Abstract
Watercress, Nasturtium officinale, is an edible semi-aquatic plant. It is considered to be the principal source of infection for human fascioliasis in Puerto Rico and elsewhere in the world. Commercially grown and natural watercress areas on the island were examined to determine the existing conditions which would contribute to the dissemination of Fasciola hepatica. The factors considered were: 1) the presence of the snail intermediate host (infected and uninfected) in the cress cultivation areas; 2) the presence of parasitized mammals in the area where contaminated fecal matter could be washed into the cress growing sites; 3) the presence of viable metacercariae encysted on watercress; and 4) human consumption of watercress from contaminated sites. The nine commercial watercress cultivation sites examined were found free of infected snails, free of watercress with viable metacercariae, and free of infected mammals in the area. On the other hand, of the 18 natural, unattended watercress growing sites, seven were found with infected snails, six of the sites had watercress with viable metacercaria, and nine of the sites had susceptible animals in the area.