Toxoplasmosis

In addition to spreading through cats' feces, the parasite can be spread in other ways as well.

• Cats most often catch the parasite by eating infected prey (like rodents or birds) with Toxoplasma cysts in their tissues, and this can happen for other prey-eating animals, too.
• People and animals can become infected by consuming foods like these:
  • Raw or undercooked meat (especially pork, goat meat, lamb/mutton, and game meat) from infected animals
  • Unpasteurized milk (including goat's milk) or milk products from infected animals
  • Unwashed fruits and vegetables contaminated with soil containing infective oocysts
  • Raw oysters, clams, and mussels obtained from oocyst-contaminated seawater
• People can become infected through gardening and other activities involving direct contact with soil or water contaminated with cat feces and infective oocysts.
• Children may become infected by playing in sandboxes, which cats may use as litter boxes.
• People and animals that become infected for the first time during pregnancy can transmit the parasite to their unborn babies through the placenta.
• People who handle cat litter may accidentally swallow oocysts if their cat has recently been infected.
• Rarely, people may catch the parasite through blood transfusions or organ transplants.

About 15% to 40% of domestic cats in the U.S. have antibodies against T. gondii, meaning they became infected with the parasite at some point in their lives. For cats allowed outdoors, the most likely source of infection is prey animals containing tissue cysts. For indoor-only cats, it's raw or undercooked meat containing these cysts.

Signs of Toxoplasma infection depend on a variety of factors such as the cat's age, immune status, and stage of infection. Most infected adult cats appear healthy. However, kittens and some cats may develop disease, with signs like the following:

• Fever
• Lethargy
• Loss of appetite
• Diarrhea or vomiting
• Coughing or difficulty breathing/pneumonia
• Personality changes
• Neurological problems, like seizures, incoordination, or tremors
• Eye problems

For developing feline fetuses and newborn cats infected through their mothers, outcomes are typically severe, with effects like these:

• Abortion or stillbirth
• Severe neurological defects, including brain damage
• Eye damage, including impaired vision
• Poor growth and developmental delays

The U.S. Centers for Disease Control and Prevention (CDC) estimates that over 40 million people in the U.S. are infected with T. gondii. This infection may last for a lifetime.

While most people don't even know they're infected due to a lack of symptoms, some pregnant women and many immunocompromised people are at risk of severe complications. Women infected prior to pregnancy usually will have immune protection (antibodies) against the parasite, and are not considered at risk of illness themselves, or of passing the infection to their unborn child. The situation is different for women infected for the first time while pregnant. In those cases, infection can cause complications that mostly affect the developing fetus: such as miscarriage, stillbirth, or birth defects similar to those described for feline fetuses and newborn kittens. These complications tend to be more severe if the mother is infected during the first trimester, rather than later on. Although most infected infants show no symptoms at birth, many are likely to have symptoms later in life.

Immunocompromised people, such as those with HIV or receiving certain chemotherapy, may experience severe disease, regardless of when they were first infected. Symptoms can include fever, confusion, headache, seizures, nausea, and poor coordination.

The good news is that it's certainly possible for these higher risk groups to have cats and enjoy the many benefits they bring, without needing to give them up. In fact, simply handling cats is unlikely to cause an infection. If you're pregnant or immunocompromised, be sure to discuss any concerns with your healthcare provider and veterinarian and to follow tips for preventing infection.

No vaccine is available to protect against T. gondii, but some simple precautions can reduce the risk of exposure to the parasite and subsequent infection. Keep in mind that you're more likely to be infected with T. gondii from undercooked meat or the environment than you are from your cat.

General precautions

• Wear gloves when gardening or touching soil or sand that may be contaminated with cat feces.
• Wash your hands with soap and water immediately after working with soil or after handling raw or undercooked meat, vegetables, or unpasteurized dairy products.
• Avoid consuming or feeding pets unpasteurized milk or other unpasteurized dairy products.
• Wash fruits and vegetables thoroughly under running water before eating, especially those grown in backyard gardens.
• Cook meat to temperatures capable of destroying Toxoplasma and other infectious organisms. For details, see this CDC resource.
• Thoroughly wash with hot, soapy water cutting boards, knives, sinks, and countertops immediately after cutting meats.
• Cover any outdoor sandboxes when not in use to prevent cats from using them as litter boxes.

Additional precautions for cat owners

• Keep your cat indoors to prevent them from hunting rodents and birds.
• Avoid feeding your cat raw foods.
• Remove waste from the cat litter box daily, before any Toxoplasma oocysts in the feces have a chance to become infective. Ideally, the litter itself would be replaced daily, especially if it's the non-clumping kind. However, this frequency may not always be feasible or necessary, particularly if the cat is unlikely to become newly infected, as when kept indoors and fed canned, dry, or well-cooked food. Remember: previously infected cats usually pose little risk to others.
• Wash your hands after scooping out waste from the litter box, and dispose of used cat litter safely, preferably in a sealed plastic bag.
• If your cat has long hair on their rear end that tends to collect fecal material, carefully trim the area or have your cat professionally groomed to keep the area clean. Similarly, if your cat is too overweight, ill, or arthritic to adequately groom themself, you may need to groom the cat (wash your hands afterward) or have them professionally groomed.

Additional precautions for pregnant or immunocompromised people

• If possible, avoid handling stray cats or adopting new cats during your pregnancy or illness. If a new cat joins your family during this time, have it thoroughly examined by a veterinarian immediately to ensure it is healthy and to answer any questions you may have.
• If you own a cat, ask another person to clean the litter box, if possible. If not possible, change the litter daily (to avoid contact with oocysts after they have had sufficient time to become infectious), use rubber gloves when doing so, and wash your hands thoroughly afterwards.