It is very rare that scientists openly discuss how to wipe out an entire species, but recently, researchers in Mexico are seeing this as a means to stop the spread of dengue fever. Currently a major contagious endemic in more than 11 countries spread across three continents, it is contracted from the bite of a specific species of mosquito known as A. aegypti. The solution, researchers suggest, is to create genetically modified mosquitoes that sexually transmit a gene inhibiting the development of flight muscles in mosquito offspring. This only affects the female carrier who, after emerging from the pupal stage, cannot fly and reproduce. The males, meanwhile, are unaffected and continue passing on the gene. Eventually a population drop will occur as the lack of females will render reproduction impossible. Tests in isolated environments have given the desired results so far, with an overall decrease of about 80% in the wild mosquito population.
To create these genetically modified mosquitoes, engineered DNA is inserted into fertilised mosquito eggs. A mixture of the antidote is introduced as well so that the carriers can crossbreed to produce a large number of eggs contaminated with the artificial DNA. The genetically modified males then mate with wild mosquitoes in the ecosystem, thereby passing on the gene. The release of a toxin in the female progeny that halts the development of flight muscles is triggered when they have developed from larvae to full adults.
From the start of the 20th century, the alarming spread of the dengue virus has been the subject of growing concern in many countries. It affects about 100 million people annually with symptoms including headaches, joint and muscle pains, and in serious cases dangerously low levels of blood platelets and low blood pressure. No vaccine for the disease exists as of yet due to the virus? ambiguous nature. It comes in four different types, where contacting one form and subsequently catching another gives rise to medical complications. The World Health Organisation has meanwhile encouraged communities to take preventive measures such as reducing open collections of water where mosquitoes lay their eggs, wearing clothing that fully covers the skin and even using pesticides such as DEET to reduce mosquito numbers. These efforts, however, have thus far failed to significantly affect the spread of the disease.
Experiments have up until now yielded promising results in isolated systems but there is still the question of how they will work in an open ecosystem. Some people question the ethical issues of eliminating an entire species while others argue that this will cause an imbalance in the food chain, producing unintended consequences for other species. Whatever the argument, it is clear that there is a growing need to address the problem of the spreading dengue fever.