Toxoplasmosis (Toxo)

Toxoplasmosis is an infection caused by a single-celled protozoan parasite called Toxoplasma gondii, which affects warm-blooded animals, including humans. The infection is commonly acquired from contact with cats and their feces or with raw or undercooked meat.

The U.S. Centers for Disease Control and Prevention (CDC) estimates that over 60 million people in the United States may carry the Toxoplasma gondii parasite, and it infects up to one-third of the world’s population, but very few have symptoms because a healthy immune system usually keeps the parasite from causing illness.

What is the cause of toxoplasmosis?

There are only a few ways to acquire the Toxoplasma gondii parasite:

• Contact with cats or cat feces
• Eating raw or undercooked meat
• Drinking raw milk from an infected goat (Goats can be an intermediate host for the parasite.)
• Organ transplantation or blood transfusion from an infected person

Cats are the most common host for Toxoplasma gondii. Oocysts, one of the life cycle stages of T. gondii, are shed in cat feces, which can transmit the infection when ingested orally. Warm-blooded animals, including humans, pigs, cows, goats, and deer, can serve as an intermediate host where tissue cysts (containing bradyzoites) develop. Infection can also occur due to accidental ingestion of these tissue cysts when undercooked or raw meat is eaten.

What are risk factors for acquiring toxo?

The following risk factors and situations potentially expose a person to the Toxoplasma gondii parasite and increase the risk of acquiring toxoplasmosis infection:

• Touching hands to mouth after gardening, cleaning a cat’s litter box, or anything that came into contact with cat feces
• Eating raw or partly cooked meat, especially pork, lamb, or venison
• Using utensils or cutting boards that have not been properly cleaned after contact with raw meat
• Drinking raw goat’s milk
• Touching hands to mouth after contact with raw or undercooked meat
• Organ transplantation or transfusion (rare)

If a woman is pregnant when infected with toxo, the infection can be transmitted to the baby with sometimes catastrophic consequences.

What are the usual signs and symptoms of toxoplasmosis?

Although people infected with toxoplasmosis are often unaware of having this disease, typical symptoms are flulike symptoms, including swollen lymph nodes and muscle aches and pains that last from a few days to several weeks. If immune system is normal, cannot get the infection again.

Why do some people develop severe problems from toxo?

Few people with toxoplasmosis infection develop symptoms because the immune system usually keeps the parasite from causing illness. However, anyone with compromised immune system is at risk for serious and even life-threatening problems from toxo. Immunocompromised individuals include those undergoing chemotherapy, people with HIV/AIDS or other immune disorders, and recent organ-transplant recipients.

In these people, an infection that occurred anytime during life can reactivate and cause severe symptoms of toxoplasmosis such as damage to the eye, brain, or other organs.

Ocular toxoplasmosis, which damages the eyes, can lead to reduced vision, blurred vision, pain (often with bright light), redness of the eye, and sometimes tearing, according to the CDC.

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Can toxoplasmosis develop into more serious illness in babies?

Yes, immune system in infants is not fully mature until after birth. Congenital toxoplasmosis occurs when a fetus is infected.

Babies of women who were exposed to toxo within a few months of becoming pregnant or during pregnancy are at increased risk for developing severe case of toxo. Pregnant women who newly contract toxoplasmosis parasite have 20% chance of transmitting it to their unborn child, according to Organization of Teratology Specialists. When mother is infected in first trimester, there is 10%-15% chance of passing parasite on to her child. In U.S., estimated that up to 4,000 babies are born with congenital toxoplasmosis annually. Women who were first exposed to toxo more than six months before becoming pregnant are not likely to pass infection to their children.

Most newborns have no symptoms, but small percentage may be born with birth defects such as congenital eye or brain damage. Unfortunately, signs and symptoms of disease often appear few months after birth.

Some signs of congenital toxoplasmosis may be present at birth, such as jaundice, skin rash, and enlarged lymph nodes.

What is meant by baby developing "more severe case of toxo"?

Children born with toxoplasmosis can be afflicted with birth defects, including intellectual disabilities, convulsions, spasticity, cerebral palsy, deafness, and severely impaired vision. Infant’s head may be abnormally small (microcephaly) or abnormally large due to increased pressure on brain (hydrocephalus).

