Genetic diversity among capybara (Hydrochaeris hydrochaeris) isolates of Toxoplasma gondii from Brazil

Recent studies indicate that Toxoplasma gondii isolates of many domestic hosts from Brazil are genetically and biologically different from T. gondii isolates from USA and Europe. However, little is known about genetics of T. gondii isolates from wild mammals in Brazil. In this study, genotypes of 36 T. gondii isolates from capybaras (Hydrochaeris hydrochaeris) from six counties in São Paulo state, Brazil, were determined. Sixteen genotypes were identified using 11 genetic markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico and CS3. No classical clonal Type I and Type II isolates were found, confirming other findings that these lineages are rare in Brazil. Eight of these 36 isolates were grouped into the common clonal lineages in Brazil, previously designed as Types BrI, BrII and BrIII. Seven of the 16 genotypes were reported for the first time in this study. Three of the 36 isolates showed mixed infections. Analysis of mortality rates in infected mice indicated that Type BrI is highly virulent, Type BrII is intermediately virulent and Type BrIII is non-virulent, which is in agreement with previous report. The allele types at the CS3 locus are strongly linked to mouse-virulence of the parasite. These genotyping results support previous findings that the T. gondii population is highly diverse in Brazil.