If you took a peek at the photo in that article, you'll see that it's a very large worm to live in such a little fish. This video was not taken at the reservoir in France, but instead at at Lake Nyasa, a huge lake siatuated between Malawi, Mozambique and Tanzania. It gives you a sense of the size of this parasite in comparison to its host:
A lot of fishies in Lake Nyasa are apparently infected with L. intestinalis--and the parasite attacks many different species there. This is a bad thing, because it can prevent its fish host from reproducing by inhibiting puberty! L. intestinalis also effects behavior, and can negatively affect fishing in the lake. Now something else about Lake Nyasa... is that it's SHAPED like a fish! (This is a view from orbit, taken by NASA.) Sometimes nature can be so CLEVER.
One more neat thing about the lake region is that a pack of 17 African Painted Dogs were recently discovered on the Malawi side of the lake--where these carnivores had long been thought to be extinct. I think these guys are some of the most beautiful critters in existence. Also, those wide, snouty faces look so kissable... although I'd probably get my lips ripped off if I tried.
Painted Dogs drinking, Perth Zoo, 2009, by Helenabella.