Toxoplasmosis (tok-so-plaz-MOE-sis) is an infection with a parasite called Toxoplasma gondii. People often get the infection from eating undercooked meat. You can also get it from contact with cat feces. The parasite can pass to a baby during pregnancy.

Most people infected with the parasite do not have symptoms. Some people get flu-like symptoms. Serious disease most often affects infants and people with weakened immune systems. Toxoplasmosis during pregnancy may cause miscarriage and birth defects.

Most infections don't need treatment. Drug treatment is used for people with more-serious cases, pregnant people, newborns and people with weakened immune systems. Several steps to prevent toxoplasmosis can lower the risk of infection.

Most people infected with toxoplasmosis do not have any symptoms. They often don't know they're infected. Some people have flu-like symptoms, including:

• Fever.
• Swollen lymph nodes that may last for weeks.
• Headache.
• Muscle aches.
• Skin rash.

Symptoms of eye disease

The toxoplasma parasites may infect tissues of the inner eye. This can occur in people with healthy immune systems. But the disease is more serious in people with weakened immunity. An infection in the eye is called ocular toxoplasmosis. Symptoms may include:

• Eye pain.
• Poor vision.
• Floaters, which are specks that seem to swim in your vision.

Untreated eye disease can cause blindness.

Effect on people with weakened immune systems

People with weakened immune systems are likely to have more-serious disease from toxoplasmosis. A toxoplasmosis infection from earlier in life may become active again. People at risk include those living with HIV/AIDS, people receiving cancer treatment and people with a transplanted organ.

In addition to serious eye disease, toxoplasmosis can cause severe lung or brain disease for a person with weakened immunity. Rarely, the infection can show up in other tissues throughout the body.

Lung infection may cause:

• Breathing problems.
• Fever.
• Cough.

Toxoplasmosis may cause inflammation of the brain, also called encephalitis. Symptoms may include:

• Confusion.
• Poor coordination.
• Muscle weakness.
• Seizures.
• Changes in alertness.

Effect on fetus or infant

Toxoplasmosis can pass from the mother to the fetus during a pregnancy. This is called congenital toxoplasmosis.

Infection during the first trimester often causes more-severe disease. It also may result in miscarriage. For some babies with toxoplasmosis, serious disease may be present at birth or appear early in infancy. Medical problems may include:

• Too much fluid in or around the brain, also called hydrocephalus.
• Severe eye infection.
• Irregularities in brain tissues.
• An enlarged liver or spleen.

Symptoms of severe disease vary. They may include:

• Problems with mental or motor skills.
• Blindness or other vision problems.
• Hearing problems.
• Seizures.
• Heart disorders.
• Yellowing of the skin and whites of the eyes, also called jaundice.
• Rash.

Most babies with toxoplasmosis do not show symptoms. But problems may show up later in childhood or teenage years. These include:

• Return of eye infections.
• Problems with motor skill development.
• Problems with thinking and learning.
• Hearing loss.
• Slowed growth.
• Early puberty.

When to see a doctor

Talk to your health care provider about a test if you are worried about exposure to the parasite. If you are planning a pregnancy or are pregnant, see your provider if you suspect exposure.

The symptoms of severe toxoplasmosis include blurred vision, confusion and loss of coordination. These need immediate medical care, particularly if you have a weakened immune system.

Toxoplasma gondii is a parasite that can infect most animals and birds. It can only go through the entire cycle of reproduction in domestic and wild cats. These are the main hosts for the parasite.

Immature eggs, a middle stage of reproduction, can be in the feces of cats. This immature egg allows for the parasite to make its way through the food chain. It can pass from soil and water to plants, animals and humans. Once the parasite has a new host, the reproduction cycle goes on and causes an infection.

If you're in typical health, your immune system keeps the parasites in check. They stay in your body but are not active. This often gives you lifelong immunity. If you're exposed to the parasite again, your immune system would clear it out.

If your immune system is weakened later in life, parasite reproduction can start again. This causes a new active infection that can lead to serious disease and complications.

People often get a toxoplasma infection one of the following ways:

• Cat feces with the parasite. Cats that hunt or who are fed raw meat are more likely to carry toxoplasma parasites. You may get infected if you touch your mouth after touching anything that has been in contact with cat feces. This may be gardening or cleaning a litter box.
• Contaminated food or water. Undercooked beef, lamb, pork, venison, chicken and shellfish are all known carriers of the parasite. Unpasteurized goat milk and untreated drinking water also may be carriers.
• Unwashed fruits and vegetables. The surface of fruits and vegetables may have the parasite on them.
• Contaminated kitchen tool. Parasites may be on cutting boards, knives and other utensils that come into contact with raw meat or unwashed fruits and vegetables.
• Infected organ transplant or transfused blood. Rarely, toxoplasma parasites are passed through an organ transplant or blood transfusion.

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

Risks of serious disease from toxoplasmosis include things that prevent the immune system from fighting infections, such as:

• Infection with HIV/AIDS.
• Chemotherapy treatment for cancer.
• High-dose steroids.
• Drugs that prevent the rejection of transplanted organs.

