A Method for Assessing the Viability of Nematode Eggs in Sludge

Abstract

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 µm and 100 µm 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°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° 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.