Fate of Ascaris at various pH, temperature and moisture levels

Soil-transmitted helminths (STH) are intestinal worms that infect 24% of the world's population. Stopping the spread of STH is difficult, as the eggs are resilient (can withstand high pH) and persistent (can remain viable in soils for several years). To ensure that new sanitation systems can inactivate STH, a better understanding of their resilience is required. This study assessed the inactivation ofAscariseggs under various conditions, in terms of moisture content (MC) (90%), temperature (20-50 degrees C) and pH (7-12.5). The results highlight that the exposure ofAscariseggs to elevated pH (10.5-12.5) at temperatures <= 27.5 degrees C for >70 days had no effect on egg viability. Compounding effects of alkaline pH (>= 10.5) or decreasing MC (<20%) was observed at 35 degrees C, with pH having more of an effect than decreasing MC. To accelerate the inactivation of STH, an increase in the treatment temperature is more effective than pH increase. Alkaline pH alone did not inactivate the eggs but can enhance the effect of ammonia, which is likely to be present in organic wastes.