Molecular detection of Toxoplasma gondii in irrigation waters and agricultural soils of Central Luzon, Philippines: implications to human health

Toxoplasma gondii, a parasitic protozoan that causes toxoplasmosis, is estimated to infect a significant percentage of the world's population. One of the main routes is through consumption of contaminated water, soil, or food containing oocysts. Large scale outbreaks through water contamination were reported across various regions. However, in the Philippines, there is still no data on the occurrence of T. gondii oocysts in environmental matrices. In this study, T. gondii oocysts DNA were detected in irrigation waters and agricultural soils from selected sites in Central Luzon, Philippines, and the genetic diversity of the detected parasite was examined. Using nested PCR amplifying the RE gene, the prevalence of T. gondii oocyst DNA in irrigation water (n = 40) and agricultural soil (n = 40) was at 35 and 25%, respectively. One isolate (W11) was genotyped and showed a mixed genotype (Type I/TypeIII) suggesting recombination or diverse strain exposure. Phylogenetic analysis revealed clustering with CTG strain (GenBank accession no. PX505257), a Type III non-virulent genotype to mice, but associated to cause ocular toxoplasmosis in humans and toxoplasmic encephalitis in immunocompromised patients. Our findings suggest that T. gondii movement in environmental matrices can possibly facilitate transmission of infection and therefore poses a threat to human and animal health.