Toxoplasmosis is caused by a protozoan that infects warm-blooded animals. Cats are the definitive host, but other animals, including dogs and humans, can act as intermediate hosts. It is not very common in dogs. The principal mode of transmission in dogs & people is raw or under-cooked meat (pork, beef, mutton, or veal) that contains the organism Toxoplasma gondii. Oocysts excreted in the stools of infected cats, or ingesting spores, are other potential sources of infection. Oocysts require one to three days under ideal conditions of warm temperature and high humidity to produce spores. These infective spores can survive in the environment for months or years.

Only cats excrete the oocytes in their stool. The dog is therefore not capable of infecting other dogs and humans in this way. Most dogs with toxoplasmosis experience no symptoms.

Clinical signs include fever, loss of appetite, lethargy, cough, and rapid breathing. Other signs are weight loss, diarrhea, lymph node enlargement, and swelling of the abdomen. Young puppies with toxoplasmosis may show signs of pneumonia, hepatitis, or encephalitis. In brood bitches, intrauterine infection can result in abortion, stillbirths, and the birth of sick puppies who die within the first week of life.

The diagnosis is accomplished by indirect haemagglutination assay, indirect fluorescent antibody assay, latex agglutination test, or ELISA. IgM antibodies appear sooner after infection than IgG antibodies but generally do not persist past 3 mo after infection. T gondii is morphologically similar to other protozoan parasites and must be differentiated from Sarcocystis species and Neospora caninum.


Sulfadiazine (15–25 mg/kg) and pyrimethamine (0.44 mg/kg) are widely used for treatment of toxoplasmosis. Although these drugs are beneficial if given in the acute stage of the disease when there is active multiplication of the parasite, they will not usually eradicate infection. These drugs are believed to have little effect on the bradyzoite stage. Other drugs diaminodiphenylsulfone, atovaquone, and spiramycin are also used to treat toxoplasmosis in chronic & difficult cases. Clindamycin is the treatment of choice for toxoplasmosis in dogs at 10–40 mg/kg for 14–21 days.


Prevent the disease by keeping your pet from roaming and hunting. Cook all fresh meat (both yours and your pets’) to a temperature of at least 150°F (65.5°C). Wash your hands with soap and water after handling raw meat. Always clean kitchen surfaces that come in contact with raw meat. Always wash the vegetables before use.

Zoonotic Risk:

Toxoplasma gondii is a zoonotic aganet & causes disease to human beings. It may cause meningoencephalitis.

It may also cause still births in pregnant women. Actually tachyzoites can migrate transplacentally and cause birth defects in human fetuses.