside and not adopt or handle stray cats. Cats should be fed only canned or dried commercial food or well-cooked table food, not raw or undercooked meats.

Toxoplasmosis Pneumonia

Toxoplasmosis pneumonia is the inflammation of the lungs caused by Toxoplasma gondii; it is a hidden infection caused by invasion of the human body by pathogens, and the symptoms vary. T gondii mainly affects the eyes, brain, heart, liver, lymph nodes and other organs but rarely affects the lungs. The patients affected by toxoplasmosis pneumonia had not come into contact with any cats, dogs, pigs or other mammals. Most patients with acute onset experience headaches, muscle pain, dry cough and other symptoms, whereas other patients cough mucus bloody sputum, which are symptoms similar to those of upper respiratory tract infection.


  1. Parasitic Disease Information
  2. Audra Charron, Sebastian Hakansson and Dana Mordue. Invasion and Intracellular Survival of Toxoplasma (In: Protozoans in Macrophages)
  3. Toxoplasma gondii Pneumonia in an Immunocompetent Individual


Related Conditions

Ascarids & Hookworms


Canine Hepatozoonosis

Canine Leishmaniasis

Canine Monocytic Ehrlichiosis

Canine Protothecosis

Chagas' disease (American Trypanosomiasis)





Internal Parasites



Protozoal Infections

Respiratory System Parasites

Rickettsial Diseases


Toxoplasmosis and Neosporosis

Diseases Transmissible Between Dogs and People

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