Could My Cat Be A Problem For Me During Pregnancy?

My husband and I have been trying to get pregnant for a while now. We just recently heard about there maybe being a problem with the cat box. Some people say that it is the litter that you use, and other people say that it is something in the feces of the cats. I am curious to know which one is the problem and what you can do about it? We live in an apartment, so it is kind of hard for me to stay away from the cat box. Is that bad?

By referring to your cat and the cat litter, I think you must have been told about the infection called toxoplasmosis, which can be caught from infected cats. As far as I am aware, it does not cause infertility, but under certain circumstances may prove harmful to a fetus.

Toxoplasmosis is caused by an intracellular parasite, not a virus or a bacterium. Intracellular means that unlike most parasites, worms and so forth, it must live inside the cells of its host. All mammals and birds are able to be infected by the parasite, but only cats (including, I would suppose, lions and tigers) serve as the definitive host of the parasite, that is, the host in which the parasite’s sexual reproduction takes place.

Humans acquire toxoplasmosis either by ingesting the cysts that are passed in the feces of a cat that is infected, or by eating the cysts when rare or underdone meat is eaten, since the parasite is pretty prevalent in pork and lamb, though less so in beef. Estimates of the percentage of people infected in the United States vary widely, from around 20 percent of individuals under age 20, to 50 percent of people over age 50. In some countries, France and Brazil for example, infection is much more common, and it is estimated that 90 percent of the population in those countries is infected by age 40.

Obviously with such high percentages of people being infected, we would all have heard a lot more about toxoplasmosis if it were a disease that caused lots of symptoms, disability or death. Fortunately it is one of the many diseases which most people get without even being aware of it, and probably carry in their bodies for life without it ever becoming obvious. In a person older than a newborn, with a normal immune system, the acute infection is rarely diagnosed. Swollen lymph nodes in the neck are the most common sign; fever is uncommon. The nodes go away in a couple of weeks, so unless someone sees a doctor who is thinking about toxoplasmosis, and does the special blood tests necessary to diagnose it, the person will never know they had the disease.

Two populations are at risk of becoming seriously ill with toxoplasmosis. One consists of fetuses being carried by women who first become infected during their pregnancy, and the other, people with severe immune deficiency, particularly people with AIDS. People with normal immune systems are able to force the toxoplasma into cysts, mostly in the brain and in muscle, and the parasites are kept in those cysts, where they can do no harm, by the healthy immune system. In people with AIDS those cysts may break open, releasing parasites which can then cause severe, life-threatening disease. Less commonly, someone with AIDS will pick up a new infection, either by eating under-cooked meat or by being around a cat litter box.

Since the sources of infection for humans are cysts either from contact with cat feces or swallowed in under-cooked meat, it is recommended that pregnant women also avoid cat litter boxes, and only eat meat that is well cooked. A woman who becomes infected while pregnant may pass the infection on to her fetus, and the fetus’ immune system is not strong enough to protect it. In France all pregnant women are required to be tested for toxoplasma infection. If a woman tests positive early in pregnancy it means she got the infection before becoming pregnant, and will not pass it on to the fetus. If she tests negative early in pregnancy, then she is retested periodically during the pregnancy. If one of those later tests shows positive, it means that the pregnant woman has acquired the infection while pregnant, and treatment is given to reduce the chances of damage to the fetus. Since there is much less toxoplasmosis in this country, there are no rules regarding testing, although many experts do recommend it early in pregnancy.

Because cats catch toxoplasmosis in much the same way that we do, by eating under-cooked mice and other rodents, a cat that has been indoors eating commercial cooked cat food is not very likely to be infected. I should think that it is possible to do a blood test on a cat to see for sure if it is infected, and if the writer of today’s letter will be near her cat and its litter box during her pregnancy, that might be something to check out with the cat’s vet. Even before doing that she might want to ask her doctor to do a toxoplasmosis test on her. If she is already infected, then there should be no risk to her future children, no matter how much she changes the litter, or how much rare meat she eats.

No one recommends treating a healthy person who simply has a positive toxoplasmosis test, not even a pregnant woman who was positive before becoming pregnant or early in pregnancy, since such infected people do not get sick and do not pass the infection on to others. Treatment is not even recommended in people with HIV until their immune system is severely affected, at which time the same prophylactic medicines that are used to prevent pneumocystis pneumonia (another parasitic disease seen mostly in people with AIDS) seem to be effective in preventing the development of clinical toxoplasmosis.

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