It's a rare pregnant cat owner who walks into my office for her first prenatal visit and fails to express her concern over contracting Toxoplasmosis from her beloved pet. There is a risk of fetal infection with the Toxoplasma parasite in cat owners, but it is not nearly as great as most patient’s think when they arrive in my office. Only about 0.1% of pregnancies in the United States are affected by Toxoplasmosis and most of these are not the result of contact with cats.
Toxoplasmosis is usually found in and spread by cats. When a cat acquires such an infection, millions of the non-infectious form of the parasite can be found in the cat feces over the next 1-3 weeks. After 3 days, these non-infectious parasites change their form and become infectious. It is this new infectious form which persists in moist, shaded soil for more than a year.
Humans usually acquire the infection by eating contaminated pork, lamb or beef; or unwashed fruits, berries or vegetables. Less commonly, the infection may be acquired through direct contact with cat feces or from breathing in aerosolized parasites that may be encountered when cleaning a cat’s litter box.
When an infection occurs in a pregnant mother it is usually asymptomatic, but mild signs and symptoms may be present. These most commonly include fatigue, headaches, muscle aches, and enlargement of lymph nodes in the back of the neck and may last from several days to several months.
The likelihood of a fetus being affected depends on how far along the pregnancy is when the mother becomes infected. If the infection occurs in the first trimester, 13% of fetuses will be infected; whereas if the infection occurs in the second or third trimester, 30% or 60% of fetuses may be affected, respectively.
If a fetus does become infected, the severity of that infection also depends on the stage of the pregnancy at the time of the infection. Up to 75% of fetuses infected in the first trimester will have severe manifestations of the disease or be stillborn compared to 20% in the second trimester and 0% in the third trimester.
Severe manifestations of the infections in newborns include severe mental retardation, seizure disorders, liver problems, and visual impairment. Milder forms of infection may result in learning and physical disabilities as well as varying degrees of hearing and visual loss.
The diagnosis of infection during pregnancy relies on the use of both blood tests to look for antibodies directed against the parasite and ultrasound evaluation of the fetus to look for signs of infection. Unfortunately the difficulties in standardization of laboratory results and in interpreting results even from a single laboratory have made it impractical to routinely screen all patients, or even patients at increased risk, for infection.
Under these circumstances, several measures can be taken to reduce one’s risk of infection:
Education alone has been shown to reduce the risk of infection with the Toxoplasma parasite by 60%.
This article is meant for informational purposes only. If you feel that you may have contracted Toxoplasmosis, this should be discussed with your physician.
Walter J. Hodges Jr., M.D., F.A.C.O.G.