Toxoplasmosis: Symptoms, Causes, Treatment

Toxoplasmosis (synonyms: toxoplasma infection; toxoplasma gondii infection; toxoplasma; toxoplasmosis; ICD-10 B58.-: Toxoplasmosis) is an infectious disease caused by Toxoplasma gondii, a protozoan (single-celled organism). Toxoplasma gondii is considered an obligate intracellular (“inside the cell”) parasite, meaning that the parasite is dependent on essential host molecules and therefore cannot grow extracellularly (“outside the cell”). The disease belongs to the group of parasitic zoonoses (animal diseases). Due to a two-host development cycle, a distinction is made between intermediate hosts and a final host: intermediate hosts are rodents (especially mice), sheep, pigs, cattle, birds/poultry and humans. Final hosts are Felidae, such as cats. They excrete a feces containing oocysts that is infectious in the environment for a long time. Occurrence: Infection occurs worldwide; approximately one-third of the world’s population is affected. Transmission of the pathogen (route of infection) can occur through contaminated food/undercooked meat, especially lamb and pork (tachy- and bradyzoites; about 20% of pork is infected) or direct handling of infected cats. Another source of human T. gondii infection is insufficiently washed fruit and vegetables contaminated with oocystsFurthermore, infection occurs via soil, for example during gardening, via contaminated surface water, or diaplacentally, i.e., from the mother to the unborn child. In addition, there is a small risk of becoming infected with the pathogen during blood transfusions and organ transplants. The incubation period (time from infection to onset of the disease) is usually 14-21 days. Three different forms of toxoplasmosis can be distinguished, depending on the clinical symptoms:

  • Postnatal infection in immunocompetent individuals – infection after birth in individuals with competent immune defenses.
  • Postnatal infection in immunocompromised individuals (reactive toxoplasmosis) – in individuals with an asymptomatic Toxoplasma infection, a usually severe reactivation of the Toxoplasma infection can occur due to a weakening of the immune system (especially in AIDS)
  • Prenatal (connatal) infection – infection of the unborn child by the mother during pregnancy; in this case, the risk of transmission to the child increases with the duration of pregnancy, but the severity of the infection decreases

The T. gondii IgG seroprevalence (percentage of patients tested serologically positive) is almost 50% in adults (18-79 years) in Germany; in seniors (70-79 years, the value is 77%.Pregnant women show no immunity in up to 75% of cases.Once infected, you remain infected for life, so reactivation is also possible. Reactivation can occur at any time in immunosuppressed individuals. The incidence (frequency of new cases) of T. gondii infection in infected donor (organ donor) and seronegative recipient (transplant recipient) is reported to be 25-75% in recipients without appropriate prophylaxis. Course and prognosis: In otherwise healthy individuals, the infection is asymptomatic (without identifiable causes). Infection during gravidity (pregnancy) in the first and second trimester (third trimester) usually leads to miscarriage. In the third trimester, initially approx. 85% of newborns are initially inconspicuous and without adequate therapy develop late symptoms (chorioretinitis (inflammation of the choroid with involvement of the retina), iritis (inflammation of the iris), deafness, encephalitis (inflammation of the brain), microcephaly (cranial malformation in which the skull is too small compared to normal), epilepsy (seizures), psychomotor retardation). People with immunodeficiency (immune deficiency) are also referred to as high-risk patients, who may develop severe courses with encephalitis or damage to the heart and retina (retina).In transplant recipients with toxoplasmosis outbreaks, mortality (number of deaths in a given period of time, based on the number of the population in question) is 63-80%. Note: Mild symptoms due to prenatal infection are well recognized after birth, but are usually not attributed to the Toxoplasma gondii pathogen. In Germany, direct or indirect detection of the pathogen is reportable according to the Infection Protection Act (IfSG), as far as the evidence points to a connatal infection.