Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at March 15, 2016

Toxoplasmosis is a parasitic disease that infects many warm-blooded animals with some estimates stating that up to half of the world’s human population has toxoplasmosis. In most healthy adults, there are no symptoms of toxoplasmosis, but in rare cases, it can have dangerous consequences.


Definition & Facts

Toxoplasmosis occurs when a person is infected with the Toxoplasma gondii parasite. Though the parasite only reproduces sexually if its host is a cat, it can be spread to any type of warm-blooded animal. It is incredibly common, but this parasite was not medically recognized until 1908 because it rarely results in severe symptoms.

People who have a weakened immune system, pregnant women, and young children are most at risk from toxoplasmosis. About 23 percent of people over the age of twelve in the United States have toxoplasmosis, and in some underdeveloped areas of the world, the infection rate is as high as 95 percent.

Symptoms & Complaints

During the first few weeks after being exposed to Toxoplasma gondii, some people may develop mild flu-like symptoms, including headaches, fatigue, fever, aching muscles, and swollen lymph nodes. Most healthy adults will not experience or notice these symptoms, and they will enter the latent stage of toxoplasmosis, during which time no symptoms are present.

Though it is possible for a person with a fully functioning immune system to develop more severe symptoms, it is more common among people with immune systems weakened due to HIV, or other illnesses. Severe symptoms of toxoplasmosis are blurred vision, seizures, pneumonia, lung problems, confusion, bad coordination, or encephalitis, which is a severe and potentially fatal brain infection.

In extremely rare cases, toxoplasmosis may cause skin lesions. If a woman is infected with toxoplasmosis right before or during her pregnancy, she may lose the pregnancy or pass toxoplasmosis on to her child. Children born with toxoplasmosis may be born with an enlarged liver and enlarged spleen, jaundice, seizures, severe eye infections, hearing loss, or mental disabilities.


Toxoplasmosis is caused by the single-celled parasitic protozoan, Toxoplasma gondii. People may be infected with this parasite in a variety of ways. This parasite can infect most animals, but it reproduces through cats, making them one of the main causes of toxoplasmosis. Cats who eat raw meat are particularly likely to have toxoplasmosis, and then it is passed on through contact with their feces. People may get toxoplasmosis from cats by cleaning a litter box, getting scratched by a cat, or gardening in an area where a cat eliminates waste.

It can also be caused by eating any food that is contaminated with Toxoplasma gondii. Meat that is not cooked thoroughly can cause toxoplasmosis, and this is most common among lamb, pork, and venison cuts of meat. Fruits or vegetables may also have trace amounts of the parasite on them, so people may get toxoplasmosis by eating unwashed fruits or vegetables.

Water can occasionally transmit Toxoplasma gondii, but unpasteurized dairy is the liquid most likely to contain the parasite. Contact with a cat or food item contaminated by the parasite is the most likely cause of toxoplasmosis, but an organ transplant or blood transfusion can also infect a person with the parasite.

Diagnosis & Tests

Since the symptoms are so mild, basic medical observation typically cannot diagnose toxoplasmosis. It is typically diagnosed with a blood test that examines the blood for toxoplasmosis antibodies or parasites. Since the blood test diagnoses toxoplasmosis by seeing if the body has produced antibodies to fight off the parasite, testing during the early stages of toxoplasmosis may not reveal any information.

For people who develop the life threatening symptoms of toxoplasmosis, it can be diagnosed by an MRI that checks the brain for the lesions and microbial cysts that cause seizures or encephalitis. Brain biopsies can also be used to test for these cysts of Toxoplasma gondii.

There are also tests that can be done to see if a fetus is infected with toxoplasmosis during a woman’s pregnancy. An ultrasound scan can diagnose the fluid buildup in a fetus’ brain that is a trademark of congenital toxoplasmosis. It can also be diagnosed by an amniocentesis that collects fluid from the amniotic sac which is tested for toxoplasmosis.

Treatment & Therapy

Treatment for toxoplasmosis depends on how it is affecting you. Many people experience no symptoms, and therefore they do not receive any sort of treatment. For people who experience the more acute symptoms of toxoplasmosis, antibiotics may be administered to treat the disease. The most common antibiotics used to treat toxoplasmosis are spiramycin, sulfadiazine, atovaquone, and clindamycin. Pyrimethamine is another commonly administered medicine, which works by preventing the parasite cells from replicating.

People with HIV/AIDs are commonly treated with both antibiotics and pyrimethamine for very long periods of time. Any person who is treated for toxoplasmosis with pyrimethamine will typically also be required to take folic acid, because the pyrimethamine prevents the body from properly absorbing the vitamin. Pregnant women who have toxoplasmosis are treated with spiramycin, an antibiotic that greatly lowers the risk of the fetus developing severe neurological issues from toxoplasmosis.

Prevention & Prophylaxis

A few simple lifestyle changes can greatly reduce the risk of a person catching toxoplasmosis. Eating meat that has been thoroughly cooked, washing any fruits and vegetables before consumption, avoiding unpasteurized dairy products, and washing kitchen utensils in hot soapy water can help to prevent people from being infected with the parasite through their diet.

Gloves should be worn while gardening and children’s sandboxes should be covered while not in use to prevent contact with cat feces. Cat owners should not give their cats raw meat, in order to avoid infecting the cat, and owners can also wear gloves and a mask while changing litter to prevent Toxoplasma gondii exposure. Pregnant women should avoid contact with cat litter as much as possible.