Symptoms and causes

Symptoms

Most healthy people who are infected with toxoplasmosis have no signs or symptoms and aren't aware that they're infected. Some people, however, develop signs and symptoms similar to those of the flu, including:

  • Body aches
  • Swollen lymph nodes
  • Headache
  • Fever
  • Fatigue

In people with weakened immune systems

If you have HIV/AIDS, are receiving chemotherapy or have recently had an organ transplant, a previous toxoplasma infection may reactivate. In that case, you may develop more-severe signs and symptoms of infection, including:

  • Headache
  • Confusion
  • Poor coordination
  • Seizures
  • Lung problems that may resemble tuberculosis or Pneumocystis jiroveci pneumonia, a common opportunistic infection that occurs in people with AIDS
  • Blurred vision caused by severe inflammation of your retina (ocular toxoplasmosis)

In babies

If you become infected for the first time just before or during your pregnancy, you can pass the infection to your baby (congenital toxoplasmosis), even if you don't have signs and symptoms yourself.

Your baby is most at risk of contracting toxoplasmosis if you become infected in the third trimester and least at risk if you become infected during the first trimester. On the other hand, the earlier in your pregnancy the infection occurs, the more serious the outcome for your baby.

Many early infections end in stillbirth or miscarriage. Infants who survive are likely to be born with serious problems, such as:

  • Seizures
  • An enlarged liver and spleen
  • Yellowing of the skin and whites of the eyes (jaundice)
  • Severe eye infections

Only a small number of babies who have toxoplasmosis show signs of the disease at birth. Often, infants who are infected don't develop signs — which may include hearing loss, mental disability or serious eye infections — until their teens or later.

When to see a doctor

If you are living with HIV or AIDS or are pregnant or thinking of becoming pregnant, talk to your doctor about being tested if you think you may have been exposed to toxoplasmosis.

The signs and symptoms of severe toxoplasmosis — blurred vision, confusion, loss of coordination — require immediate medical care, particularly if your immune system has been weakened.

Causes

Toxoplasma gondii (T. gondii) is a single-celled parasitic organism that can infect most animals and birds. Because it reproduces only in cats, wild and domestic cats are the parasite's ultimate host.

When a person becomes infected with T. gondii, the parasite forms cysts that can affect almost any part of the body — often your brain and muscle tissue of different organs, including the heart.

If you're generally healthy, your immune system keeps the parasites in check. They remain in your body in an inactive state, providing you with lifelong immunity so that you can't become infected with the parasite again. But if your immune system is weakened by disease or certain medications, the infection can be reactivated, leading to serious complications.

Although you can't "catch" toxoplasmosis from an infected child or adult, you can become infected if you:

  • Come into contact with cat feces that contain the parasite. You may accidentally ingest the parasites if you touch your mouth after gardening, cleaning a litter box or touching anything that has come in contact with infected cat feces. Cats who hunt or who are fed raw meat are most likely to harbor T. gondii.
  • Eat or drink contaminated food or water. Lamb, pork and venison are especially likely to be infected with T. gondii. Occasionally, unpasteurized dairy products also may contain the parasite. Water contaminated with T. gondii isn't common in the United States.
  • Use contaminated knives, cutting boards or other utensils. Kitchen utensils that come into contact with raw meat can harbor the parasites unless the utensils are washed thoroughly in hot, soapy water.
  • Eat unwashed fruits and vegetables. The surface of fruits and vegetables may contain the parasite. To be safe, thoroughly wash and peel all produce, especially any you eat raw.
  • Receive an infected organ transplant or transfused blood. In rare cases, toxoplasmosis can be transmitted through an organ transplant or blood transfusion.

Risk factors

Anyone can become infected with toxoplasmosis. The parasite is found throughout the world.

You're at risk of serious health problems from toxoplasmosis infection if:

  • You have HIV/AIDS. Many people with HIV/AIDS also have toxoplasmosis, either a recent infection or an old infection that has reactivated.
  • You're undergoing chemotherapy. Chemotherapy affects your immune system, making it difficult for your body to fight even minor infections.
  • You take steroids or other immunosuppressant drugs. Medications used to treat certain nonmalignant conditions suppress your immune system and make you more likely to develop complications of toxoplasmosis.

Complications

If you have a normal immune system, you're not likely to experience complications of toxoplasmosis, although otherwise healthy people sometimes develop eye infections. Untreated, these infections can lead to blindness.

But if your immune system is weakened, especially as a result of HIV/AIDS, toxoplasmosis can lead to seizures and life-threatening illnesses such as encephalitis — a serious brain infection.

In people with AIDS, untreated encephalitis from toxoplasmosis is fatal. Relapse is a constant concern for people with toxoplasmosis who also have a weakened immune system.

Children with congenital toxoplasmosis may develop disabling complications, including hearing loss, mental disability and blindness.

July 15, 2017
References
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  3. Guerina NG. Congenital toxoplasmosis: Clinical features and diagnosis. http://www.uptodate.com/home. Accessed Jan. 31, 2017.
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