Toxoplasmosis (tok-so-plaz-MOE-sis) is a disease that results from infection with the Toxoplasma gondii parasite, one of the world's most common parasites.
Toxoplasmosis may cause flu-like symptoms in some people, but most people affected never develop signs and symptoms. For infants born to infected mothers and for people with weakened immune systems, toxoplasmosis can cause extremely serious complications.
If you're generally healthy, you probably won't need any treatment for toxoplasmosis. If you are pregnant or have lowered immunity, certain medications can help reduce the infection's severity. The best approach, though, is prevention.
If you're healthy, you probably won't know you've contracted toxoplasmosis. Some people, however, develop signs and symptoms similar to those of the flu, including:
Swollen lymph nodes
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're more likely to develop signs and symptoms of severe infection, including:
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)
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. Children who survive are likely to be born with serious problems, such as:
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, infected children don't develop signs and symptoms — including 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.
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.
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 felines 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 muscles, 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 resistance 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 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.
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.
You're pregnant. If you have active toxoplasmosis, treatment can reduce the risk to your baby. If you had toxoplasmosis before becoming pregnant, you generally can't pass the infection to your baby.
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.
Certain precautions can help prevent toxoplasmosis:
Wear gloves when you garden or handle soil. Wear gloves whenever you work outdoors and wash your hands thoroughly with soap and water afterward.
Don't eat raw or undercooked meat. Meat, especially lamb, pork and beef, can harbor toxoplasma organisms. Don't taste meat before it's fully cooked. Avoid raw cured meat.
Wash kitchen utensils thoroughly. After preparing raw meat, wash cutting boards, knives and other utensils in hot, soapy water to prevent cross contamination of other foods. Wash your hands after handling raw meat.
Wash all fruits and vegetables. Scrub fresh fruits and vegetables, especially if you plan to eat them raw. Remove peels when possible, but only after washing.
Don't drink unpasteurized milk. Unpasteurized milk and other dairy products may contain toxoplasma parasites.
Cover children's sandboxes. If you have a sandbox, cover it when your children aren't playing in it to keep cats from using it as a litter box.
For cat lovers
If you're pregnant or otherwise at risk of toxoplasmosis or its complications, take these steps to protect yourself:
Help your cat stay healthy. Keep your cat indoors and feed it dry or canned cat food, not raw meat. Cats can become infected after eating infected prey or undercooked meat that contains the parasite.
Avoid stray cats or kittens. Although all stray animals need good homes, it's best to let someone else adopt them. Most cats don't show signs of T. gondii infection, and although they can be tested for toxoplasmosis, it may take up to a month to get the results.
Have someone else clean your cat's litter box. If that's not possible, wear gloves and a face mask to change the litter. Then wash your hands well. Change the litter daily so that excreted cysts don't have time to become infectious.
You're likely to start by seeing your family doctor, or if you're pregnant, your obstetrician. You may be referred to a doctor who specializes in infectious diseases. If you're pregnant, you may be referred to a doctor who specializes in fetal health (perinatologist) or newborn health (neonatologist).
Here's some information to help you get ready for your appointment.
What you can do
You may want to write a list that includes:
Descriptions of your symptoms
Information about medical problems you've had
Information about the medical problems of your parents or siblings
Medications and dietary supplements you take
Questions you want to ask the doctor
For toxoplasmosis, some basic questions to ask your doctor include:
What tests do I need?
What treatments are available, and which do you recommend?
What side effects might I expect from treatment?
I'm pregnant. What effect will this have on my baby?
I have other heath problems. How can I manage them together?
Are there brochures or other printed materials I can have? What websites do you recommend?
Don't hesitate to ask other questions, as well.
What to expect from your doctor
Your doctor is likely to ask you a number of questions, such as:
When did your symptoms start?
How severe are your symptoms?
Have you recently consumed raw or undercooked meat?
Do you own or care for a cat? Who changes the litter box?
Do you wear gloves when gardening or working with soil?
Do you have conditions or take medications that affect your immune system?
Most pregnant women in the United States aren't routinely screened for toxoplasmosis, and most states don't screen infants for the infection. Without specific screening, toxoplasmosis is often difficult to diagnose because signs and symptoms, when they occur, are similar to those of more common illnesses, such as the flu and mononucleosis.
Testing during pregnancy
If your doctor suspects you have the infection, you may have blood tests that check for antibodies to the parasite. Antibodies are proteins produced by your immune system in response to the presence of foreign substances, such as parasites. Because these antibody tests can be difficult to interpret, the Centers for Disease Control and Prevention recommends that all positive results be confirmed by a laboratory that specializes in diagnosing toxoplasmosis.
