Mosquitoes

Through her blood sucking, the female mosquito carries diseases like malaria and yellow fever to human beings. While it has been wiped out in some parts of the world, malaria is a disease that is still contracted in many places of the world. The illness is characterized by periodic fever and chills in the victim. Malaria is caused by a protozoa that was first identified by English physician Ronald Ross (1857-1932) in 1898. Not all mosquitoes carry the protozoa that causes malaria, but those that do deposit a parasite in the bloodstream that is capable of destroying the person. There are effective drug treatments and preventions for malaria today, but those who have had the disease are susceptible to relapses. The main vector of the malarial parasite are species of Anopheles mosquito. Open control measures for the disease include spraying against adult flies and treating water sources where the larvae develop.

Yellow fever is another mosquito-borne disease, which causes jaundice in the victim. The mosquito that carries the yellow fever virus to humans during its blood meal is Aedes aegypti. Jaundice causes a person to appear yellow in color, hence the name. While there is no exact treatment for yellow fever, most people recover and have an immunity to the disease for the rest of their lives. Immunization against the disease is available through vaccination, but the most effective method used to prevent yellow fever is through measures to control mosquito populations that transmit the disease to humans.

A great deal of resources have been dedicated to mosquito research. Because they are such a nuisance to people, and because they transmit so much disease globally, billions of dollars are spent in finding ways to control their numbers. One area of research has been in finding the genetic basis of insecticide resistance. In the past, pesticides like DDT were very effective against mosquitoes and helped reduce the incidence of disease and death in malaria-stricken areas of the world. Mosquito populations, however, developed resistance to insecticides relatively rapidly so that now, many insecticides are ineffective and the toxic effects to the environment and to humans directly outweigh their use in killing mosquitoes. Research is underway at many institutions to identify the genes within mosquitoes that allow them to develop resistance to chemical insecticides. Once identified, scientists hope to create transgenic, or genetically engineered, mosquitoes that will no longer carry the resistance genes. The new susceptible mosquitoes would then be bred in mass numbers and released into the wild to breed with existing mosquitoes, breeding-out the ability to adapt to pesticides in the process.

Similarly, geneticists hope to use mosquitoes as vectors to breed out the ability to transmit malaria. By creating transgenic mosquitoes that lack the ability to act as a host to the parasite causing malaria in humans, scientists hope to breed-out, or replace, natural populations with new mosquitoes that do not transmit malaria. Genes conferring resistance to malarial infection have already been identified in malaria transmitting species of mosquitoes. Research is now underway to splice the genes into developing mosquito eggs in order to create the new malaraia-resistant transgenic mosquitoes to be released into the wild.