It’s Not Just You, Mosquitoes Are Getting Worse

Summer is coming to an end, but mosquitoes continue to be more than a nuisance.

I knew the mosquitoes in Michigan were bad, but I didn’t realize how bad until I spent a week in the Amazon jungle in Peru. I got more mosquito bites the first few days back in Michigan than the entire week in the middle of the jungle.

Mosquitoes are a global pest. From stinging bites to deadly disease, they’ve been with us since the dinosaurs. It’s difficult to compare “how bad” mosquitoes are in Michigan compared to somewhere like Peru where mosquito-borne diseases like dengue and yellow fever are life-threatening. Still the sheer volume and aggressiveness of the East Lansing mosquitoes was surprising. 

There are mosquito-borne diseases in Michigan. As of Aug. 30, the Michigan Department of Health and Human Services has reported five human cases of West Nile virus and two of Jamestown Canyon virus this year. Both are arboviruses, a group of viruses carried by arthropods, in this case mosquitoes, and transmitted while feeding on blood. There have also been 37 animal arbovirus infections. Most recently, a falcon infected with WNV was found dead in Detroit. 

However, most of the mosquitoes we encounter do not carry infectious disease.

“We have about 70 species of mosquitoes in Michigan,” said Edward “Ned” Walker, a professor of entomology at Michigan State University with expertise in emerging infectious diseases. “For some of them, their abundance is directly related to how much rainfall we get. We’ve had a lot of rain this summer and accordingly we’ve had these broods of mosquitoes.”

“They are mostly pest mosquitoes associated with the group that we call summer floodwater species, and they’re the ones that people notice the most,” he said.

This summer has seen above normal rainfall in Michigan, which can be easily connected to climate change.

“Unfortunately, it’s all kind of connected,” said Amanda Lorenz-Reaves at MSU’s department of entomology. “We’re definitely seeing an increase in temperature, most parts of Michigan have increased by a couple of degrees in terms of average per year. There’s broadly predicted to be more flooding and precipitation as a result of climate change.

“Both have the potential to increase the mosquito population,” she said. “And that’s because mosquitoes, like all other bugs, they’re exothermic. They don’t actively regulate their temperature the way that warm-blooded animals do. Instead, they rely on whatever the ambient temperature is. So the warmer it is, the more active they tend to be.”

This means that warmer weather leads to more active mosquitoes, including more reproduction. 

“Potentially, we could even see additional generations of mosquitoes as a result of temperature increase,” Lorenz-Reaves said. 

Other factors, such as ineffective infrastructure, can worsen the impacts of climate change.

“There’s a lot more to mosquitoes than just rainfall,” said Walker. “Our West Nile virus mosquitoes are really associated with human made environments like street catch basins, abandoned swimming pools, wastewater lagoons and other places that are not associated with rainfall per se.

“In fact, paradoxically, the more rainfall we get, the less West Nile we would anticipate because, at least for our street catch basins, it washes them out,” he said. 

Walker also explained how more rainfall could lead to less WNV since the species carrying it favor hot dry summers. So while the increased rainfall has led to more pest mosquitoes, it doesn’t necessarily mean there’s a greater risk for WNV. 

Climate change also means longer summers.

“That has some pretty major implications, I have to be honest with you,” Walker said. “At our latitude here in Michigan, we would see our first frost maybe mid-September and now we don’t really see it until mid-October.”

This means that transmission can extend into mid-October.

“I suspect that we’ll see more human cases in urban and suburban areas,” Walker said. 

As Michigan warms and summers grow longer, new species of mosquitoes close in.

“I mentioned we have 70 species of mosquitoes in Michigan, but 10 or 15 years ago I would have said 65,” Walker said. “We’ve had several invasions and range expansions so we have new species that are established here now and that’s because of climate change.”

He mentioned one particular species that wasn’t here 15 years ago, but is now common in Michigan and is a notoriously awful biter.

Humans aren’t the only ones at risk.

“Can you imagine being a deer under conditions like we have right now?” Walker said. “It’s got to be absolutely miserable.

“A lot of animals will change their behavior to avoid being bitten,” Walker said. “For example, our most common mosquito borne disease in Michigan is dog heartworm, which is a parasitic nematode carried by mosquito bite from one infected dog to another.”

Coyotes and foxes are also at risk and mosquitoes can transmit the disease from them to domestic dogs.

“Half of all coyotes are infected with dog heartworm,” Walker said.

Birds are also infected with arboviruses.

“It’s the same mosquitoes that carry West Nile virus that also carry bird malaria,” Walker said. “It’s very common in our sparrow and robin populations.”

Domestic birds and birds in zoos are also impacted by the increase in mosquitoes. 

“There are a few penguins at the Potter Park Zoo here in Lansing and the zoo veterinarians have to put them on anti-malarial drugs all summer long because they’re highly susceptible to bird malaria, which they would get by local mosquitoes carrying the malaria from local birds,” Walker said.

What can be done? Prevention and adaptation is key.

MDHHS recommends insect repellents with, “DEET, picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol products.” Long sleeves and pants are also good protection. 

“Wearing lighter colored and looser fitting clothing in the warmer months can help reduce the potential for a bite,” Lorenz-Reaves said. “Turns out, mosquitoes tend to go towards dark colors.”

Lorenz-Reaves and MDHHS also recommend removing any standing water from properties. However, Walker emphasized that this method’s effectiveness is limited when there are so many breeding grounds built into the infrastructure. 

“Human beings have created thousands of little mosquito nurseries all along our streets,” he said. “So if we think the solution to our mosquito problem is to periodically dump out our birdbaths, that’s incorrect.”

When asked what he’d like to see East Lansing do to address the issue, he asked, “how much are you willing to pay?”

“As a citizen now, if you go through a summer like this, let’s say you buy two or three containers of repellant, that’s about how much in tax money you might pay for a mosquito control program in the county.”

According to Walker, there are four county-level and 32 township-level mosquito control programs in Michigan funded by tax millages. There’s clear demand for them too, they are approved by voters at a higher rate than school millages.

“Mosquito control, when done in a modern way, can be accomplished with environmental acceptability and in a highly professional way by very competent people,” Walker said. 

There’s a misconception that mosquito control programs are just big trucks spraying pesticides, but Walker explained that these programs mostly address the larval stages using less harsh products and engineering.

“They are very effective,” Walker said. “Even if they are using pesticides, it’s probably much less than the pesticides that would be needed to deal with them once they’re fully grown and already causing problems.”

He said that it’s healthier for people to have a mosquito management program than it is for them to be using large amounts of repellants and pesticides themselves.

“Prevention is the best thing, but that requires public agreement, infrastructure and employees,” he said.