Effect of Temperature on Embryonation of Ascaris suum Eggs in an Environmental Chamber

The influence of temperature on the development and embryonation of Ascaris suum eggs was studied using coarse sand medium in an environmental chamber with 50% humidity. The time required for development and embryo- nation of eggs was examined under 3 different temperature conditions, 5°C, 25°C, and 35°C. A. suum eggs did not de- velop over 1 month at the temperature of 5°C. However, other temperature conditions, 25°C and 35°C, induced egg de- velopment to the 8-cell-stage at days 5-6 after incubation. All eggs examined developed to the 8-cell stage at day 6 after incubation in the sand medium at 25°C. The higher temperature, 35°C, slightly accelerated the A. suum egg development compared to 25°C, and the development to the 8-cell stage occurred within day 5 after incubation. The formation of lar- vae in A. suum eggs at temperatures of 35°C and 25°C appeared at days 17 and 19 after incubation, respectively. These findings show that 35°C condition shortens the time for the development of A. suum eggs to the 8-cell-stage in compari- son to 25°C, and suggest the possibility of accelerated transmission of this parasite, resulting from global warming and ecosystem changes.