world health day 2014 put the spotlight on some of the most commonly known vectors – such as mosquitoes, sandflies, bugs, ticks and snails – responsible for transmitting a wide range of parasites and pathogens that can cause many different illnesses. mosquitoes, for example, transmit malaria – the most deadly vector-borne disease, causing an estimated 660 000 deaths annually worldwide – as well as dengue fever, lymphatic filariasis, chikungunya, japanese encephalitis and yellow fever. more than half of the world’s population is at risk of these diseases.