Mosquito net. View of people sleeping outdoors under a mosquito net during very hot weather. The net may be impregnated with insecticide to increase the amount of protection. Physical barriers are becoming increasingly important in preventing malaria as the malarial parasite becomes resistant to traditional anti-malarial drugs. Malaria is caused by a parasitic protozoan carried in the saliva of blood-sucking Anopheles mosquitoes. The disease can be fatal. The net also protects against sand-flies, whose bite spreads the disease leishmaniasis. Photographed in Iran.