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SYFY WIRE entomology

Malaria pathogens help mosquitoes smell fresh blood and feel younger

Mosquitoes and malaria are in a symbiotic relationship; malaria pathogens give them an edge in smelling prey.

By Elizabeth Rayne
Liz Mosquito Biting Skin

Mosquitoes and the malaria pathogen infamous for infecting them (and the humans they feed off of) have been found to be almost inseparable.

Malaria has been the bane of humanity for ages, but it gets worse. The pathogen gives mosquitoes heightened olfactory function that improves their ability to find hosts (like you) through the smell of blood. Malaria is also apparently the fountain of youth for mosquitoes, letting them hold on to younger characteristics for longer, including a stronger immune system, physical fitness, and reproductive ability. As if we need these things breeding en masse.

Biologist Laurence Zwiebel of Vanderbilt University has had it with these pests just like everyone else on the planet. He and his research team, who recently published a study in Scientific Reports, were itching to find out why mosquitos and malaria go together so symbiotically. By recreating the hot, humid conditions they are used to, he found out about the twisted love affair between one of the most irritating bugs of all time and one of the deadliest diseases.

“We want to examine the broad mechanisms by which malaria infection impacts the mosquito’s olfactory system by using natural levels of infection and then molecular approaches to examine the gene regulatory pathways that we believe drive the response,” Zwiebel told SYFY WIRE.

Unlike the viruses often associated with mosquitoes, from Dengue to West Nile to Zika, malaria is a protozoan pathogen that is technically a parasite. Sub-Saharan Africa and Southeast Asia are especially infested by mosquitoes that carry this microscopic beast. About 1-3 million deaths are caused by malaria every year, and most victims are tragically African children 5 years old or younger.

To replicate natural conditions for the mosquitoes they studied, Zwiebel and his team needed to make sure that only a few of the parasites latched on to each mosquito. Getting only a few micro-monsters onto each insect meant diluting the pathogens until their concentrations were low enough to replicate the low-intensity infections which usually happen. Most of the mosquitoes didn't even get infected, which meant the team had to painstakingly pick them out and get rid of them, something that has not been done in most other studies because it was seen as needing too much unnecessary effort –– but  the infection rates in those studies were inaccurate. Zwiebel needed to see exactly what was abuzz with the creatures.

“In contrast to their uninfected middle aged siblings, since mosquitoes have to age a bit before they can transmit malaria, infected mosquitoes that are ready to transmit malaria seem to retain their focus on reproduction, host seeking, and other ‘youthful’ activities,” he said.

Not that we actually want even more of them self-replicating and spreading malaria, which is what makes this study such a breakthrough. Seeing this behavior is the reason Zwiebel plans to get a closer look. He wants to observe infected mosquitoes on a molecular level, to see what kind of reprogramming happens to create this almost eternal youth, at least for a creature that lives only an average of 10 days. He thinks that's due to changes in hormones and neuropeptides, certain chemical signals in the brain. Neurons synthesize and then release these signals.

At least one assumption about mosquitoes and malaria has now been disproved. Malaria is not pathogenic towards mosquitoes; the insect and the microbe have a symbiotic relationship that benefits both of them. New strategies for mosquito control and malaria prevention no longer have to look at malaria as something the skeeters need to fight off. It is the high frequency of mosquito bites that ends up in so many people being infected with malaria, and most bug sprays can’t get enough of them to buzz off.

“We believe our work will help researchers better understand the relationship between the mosquito vector and human pathogen,” Zwiebel said. “We are working on a next-gen mosquito repellent that will further reduce close encounters between infected mosquitoes and humans.”