Mosquito. Close-up of a mosquito on human skin. Its body is engorged with blood that it has sucked from its human host. Mosquitoes transmit diseases such as malaria, viral encephalitis, yellow fever, filariasis and dengue. Malaria is a major health problem in Africa, Asia, India & South America. Malaria causes a severe fever & can lead to complications affecting the liver, brain & blood that can be fatal. Preventative measures against mosquitoes are important, as the malaria parasites are developing resistance to anti-malarial drugs. Measures include using mosquito nets, protective clothing, insecticides & releasing sterile males.