Environmental change, urbanization and human movement are helping mosquitos spread

 

By 2050, half the world’s population could be at risk of mosquito-borne diseases like dengue fever or the Zika virus, new research suggests.

Climate change may put even more people at risk further into the future.

 

A combination of environmental change, urbanization and human movements around the world are helping mosquitoes spread into new areas, according to the findings, reported Monday in the journal Nature Microbiology.

 

“We find evidence that if no action is taken to reduce the current rate at which the climate is warming, pockets of habitat will open up across many urban areas with vast amounts of individuals susceptible to infection,” said lead study author Moritz Kraemer, with the Boston Children’s Hospital and University of Oxford, in a statement.

 

The research focuses on the mosquito species Aedes aegypti and Aedes albopictus, both known for their ability to carry and transmit disease.

These maps show the predicted global ranges of Aedes aegypti (above) and Aedes albopictus (below) in 2050 assuming a “medium” climate scenario in which greenhouse gas emissions peak in 2080 and then begin to decline. The darker areas have the highest predicted prevalence of mosquitoes. Credit: Moritz Kraemer for Nature Microbiology

The new study analyzed mosquito tracking data from the United States and Europe, incorporating a variety of factors into a model to predict the species’ spread over the coming decades. The researchers ran the simulations under three different potential climate scenarios, assuming moderate, high and severe levels of future climate change.

 

Currently, data suggest that Aedes aegypti is spreading across the United States — mainly up from the Southern states — at a rate of about 37 miles per year, although it has spread at faster rates in the past. On the other hand, Aedes albopictus seems to be spreading at ever faster rates across Europe, currently at a rate of about 93 miles per year.

 

The research suggests that both species will continue to spread throughout the world in the coming decades, although the factors driving them may change as time passes.

 

In the short term, the study finds that environmental changes are not likely to make much difference in the spread rate, as the mosquitoes naturally expand throughout their current ranges. In other words, even under current climate conditions, both species are expected to keep moving into new areas.

 

In the long term, however, climate change and other factors like rising population density and urbanization are expected to become major influences on the number of people exposed to mosquito-borne diseases. Between 2030 and 2050, climate change — which may make previously unsuitable areas habitable for the mosquitoes through the combined influence of rising temperatures and wetter conditions — is likely to become a primary driver. The more severe the future climate change scenario, the greater the population at risk.

 

Overall, the research finds that at least 49 percent of the global population is likely to be at risk of mosquito-borne disease by 2050. And this percentage will continue to grow, even under moderate climate scenarios.

 

As a result, the researchers note that “reducing emissions of greenhouse gases would be desirable to limit the increase in suitable habitats for Ae. aegypti and Ae. albopictus.”

 

They also add that the findings are likely to be on the conservative side. The study relies mainly on data from the United States and Europe, which have some of the strongest mosquito tracking and surveillance systems in place, to draw conclusions about the factors that affect mosquito movements worldwide.

 

However, these tracking systems may also make it easier for these nations to tackle mosquito infestations and slow their spread. In other places around the world, mosquitoes may be able to move into new areas at faster rates than those predicted by the study’s models.

 

In general, the spread of mosquitoes and other disease-carrying insects is a rising concern as the threat of climate change continues to grow. Just last year, a study from the Centers for Disease Control and Prevention found that cases of diseases caused by mosquitoes, fleas and ticks in the United States had tripled within the last 15 years alone (Climatewire, May 2, 2018).

 

While the study didn’t delve into the exact causes behind the uptick, experts suggested climate change was a likely contributor.

 

Credits: James Gathany CDC, Scientific American, E&ENews