Australasian Science: Australia's authority on science since 1938

Resistance Turned Against Mozzie Diseases

By Stephen Luntz

Insecticide resistance has allowed diseases like malaria and dengue to kill millions, but its introduction could prove the key to their defeat according to Prof Ary Hoffman of the University of Melbourne’s Department of Genetics.

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The Wolbachia bacterium infects many insects and other arthropods. It is symbiotic with some species, but Hoffmann has demonstrated that certain Wolbachia strains shorten mosquito lifespans (AS, August 2005, p.9). Infectious diseases require time to develop within mosquitos to become transmissible, so only older mosquitos spread disease. As Wolbachia only affects older members of the population it is unlikely that resistance to it will develop.

Hoffmann says that once Wolbachia becomes established in a mosquito population it tends to be maintained. “Wolbachia causes cytoplasmic incompatibility, where when an infected male mates with an uninfected female 100% of the embryos die,” he says.

Infected females pass the bacterium to their offspring irrespective of the father’s infection status. Once a threshold has been reached, the chances of uninfected males and females mating is low enough that the infected population maintains its dominance.

The challenge is to make Wolbachia the norm. One path lies with the wMelPop strain, which isn’t particularly effective at killing the older mosquitos and even seems to offer some advantage, allowing its rapid spread. However, it also blocks the transmission of dengue and other viruses, although malaria-carrying mosquito species have proven harder to infect.

In a study published in Proceedings of the Royal...

The full text of this article can be purchased from Informit.