Toxoplasmosis refers to the disease caused by the parasite Toxoplasma gondii. Toxoplasma gondii is related to the parasites that cause malaria, cryptosporidial diarrhea and babesiosis. The parasite is 3-5 microns in length and visible with a microscope. In the acute infection the parasite is in a form that multiplies rapidly called a “tachyzoite”. If the immune response to the parasite is normal, the parasite then forms a cyst that contains slowly replicating “bradyzoites”. Bradyzoites persist for the remainder of an infected individual’s/animal’s life. If a member of the cat family eats meat containing bradyzoites in cysts, or oocysts excreted by other cats, male and female parasite gametes form in the cat intestine. These gametes create highly infectious oocysts which are excreted for several weeks. Oocysts then are present in materials contaminated by cat feces (e.g., cat litter, garden soil, sandboxes, and fruits and vegetables that come into contact with cat feces and then are not thoroughly washed). Only members of the cat family excrete oocysts. All animals can be infected by bradyzoites and oocysts.
T. gondii is acquired from meat not cooked to well done or oocysts in materials contaminated with cat feces. A woman who is infected for the first time while pregnant may transmit the infection to her baby while she is pregnant. Immunocompromised individuals may develop serious medical problems from acute or chronic Toxoplasma infection.
Currently 30% to 50% of people throughout the world, 2 to 3 billion people in 2006, are infected with Toxoplasma gondii. The infection is most commonly passed from mother to fetus during pregnancy. Congenital infection occurs in between 1 in 1000 and 1 in 15,000 live births in the US. Immunologically compromised persons, such as those with autoimmune disorders, organ and bone marrow transplants and AIDS, are also at risk of developing the disease.
The estimated costs for care of children born with toxoplasmosis in one year in the US are between one half and eight billion dollars. Disease caused by this infection in immune compromised individuals is costly and frequent.
Source: Centers for Disease Control and Prevention, National Center for Infectious Diseases. “Food-Related Illness and Death in the United States,” Emerging Infectious Diseases, Vol. 5, No. 5, 1999.
Incidence of infection in those of childbearing age (outside parentheses) and of children under the age of 10 years (inside parentheses)
There are more than 4000 species of apicomplexan parasites. The apicomplexan parasites that cause diseases in humans include Toxoplasma gondii (top) that infects two billion people worldwide and can harm the brain and eye of a baby or those who are immunocompromised. Malaria (middle) kills one million children a year. Cryptosporidium parvum (bottom) causes diarrheal disease and dehydration.