A new study in Panama raises concerns over the strategy of releasing genetically modified (GM) mosquitoes to control diseases.

The study, published in PLoS Neglected Tropical Diseases, maps the expansion of the invasive Asian tiger mosquito, Aedes albopictus, which carries many viral pathogens including Dengue, Yellow Fever and Chikungunya and is also implicated in the transmission of LaCrosse encephalitis virus to humans in the US. Chikungunya virus is native to tropical regions of Africa but is now considered an emerging global pathogen since its detection in non-native regions in 2006. Dengue fever is increasingly common, with global rates rising 30-fold between 1960 and 2010.

Current strategies in dealing with the spread of these diseases focus on another species of mosquito, the Yellow Fever mosquito, Aedes aegypti which has been in the Americas since the 1500s and considered the most common carrier of Dengue as well as Chikungunya and Yellow fever. The study highlights the limitations of strategies such as GM mosquito releases to eradicate disease through failure to deal with other species of mosquito. GM mosquito releases are hence predicted to be ineffective, costly and certainly not free of biosafety risks.

Government data used to map spread of disease-carrying Asian tiger mosquito

Researchers led by Dr Loaiza at the Smithsonian Tropical Research Institute, Panama aimed to understand the causes for the expansion of the Tiger Mosquito in the country. The species is native to South East Asian. It was first detected in Panama in 2002, but had been in other parts of the Americas since the 1980s. It had also spread to Europe in the 1970s and Africa in the 1990s.

Mapping the expansion of its range, the researchers used models to see which factors promoted the spread of the Asian tiger mosquito in Panama. By looking at models of road networks, population density, climate, as well as all these factors combined, they found that road networks most accurately correlated with Asian tiger mosquito expansion, while climactic factors correlated most poorly. This may be due to the fact that the whole country has the right climate for the mosquito to survive and flourish. As shown in figure 1, since 2002, the Asian tiger mosquito has spread from the eastern neighbourhood of Panama City to the Caribbean coast and western parts of the country by 2013. Their modelling data suggests that controlling the transportation of larval and adult mosquitoes need to be priority if the spread of the species is to be controlled.