Cats are most commonly infected with T. gondii when they prey on infected mice, birds and other small animals. For indoor-only cats, the most likely source of infection is uncooked meat scraps or raw meat. When initially infected with T. gondii, a cat can shed millions of oocysts in its stool each day for several days. After the initial shedding period, most cats will not continue to pass oocysts in their feces.
Most infected adult cats appear healthy, with no visible signs of illness. However, some cats may develop pneumonia, liver damage and other health problems. Signs of illness in cats include lethargy, loss of appetite, coughing, difficulty breathing, diarrhea, jaundice, blindness, personality changes, eye problems and other neurologic problems. There is currently no vaccine available for T. gondii, but treatment can be effective if the disease is diagnosed early. A blood test for T. gondii antibodies can help in the diagnosis of toxoplasmosis in sick cats.
Although infection with the parasite is relatively common in people, actual disease is rare. People can be infected with Toxoplasma gondii by handling or consuming undercooked or raw meat (particularly pork); consuming raw, unpasteurized milk (including goat’s milk) and milk products; handling or consuming unwashed fruit or vegetables that may have been contaminated with soil containing infective oocysts; the consumption of raw oysters, clams or mussels; the ingestion of infectious oocysts from the environment; and transmission directly to an unborn child from the mother when she becomes infected with T. gondii during pregnancy. Pregnant women and immunocompromised people are at higher risk for toxoplasmosis.
It has been suggested that handling cats poses a risk of infection, but this activity is unlikely to pose a risk of T. gondii infection for humans. Since most healthy cats groom themselves frequently, and it takes a minimum of 24 hours before the oocysts in the feces are infectious, it is unlikely that feces would remain on their fur long enough for any oocysts to become infectious.
Common sense measures can prevent the spread of T. gondii:
If you’re a cat owner, remember:
The content on this page is a condensed version of our brochure, Toxoplasmosis, available in English and Spanish.