Infection with Toxoplasma gondii during pregnancy: seroepidemiological studies in Austria

Seropositivity among pregnant woman in Austria has decreased from 48% to 50% at the end of the 1970s to 35% in recent years. Despite this decrease, knowledge of possible sources and risk factors for Toxoplasma infection remains important. We reviewed seroepidemiological studies that were undertaken to assess the roles of undercooked meat and oocysts in cat faeces as potential sources of infection in pregnant women. Improved management and hygiene in pig herds raised in confinement have resulted in less contact of pigs with cats and a decrease of infected pigs within one decade from 14% in 1982 to 0.9% in 1992. In Austrian wild boar populations, however, seroprevalences remained essentially unchanged during the same decade (18% in 1983 and 19% in 1990-1993). Austrian sheep and goats are usually kept on small farms where cats abound and are predominantly seropositive (66% in sheep and 69% in goats). The seroprevalence in cats has decreased from approximately 81% in 1987 to 59% in 1996; presumably because of cats' increased consumption of processed food. Despite the decrease of infection in pregnant women via the cat-to-pig pathway, it may be offset by a recent concomitant increase in mutton consumption. Free-ranging chickens are a good indicator of the prevalence of T. gondii oocysts in the soil because chickens are ground feeders. Antibodies to T. gondii, as evaluated by the modified agglutination test, were found in 36% of chickens from 12 Austrian 'biofarms'. Because Austrians rarely consume raw pork, the fraction of human T. gondii infections associated with pig meat consumption is likely small. As meat consumption and lifestyle patterns change in Austria, the risk of human infection with T. gondii via different pathways needs re-evaluation and targeted educational efforts to control transmission.