Falciparum malaria isn't just in the Gambia. There are cases in the Indian subcontinent, particularly in the north, and all over the Far East. In fact, throughout the Tropics. And the falciparum form of the disease is only one of four different types of malaria that infest these countries. A stands for awareness of the risk.
B is for avoiding Being Bitten.
Malaria is spread by mosquitoes. As you enter it, use a fly spray to kill any mosquitoes that have entered it during the day. Always use mosquito nets around the bed that have been sprayed with permethrin. Use an electric mat to vaporise anti-mosquito repellents overnight. Wear long sleeves and long trousers outdoors at and after dusk.