As clouds gather and humidity rises across west Africa, whose annual rains bring an uptick of deadly, malaria-carrying mosquitoes, Musa Adamu Ibrahim, a nurse, is sitting at home, unemployed.As downpours progressively cascade across west Africa -- Nigeria's have just started, while Senegal's rains won't arrive until May -- countries that have made in some cases significant progress in stamping out malaria in recent decades will now be doing so without a major financial backer.