February 9, 2010

This is always a hot topic of conversation when a couple is starting a family. Doctors used to recommend that pregnant women get rid of their cats during pregnancy, but fortunately, education has prevailed and now pregnant women are simply taught the basic hygienic procedures to prevent infection with Toxoplasmosis during pregnancy.

Toxoplasmosis is a coccidian parasite with a rather complicated life cycle. Cats are the only host in which Toxoplasmosis can complete its life cycle, but most mammals (including humans) and birds can serve as intermediate hosts if they ingest the infective form of the parasite called an oocyst.

Here is what happens: A cat passes an unsporulated oocyst in its feces. By 24 hours, the oocysts have sporulated, becoming infectious for an intermediate host such as a mouse. The mouse gets infected and forms a cyst in its muscle tissue. Another cat would then eat the mouse and so the life cycle goes. Most infected cats have no symptoms unless they are immunocompromised or elderly. If they do have symptoms, they are vague and non-specific such as fever, cough, vomiting or enlarged lymph nodes. There are several antibiotics that are effective in treating this condition in cats.

Toxoplasmosis gets interesting when an unusual intermediate host eats the sporulated oocyst and this is how humans become involved. Humans become infected in one of three ways:
Accidental ingestion of infective oocysts when cleaning the litter box at more than 24 hour intervals, which is quite rare, or more often, from vegetables that have been contaminated by cat feces in the garden
Ingestion of cysts in undercooked meat from an animal who ate the infective oocysts. In the US, pork appears to be the most likely source of cysts for humans.
Transmission through the placenta from an infected mother to her baby

Toxoplasmosis infection in humans rarely poses a problem unless the person is pregnant when she becomes infected. Effects are most serious if infection occurs between the 10th and 24th week of pregnancy. When my co-worker decided to start a family, her doctor tested her for Toxoplasmosis. It was a bit surprising that she tested negative for the disease (many veterinarians do test positive), but this actually was disconcerting, because actually having the disease is not a problem for a fetus. It is acquiring the infection during pregnancy that results in problems. It is during these early stages of infection that the parasite affects the fetus and could cause serious defects. Fortunately, thanks to some basic hygiene practices, she still tested negative after her 24th week of pregnancy and all went well.

Cats can be tested for the presence of antibodies to the parasite, but this doesn’t help determine the likelihood of shedding oocysts at any particular time, so it doesn’t help perspective mothers determine their likelihood of acquiring the infection during her pregnancy. Most infected mothers have acquired the parasite via undercooked meat or oocysts found in poorly washed garden vegetables.

Here are the things to do to prevent infection during pregnancy. Immunosuppressed individuals should maintain these practices at all times to prevent infection because immune compromised individuals could become ill from the presence of the parasite.

For the cat:
Do not feed raw or rare meat
Do not allow the cat to hunt

Do not eat raw or rare meat
After handling or preparing raw meat, wash hands and surfaces with warm soapy water
Wash all fruits and vegetables before eating
Wear gloves while gardening or wash with warm soapy water after gardening
Change litter box daily, before the oocysts become infected
Pregnant and immunosuppressed individuals should avoid the litter box

Attempts to isolate infective oocysts on cat fur have been unsuccessful. Thus, it is thought that handling cats is not a source of accidental infection.


One Response to “Toxoplasmosis”

  1. eL Says:


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