Mosquitoes carrying dengue fever annually cause more than 50 million infections worldwide and at least 12,000 deaths. Striking at the bloodsuckers directly, Brian Kay of the Royal Brisbane Hospital in Australia and Vu Sinh Nam of the Ministry of Health in Hanoi sicced the crustacean Mesocyclops on the larvae of the mosquito Aedes aegypti. From 1998 to 2003 the tiny predator was spread in water tanks, and villages cleared away discarded containers likely to collect water. The result, presented in the February 12 Lancet, was the elimination of the mosquito in 32 Vietnamese communes and drastic reduction in five others. No dengue was reported in any of the 37 communes after 2002, meaning that some 380,000 people were protected. (The annual incidence rate before the program began ranged up to 146 cases per 100,000.) This solution might not prove effective everywhere, given the dislike many people have for visible organisms in the drinking water.
This article was originally published with the title "Crustaceans against Dengue Fever" in Scientific American 292, 4, 34 (April 2005)