What tests do health care providers use to diagnose toxo in lab?

Toxoplasmosis blood test checks for presence of Toxoplasma gondii in blood. Results can determine if patient has had toxo and whether infection is recent ("acute") or not.

Is it possible to prevent toxoplasmosis?

Since Toxoplasma gondii infection usually causes mild to no symptoms, and healthy immune system prevents any remaining parasites in body from causing further symptoms, most people don’t need to worry about getting disease. Currently, no vaccine for toxoplasmosis in humans.

However, if have weakened immune system or are pregnant, there are several steps should take to prevent exposure to toxoplasmosis.

• If have weakened immune system, get blood test for toxoplasmosis. If test is positive, doctor can tell if and when need to take medicine to prevent infection from reactivating.
• If planning on becoming pregnant, talk to doctor about being tested for toxo. If test is positive, no need to worry about passing infection to baby (since should have immunity against parasite).
• If already pregnant, discuss risk of toxoplasmosis with doctor who may order blood sample for testing.
• Wear gloves when garden or do anything outdoors that involves handling soil since cats often use gardens and sandboxes as litter boxes. Wash hands well with soap and warm water after outdoor activities, especially before eat or prepare food.
• Have someone else handle raw meat for you. If not possible, wear clean latex or nitrile gloves and thoroughly wash with soap and hot water any cutting boards, sinks, knives, and other utensils that might have touched raw meat. Wash hands well with soap and warm water afterward.
• Cook all meat thoroughly, especially pork or veal.
• Take note of recommendations listed below regarding cats.

Am I able to keep my cat?

Yes, but if have weakened immune system or are pregnant, there are some steps to take to avoid being exposed to toxo, according to Cornell College of Veterinary Medicine.

Most importantly, can help prevent cats from getting infected with toxo. Feed them dry or canned cat food and keep them indoors. Cats can become infected by eating or being fed raw or undercooked meat infected with parasite, or by eating infected prey such as birds or rodents. Any cat that is allowed access to outdoors should be kept off beds, pillows, or other furniture that also use. Don’t bring new cat into house that might have been outdoor cat or might have been fed raw meat. Avoid handling stray cats and kittens. Have cat tested for parasite. Vet can answer any other questions may have regarding cat and risk for toxoplasmosis.

Have someone who is healthy and not pregnant change cat’s litter box. If not possible, wear gloves and clean litter box daily (parasite found in cat feces needs few days after being passed to become infectious). Wash hands well with soap and warm water afterward.

Once infected with toxo, is my cat always able to spread infection to me?

No, cats can only spread toxo in their feces for few weeks after they are first infected with parasite. Like humans, cats rarely have symptoms when first infected, so most people don’t know if their cat has been exposed to toxo. Most infected cats appear healthy. There are no good tests available to determine if your cat is passing toxo in its feces.

What is treatment for toxoplasmosis?

Once diagnosis of toxoplasmosis is confirmed, and doctor should discuss whether treatment is necessary. In otherwise healthy person who is not pregnant, treatment is not needed. Symptoms will usually go away within few weeks.

For pregnant women or people who have weakened immune systems, drugs are available to treat parasite that causes toxoplasmosis. Doctors prescribe drugs in combination, most commonly pyrimethamine plus sulfadiazine or trisulfapyrimidines. Pregnant women may also use spiramycin.

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What is prognosis for toxoplasmosis?

Majority of people who get toxoplasmosis who have healthy immune response will have no significant long-term effects.

An infected fetus or infant has variable prognosis, depending on severity of effects of disease. Earlier fetus is infected, worse prognosis. Woman carrying severely affected fetus may experience spontaneous abortion (miscarriage), and newborns may develop significant physical or mental problems.

Patients with compromised immune systems have variable prognosis, depending on their response to treatment. Patients with HIV or long-term immunocompromised states will need to continue treatment for life.

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"Toxoplasmosis." Organization of Teratology Information Specialists. .

"Toxoplasmosis in Cats." Cornell University College of Veterinary Medicine. Apr. 8, 2008. .

"Toxoplasmosis in Cats." Cornell University College of Veterinary Medicine. Apr. 8, 2008. .