Global Warming could Limit Dengue Fever Spread


“Dengue fever, a potentially lethal disease for which no treatment exists, is caused by a virus, spread by the bite of the mosquito Aedes aegypti. This mosquito is also responsible for transmitting a number of disease-causing viruses, including Zika, chikungunya and yellow fever,” stated Elizabeth McGraw, professor and head of the Department of Biology, Penn State. “Aided by increasing urbanization and climate change, this mosquito’s range is expected to overlap with 50% of the world’s population by 2050, dramatically increasing the number of people who could potentially be exposed to these viruses.”

‘At higher temperatures, while the dengue virus may replicate faster, the study suggests that a corresponding reduction in mosquito thermal tolerance may act as a counterforce on mosquito survival that could help to reduce transmission and potentially human disease incidence in hotter, more climate-variable regions.’

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In current years, analysis teams world wide have tried to regulate these viruses by infecting Ae. aegypti with the bacterium Wolbachia pipientis after which releasing the mosquitoes into the atmosphere, McGraw defined.

“Wolbachia have been shown to prevent viruses, including dengue, from replicating inside mosquitoes,” she stated. “Importantly, Wolbachia are passed down to the mosquitoes’ offspring, making them a self-propagating and lower-maintenance approach to disease control in the field.”

McGraw famous that each dengue virus and Wolbachia infect quite a lot of tissues all through a mosquito’s physique, and though they don’t seem to be poisonous, they do evoke an immune stress response.

“Since mosquitoes that are infected with dengue virus and/or Wolbachia are already suffering a stress response, we thought that they would be less well equipped to deal with an additional stressor, such as heat,” she stated.

To examine the results of warmth on dengue and Wolbachia-infected mosquitoes, the crew positioned contaminated mosquitoes in sealed vials after which submerged the vials right into a water tub heated to 42°C — a sensible temperature excessive {that a} mosquito would possibly encounter within the wild. The researchers then measured how lengthy it took for the mosquitoes to develop into immobilized and in contrast the time to uninfected management mosquitoes. Their findings seem at this time (July 22) within the journal PLOS Neglected Tropical Diseases.

“After a lot of trial and error, we were successfully able to adapt a heat-based physiological assay commonly used in Drosophila [a model fruit fly species] to our mosquito species to examine the impact of both dengue virus and Wolbachia infections on thermal sensitivity,” stated Fhallon Ware-Gilmore, graduate scholar within the Department of Entomology and Center for infectious Disease Dynamics at Penn State who led the undertaking.

The crew discovered that mosquitoes contaminated with dengue virus confirmed better sensitivity to warmth; they turned immobilized nearly 3 times quicker than uninfected mosquitoes when positioned within the sizzling water tub. Similarly, mosquitoes contaminated with Wolbachia turned immobilized 4 instances quicker than uninfected mosquitoes.

Interestingly, Ware-Gilmore stated, the 2 brokers — dengue virus and Wolbachia micro organism — didn’t have an additive impact on mosquito thermal tolerance.

“You might expect that mosquitoes infected with both dengue virus and Wolbachia might become immobilized even faster than mosquitoes infected with only one or the other microbe, but we did not find an additive effect,” she stated. “We are, however, the first to show that viral infection can affect mosquito thermal tolerance, specifically by reducing mosquito survival during exposure to high heat. And, while there are some known interactions between heat and Wolbachia, particularly in immature stages, this is also the first study to show that adult infected-mosquitoes have reduced survival during heat stress.”

Ware-Gilmore famous that future local weather fashions level to growing frequencies of utmost temperature occasions, making quick exposures to excessive temperatures a menace to the survival of dengue and Wolbachia contaminated mosquitoes.

Source: Eurekalert

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