Toxoplasma gondii is one of the most widespread zoonotic pathogens in the world. Toxoplasma is a protozoal parasite that can infect almost any warm-blooded animal, including humans. In most people and animals, infection doesn’t cause any illness at all, and after the initial infection, the body usually produces strong immunity which protects it from subsequent Toxoplasma infection. Problems arise when infection occurs in a person with a weakened immune system. For example, toxoplasmosis (i.e. illness due to Toxoplasma) has been a major problem in HIV/AIDS patients, although better HIV treatments have decrased the incidence of the disease in this group in recent years. Toxoplasma can also cause problems when a woman is infected for the first time, before her body has developed immunity to the parasite, while she is pregnant. In these cases, the parasite can infect the fetus. This may result in birth defects or loss of the pregnancy altogether.

Our friendly feline companions have the unfortunate distinction of being what is called the “definitive host” of Toxoplasma. This means that even though the parasite can infect many species of animals, cats are the only species that shed the parasite “eggs” (which are called oocysts in this case) in their stool after they’re infected. But what most people don’t realize is that the number of cats that are shedding oocysts at any one time is very small – usually less than 1 in 100. And after the first time a cat is infected, it usually doesn’t shed oocysts again, and if it does it sheds them in very low numbers.

Depending on individual lifestyle and eating habits, a person is just as likely or more likely to be exposed to Toxoplasma from working in the garden or eating undercooked meat (particularly free-range pork or wild game). People who are pregnant or who have a weakened immune system do NOT need to get rid of their cats because of Toxoplasma, but they DO need to take steps to avoid exposure to Toxoplasma from all sources.  This includes avoiding contact with cat stool and kitty litter by asking someone else to clean their cat’s litter box for them if possible, or wearing rubber gloves and being very careful to wash their hand very well afterwards if they need to clean the box themselves. Here are a few more tips that can help reduce their risk of exposure to Toxoplasma:

  • Clean your cat’s litter box every day. The oocysts usually take about 24 hours to become infective once they’ve been passed in your cat’s stool, so daily cleaning helps remove them before they reach this stage.
  • Always wash your hands with soap and water after cleaning your cat’s litter box, after working in the garden or in any soil, and after handling raw meat.
  • Cook all meat, especially pork, lamb, mutton and wild game, to an internal temperature of 67ºC/153ºF or higher.
  • Keep sandboxes covered so outdoor cats don’t contaminate them with stool.
  • Keep your cat indoors. Outdoor cats are more likely to be exposed to Toxoplasma and shed oocysts in their stool.

You can find more information about Toxoplasma on the Worms & Germs Resources page.