A new study finds that mosquitoes don't just bite for food; they bite even more aggressively to quench their thirst during drought.
There is a whole host of reasons why mosquitoes bite some people more than others, but it all starts with the she-mosquito’s need for protein to lay her eggs. But now researchers have found what may be an even stronger pull: Their need for a drink during times of drought.
Alas, we may have thought we’re off the hook after the rainy season is over. But no, according to the biologists from the University of Cincinnati who made the discovery by accident – dry conditions provide little protection from the disease-delivering pests. They are now hoping to find out just how often mosquitoes need to bite to maintain hydration, which could help doctors fight illnesses such as malaria.
"It makes sense," UC biology student and study co-author Elise Didion says. "We find the highest transmission rates of West Nile virus during droughts because mosquitoes may use blood meals to replace the water they lose."
As the deadliest animal on the planet (they kill more humans than even humans do), every bit of information about these tiny killers is valuable in the fight against mosquito-borne illness. With malaria alone killing more than 400,000 people every year – and with yellow fever, dengue, encephalitis, West Nile, Eastern equine encephalitis and zika added to the mix – the more we can understand their physiology and behavior, the better.
"It will make for better modeling for when disease outbreaks occur," UC biology professor Joshua Benoit says. "When it's dry, it might be easier for a mosquito to locate a host than limited supplies of water or nectar."
The discovery was a bit of a surprise, the researchers say, which came about when they were studying mosquitoes in dehydrated conditions. When some escaped, they noticed that they were “unusually aggressive.” Didion says, "they were all trying to bite."
Benoit says that when mosquitoes have adequate hydration, they bite much less frequently.
"Normally only 5 or 10 percent of female mosquitoes will feed at any time, depending on the species," he says. "Dehydration has a big impact on whether they feed normally or not."
In doing their research, they found that dehydration inspired as many as 30 percent of female mosquitoes to seek a blood meal. The results shine light on why some researchers have found that disease infection numbers are high between seasons, when water levels recede and the flowers dry up.
And unfortunately, it doesn’t take long for mosquitoes to start acting on their thirst.
"We saw the behavioral effects within two or three hours under low humidities and higher temperatures," Benoit says. "It was completely changing their behavior."
It really feels like this throws a monkey wrench into our best-laid plans for mosquito control, as if the little imps are gaming us. Give them water and they lay their eggs in it; take it away and they come directly for us. And with the longer, more severe droughts that climate change promises to deliver? Thirstier mosquitoes hell-bent on getting a nice warm drink. Good times, good times...
The study was published in Scientific Reports.