Anti- Toxoplasma gondii Antibodies in European Residents: A Systematic Review and Meta-Analysis of Studies Published between 2000 and 2020

Abstract

Toxoplasmosis has a major impact on animal and public health. Information regarding the seroprevalence of human Toxoplasma gondii infections from a European perspective has not yet been compiled to date. Thus, the present review summarized available resident data from the period 2000-2020. The overall seroprevalence of anti-T. gondii IgG was 32.1%, with great variability between countries (n = 30). The subgroup analysis identified different pooled prevalence data depending on the geographic area (p < 0.0001), target population (p = 0.0147), and serological diagnosis assays used (p = 0.0059). A high heterogeneity (I² = 100%, p < 0.001; Q = 3.5e+05, d.f. = 135, p < 0.001) and degree of publication bias (Egger's test = 6.14, p < 0.001) were observed among the 134 studies considered. The occurrence of anti-T. gondii IgM, which was reported in 64.7% of studies, reached a pooled seroprevalence of 0.6%. In addition, among the eight main risk factors identified, "contact with soil", "consumption of undercooked beef", and "intake of unwashed vegetables" were the most significantly associated with infections. The fact that one-third of the European population has been exposed to T. gondii justifies extra efforts to harmonize surveillance systems and develop additional risk-factor analyses based on detailed source attribution assessment.

Keywords: Europe; Toxoplasma gondii; human; meta-analysis; risk factors; seroprevalence.

Figure 1

Flowchart describing the study design process. Description of the study search and selection for publications related to (A) seroprevalence of IgG and IgM anti-T. gondii antibodies, and (B) risk factors analyses. (*) A secondary search was carried out based on references included in articles examined for eligibility.

Figure 2

Pooled seroprevalences of T. gondii IgG (A) and IgM (B) antibodies in European residents between 2000 and 2020. AL (Albania), AU (Austria), BH (Bosnia and Herzegovina), CR (Croatia), CY (Cyprus), CZ (Czech Republic), ES (Spain), ET (Estonia), FL (Finland), GE (Germany), GR (Greece), HU (Hungary), IC (Iceland), IR (Ireland), IT (Italy), MA (North Macedonia), NE (Netherlands), NO (Norway), PO (Poland), PT (Portugal), RO (Romania), RS (Russia), SE (Serbia), SK (Slovakia), SL (Slovenia), SW (Sweden), SZ (Switzerland), UK (United Kingdom).

Figure 3

Summary of the risk factors identified for T. gondii infection in human populations residing in Europe. Each bar indicates the number of studies that considered such potential risk factors and the numbers of them resulting in a statistical association were evaluated with odds ratio or relative risk. Brackets indicate the proportions of studies considering such factors as statistically significant (p < 0.05). Raw data are presented in Supplementary Table S2.