In reply to Xharlie:
I've drunk water from just downstream from a dead sheep... it did me no harm but I always look a few metres up now just to avoid the ewww factor.
I often swim in Crazywell pool on Dartmoor which is bound to be less clean than some of the sparkling streams and leats and have never had any ill effects.
Like you I've drunk from Streams in Africa and when we cycle toured in Australia, rivers in the rain forests and stuff out of bore holes that smelled of rotten eggs... no ill effects. You just need to be aware of the environment and make a judgement call.
Since doing a few triathlons I've swum in some horrible water with no terrible upsets so am now rather relaxed about drinking water... no doubt this will bite me in the a**e at some point :-O
Cheers & have a great trip.
Toby