And if so, are there any other examples of 'biological warfare' in the distant past/ what is the earliest examples? (apart from the whole 'catapult animal carcasses into fortresses' thing, unless that's not true either).
Yes, see this thread:
http://www.reddit.com/r/AskHistorians/comments/1xqab9/did_europeans_intentionally_spread_diseases_to/