Just out of interest as i'd never heard of it until now, how would you know if weils disease was prevalent? I just googled it and it doesn't sound pleasant!
You don't! Also bear in mind that Weils disease can be spread by Rats, Squirrels, Foxes, Badgers and some other mammals as well. Obviously if Rats are present and a problem you are not going to be licking your line.
ohps, at the weir i fish all the time i always lick the knots and keep the boilie stops in my mouth so i dont loose them while im re baiting and there are hundreds of rats there (literally)