Seems a long shot to me also, but the modification could be doing any number of other things to the worms, including stuff only a geneticist might even think of.

I would have considered this whole "worm" idea insane not long ago, and it's still just conjecture -- a theory, as OP says -- but these malicious, out-of-control science experiments being injected into people are already so over-the-top that anything seems possible at this point.