Toxoplasmosis is caused by the unicellular parasite Toxoplasma (T.) gondii. When first infected during pregnancy, the toxoplasmas can be transmitted to the unborn child (connatal infection) and cause severe damage to the unborn child, even death. About half of all toxoplasmoses are said to be foodborne.

Worldwide

Cats and other felids are the final hosts, and sexual reproduction of the parasites can take place in them. If cats eat rodents or birds that contain toxoplasma cysts in their tissues, or if they are fed raw meat that contains toxoplasma cysts, the parasites undergo a sexual reproduction cycle and are excreted as oocysts in the feces. The spectrum of possible intermediate hosts that can be infected by oocysts includes humans, sheep, goats, rodents, pigs, cattle, chickens and birds.

Intermediate hosts, including humans, acquire infection by oral ingestion of oocysts during contact with infected cats, by ingestion of food contaminated with cat feces, or by oral ingestion of permanent forms (Toxoplasma cysts) in the tissues of an intermediate host (e.g., undercooked sheep meat). If a first-time infection with parasitemia (appearance of parasites in the blood) occurs during pregnancy, the toxoplasmas can also be transmitted diaplacentally to the unborn child by the blood route.

10-23 days after consumption of cysts in raw meat or 5-20 days after ingestion of oocysts (e.g., from vegetables contaminated with cat feces).

In healthy adults, infection with T. gondii usually proceeds without signs of illness or with uncharacteristic symptoms. In the majority, infection in the first trimester of pregnancy results in fetal death. In the second third of pregnancy, hydrocephalus, calcifications in the brain, or severe eye damage may occur. In the last third, infection leads to mostly clinically inconspicuous newborns; late damage may occur only after months or years, in the form of developmental disorders, mental retardation or eye changes, even blindness. In immunocompromised persons (e.g. AIDS), infection can lead to uninhibited multiplication of the toxoplasma cysts, with the development of brain toxoplasmosis in the form of encephalitis.

Treatment with existing symptoms is carried out with medication

Pregnant women who have tested negative for antibodies should avoid contact with new cats (cats that have not lived in the household for a long time and cats whose feeding habits cannot be controlled), as well as avoid undercooked meat and wash vegetables thoroughly before consumption. Wear work gloves when gardening because of the possibility of contact with cat feces.

In Austria, there is no official obligation to report toxoplasmosis. In 2018, the toxoplasmosis screening of the University Department of Pediatrics and Adolescent Medicine of the Medical University of Vienna found 96 pregnant women with infection and treated them antiparasitically. Eight confirmed connatal infections with Toxoplasma gondii were diagnosed.

For livestock and cats, samples from animals are sent to laboratories for testing for T. gondii only after clinical suspicion, such as after abortions, out of private interest, or as part of studies. In 2018, 35 samples from cattle, 21 from sheep, and 30 samples from goats came for serological testing. Toxoplasma antibodies were present in five samples from cattle, 11 from sheep, and 19 from goats; the pathogen was not directly detectable in any sample (four samples from cattle, 23 from sheep, and 15 from goats).

In Austria, there is no official obligation to report toxoplasmosis. The toxoplasmosis laboratory of the Department of Pediatrics and Adolescent Medicine of the Medical University of Vienna processes amniotic fluid samples for PCR analysis from the Austrian prenatal centers, and umbilical cord blood from children of infected pregnant women is also examined throughout Austria for the purpose of quality control. This allows a follow-up of children of infected mothers and a survey of the infection status of the children.

Serological antibody detection from blood samples is the primary routine method. In addition to indirect pathogen detection, direct microscopic detection methods and nucleic acid detection by polymerase chain reaction (PCR) are also available for amniotic fluid, spinal fluid, bronchial lavage, eye chamber fluid or placental material.