You might know about the infection toxoplasmosis in relation to avoiding it during pregnancy by taking precautions with certain foods and the cat's litter box. According to the Centers for Disease Control and Preventing (CDC), some 60 million people in the United States could have toxoplasmosis. Many don't even know it because it can cause an infection with no symptoms or ones that are common to other illnesses.

This infection is caused by a microscopic parasite that can live inside the cells of humans and animals, especially cats and farm animals.

How It Spreads

People can catch toxoplasmosis from:

• touching or coming into contact with infected cat feces (cats get the infection from eating infected rodents, birds, or other small animals)
• eating raw or undercooked meat that's contaminated
• eating uncooked, unwashed fruits or vegetables that have been contaminated by manure
• being born with it (a woman who gets a toxoplasmosis infection while pregnant may pass the parasite on to her unborn child through the bloodstream)

Although infection doesn't normally spread from person to person except through pregnancy, in rare instances toxoplasmosis can contaminate blood transfusions and organs donated for transplantation.

Signs and Symptoms

Toxoplasmosis passes from animals to humans, sometimes without causing any symptoms. When kids do have symptoms, they vary depending on the child's age and the immune system's response to the infection. (As with humans, infected cats often don't show any signs of a toxoplasmosis infection.)

Toxoplasmosis infections in people fall into three basic patterns:

1. congenital toxoplasmosis, in which a child becomes infected before birth
2. toxoplasmosis in otherwise healthy kids (with the same symptoms a pregnant woman may have)
3. toxoplasmosis in kids with weakened immune systems

Congenital Toxoplasmosis

When a pregnant woman (even one who has no symptoms) catches toxoplasmosis during pregnancy and remains untreated, there's a chance that she could pass the infection on to her developing fetus. Babies who become infected during their mother's first trimester tend to have the most severe symptoms.

However, it's rare that a woman who got toxoplasmosis before getting pregnant will pass the infection on to her unborn baby because she (and, therefore, her baby) will have built up immunity to the infection. It can occur, though, if a pregnant woman who's had a previous infection becomes immunocompromised and her infection is reactivated. Generally, it's probably a good idea to wait to try to get pregnant until at least 6 months after a toxoplasmosis infection.

Up to 90% of children born with congenital toxoplasmosis have no symptoms early in infancy, but a large percentage will show signs of infection months to years later. The few who show clear signs of infection at birth or shortly after may be born prematurely or are unusually small at birth.

Other signs and symptoms, if there are any, may include:

• fever
• swollen glands (lymph nodes)
• jaundice (yellowed skin and eyes caused by abnormal levels of the liver chemical bilirubin)
• an unusually large or small head
• rash
• bruises or bleeding under the skin
• anemia
• enlarged liver or spleen

Some babies with congenital toxoplasmosis have brain and nervous system abnormalities that cause:

• seizures
• limp muscle tone
• feeding difficulties
• hearing loss
• mental retardation

They're also at high risk for eye damage involving the retina (the light-sensitive lining at the back of the eye responsible for sight), resulting in severe vision problems.

If a child is born with congenital toxoplasmosis and remains untreated during infancy, there's almost always some sign of the infection (often eye damage) by early childhood to adolescence.

Toxoplasmosis in Otherwise Healthy Kids

A healthy child who becomes infected with toxoplasmosis may have no symptoms of infection or only a few swollen glands that:

• usually appear in the neck
• are sometimes tender to the touch
• may become larger and smaller over several months

Most kids won't experience any long-term problems if they go undiagnosed and untreated.

Toxoplasmosis in Kids With Weakened Immune Systems

Kids whose immune systems are weakened (for example, by AIDS, cancer, or medications taken after organ transplants) are at special risk for severe toxoplasmosis infections. Especially in children with AIDS, toxoplasmosis can attack the brain and nervous system, causing toxoplasmic encephalitis (an inflammation of the brain) with symptoms that include:

• fever
• seizures
• headache
• psychosis (a type of severe mental illness)
• problems with vision, speech, movement, or thinking

Duration

Although toxoplasmosis parasites may grow and multiply within a week of entering a person's body, it may be weeks or months before symptoms of infection appear (if they appear at all).

Once someone becomes infected with toxoplasmosis, the infection remains in the body for life, usually in a latent (inactive) form that won't cause side effects or harm. The infection can be reactivated, however, if the immune system becomes compromised by an HIV infection or cancer therapy.

