Association between Toxoplasma gondii types and outcomes of human infection: A meta-analysis

The virulence and pathogenicity of various types of Toxoplasma gondii differ considerably in mice. Recent studies have claimed that similar phenomenon was observed in humans, but no relevant studies have been performed to validate this finding. In addition, reports showing association between a given T. gondii type and outcomes of human infection yielded conflicting results. To provide a more precise estimation of the association and a more reliable conclusion on this subject, we performed this meta-analysis. Relevant literatures were identified in multiple databases and selected based on strict screening. T. gondii-type proportions among different severities of infection were calculated and compared using Fisher's exact test. Pooled odds ratios (OR) were calculated. Our results showed that the difference among T. gondii-type proportions was significant (p < 0.0001). In addition, significant associations were detected between Type I strains infection and congenital toxoplasmosis (OR: 1.91, p = 0.0009), Type III strains infection and pulmonary toxoplasmosis (OR: 5.15, p = 0.04). In our subgroup analysis, Type I strains were significantly associated with cerebral toxoplasmosis in offspring (OR: 1.81, p = 0.02). This result indicated that different types of T. gondii exhibited different virulence and caused different outcomes in humans.