Ian, you're amazing even to WANT to run! I'd have thought malaria was one of the least of the hazards you'd face in Sierra Leone.
Mefloquine has had a lot of bad publicity, but it is still available and most people who take it are absolutely fine (I was going to add "like Ratbag", but somebody would make a smartass comment if I did). About one in a hundred will get psychological toxicity with sleep disturbances and mood changes, and about one in e thousand will get a full-blown psychotic illness. Malorone is probably safer and possibly as effective but doubts have been expressed there. It's certainly a viable alternative.
There's no substitute for not getting bitten in the first place, but that's completely unrealistic for anyone who has to work in an anopheles-infested zone.
Good luck! Hope you feel better soon. I shall add you to my list of "people whose jobs I could never handle".
Cheers, V-rap.