Cats get toxoplasmosis primarily by eating infected prey, most commonly rodents, birds, and other small animals that carry the parasite Toxoplasma gondii in their tissue. Cats are the only animals in which this parasite can complete its full reproductive cycle, which is why they play a central role in its spread. But the ways a cat encounters the parasite are more varied than most people realize.
Hunting Infected Prey
The most common route of infection is straightforward: a cat catches and eats a mouse, bird, or other small animal whose muscles or organs contain dormant parasite cysts. These tissue cysts are microscopic and impossible to detect by looking at the prey. Once swallowed, the cysts break open in the cat’s digestive tract, releasing the parasite into the intestinal lining where it begins reproducing.
This is why outdoor cats and feral cats face the highest risk. Any cat that hunts, even occasionally, has a meaningful chance of encountering an infected animal. Seroprevalence studies show wide variation depending on geography and lifestyle. A large study in Brazil found that roughly 27% of domestic cats tested positive for antibodies against the parasite, though prevalence across Brazilian regions has ranged from 4% to nearly 83% depending on the population studied. Cats in rural environments with abundant prey tend to show higher infection rates than urban indoor cats.
Raw Meat in the Diet
Cats don’t need to hunt live prey to be exposed. Raw or undercooked meat from any warm-blooded animal, including beef, pork, lamb, and poultry, can contain tissue cysts. If you feed your cat a raw meat diet, whether homemade or commercial, this is a real concern. Research from Tufts University found that raw cat foods contained DNA from parasites, and that all forms of raw pet food carry the risk of parasitic contamination. Cooking meat to safe temperatures kills the cysts, which is why standard commercial cat food (kibble and canned) poses no risk.
Oocysts in the Environment
Cats can also pick up the parasite without eating prey at all. When an infected cat sheds parasite eggs (called oocysts) in its feces, those oocysts become infectious within one to five days and can survive in soil, water, and vegetation for months to years. A cat that walks through contaminated soil, drinks from a puddle, or grooms dirt off its paws can ingest these oocysts and become infected.
This pathway is especially relevant in areas where stray or feral cat populations are dense, since contaminated soil accumulates over time. Even indoor cats can theoretically be exposed if contaminated soil is tracked into the home on shoes or gardening tools, though this risk is low compared to direct hunting.
What Happens Inside the Cat
Once a cat swallows infected tissue or oocysts, the parasite invades the cells lining the small intestine. This is the only place in nature where Toxoplasma gondii undergoes sexual reproduction, producing new oocysts that the cat then passes in its feces. A newly infected cat typically begins shedding oocysts three to ten days after eating contaminated tissue and continues shedding for about 10 to 14 days. During that window, the cat can excrete millions of oocysts.
Here’s the reassuring part: this massive shedding event generally happens only once in a cat’s lifetime. After the initial infection, the cat’s immune system builds a strong enough response that re-exposure rarely triggers another round of shedding. Even cats whose immune systems are later weakened are unlikely to shed oocysts again. So while the initial shedding period is significant, it’s a brief chapter in the cat’s life.
Which Cats Are Most at Risk
The cats most likely to become infected are those with the greatest opportunity to encounter the parasite:
- Outdoor cats that hunt face the highest risk, since rodents and birds are the primary carriers of tissue cysts.
- Cats fed raw meat diets have ongoing exposure through uncooked animal tissue.
- Feral and stray cats living in colonies where soil contamination is heavy may pick up oocysts from their environment.
- Kittens and young cats encountering the parasite for the first time are the ones that will shed oocysts, since most older cats have already been exposed and developed immunity.
Strictly indoor cats that eat only commercial cooked food have the lowest risk. They would need to encounter the parasite through an unusual route, like a mouse that got inside the house or contaminated material brought in from outdoors.
Signs of Infection in Cats
Most cats that contract toxoplasmosis show no symptoms at all. The parasite typically establishes a quiet, chronic infection that the immune system keeps in check indefinitely. When symptoms do appear, they’re most common in kittens or cats with weakened immune systems. Signs can include lethargy, loss of appetite, fever, and occasionally eye inflammation or breathing difficulties. Many cat owners never know their cat was infected unless a blood test reveals antibodies.
Because the shedding window is short and most cats appear perfectly healthy during it, the infection often goes entirely unnoticed. By the time a cat tests positive for antibodies, it has almost certainly already finished its one-time shedding phase and is no longer releasing oocysts into the environment.