Toxoplasma gondii Genotypes Isolated from Humans: A Systematic Review

Toxoplasma gondii has the capacity to infect several animals, including humans. This parasite has great genetic variability due to crossing over in felines’ gut. These new atypical and exotic genotypes are complex, requiring genotyping research to help elucidate virulence mechanisms. For the purpose of the study, five English language databases reporting data on T. gondii genotyping in humans were searched. The searching process resulted in the inclusion of 28 articles published from 2000 to September 2020. The data revealed that 1,167 samples were genotyped into 470 T. gondii isolates. In the world, type II was predominant (53.65%, n = 257). Atypical genotypes were the second most common (22.33%, n = 107). The results suggest greater genetic diversity in Asia and America than in the European and African continents. The genotype #9 was prevalent in Asia. Furthermore, atypical strains were predominant in 50 isolates from patients with ocular toxoplasmosis (52%, n = 26). In individuals with congenital toxoplasmosis, type II was predominant presenting a prevalence of 46.49% (n = 73). Type II strains were predominant in immunocompromised with a prevalence of 75.6% (n = 31). In cancer patients, there was a predominance of atypical strains with 67.14% (n = 47) and genotype #17 was specific for this group. In general, this systematic review indicated a great degree of genetic diversity and circulation of virulent T. gondii strains in humans. However, further studies are needed to better understand the population structure of T. gondii and its clinical characteristics.