A method for assessing the viability of nematode eggs in sludge

Helminth eggs are found in urban sludge used in agriculture. Then, to evaluate the parasitic risk, a method was developed to estimate the viability of these eggs. The extraction of these eggs was performed with a diphasic treatment (SDS 0.01 % - Ethylacetate) coupled with a filtration on 500 mu m and 100 mu m sieves followed by concentration using two flotations with NaCl (d = 1.19). For the culture, 3 parameters tested showed a faster egg development at 30 degrees C in deionized water with continuous aeration, whereas organic compounds reduced this development. This culture was performed during respectively 13, 10 and 8 days to obtain Ascaris suum, Toxocara canis and Capillaria sp larva, and 16 days for Trichuris vulpis which presented a slower development. The quantification was realized by microscopic examination (100 X) after sonication and sodium hypochlorite (0.5 degrees Chl) treatment. The eggs reaching the larva stage were considered as viable and the percent of viability was expressed by the ratio: nematode eggs at the larva stage/total of Nematode eggs counted.