On Sun, 23 Sep 2012 14:11:23 +0100, Farmer Giles wrote:

The thing is that, despite a lot of searching, I'm not sure how liver
fluke is transmitted via watercress - ie is it taken up by the plants
or do the flukes somehow attach themselves to it?

Didn't take me long, one google on Liver Fluke and the second hit
"Fasciola hepatica - Wikipedia, the free encyclopedia" told me that it's
the ingestion of uncooked contaminated food, like watercress or drinking
contaminated water. Note this is contamination with part of the flukes
life cycle rather than adult flukes,

--
Cheers
Dave.