Mosquitoes can endure extended dry spells by consuming blood, shedding light on why the frequency of illnesses transmitted by mosquitoes doesn’t necessarily drop during dry spells.
Researchers at the University of Cincinnati indicate that mosquitoes can survive extended droughts by feeding on blood, which explains their rapid population growth once it finally rains.
Christopher Holmes, a postdoctoral researcher at UC, led a study that explored how two types of mosquitoes, notorious for spreading diseases like malaria, managed to survive for nearly three weeks without rainfall.
The results of the study may clarify why reported cases of mosquito-borne diseases don’t consistently decrease during droughts. Even though the number of mosquitoes may be lower, those that do survive tend to bite humans more frequently.
“We are discovering that mosquitoes are biting people more than we previously thought, unfortunately,” stated Holmes.
Holmes noted that mosquitoes seem to be thriving with climate change as winters become milder.
The research appeared in the journal iScience.
According to Holmes, under optimal conditions, female mosquitoes extract blood from a host to produce eggs. Around four days later, they lay their eggs and search for another blood meal to repeat the cycle.
However, during droughts, mosquitoes may augment their initial blood meal by feeding repeatedly to maintain hydration before laying eggs. This behavior could increase their chances of transmitting diseases like dengue, Zika, or malaria, he explained.
“Many assume that drought leads to fewer mosquitoes, resulting in less chance of spreading mosquito-borne diseases. But the models suggest otherwise,” co-author and UC Professor Joshua Benoit remarked.
The research looked at genetically modified mosquitoes to impair specific senses, such as their ability to detect carbon dioxide—an essential factor in locating hosts to bite. Some mosquitoes also had altered abilities to sense humidity changes.
Findings revealed that mosquitoes with impaired carbon dioxide detection didn’t survive dry spells because they struggled to find hosts to bite.
Co-author and UC doctoral student Souvik Chakraborty noted that even mosquito eggs possess remarkable drought-resistant capabilities.
“The Aedes aegypti mosquito can withstand drying out, with its eggs sometimes surviving for up to a year,” he stated. “When rain falls and the water level rises, the eggs hatch almost magically.”
Additionally, UC postdoctoral researcher and co-author Oluwaseun Ajayi pointed out that mosquitoes from the Culex genus, found worldwide, can also endure cold temperatures.
“These are often referred to as house mosquitoes,” Holmes added. “They tend to hide in basements or drainage systems. Before winter, they feed on nectar to gain weight and accumulate fat. Once temperatures rise, they quickly seek out a blood meal, lay eggs, and then die.”
Holmes, the lead researcher, expressed that the team’s recent discoveries have deepened his appreciation for the unexpectedly lengthy existence of mosquitoes on our planet. The oldest mosquito fossils date back to the early Cretaceous period, approximately 125 million years ago. Mosquitoes are vital components of the food web, supporting species from fish and birds to bats and other insects.
Currently, the diseases they transmit result in over 700,000 fatalities globally every year.
Benoit emphasized that the study reveals the remarkable resilience of these insects, which existed long before dinosaurs.
“They inhabit nearly every part of the world except for Antarctica, and they thrive in a broad range of environments,” he said. “Understanding their biology is essential to grasp how they survive and reproduce.”
