Survival of Trichinella spiralis larvae in sewage sludge anaerobic digesters.

The survival of some bacteria, viruses, protozoans, and helminths through the sewage digestion process has been a question of considerable concern among researchers throughout the world. Among the most resistant organisms are some of the pathogenic roundworms and tapeworms. Encysted larvae of Trichinella spiralis are sometimes present in animal tissues discarded as waste from slaughterhouses, restaurants or other sources. In experimental anaerobic sewage digesters, encysted larvae of T. spiralis, in rat muscle, were able to survive a maximum of 96 hr in a "batch" digester. In a digester "fed" daily with small numbers of encysted larvae, "draw-off" remained infective for white rats throughout a 16-day experimental period. Potentially infective material could be present when there is continuous "draw-off" from the anaerobic digesters.