What is Toxoplasmosis?

What is Toxoplasmosis?  Toxoplasma gondii is a protozoan bug that causes the illness known as Toxoplasmosis.  It is concerning to the pets/people relationship because of the risk that cats (who can carry the Toxoplasma bug without any signs of illness) could possibly become a source of infection for pregnant women, with significant risk to the fetus.

How do I know if my cat has Toxoplasmosis, and how concerned should I be? Some cats can be infected with Toxoplasma without any clinical signs of illness.  Others can become severely ill with the infection and present with signs of infection in various organ systems – lungs and the neurologic system most commonly.

The concern for humans is that their pet cat can carry the Toxoplasmosis organism without signs, and if the cat then passes to infection to a pregnant woman there can be risk to the fetus for eye or brain defects.  The same concern exists for immunocompromised individuals (i.e., people with HIV, or undergoing chemotherapy for cancer).

How can my cat get it?   Cats are infected with Toxoplasmosis when hunting rodents infected with Toxoplasma gondii.  Some cats will then harbor these organisms with minimal to no signs of illness.  Most of these will have immune systems capable of eradicating the organism and thereby not have any clinical signs of illness.  A smaller percentage may develop signs of acute illness.  Others can harbor the organism for years with no signs of infection, but then develop the signs of infection should they become immunocompromised with another illness or with certain medications.

I’ve heard that pregnant women shouldn’t clean their cat’s litterbox.  Why?  There exists a concern that pet cats can shed infective Toxoplasmosis oocysts (eggs) to a susceptible pregnant woman or immunocompromised individual.  However, to do so, the cat must be infected via consumption of an infected rodent, the organism has to pass through the cat’s GI system, then passed out into the feces.  Toxoplasma gondii does not become infective in the feces until 1-5 days.  A person can only be infected during that time frame and through the fecal-oral route.

So the risk of human infection from a pet cat can be essentially eliminated via these simple steps:

1. Scoop litter once to twice daily.
2. At risk people wear gloves to scoop litter, and wash hands well with soap and water afterwards.  Better yet, get the spouse to do it!
3. Don’t let your cat out to hunt.
4. If you are pregnant or planning to become pregnant, your health care provider may test you for Toxoplasma gondii. If the test is positive it means you have already been infected sometime in your life. There usually is little need to worry about passing the infection to your baby. If the test is negative, take necessary precautions to avoid infection.
5. The vast majority of Toxoplasmosis cases come from eating undercooked meats (especially lamb and pork), and not from pet cats.

Can dogs get it?  Dogs can become infected with Toxoplasmosis only rarely and typically through eating raw meat.  Dogs, however, cannot pass the organism on to another animal or human.  Dogs, like people, are “dead end” hosts to Toxoplasma gondii.

What puts my cat at risk?  Cats of any age can be infected, obviously those who are hunters are most at risk.

How do I know if my cat has Toxoplasmosis, and is treatment available?  Blood tests and titers can help determine if an ill cat’s symptoms are due to an active Toxoplasmosis infection.  Antibiotics are then started to kill the organism.

What is the prognosis?  Variable, and depends on the state and site of the infection.  As noted before, many cats (and people) can become infected but a healthy immune system can successfully eliminate the infection.