Certain precautions can help prevent toxoplasmosis:

• Wear gloves when you garden or handle soil. Wear gloves when you work outdoors. Wash your hands with soap and water afterward.
• Don't eat raw or undercooked meat. Use a meat thermometer to make sure meat is cooked enough. Cook whole meats and fish to at least 145 F (63 C) and let rest for at least three minutes. Cook ground meat to at least 160 F (71 C). Cook whole and ground poultry to at least 165 F (74 C).
• Don't eat raw shellfish. Do not eat raw clams, mussels or oysters, particularly during pregnancy.
• Wash kitchen utensils thoroughly. Wash cutting boards, knives and other utensils with soapy water after contact with raw meats or unwashed fruits and vegetables. Wash your hands thoroughly before and after preparing foods.
• Wash all fruits and vegetables. Wash fresh fruits and vegetables before eating, peeling or cooking.
• Don't drink unpasteurized goat milk. Avoid unpasteurized goat milk or products made from the milk.
• Don't drink untreated water. During pregnancy, do not drink untreated water.
• Cover children's sandboxes. Cover sandboxes to prevent outdoor cats from using them as litter boxes.

For cat lovers

If you're pregnant or otherwise at risk of toxoplasmosis, take these steps to protect yourself:

• Help your cat stay healthy. Keep your cat indoors. Feed it dry or canned cat food, not raw or undercooked meat.
• Avoid stray cats or kittens. Avoid stray cats, especially kittens. Do not get a new cat when you're pregnant.
• Have someone else clean the litter box. Clean the box daily, if possible. If someone else can't clean it, wear gloves and a face mask to change the litter. Then wash your hands well.

A diagnosis of toxoplasmosis is based on blood tests. Laboratory tests can detect two types of antibodies. One antibody is an immune system agent that is present during a new and active infection with the parasite. The other antibody is present if you had an infection at any time in the past. Depending on the results, your health care provider may repeat a test after two weeks.

More diagnostic tests are used depending on other symptoms, your health and other factors.

Eye symptoms

If you have eye symptoms, you will need an exam by a doctor who specializes in eye disease, called an ophthalmologist. An exam may include the use of special lenses or cameras that allow the doctor to see tissues inside the eye.

Brain and other nervous system symptoms

If there are symptoms of brain inflammation, tests might include the following:

• Brain imaging. MRI or CT scans are used to create images of the brain. These may detect irregular structures in the brain related to toxoplasmosis.
• Cerebral spinal fluid (CSF) test. CSF is the fluid that surrounds and protects the brain and spinal cord. Laboratory tests may detect toxoplasma in CSF if there is infection in the brain.
• Brain tissue. Rarely, tissue is removed from the brain to detect the parasite.

Pregnancy

In the United States, pregnant people are not routinely screened for toxoplasmosis. Recommendations for screening vary in other countries.

Your health care provider may order a diagnostic blood test for you if:

• Your symptoms might be from an active toxoplasma infection.
• Ultrasound images of your baby show irregular features linked to toxoplasmosis.

If you have an active infection, it may pass to your baby in the womb. A diagnosis is based on tests of the fluid surrounding the baby, called amniotic fluid. The sample is taken with a fine needle that goes through your skin and into the fluid-filled sac holding the baby.

Your care provider will order a test if:

• You test positive for the parasite.
• Your test results are not clear.
• Ultrasound images of the fetus show irregular features linked to toxoplasmosis.

Newborn

Blood tests are ordered for diagnosis of toxoplasmosis in a newborn baby if infection is suspected. A baby who tests positive will have many tests to detect and keep an eye on the disease. These would likely include:

• Ultrasound or CT imaging of the brain.
• Tests of the fluid surrounding the brain and spinal column.
• Eye tests.
• Hearing tests.
• Test of brain activity, called electrocephalogram.

Medication is used to treat active infections. How much and how long you take medicine depends on different factors. These include how seriously ill you are, your immune system health and where the infection is located. Your stage of pregnancy is also a factor.

Your provider may give you a combination of prescription drugs. They include:

• Pyrimethamine (Daraprim). This fights infections caused by microscopic organisms. It can block the body's use of folic acid. Other possible side effects with long-term use include bone marrow suppression and liver toxicity.
• Leucovorin calcium helps correct the effects of pyrimethamine on folic acid activity.
• Sulfadiazine is an antibiotic often prescribed with pyrimethamine. Other medication includes clindamycin (Cleocin), azithromycin (Zithromax) and others.

Treatment for infants

Drug treatment for infants may last 1 to 2 years. Regular and frequent follow-up appointments are needed to watch for side effects, vision problems, and physical, intellectual and overall development.

Additional treatment for eye disease

In addition to the regular drug treatment, eye disease also may be treated with anti-inflammatory steroids called glucocorticosteroids.

You're likely to start by seeing your health care provider. If you're pregnant, you'll likely see your obstetrician. You also may see a provider who specializes in fetal health, called a perinatologist. In some cases, you'll see a provider who specializes in infectious diseases.

You can prepare for your appointment by being ready to answer the following questions:

• What are your symptoms?
• When did they start?
• Have you been diagnosed with toxoplasmosis in the past?
• Do you have a cat? Is it an indoor or outdoor cat? Do you change the litter?
• Have you recently eaten raw or undercooked meat or fish?
• Have you had unpasteurized goat's milk products?
• Do you garden or work outdoors? Do you wear gloves?
• What medications, vitamins or supplements do you take?