- Toxoplasmosis (toxo) is a disease caused by a protozoan parasite called Toxoplasma gondii.
- Toxoplasma infection is acquired from contact with cats and their feces.
- Toxo is also acquired from eating or touching raw or partly cooked meat.
- Toxoplasmosis symptoms can range from none to very severe.
- A woman who contracts toxo right before or during pregnancy can transmit it to her baby with catastrophic consequences.
- People with immune deficiencies are at high risk for developing severe signs and symptoms of toxoplasma infection.
What is toxoplasmosis?
Toxoplasmosis is an infection caused by a single-celled protozoan parasite called Toxoplasma gondii, which usually affects warm-blooded animals, including humans. The infection is most 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 more than 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 in which tissue cysts (containing bradyzoites) develop. Infection can also occur due to accidental ingestion of these tissue cysts when undercooked or raw meat is eaten.
Swollen Lymph Nodes
- Lymph nodes are an important part of the body's immune system and to help fight infections. Swollen lymph nodes usually caused by infection are referred to as lymphadenitis.
- Lymph is a watery fluid that circulates within the lymphatic vessels. Lymph nodes are found near these vessels.
- Within the capsule, lymph nodes contain certain kinds of immune cells. These cells are mainly lymphocytes, which produce proteins that capture and fight viruses and other microbes, and macrophages, which destroy and remove the captured material.
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 your hands to your 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 they have had contact with raw meat
- Drinking raw goat's milk
- Touching your hands to your mouth after contact with raw or undercooked meat
- Organ transplantation or transfusion (this is rare)
If a woman is pregnant when she is infected with toxo, the infection can be transmitted to the baby with sometimes catastrophic consequences.
What are the usual symptoms of toxoplasmosis?
Although people infected with toxoplasmosis are often unaware of having this disease, typical symptoms of toxo are flulike symptoms, including swollen lymph nodes and muscle aches and pains that last from a few days to several weeks. If your immune system is normal, you 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 a 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 the 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.
Can toxoplasmosis develop into a more serious illness in babies?
Yes, the immune system in infants is not fully mature until after birth. Congenital toxoplasmosis occurs when a fetus is infected.
The babies of women who were exposed to toxo within a few months of becoming pregnant or during pregnancy are at an increased risk for developing a severe case of toxo. Pregnant women who newly contract the toxoplasmosis parasite have a 20% chance of transmitting it to their unborn child, according to the Organization of Teratology Specialists. When the mother is infected in the first trimester, there is a 10%-15% chance of passing the parasite on to her child. In the U.S., it is 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 the infection to their children.
Most newborns have no symptoms, but a small percentage may be born with birth defects such as congenital eye or brain damage. Unfortunately, the signs and symptoms of the disease often appear a few months after birth.
Some signs of congenital toxoplasmosis may be present at birth, such as jaundice, skin rash, and enlarged lymph nodes.
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What is meant by a baby developing "a 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. The infant's head may be abnormally small (microcephaly) or abnormally large due to increased pressure on the brain (hydrocephalus).
What tests do health care providers use to diagnose toxo in the lab?
A toxoplasmosis blood test checks for the presence of Toxoplasma gondii in the blood. The results can determine if the patient has had toxo and whether the infection is recent ("acute") or not.
Is it possible to prevent toxoplasmosis?
Since Toxoplasma gondii infection usually causes mild to no symptoms, and a healthy immune system prevents any remaining parasites in the body from causing further symptoms, most people don't need to worry about getting this disease. Currently, there is no vaccine for toxoplasmosis in humans.
However, if you have a weakened immune system or are pregnant, there are several steps you should take to prevent exposure to toxoplasmosis.
- If you have a weakened immune system, get a blood test for toxoplasmosis. If your test is positive, your doctor can tell you if and when you need to take medicine to prevent the infection from reactivating.
- If you are planning on becoming pregnant, talk to a doctor about being tested for toxo. If the test is positive, there is no need to worry about passing the infection to your baby (since you should have immunity against the parasite).
- If you are already pregnant, you should discuss your risk of toxoplasmosis with your doctor who may order a blood sample for testing.
- Wear gloves when you garden or do anything outdoors that involves handling soil since cats often use gardens and sandboxes as litter boxes. Wash your hands well with soap and warm water after outdoor activities, especially before you eat or prepare food.
- Have someone else handle raw meat for you. If this is 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 the raw meat. Wash your hands well with soap and warm water afterward.
- Cook all meat thoroughly, especially pork or veal.
- Take note of the recommendations listed below regarding cats.
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Am I able to keep my cat?
Yes, but if you have a weakened immune system or are pregnant, there are some steps to take to avoid being exposed to toxo, according to the Cornell College of Veterinary Medicine.
Most importantly, you can help prevent your 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 that is infected with the 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 you also use. Don't bring a new cat into your house that might have been an outdoor cat or might have been fed raw meat. Avoid handling stray cats and kittens. Have your cat tested for the parasite. Your vet can answer any other questions you may have regarding your cat and the risk for toxoplasmosis.
Have someone who is healthy and not pregnant change your cat's litter box. If this is not possible, wear gloves and clean the litter box daily (the parasite found in cat feces needs a few days after being passed to become infectious). Wash your hands well with soap and warm water afterward.
Once infected with toxo, is my cat always able to spread the infection to me?
No, cats can only spread toxo in their feces for a few weeks after they are first infected with the 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 the treatment for toxoplasmosis?
Once the diagnosis of toxoplasmosis is confirmed, you and your doctor should discuss whether treatment is necessary. In an otherwise healthy person who is not pregnant, treatment is not needed. Symptoms will usually go away within a few weeks.
For pregnant women or people who have weakened immune systems, drugs are available to treat the parasite that causes toxoplasmosis. Doctors prescribe drugs in combination, most commonly pyrimethamine plus sulfadiazine or trisulfapyrimidines. Pregnant women may also use spiramycin.
What is the prognosis for toxoplasmosis?
The majority of people who get toxoplasmosis who have a healthy immune response will have no significant long-term effects.
An infected fetus or infant has a variable prognosis, depending on the severity of the effects of the disease. The earlier the fetus is infected, the worse the prognosis. A woman carrying a severely affected fetus may experience a spontaneous abortion (miscarriage), and newborns may develop significant physical or mental problems.
Patients with compromised immune systems have a variable prognosis, depending on their response to treatment. Patients with HIV or long-term immunocompromised states will need to continue treatment for life.
Medically Reviewed on 9/27/2018
Halonen, Sandra K., and Louis W. Weiss. "Toxoplasmosis." July 31, 2018. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4157368/>.
Hökelek, Murat. "Toxoplasmosis Medication." Sept. 19, 2017. <https://emedicine.medscape.com/article/229969-medication?pa=S6O%2BXD6GGJ55wZR41xVvn9BCt3FsIRMs4jFlcQbUCLffQaWYaKTIVc1nU8%2FuEn%2Fb8SIvl8zjYv73GUyW5rsbWA%3D%3D>.
"Toxoplasmosis." Organization of Teratology Infomration Specialists. <http://www.otispregnancy.org/otis-fact-sheets-p135727>.
"Toxoplasmosis in Cats." Cornell University College of Veterinary Medicine. Apr. 8, 2008. <http://www.vet.cornell.edu/fhc/brochures/toxo.html>.