Even though some places are mosquito free , due to the lack of water, most are not. Like in all coastal regions in Madagascar, there is malaria, especially during the 'rainy' season. So, even for a short stay, think about preventing it with tablets, such as savarine or others (ask your favorite physician); the best prevention being not getting stung, wear light coloured clothing, on the evening long pants and long sleeved shirts, and don't forget mosquito repellents and mosquito nets.
Be careful about "tourista" ! Our malagasy bacterias are not meaner than yours, they're simply different. One have to get used to them. A clean way of life for sure will help, but get the proper medecines (most of them available in Madagascar) can save some of your precious days here.
There is no bank in Mangily, no cashbox. Quite a few places would accept your credit card, and you'll exchange currencies in hotels at a very poor rate. Think of money in Toliara !
Aids is a reality here like it is anywhere else. Don't take any chance, don't endanger anyone!
Condoms, ladies and gentlemen !
We don't have to tell you what you have to do. Everyone will react his own way not only to the poverty of the inhabitants, but to their extreme kindness. Just our advice : before giving anything or getting mad or doing anything, take enough time to look around and closer and try to understand...