Fig 1. The different steps of the optimized straining-flotation method to detect and quantify STH eggs/larvae in soil.

The optimized straining-flotation method consists of 9 consecutive steps, including the homogenization of the soil sample (step 1), sieving of the sample (step 2), the transfer of the sieved soil into a 50 mL tube (step 3), centrifugation of this test tube at 2,000 g for 5 min (step 4), discard supernatant, add water to bring the pellet to suspension, equally divide suspension over two 15 mL tubes, and repeat the centrifugation step (step 5), discard supernatants and add flotation solution to each of the test tubes (step 6), centrifuge the tubes at 2,000 g for 2 min (step 7) and put the supernatants over a PuriStrainer sieve (step 8), transfer the material from the PuriStrainer sieve to a microscopic slide or in a 2 mL tube for microscopic or molecular analysis, respectively (step 9).