I could see training teams of dogs to hunt them. A pack of trained dogs will go after a bear, they surely could handle a lizard. And if they tree it, boom.
I see a huge tourist potential, hunting big lizards with dogs. I'll bet a good Plot or Walker hound (Keep your "There Ain't no good Walkers" comments to yourself, please) would be just the thing. If the lizards are bad to fight we could breed a little pit bull into the hound.
A pack of dogs can be trained to hunt them, and a pack can do a good job if they trap one away from scrubland and marsh (in those areas a monitor can shimmy away so fast you'd swear it could outrun a rifle slug). Although a full grown Nile Monitor can cause serious hard ....I once watched a Savannah monitor (a similar species to the Nile ....also pretty long but a little smaller than the Nile) fight a lion to a standstill. The lion could have easily killed it, but the lizard was position itself where the lion would have been either bitten or whacked with the tail. I guess the lion decided lizard meat was not worth the momentary pain. (oh, I've also seen a monitor bite. Those lizards have a line of the most vicious razor teeth this side of Aliens! Thin curved sharp teeth ....a mouth of razors. Again, can't kill you, but a 7 footer will give you something to remember).
The thing this thread does is answer my question about the introduction of foreign reptilian fauna to climates that dip in temperature. It says the lizards simply become topor during cold weather ....hibernate! In africa they obviously do not do that. Meaning, other tropical reptile species can do the same.
I've always wondered what would happen if someone purchased several hundred Kraits, Taipans and Mambas and sprinkled them in some grove or swamp. After all, anyone can buy them and the govt doesn't seem to think licenses are required for dangerous exotics!