Faecal examination by the quantitative formalin-ethyl acetate concentration technique (FECT)

The procedure for quantitative FECT was similar to the procedure detailed in the previous report [29]. In brief, 2 grams of fresh stool were fixed in 10% formalin and kept at room temperature until processing. After vigorous shaking, the specimens were centrifuged at 2,500 rpm for 5 minutes and the sediment re-suspended with NSS and strained through two layers of gauze. The tube was then centrifuged at 2,500 rpm for 5 minutes and the supernatant discarded. Seven milliliters of 0.85% saline were added to the sediment and mixed, then 3 ml of ethyl acetate were added to the sample tube, mixed thoroughly, and centrifuged at 2,500 rpm for 5 minutes. After removal of the top three layers, the sediment was re-suspended with 1 ml of 10% formalin. The final suspension was examined blind by two parasitologists and the number of O. viverrini eggs were counted in 2 drops sampled from the total suspension. The number of eggs per gram of feces (EPG) was calculated to determine the intensity of O. viverrini and other parasitic infection.