You get toxoplasmosis by swallowing the parasite Toxoplasma gondii, most commonly through undercooked meat, contact with contaminated cat feces, or contaminated soil and water. About 11% of the U.S. population aged six and older has been infected at some point, though most people never realize it because the infection rarely causes symptoms in healthy adults.
Undercooked Meat: The Most Common Route
Eating undercooked or raw meat is one of the primary ways people pick up the parasite. Pork, lamb, and venison carry the highest risk, but shellfish like oysters, clams, and mussels can also be contaminated. The parasite forms tiny cysts inside animal muscle tissue that are invisible to the naked eye. When you eat that meat without cooking it thoroughly, those cysts survive and release the parasite into your digestive system.
Cross-contamination in the kitchen matters too. If you handle raw meat and then touch other food, utensils, or your mouth without washing your hands, you can transfer the parasite. Cutting boards and knives used on raw meat can contaminate vegetables or other ready-to-eat foods. The parasite can’t penetrate intact skin, so simply touching contaminated meat won’t infect you. The issue is hand-to-mouth transfer.
To kill the parasite, cook whole cuts of meat (excluding poultry) to at least 145°F (63°C), measured with a food thermometer in the thickest part, and let the meat rest for three minutes before cutting or eating. Ground meat needs to reach 160°F (71°C) and doesn’t require a rest period. That rest time matters because the internal temperature continues rising after you remove the meat from heat, finishing off any surviving parasites.
Cat Feces and the Litter Box
Cats are the only animals that shed the infectious form of the parasite in their feces. When a cat becomes infected for the first time (usually by hunting and eating rodents or birds), it sheds massive numbers of parasite eggs, called oocysts, in its stool for one to three weeks. Those oocysts aren’t immediately dangerous. They need one to five days in the environment to mature into their infectious form.
This timing detail is important: if you scoop a litter box daily, you significantly reduce your risk because the oocysts haven’t had time to become infectious yet. The danger increases when litter sits unchanged for several days, giving the parasites time to mature. Infection happens when you accidentally ingest the parasite after cleaning the litter box and not washing your hands thoroughly, or when contaminated material touches food or surfaces.
Indoor cats that eat only commercial cat food have a much lower chance of carrying the parasite than outdoor cats that hunt prey. And once a cat has been infected, it typically only sheds oocysts during that initial one-to-three-week window, not for the rest of its life.
Soil, Water, and Garden Produce
Outdoor cats bury their feces in soil, and the oocysts they leave behind are remarkably durable. In soil, the parasite can remain infectious for at least 18 months under various temperature conditions. In water, oocysts can survive for over four years at refrigerator-like temperatures. Standard household disinfectants, including bleach solutions, do very little to neutralize them. Even a 6% sodium hypochlorite solution (much stronger than typical household bleach) needs hours of direct contact to significantly reduce the parasite’s viability.
This environmental toughness is why gardening is a real transmission route. Working in soil where cats have defecated and then touching your face or eating without washing your hands can lead to infection. Fruits and vegetables grown in contaminated soil can carry oocysts on their surface. Washing produce thoroughly before eating is a simple but effective precaution. Wearing gloves while gardening and washing your hands afterward reduces risk further.
Contaminated water sources can also spread the parasite, particularly untreated or poorly filtered water supplies.
Unpasteurized Dairy Products
Raw goat’s milk is an established but often overlooked transmission route. Infected goats can excrete live parasites directly into their milk, and the organism survives the cheese-making process when cold-enzyme methods are used. Pasteurization or boiling the milk kills the parasite effectively. This risk applies mainly to people who drink raw goat’s milk or eat fresh, unpasteurized goat cheese, particularly from small farms or homesteads.
Mother-to-Child Transmission
A woman who becomes newly infected with Toxoplasma during pregnancy, or just before becoming pregnant, can pass the parasite to her unborn child. About half of untreated maternal infections are transmitted to the fetus. The timing of infection during pregnancy shapes the outcome in a counterintuitive way: infections earlier in pregnancy are less likely to reach the fetus, but when they do, the damage tends to be more severe. Infections later in pregnancy cross to the baby more easily, but typically cause milder problems.
A woman who was already infected well before pregnancy generally poses no risk to her baby, because her immune system has already contained the parasite. The concern is specifically about first-time infections during or shortly before pregnancy.
What Happens Inside Your Body
Once you swallow the parasite, it enters your gut and begins multiplying rapidly. During this initial phase, the fast-replicating form of the parasite spreads through your bloodstream to tissues throughout your body, including muscle, brain, and eyes. Within about 10 to 14 days, your immune system forces the parasite to shift into a slow-growing, dormant form that encases itself in tiny cysts within your tissues.
These cysts can persist for life, quietly kept in check by your immune system. For most healthy people, that’s the end of the story. You’ll never know the cysts are there. But if your immune system becomes severely weakened, whether from HIV/AIDS, certain cancers, or immunosuppressive medications after an organ transplant, those dormant cysts can reactivate. The parasite shifts back to its fast-multiplying form, potentially causing serious illness including brain inflammation.
How Infection Is Detected
Most people with toxoplasmosis have no symptoms at all, or they experience mild flu-like symptoms (swollen lymph nodes, muscle aches, fatigue) that resolve on their own. Because of this, infection is usually identified through a blood test that looks for antibodies your immune system produces in response to the parasite.
Two types of antibodies help distinguish between a new and old infection. One type appears early and fades over months, indicating a recent infection. The other type persists for life and simply tells you that you were infected at some point. This distinction is especially important during pregnancy, since only a new infection poses a risk to the fetus. For people with weakened immune systems, interpreting test results is more complex and needs to be considered alongside actual symptoms.
Practical Steps to Avoid Infection
- Cook meat thoroughly. Use a food thermometer: 145°F for whole cuts with a three-minute rest, 160°F for ground meat.
- Wash hands after handling raw meat. Clean cutting boards, knives, and countertops that touched raw meat before using them for other food.
- Scoop the litter box daily. Oocysts need one to five days to become infectious, so daily cleaning dramatically cuts your risk.
- Wear gloves while gardening. Wash your hands thoroughly afterward, especially before eating.
- Wash fruits and vegetables. Rinse all produce under running water before eating, particularly anything grown in garden soil.
- Avoid unpasteurized goat’s milk and fresh goat cheese unless the milk has been boiled or properly pasteurized.
- Keep cats indoors to reduce their chance of becoming infected through hunting.
If you’re pregnant or planning to become pregnant, these precautions are especially important. Having someone else handle litter box duties during pregnancy is a straightforward way to eliminate one of the main exposure risks.