Survival and viability of Toxoplasma gondii oocysts under natural dry season conditions in the Brazilian semi-arid region.

Abstract

Due to the outbreaks of toxoplasmosis in Brazil, primarily caused by oocysts, the objective of this study was to evaluate how Toxoplasma gondii oocysts behave in the Brazilian semi-arid region and the influence of environmental conditions on the occurrence of outbreaks in the region. Cats were infected with mouse brains containing T. gondii cysts and subjected to five different environmental conditions: Group 1: Positive fecal samples exposed to sunlight and covered with 2 cm of common sand; Group 2: Positive fecal samples exposed to sunlight on the surface of the sand; Group 3: Positive fecal samples in the shade, covered with 2 cm of common sand; Group 4: Positive fecal samples in the shade on the surface of the sand; Group 5: Positive fecal samples kept under ideal temperature and humidity conditions in Biochemical Oxygen Demand (BOD) - Control. Samples were collected initially after 12 h of environmental exposure and subsequently every 12 h to evaluate the presence of oocysts and the sporulation rate. Temperature and humidity were monitored throughout the experiment. After 24 h of exposure, the oocysts were completely destroyed, and 92% of the oocysts were sporulated within 12 h of initial exposure. Soil temperatures reached up to 57 °C, with humidity levels as low as 15%. The study concludes that high temperatures and low humidity are decisive factors in the destruction of T. gondii oocysts, which are rapidly inactivated when exposed to the semi-arid climate of Northeastern Brazil during the dry season.