A single-celled parasite called Toxoplasma gondii causes a disease known as toxoplasmosis. While the parasite is found throughout the world, more than 60 million people in the United States may be infected with the Toxoplasma parasite. Of those who are infected, very few have symptoms because a healthy person’s immune system usually keeps the parasite from causing illness. However, pregnant women and individuals who have compromised immune systems should be cautious; for them, a Toxoplasma infection could cause serious health problems.
How Toxoplasma infection occurs
• Eating undercooked, contaminated meat (especially pork, lamb, and venison).
• Accidental ingestion of undercooked, contaminated meat after handling it and not washing hands thoroughly (Toxoplasma cannot be absorbed through intact skin).
• Eating food that was contaminated by knives, utensils, cutting boards and other foods that have had contact with raw, contaminated meat.
• Drinking water contaminated with Toxoplasma gondii.
• Accidentally swallowing the parasite through contact with cat feces that contain Toxoplasma. This might happen by
1. cleaning a cat’s litter box when the cat has shed Toxoplasma in its feces
2. touching or ingesting anything that has come into contact with cat feces that contain Toxoplasma
3. accidentally ingesting contaminated soil (e.g., not washing hands after gardening or eating unwashed fruits or vegetables from a garden)
• Mother-to-child (congenital) transmission.
Symptoms of toxoplasmosis
• Most people who become infected with Toxoplasma gondii are not aware of it.
• Some people who have toxoplasmosis may feel as if they have the “flu” with swollen lymph glands or muscle aches and pains that last for a month or more.
• Severe toxoplasmosis, causing damage to the brain, eyes, or other organs, can develop from an acute Toxoplasma infection or one that had occurred earlier in life and is now reactivated. Severe cases are more likely in individuals who have weak immune systems, though occasionally, even persons with healthy immune systems may experience eye damage from toxoplasmosis.
• Signs and symptoms of ocular toxoplasmosis can include reduced vision, blurred vision, pain (often with bright light), redness of the eye, and sometimes tearing. Ophthalmologists sometimes prescribe medicine to treat active disease. Whether or not medication is recommended depends on the size of the eye lesion, the location, and the characteristics of the lesion (acute active, versus chronic not progressing). An ophthalmologist will provide the best care for ocular toxoplasmosis.
• Most infants who are infected while still in the womb have no symptoms at birth, but they may develop symptoms later in life. A small percentage of infected newborns have serious eye or brain damage at birth.
High risk for severe toxoplasmosis
• Infants born to mothers who are newly infected with Toxoplasma gondii during or just before pregnancy.
• Persons with severely weakened immune systems, such as individuals with AIDS, those taking certain types of chemotherapy, and those who have recently received an organ transplant.
What should I do if I think I am at risk for severe toxoplasmosis?
If you are planning to become pregnant, your health care provider may test you for Toxoplasma gondii. If the test is positive it means you have already been infected sometime in your life. There usually is little need to worry about passing the infection to your baby. If the test is negative, take necessary precautions to avoid infection (See below).
If you are already pregnant, you and your health care provider should discuss your risk for toxoplasmosis. Your health care provider may order a blood sample for testing.
If you have a weakened immune system, ask your doctor about having your blood tested for Toxoplasma. 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 your test is negative, it means you need to take precautions to avoid infection. (See below).
What should I do if I think I may have toxoplasmosis?
If you suspect that you may have toxoplasmosis, talk to your health care provider. Your provider may order one or more varieties of blood tests specific for toxoplasmosis. The results from the different tests can help your provider determine if you have a Toxoplasma gondii infection and whether it is a recent (acute) infection.
What is the treatment for toxoplasmosis?
In an otherwise healthy person who is not pregnant, treatment usually is not needed. If symptoms occur, they typically go away within a few weeks to months. For pregnant women or persons who have weakened immune systems, medications are available to treat toxoplasmosis.
How can I prevent toxoplasmosis?
There are several general sanitation and food safety steps you can take to reduce your chances of becoming infected with Toxoplasma gondii.
• Cook food to safe temperatures. A food thermometer should be used to measure the internal temperature of cooked meat. Do not sample meat until it is cooked. USDA recommends the following for meat preparation.
o For Whole Cuts of Meat (excluding poultry)
• Cook to at least 145° F (63° C) as measured with a food thermometer placed in the thickest part of the meat, then allow the meat to rest* for three minutes before carving or consuming.
o For Ground Meat (excluding poultry)
• Cook to at least 160° F (71° C); ground meats do not require a rest* time.
o For All Poultry (whole cuts and ground)
• Cook to at least 165° F (74° C), and for whole poultry allow the meat to rest* for three minutes before carving or consuming.
*According to USDA, “A ‘rest time’ is the amount of time the product remains at the final temperature, after it has been removed from a grill, oven, or other heat source. During the three minutes after meat is removed from the heat source, its temperature remains constant or continues to rise, which destroys pathogens.”
• Freeze meat for several days at sub-zero (0° F) temperatures before cooking to greatly reduce chance of infection.
• Peel or wash fruits and vegetables thoroughly before eating.
• Do not eat raw or undercooked oysters, mussels, or clams (these may be contaminated with Toxoplasma that has washed into sea water).
• Do not drink unpasteurized goat’s milk.
• Wash cutting boards, dishes, counters, utensils, and hands with hot soapy water after contact with raw meat, poultry, seafood, or unwashed fruits or vegetables.
• Wear gloves when gardening and during any contact with soil or sand because it might be contaminated with cat feces that contain Toxoplasma. Wash hands with soap and warm water after gardening or contact with soil or sand.
• Teach children the importance of washing hands to prevent infection.