Hi,
Last year I went to Namibia in November. On our first walk in the bush we encountered a black mamba (around 2 meters in length) after 20 min.....
I saw one more - and a "Boomslang" (not really sure how it's spelled, but a very green and quite poisinous snake).
I have been travelling Africa (non-hunting) for nearly 25 years, and seen a few poisonous snakes in my time, but in general you almost have to step on them barefooted (or brush them of the branches) to be in any kind of danger. They are very reluctant to spent their poison for "show" - so in 99.9% of the cases they will only bite if in danger or hunting. And it would have to be some snake (or a tiny hunter) to fall into the last category.....
Wear boots, watch out for "critters" in trees and bushes - and if you happen to see one: Stand perfectly still!
They will not attack anything that does not move.
I my experience you should focus more on the red wasps. I don't know them by any other name. They are BIG and their sting hurts A LOT (trust me, I know). They nest in the bushes and will attack if disturbed (so basically if the PH in front of you brushes the bush) - and they always go for the top of your head, or neck. So it goes like this:
First guy touch bush. Wasp comes out of nest. Wasp is very annoyed. Wasp attacks the next guy in line.
Hard to do much about, other than to keep an open eye - or if it's a 2:1 hunt, make sure that your buddy walks behind the PH - that'll keep you in the clear
Happy hunting. Namibia is a GREAT country for hunting