The pathogenic protozoan Toxoplasma gondii :: Essays Papers

The pathogenic protozoan Toxoplasma gondii Life History T. gondii is a parasite of warm blooded animals which is present throughout the world. It is the causative agent of the diseases known as Toxoplasmosis. The organism exhibits a definitive protozoan lifestyle.The life cycle begins with an oocyst in the intestines of cats, the definitive host of T. gondii. The oocyst contains bradyzoites or sporozoites. Oocysts enter prospective hosts through ingestion of cat fecal matter. Once inside a host, bradyzoites, after being released from the oocyst, infect the intestinal mucosa. Within the host cell, tachyzoites rapidly divide, eventually rupturing the cell. The released tachyzoites spread throughout the host, repeating the lysis process or forming zoitocysts (which are, like oocysts, filled with bradyzoites) in host tissue. Three weeks after infection, there are no longer tachyzoites present in the tissues. The cysts reenter the cycle when ingested by another host, unless the host is a cat. In this case, oocysts will be formed in the cat's intestine and will be shed. Life Cycle Illustration Microbiological characteristics T. gondii is a protozoan (eukaryote) which exists in several distinct stages. GRAPH Toxoplasmosis Most people who are infected with Toxoplasma gondii are asymptomatic. In some cases, the parasite may cause inflammation of the lymphatic system, resulting in flulike symptoms including fever and muscle aches. These symptoms can last for a month. In fewer cases, the infection results in more severe disease. T. gondii can infect the eyes and brain, often resulting in blindness and severe neurological disease. Neurological damage (encephalitis) occurs in children who contract the infection congenitally and in immunocompromised individuals. In immunocompromised individuals, encephalitis caused by toxoplasmosis progresses gradually. Patients may begin to experience headaches and dizziness, then memory loss, degradation of motor skills, and sometimes coma and death. Congenital infections may result in spontaneous abortion or birth defects including ocular damage and severe mental retardation. Epidemiological Data Toxoplasma gondii is common throughout the world. A CDC study from 2003 showed that in the United States in 1999-2000, 16% of the population aged 12 to 49 years carried IgG antibodies against the parasite. The prevalence is higher in foreign-born U.S. residents.One in one thousand infants born in the U.S. expresses antibodies against T.