Cat Toxoplasmosis: Infection, Welfare, and Zoonotic Risk

Toxoplasma gondii is a parasite for which cats are the definitive host. Understanding toxoplasmosis in cats is important for both feline welfare and human health.

Key Facts

Cats become infected with Toxoplasma gondii by eating infected prey (rodents, birds) or raw meat containing tissue cysts.
Cats are the only definitive host — meaning the sexual reproductive cycle of the parasite occurs exclusively in cats.
Most infected cats show no clinical signs, but severe toxoplasmosis can cause fever, respiratory distress, liver disease, and neurological signs.
Cats shed oocysts in their feces for only 1-3 weeks after primary infection; previously exposed cats rarely shed again.
Toxoplasmosis is a significant zoonosis — particularly dangerous to immunocompromised people and pregnant women.
Keeping cats indoors and not feeding raw meat greatly reduces the risk of infection.
Diagnosis in symptomatic cats involves serology, PCR, and sometimes tissue biopsy; treatment uses clindamycin or sulfonamide antibiotics.

Welfare Considerations

Most cats infected with Toxoplasma remain asymptomatic and suffer no apparent ill effects. However, cats that develop clinical toxoplasmosis can experience severe and life-threatening illness including pneumonia, hepatitis, and encephalitis. Immunosuppressed cats — such as those with FIV or FeLV — are at highest risk of serious disease. The welfare implications extend beyond the infected cat: misplaced fear about toxoplasmosis has historically driven cat abandonment and even culling in some communities, causing immense suffering to cats that pose little actual risk when managed responsibly. Education is critical — the risk to humans from cats is real but manageable, and does not justify harming cats.

What You Can Do

Keep cats indoors or supervised outdoors to prevent hunting and reduce infection risk.
Do not feed cats raw or undercooked meat, which can contain Toxoplasma tissue cysts.
Clean litter boxes daily, as oocysts take 1-5 days after shedding to become infective.
Pregnant women and immunocompromised individuals should have someone else clean the litter box, or wear gloves and wash hands thoroughly.
If your cat shows signs of illness such as fever, breathing difficulty, or neurological symptoms, seek veterinary care promptly.
Do not abandon cats due to toxoplasmosis fears — responsible management eliminates most human risk.