What test results mean
Sometimes you may be tested early in the course of the disease before your body has a chance to produce antibodies. In that case, you may have a negative result, even though you're infected. To be certain, your doctor may recommend retesting several weeks later.
In most cases, a negative toxoplasmosis test result means you've never been infected and therefore aren't immune to the disease. If you're at high risk, you can take certain precautions so that you don't become infected.
A positive result could mean that you have an active infection, or it could mean that you were once infected and are immune to the disease. Additional tests can pinpoint when the infection occurred, based on the types of antibodies in your blood. This is especially important if you're pregnant or you have HIV/AIDS.
Testing your baby
If you're pregnant and have a current toxoplasmosis infection, the next step is to determine whether your baby also is infected. Tests your doctor may recommend include:
Amniocentesis. In this procedure, which may be done safely after 15 weeks of pregnancy, your doctor uses a fine needle to remove a small amount of fluid from the fluid-filled sac that surrounds the fetus (amniotic sac). Tests are then performed on the fluid to check for evidence of toxoplasmosis. Amniocentesis carries a slight risk of miscarriage and minor complications, such as cramping, leaking fluid or irritation where the needle was inserted.
Ultrasound scan. This test uses sound waves to produce images of your baby in the womb. A detailed ultrasound can't diagnose toxoplasmosis. It can show whether your baby has certain signs, such as fluid buildup in the brain (hydrocephalus). However, a negative ultrasound doesn't rule out the possibility of infection. For that reason, your newborn will need an examination and follow-up blood tests during the first year of life.
Testing in severe cases
If you've developed a life-threatening illness such as encephalitis, you may need one or more imaging tests to check for lesions or cysts in your brain. These include:
Magnetic resonance imaging (MRI). This test uses a magnetic field and radio (electromagnetic) waves to create cross-sectional images of your head and brain. During the procedure, you lie inside a large, doughnut-shaped machine that contains a magnet surrounded by coils that send and receive radio waves.
In response to the radio waves, your body produces faint signals that are picked up by the coils and processed into images by a computer. MRI is noninvasive and poses no risks to your health.
Brain biopsy. In rare cases, especially if you don't respond to treatment, a neurosurgeon may take a small sample of brain tissue. The sample is then analyzed in a laboratory to check for toxoplasmosis cysts.
Most healthy people don't require toxoplasmosis treatment. But if you're otherwise healthy and have signs and symptoms of acute toxoplasmosis, your doctor may prescribe the following drugs:
Pyrimethamine (Daraprim). This medication, typically used for malaria, is a folic acid antagonist. It may prevent your body from absorbing the B vitamin folate (folic acid, vitamin B-9), especially when you take high doses over a long period. For that reason, your doctor may recommend taking additional folic acid.
Other potential side effects of pyrimethamine include bone marrow suppression and liver toxicity.
Sulfadiazine. This antibiotic is used with pyrimethamine to treat toxoplasmosis.
Treating people with HIV/AIDS
If you have HIV/AIDS, the treatment of choice for toxoplasmosis is also pyrimethamine and sulfadiazine, with folic acid. An alternative is pyrimethamine taken with clindamycin (Cleocin) — an antibiotic that can cause severe diarrhea.
You may need to take these medications for life, but it's possible your dose may be lowered. If your doctor prescribes toxoplasmosis therapy to prevent toxoplasmosis, you may be able to stop taking toxoplasmosis medication if your CD4 count — the amount of a particular white blood cell in your blood — remains high for at least three to six months.
Treating pregnant women and babies
If you're pregnant and infected with toxoplasmosis but your baby isn't affected, you may be given the antibiotic spiramycin. Use of this drug may reduce your baby's risk of neurological problems from congenital toxoplasmosis. Spiramycin is routinely used to treat toxoplasmosis in Europe. But it is still considered experimental in the United States. Your doctor can obtain it from the Food and Drug Administration.
If tests show that your unborn child has toxoplasmosis, your doctor may suggest treatment with pyrimethamine and sulfadiazine — but only in extreme circumstances and after the 16th week of pregnancy. These drugs can have serious side effects for women and their unborn babies, so they're normally not used during pregnancy.
If your infant has toxoplasmosis or is likely to have it, treatment with pyrimethamine and sulfadiazine and folic acid is recommended. Your baby's doctor will need to monitor your baby while he or she is taking these medications.