Six ponds with high Melanoides tuberculata numbers (>250 snails scooped per person per hour, maximum sample time per pond 4 h) were sampled in September 2009. The ponds were located in Nghia Lac and NghiaPhu communes, Nam Dinh province, Vietnam. Both communes have a history of endemic FZTs and are known for raw-fish-eating behavior of humans and small-scale aquaculture farming (Dung et al., 2010; Phan et al., 2011). The six fish ponds ranged in size from 290 m2 to 8190 m2. Rice was only cultivated in pond 4 in about 25% of pond area. One pond was inhabited
by ±400 ducks in an enclosure of ±2330 m2, no snails were
found within the enclosure. Further description of ponds is shown in Table 1