THE EFFECT OF SEWAGE-SLUDGE COMPOST ON THE VIABILITY OF THE EGGS OF APARASITIC NEMATODE

Ascariasis affects approximately one quarter of the world's population and is particularly prevalent in developing countries. As improvement s in sanitation in most of these countries becomes more widespread, co mposting of human excreta and sewage sludge has become a popular and c ost-effective method of treatment, as well as offering a valuable sour ce of organic fertilizer and a soil amendment. If, however, the compos ting process is not properly controlled there may be a potential risk from pathogens, helminths and other infections to workers handling the compost and to consumers of foodstuffs grown on land treated with the compost. During this study the effect of sewage sludge compost on the viability of ascarid eggs was examined. Eggs of Ascaridia galli were used as a model for the eggs of the human pathogen Ascaris lumbricoide s. Fully-developed A. galli eggs were added to sewage sludge compost s uspensions, to microorganism-free compost filtrate suspensions and to distilled water controls. The results from these experiments showed th at the compost environments had a destructive effect on the A. galli e ggs suspended in the compost. The viability of the eggs sampled from t he compost environments became reduced with increased exposure to thes e conditions. No reduction in the viability of the A. galli eggs from the microorganism-free compost filtrates or from the distilled water c ontrols was observed. A thorough microscopic examination of the eggs f rom the three environments was undertaken. Degenerate eggs from the co mpost suspensions were seen to be enlarged and swollen. No swelling wa s observed in the eggs from the control nor from the microorganism-fre e compost. The observations were believed to have been a result of act ion by microorganisms, possibly fungi, present in the compost suspensi ons but not in the microorganism free compost filtrates or the distill ed water controls.