Ascaris suum Egg Inactivation and Destruction by the Vermicomposting Worm, Eisenia foetida.

Vermicomposting is a novel means of reducing organic wastes using a living system composed of earthworms and biosolids. The end product is a highly processed material more favored by the general public. Vermicomposting must take place at temperatures below 35°C in order to maintain worm viability and be successful. This has the disadvantage that it does not reach the 55°C temperatures required by law for pathogen inactivation in composting systems. Pathogen reduction in the composting process is in a large part time and temperature dependent, so it is difficult to understand how vermicomposting can produce a pathogen free product. Although it seems likely that the earthworms may inactivate various bacterial and viral pathogens, there is some concern based on prior literature that they may not successfully inactivate the eggs of helminths that find their way into the biosolids of municipal treatment plants. Thus, this work looked at the ability of Eisenia foetida worms to kill Ascaris eggs in potting soil. Over a six-month period, there was no significant (α=0.05, p=0.563) decrease in the mean number of eggs recovered from soil containing worms sampled at 1, 5, 11, 13, 14, 18, 28, and 183 days after egg addition. In terms of viability, at 1 week after the eggs and worms were placed together, there was no significant reduction (α=0.05, p value=0.272) in the mean egg viability with or without worms being present (91.8% vs. 93%, respectively). After a period of 6 months in the presence of E. foetida earthworms, the mean viability of the eggs recovered was 77.2%. In this study, E. foetida earthworms did not achieve a one-log reduction in A. suum numbers or viability.