Colorado State University Extension
SafeFood Rapid Response Network
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Toxoplasmosis During Pregnancy
Edited by: Mary Schroeder, M.S., R.D. & Pat Kendall, Ph.D., R.D., Colorado State - Summer 2003
Pregnancy is a time in a woman's life that brings about change. Many physiological adaptations are positive, but some may have negative consequences for the pregnant woman. Hormonal changes causing suppression of the immune system increase susceptibility to infections from foodborne pathogens that would otherwise be of no concern. Toxoplasmosis is one such infection, caused by the parasite Toxoplasma gondii. T. gondii can be transmitted to humans by water, dust, soil, or through consumption of contaminated foods, such as raw or undercooked meats and unwashed fruits and vegetables.
Cats are the primary host for T. gondii, and the only host where the organism can complete its life cycle. Cats shed oocysts in their feces only once in their lives, during the first two weeks following infection with the parasite. However, the sporulated oocysts are infectious and can survive for months to years in the environment. Contact with contaminated soil or water is therefore as much of a risk factor for infection as contact with cats. If animals, such as sheep, pigs and rabbits, pick up the oocytes from the environment, they become intermediary hosts and carry the parasite in the cyst form in their tissues. If the meat of an infected animal is then eaten raw or undercooked, the parasite is passed to the human or animal who consumes the meat.
Of the estimated 1.5 million T. gondii infections that occur each year in the U.S., most individuals experience no or minor symptoms and subsequently develop a protective immunity to the parasite. However, when women acquire T. gondii infections less than 6 months before pregnancy or during pregnancy, their babies are at risk for contracting congenital toxoplasmosis, affecting approximately 3,000 babies each year. Manifestations of congenital toxoplasmosis can range from severe (mental retardation and blindness) to mild (vision impairments). Also, symptoms may not be visible at birth, but express themselves several months to years later. Because T. gondii can cause such severe problems, toxoplasmosis accounts for $3.3 billion to $7.8 billion per year in economic costs. The government ranks it as one of the most expensive forms of food poisoning.
Diagnosis of toxoplasmosis can be confirmed with an IgG antibody blood test and identification of symptoms appearing about 10 days after exposure to T. gondii, which include fever with rash, headache, muscle aches and pain, and swelling of the lymph nodes. Once a mother is diagnosed with the infection, antibiotics can reduce transmission of the parasite to the fetus, but this treatment will not change the course of the disease if the fetus has already been exposed.
To avoid infection from T. gondii, pregnant women are advised to practice safe food handling procedures, such as washing all surfaces, cutting boards and utensils that have come in contact with raw meat with hot, soapy water. Pregnant women are recommended to avoid consumption of raw or undercooked meat (particularly minced meats, mutton and pork), to wash hands often, especially after handling animals or working in the garden, and for cat owners to have the litter box changed every day, preferably by another family member.
Sources:
1) Smith, J. Foodborne Infections during Pregnancy. J. Food Protection, 62(7): 818-829, 1999.
2) Smith, J. Long-Term Consequences of Foodborne Toxoplasmosis: Effects on the Unborn, the Immunocompromised, the Elderly, and the Immunocompetent. J. Food Protection. 60(12): 1595-1611, 1997.
3) Hill, D., Dubey, J.P., Toxoplasma gondii: transmission, diagnosis and prevention. European Society of Clinical Micro. & Infect. Dis.. 8:634-640, 2002.
4) Cook, A.J.C., Gilbert, R.E., Buffolano, W., Zufferey, J. et al., Sources of toxoplasma infection in pregnant women: European multicentre case-control study. British Medical Journal 321:142-147, 2000.
