What dslr should I get for a tour in Africa?

A model below 2500$ (including lens) would be preferable. I've been doing a lot of research, but I'm having huge issues making a decision, as I've never gone dSLR shopping before. I want to be able to manipulate variables of the shot quickly and precisely, so a compact is undesirable. I need something that can withstand very extreme atmospheric conditions (extreme heat/humidity/heavy rains/etc), and it's probable that the camera will get wet... Though that can be avoided if necessary. This is going to be used to take photos for Zambart, an organisation that does research on aids, tuberculosis, and other diseases in Africa (Zambia). I would greatly appreciate a good opinion :)