To do his work, entomologist Jiayue Yan puts his hands into thick rubber gloves and protective gear. He needs the gloves because he’s facing some of the Earth’s most perilous inhabitants — mosquitoes. Not just any mosquitoes, but those carrying dengue fever, a potentially deadly virus. His battlefield? A meticulously sealed laboratory where these tiny yet formidable foes are immobilized on ice-cold petri dishes, their movements slowed, ready for study. This is the front line in the fight against a global health menace.

Yan handles an army of over 10,000 mosquito larvae and 4,000 female adults. He assigns them to one of four diets to see how this affects their susceptibility to diseases like dengue. In other words, he starves mosquitoes for science.

Hunger, mosquitoes, and disease

It’s a high-stakes research area. Every year, mosquitoes kill 2-3 million people and infect over 200 million. These insects are vectors for a range of life-threatening illnesses including malaria, dengue fever, Zika virus, West Nile virus, and yellow fever. When a mosquito bites an infected host, it can carry the pathogen to the next individual it bites, spreading diseases across communities with alarming speed.

The impact of these diseases is profound. They have high rates of morbidity and mortality, especially in regions lacking the resources for effective control and prevention measures. This makes mosquitoes a significant public health challenge, requiring concerted efforts to mitigate their deadly impact.

Previous research has shown that mosquitoes’ ability to transmit diseases is closely tied to their nutritional status. However, previous studies also returned conflicting findings. So, Yan wants to get to the bottom of things.

Half of his larvae are starved, as are half of the adults (all females). In addition, these groups are further split into two: one part is infected with Dengue, the other is not. Those without Dengue are used as controls for the findings.

It’s a laborious and time-consuming process.

For one research batch, the researcher picked up 800 females by hand, transferring them into a cup in the sealed box. He handles them with fine-tipped forceps, and takes care not to damage or affect them in any way. For all mosquitoes, he has to write down how long they lived, how many eggs they laid, and how susceptible to dengue they are.

Starved mosquitoes are more infectious

When mosquitoes are starved, they tend to live shorter lives and produce fewer eggs. That is not unsurprising. But Yan found something else: when mosquitoes are starved, they also become more susceptible to dengue virus infection.

Mosquitoes also don’t want to be infected. Their immune system fights the infection to the best of its ability. Sometimes, the immune system wins. But when the mosquito is starved, the immune system is far less likely to win. Essentially, nutritional stress dampens the immune system’s response in mosquitoes. This weakened immune defense increases the mosquitoes’ vulnerability to the dengue virus, hindering their ability to fend off infection effectively.

This is very important for measures that aim to reduce mosquito-related disease. It underscores a complex balance: while undernourished mosquitoes are less likely to survive and reproduce, those that do manage to persist may carry and transmit the dengue virus more effectively due to their compromised immunity. This dual impact of nutritional stress highlights the need for targeted interventions that consider the nuanced ways in which diet affects mosquito populations and disease transmission dynamics.

“Understanding the intricate dance between what mosquitoes consume and their disease-spreading potential is important to human health. We now know that a mosquito weakened by a poor diet is a more effective transmitter of diseases like dengue. Our new understanding could help us find new ways to manage mosquito populations and curb disease transmission,” the researcher notes.

For now, this research has focused on dengue fever only, not on other diseases like malaria. But it is plausible that something similar happens for all mosquito-borne infections. If we want to truly combat the spread of these deadly diseases, we have to consider all the relevant factors and see how we can use them to our advantage.

The fight against mosquito-borne diseases is a complex puzzle involving biology, environment, and human behavior. As Jiayue Yan continues his work, the battle against mosquitoes and the diseases they carry is far from over — but with continued research and cooperation, we stand a chance to turn the tide in humanity’s favor.

The study was published in Communications Biology.