Toxoplasmosis in Cats: Risks for Cats and People

How cats become infected

Cats usually catch the parasite by eating infected prey, such as mice and birds, or raw meat. The parasite lives in tiny cysts inside the muscles and organs of those animals. Once a cat swallows them, the parasite multiplies in the lining of the gut. Kittens can also be infected before birth or while nursing if their mother is infected during pregnancy.

After a first infection, a cat passes microscopic egg-like forms, called oocysts, in its stool. Shedding usually begins 3 to 10 days after the cat eats infected prey or meat and lasts about one to two weeks. Most cats do this only once in their life. The cat then builds immunity, and repeat shedding is rare. It has mainly been seen in cats with a weak immune system.

Fresh oocysts cannot infect anyone. They need at least a day, and usually one to five days, in air and moisture before they become infectious. Once mature, they can survive in soil and water for many months. That is how gardens, sandboxes and unwashed vegetables become a source.

Infection is common. European surveys have found antibodies in anywhere from about one in eight to more than two in three cats, depending on the country and the cat's lifestyle. Studies in Greece found them in about one in five pet and stray cats. Adult cats, cats that go outdoors, cats fed meat or kitchen scraps, and cats from rural areas test positive more often. At any one time, though, only a very small share of cats are shedding oocysts, often less than 1 in 100 in European surveys.

Signs to watch for

Most infected cats never look sick. Illness is more likely in young kittens infected before or soon after birth, and in cats with a weak immune system. That includes cats with FIV or FeLV and cats taking medicines that suppress the immune system.

When the parasite does cause disease, it can affect almost any organ. The lungs, eyes, liver, brain and muscles are common targets. Signs can include the following.

• Fever, tiredness and loss of appetite
• Fast or labored breathing, or a cough
• Red, cloudy or squinting eyes
• Yellow gums, skin or whites of the eyes (jaundice)
• Wobbly walking, poor coordination or seizures
• Muscle pain, stiffness or limping
• Weight loss or diarrhea

None of these signs is specific to toxoplasmosis. Many other illnesses look the same, so tests are needed to find the cause.

When it is an emergency

Lung disease caused by toxoplasmosis can get worse quickly and can be fatal. Contact a vet right away if your cat breathes with an open mouth or struggles to breathe, has a seizure, collapses, or has yellow gums. Very young kittens that stop eating or grow weak also need urgent care, because they can decline fast.

Sudden changes in one or both eyes deserve a prompt visit too. Eye inflammation that goes untreated can lead to painful problems such as glaucoma.

How vets diagnose and treat it

There is no single quick test. Vets usually start with a physical exam and routine blood work, then check the blood for antibodies against Toxoplasma. One type of antibody points to a recent infection, and another shows past exposure. A high level, or one that rises between two tests taken a few weeks apart, supports active disease.

In some cases the vet looks for the parasite itself in fluid or tissue samples, for example from the airways or the eye, using a microscope or a DNA test called PCR. A stool test rarely finds oocysts, because each cat sheds them for only a short time. Your vet may also test for FIV and FeLV, since these infections make illness more likely.

Treatment is usually a course of an antibiotic that works against the parasite, often given for about four weeks. Cats with eye inflammation may also need anti-inflammatory eye drops to protect the eye. Very sick cats may need a hospital stay for fluids, nutrition support or seizure control. Your vet will choose the medicines and doses and check progress along the way.

Signs such as fever and muscle pain often start to ease within a few days of treatment. Eye and nervous system signs tend to respond more slowly. The outlook is often poor when the lungs or liver are badly affected, especially in cats with a weak immune system.

Risk to people and other pets

Toxoplasmosis can pass from animals to people. Most healthy adults who catch it have no symptoms at all, or a mild illness with flu-like aches and swollen glands. Two groups need more care. A person infected for the first time during pregnancy, or just before it, can pass the parasite to the unborn baby. Babies infected this way may look healthy at birth and still develop problems later, such as vision loss. People with a weakened immune system, for example from HIV, some types of chemotherapy or an organ transplant, can become seriously ill, often with the brain and eyes affected.

Cats are rarely the direct source. A large European study of pregnant women found that contact with cats was not a risk factor. Undercooked meat and contact with soil were the main sources. Touching a cat is very unlikely to pass on the parasite, because it does not usually stay on the fur. Bites and scratches are also an unlikely route. A cat that already has antibodies is very unlikely to shed oocysts again.

Dogs and many other animals can be infected too, usually by eating infected meat or contaminated soil. Only cats and their wild relatives pass oocysts in their stool.

Safe litter box habits

Health agencies recommend a few habits that lower the risk for everyone at home. They matter most when someone is pregnant or has a weak immune system.

• Scoop the litter box every day, so oocysts are removed before they can become infectious
• If you are pregnant or immunocompromised, it is best to have someone else clean the box. If no one else can, wear disposable gloves and wash your hands with soap and water afterward
• Wash the box regularly with detergent and very hot water, since no cat litter has been shown to kill oocysts
• Keep cats indoors so they cannot hunt, and feed commercial food or well-cooked food instead of raw meat
• Wear gloves when gardening, and cover children's sandboxes when they are not in use
• Cook meat thoroughly, wash fruit and vegetables, and clean cutting boards and knives after raw meat

If someone in the home is pregnant, you can ask your vet whether testing the cat for antibodies would help. A cat with antibodies has already met the parasite and is very unlikely to shed it again. A cat without antibodies could still catch it and shed oocysts for a short time, so keeping it indoors and away from raw meat matters most.

Health authorities such as the CDC do not advise pregnant people to give up a cat they already have. Talk with your doctor about your own situation, including whether a blood test makes sense for you.

Rescued and newly adopted cats

Street cats and former hunters are more likely to have met Toxoplasma at some point. For an adult cat, that usually means the shedding phase is long over. A young rescued cat or kitten may not have been infected yet, or may be in its short shedding window. Daily scooping from the first day at home is a sensible habit either way.

At Paw Squadron, the first stops after every rescue are the vet and a bath. The vet visit includes a checkup, deworming and treatment against fleas and other parasites. Before adoption, every cat gets a checkup, treatment, vaccinations and a microchip. Good litter habits at home still matter, because a short shedding phase is easy to miss.

The CDC advises people who are pregnant or have a weakened immune system not to adopt or handle stray cats, especially kittens, and not to take in a new cat during that time. If this applies to your household, talk with your doctor and your vet before you adopt. You are welcome to mention it in an adoption inquiry, and you can find more care guides in PawPedia.