Toxoplasma gondii

Contributed by David Lindsay

Toxoplasma gondii is a protozoan parasite that infects humans and most other warm-blooded animals. Humans become infected by ingesting meat containing tissue cysts or by ingesting oocysts (cyst stages) in the environment. There are about 1,500,000 cases of toxoplasmosis in the United States each year and about 15% of those infected having clinical signs (Mead et al., 1999; Jones et al., 2001a).

Toxoplasmosis is the third leading cause of death due to foodborne pathogens in the United States (Mead et al., 1999). Congenital toxoplasmosis has long been recognized because of the devastating results it can have on the infected fetus (Jones et al., 2001b). These include hydrocephalus, blindness, and mental retardation. Congenitally infected children that are less severely infected may suffer from a variety of neurological related aliments throughout their lives (Roberts and Frenkel, 1990).

In the United States it is estimated that 85% of women of child bearing age are at risk for toxoplasmosis (Jones et al., 2001a) and that up to 4,000 cases of congenital toxoplasmosis occur each year (Jones et al., 2001b). Toxoplasmic encephalitis (TE) became recognized as an AIDS defining illness in the early 1980’s and TE is still the most important neurological component of AIDS (Luft and Chua. 2000). Toxoplasmosis is also a frequent and fatal complication in patients that receive organ transplantation (Soave, 2001). The annual economic impact of toxoplasmosis in the human population in the United States is about $7.7 billion (Buzby and Roberts, 1996).

Buzby JC, Roberts T. 1996. ERS updates US foodborne disease costs for seven pathogens. Food Rev 19:20-25.

Jones JL, Kruszon-Moran D, Wilson M, McQuillan G, Navin T, McAuley JB. 2001a. Toxoplasma gondii infection in the United States: Seroprevalence and risk factors. Am. J. Epidemiol. 154: 357-365

Jones JL, Lopez A, Wilson M, Schulkin J, Gibbs R. 2001b. Congenital toxoplasmosis: A review. Obs Gyn Survey 56: 296-305.

Luft BJ, Chua A. 2000. Central Nervous System Toxoplasmosis in HIV Pathogenesis, Diagnosis, and Therapy. Curr Infect Dis Rep 2:358-362

Mead PS, Slutsker L, Dietz V, Caig LF, Bresee JS, Shapiro C, Griffin PM, Tauxe RV. 1999. Food-Related Illness and Death in the United States Emerg Infect Dis 5:607-624.

Soave R. 2001. Prophylaxis strategies for solid-organ transplantation. Clin Infect Dis 33:S26-S31