Toxoplasmosis is considered to be a leading cause of death attributed to
foodborne illness in the United States. More than 60 million men, women, and
children in the U.S. carry the Toxoplasma parasite, but very few have
symptoms because the immune system usually keeps the parasite from causing
illness.
However, women newly infected with Toxoplasma during
pregnancy and anyone with a compromised immune system should be aware that
toxoplasmosis can have severe consequences.
Toxoplasmosis is considered one of the Neglected Parasitic Infections, a
group of five parasitic diseases that have been targeted by CDC for public
health action.
The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals (birds or mammals, including humans). Toxoplasmosis, the disease of which T. gondii is the causative agent, is usually minor and self-limiting but can have serious or even fatal effects on a fetus whose mother first contracts the disease during pregnancy or on an immunocompromised human or cat.
Around a third of people worldwide carry the parasite, with most catching it by consuming undercooked meat, especially lamb, pork and venison or by ingesting water, soil or anything contaminated by feline feces. According to the Merck Manual of Diagnosis and Therapy the standard drug to counter infection is pyrimethamine, but most immunocompetent asymptomatic people infected with T. gondii, with the exception of neonates and pregnant women, require no treatment though recent studies have indicated an influence of T. gondii on suicidal behaviors in humans which — if widely confirmed — might warrant treatment attention. However, drugs are only effective during active infection (tachyzoite stage); there is currently no way to treat latent infections (bradyzoite stage) so a host once infected is infected for life.
This is problematic when previously immunocompetent hosts become immunocompromised (for example in the case of cancer or AIDS), allowing reactivation of the infection.
