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infection caused by Toxoplasma gondii, a single-celled parasitic microorganism that can infect most warm-blooded animals but reproduces only in animals of the cat family, who shed the parasite in their feces. In most healthy persons, the immune system can prevent the parasite from causing illness, and there are no symptoms; in some cases, there are flulike symptoms. Despite a lack of symptoms and a healthy immune system, T. gondii can survive for a long time in a person or other host by forming cysts, usually in skeletal or heart muscle, the brain, or the eyes.

Infection is more severe in persons with weakened immune systems, including formerly healthy persons in whom the parasite is reactivated, and in children whose mothers become infected just before or during pregnancy. In such cases, the brain, eyes, and other organs can be harmed by the parasite. Symptoms may include headache, confusion, poor coordination, seizures, and lung problems, and blurred or reduced vision, pain (which may occur in association with bright light), redness of the eye, and tearing if an eye is involved. Infections during pregnancy can cause a miscarriage or stillbirth. Infected newborns do not usually show symptoms; seizures, jaundice, eye infections, hearing loss, mental disability, or other symptoms typically develop later, sometimes in the child's teens or after.

Toxoplasmosis is often treated with pyrimethamine and sulfadiazine in conjunction in many cases with folinic acid. Persons with weakened immune systems may be given pyrimethamine and clindamycin instead; pregnant women infected before the 16th week are given spyramycin. Because infection may result from contact with cat feces that is a day old or older, contact with contaminated soil or sand outdoors, eating meat from infected animals, eating unwashed or unpeeled raw contaminated produce, eating raw contaminated shellfish, and drinking contaminated water, such precautions as cleaning cat litter promptly, using gardening gloves, properly preparing and cooking food, and drinking treated water can help prevent infection.

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a protozoan disease of man and animals that is caused by parasites of the genus Toxoplasma gondii. The sources of infection are more than 180 species of domestic and wild animals, including dogs, cats, rabbits, predators, herbivores, rodents, and birds. Human infestation occurs through consumption of insufficiently cooked meat products or eggs; it may also occur by means of the mucous membranes and skin injuries, or through transmission. Prenatal infestation has also been observed.

In man, toxoplasmosis may be congenital or acquired, and acute or chronic. Congenital toxoplasmosis may involve the prenatal death of the fetus, the death of the newborn from general infection, or affectation of the newborn’s nervous system, as well as of its eyes and other organs. The acute acquired form of toxoplasmosis has a course similar to that of typhus, with high temperature and enlargement of the liver and spleen. The acute acquired form may also affect primarily the nervous system, with accompanying headaches, convulsions, vomiting, and paralysis. Toxoplasmosis is often chronic, and in this form is marked by subfebrile temperature, headache, enlargement of the lymph nodes and liver, and impairment of working capacity. In the chronic form, the eyes, heart, nervous system, and other organs and systems may be affected. Toxoplasmosis also occurs in a latent form.

Toxoplasmosis is detected by means of serodiagnosis and intradermal allergic tests. The disease is treated with pyrimethamine and with sulfanilamide compounds. Infestation can be prevented by controlling toxoplasmosis in domestic animals, by observing proper sanitary measures when disposing of animal waste and processing food products, and by examining pregnant women for signs of toxoplasmosis.


Kovaleva, E. P. Toksoplazmoz. Moscow, 1967.
Domestic and wild mammals, as well as birds, are affected by toxoplasmosis. The disease is naturally endemic, and has been recorded in every country of the world. Infestation occurs by ingestión or contamination, and occasionally by means of airborne droplets. Prenatal infestation may also occur. The cysts of the parasites may remain alive within an animal for years, particularly in the brain and skeletal musculature.
In animals, the causative agent of toxoplasmosis is discharged from infected or recovered animals with aborted or stillborn fetuses, as well as with the amniotic fluid, placenta, and vaginal discharges. The causative agent also occurs in the milk, saliva, and discharges from the nose and eyes. In cats, the causative agent may be discharged with the feces.
Depending on the species of the animal affected, miscarriages, intestinal disturbances, and disorders of the skin and nervous system may develop in connection with toxoplasmosis. Toxoplasmosis in animals may be acute or chronic; the disease sometimes results in the affected animal’s death. Diagnosis is based on the findings of epizootiology and is conducted by observing external symptoms, examining the blood serum, and studying animal discharges with a microscope.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


Infection by the protozoan Toxoplasma gondii, manifested clinically in severe cases by jaundice, hepatomegaly, and splenomegaly.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.