In a child with a healthy immune system, mild symptoms of toxoplasmosis (such as swollen glands) usually pass within a few months, even without medical treatment. But kids born with severe congenital toxoplasmosis may have permanent vision problems or mental retardation. And in a child with a weakened immune system, toxoplasmosis can be fatal.

Diagnosis

Doctors can, but rarely do, diagnose toxoplasmosis through laboratory tests that check for microscopic parasites in the blood, spinal fluid, amniotic fluid, placenta, lymph nodes, bone marrow, or other body tissues.

More frequently doctors order blood tests to measure the level of antibodies (substances that are part of the body's defensive immune reaction) produced to fight the parasites.

Sophisticated new genetic tests can identify the DNA-containing genes of toxoplasmosis parasites once they've invaded the body. These tests are especially useful for checking the amniotic fluid for evidence of congenital toxoplasmosis in a fetus. Obstetricians may use ultrasounds to help diagnose congenital toxoplasmosis. But these tests aren't 100% accurate and can lead to false-positive results.

Treatment

Unless someone has a weakened immune system or is pregnant, there's often no need to treat a toxoplasmosis infection — symptoms (such as swollen glands) usually go away on their own in a few weeks or months. However, kids should always be checked by a doctor because swollen glands can be a sign of other illnesses.

If a pregnant woman develops an infection, a treatment plan will be developed in consultation with her doctor and an infectious disease specialist. Research has shown that treating the mother can help decrease the severity of the disease in the infant but won't necessarily prevent transmission of the infection from mother to child.

Children born with congenital toxoplasmosis are treated with different combinations of anti-toxoplasmosis medications, usually for 1 year after birth. A specialist typically will determine which medications to use and for how long.

In healthy older kids who develop serious toxoplasmosis infections, treatment usually lasts 4 to 6 weeks (or at least 2 weeks after symptoms are gone). Kids with weakened immune systems often need to be hospitalized when they develop toxoplasmosis, and those with AIDS may need to take anti-toxoplasmosis medication for life.

When to Call the Doctor

Call your doctor immediately if your child develops symptoms of toxoplasmosis and:

• is already being treated for AIDS or cancer
• has a condition that affects the immune system
• has been taking medications that weaken the immune system

Also call the doctor if your otherwise healthy child develops any of the symptoms of toxoplasmosis.

If you're pregnant, call your doctor immediately if you notice even one swollen gland, especially if you've been exposed to cats or have eaten raw or undercooked meat.

Prevention

If your cat is kept indoors and never fed raw or undercooked meat, then your family's feline probably has a low risk of catching or spreading toxoplasmosis. Still, you can also catch it from eating raw meats or uncooked produce that's contaminated.

To help prevent toxoplasmosis in your family:

Food Tips

• Cook meats thoroughly.
• Wash your hands with soap and water after handling raw meat or unwashed vegetables.
• Wash all fruits and vegetables before serving. You may also want to peel them.
• Freeze meat for a few days before cooking it, which helps to reduce the likelihood of toxoplasmosis infection, says the CDC.
• Thoroughly wash all cutting boards, utensils, and kitchen surfaces (especially those that come into contact with raw meat) with hot soapy water after each use.
• Cook all meats completely (the juices should be clear and there should be no pink areas).

Cat Tips

• If you're pregnant, have someone else change your cat's litter box daily. And ask that he or she use detergent and hot water to clean it, then wash his or her hands after changing the litter. If you are unable to have someone else change the litter box, wear gloves when you do it and wash hands thoroughly afterward.
• Keep your cat inside at all times to keep your pet from getting toxoplasmosis from the soil and/or small infected animals it tries to catch or eat.
• Keep your child's outdoor sandbox covered, especially overnight, to prevent wandering cats from using it as a litter box.
• Don't feed your cat raw meat.
• Steer clear of stray cats.
• Don't take in a new cat if you're pregnant.

General and Household Tips

• Wear gloves when gardening and wash your hands afterward.
• Use window screens to try to keep your home bug-free (cat feces are a favorite haunt of flies and cockroaches and the bugs can spread the feces, and the toxoplasmosis, onto food).
• Don't drink untreated water, especially if you're traveling in underdeveloped countries.

Reviewed by: Joel Klein, MD
Date reviewed: September 2011