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Study: Lower Income Neighborhoods have Bigger Mosquitoes That May Be More Efficient At Transmitting Diseases

October 17, 2019 / 1:46 PM EDT / CBS Detroit

(CNN) -- As if life wasn't already challenging enough for residents in low-income urban neighborhoods, new research suggests such communities are more at risk from particularly harmful, aggressive mosquitoes.

Not only are there more mosquitos in such areas, but they may also be larger-bodied and more efficient at transmitting diseases, according to a study published by the Cary Institute of Ecosystem Studies.

Scientists at the Cary Institute have been researching how environmental and social conditions affected mosquito numbers as part of a study on the ecosystem of Baltimore.

The team focused on tiger mosquitoes (Aedes albopictus), as they dominate urban areas and are an "aggressive day-biter that targets people and can transmit an array of viruses."

"Invasive species like the tiger mosquito increasingly thrive in temperate urban areas, living among us and fundamentally altering the risk of local disease emergence," senior study author and Cary Institute disease ecologist Shannon LaDeau says.

Capturing mosquitoes

The researchers used carbon dioxide and a mammal derived attractant to capture the mosquitoes.

"Female mosquitoes require a blood meal to reproduce and they use respired CO2 and other pheromone markers to detect their prey," LaDeau told CNN.

In order to capture the mosquitoes, the researchers placed traps at ground level where mosquitoes that bite mammals are most likely to be found.

They used dry ice to generate CO2 and had a lure that releases substances that are commonly found on human skin -- ammonia, lactic acid and caproic acid -- to mimic the presence of a human.

Using this approach, the researchers were able to capture 1,097 mosquitoes over three years spread across 13 residential blocks in five Baltimore neighborhoods.

Clear findings

Wing length has been shown to be an accurate proxy for body size in mosquitoes in previous studies, according to LaDeau.

Using that as a marker, the researchers measured the wing length of tiger mosquitoes trapped across a continuum of neighborhoods in Baltimore.

What the researchers found was clear: the mosquitoes that were trapped in low-income neighborhoods were larger than those from more affluent areas.

The difference in wing length can affect traits such as the ability to reproduce and longevity. More importantly, a mosquito's body size can influence traits that are important to disease transmission, according to the researchers.

Mosquitoes can thrive in less managed areas with abandoned infrastructures. With less maintenance and more garbage left out, mosquitoes have more areas to breed. For instance, mosquitoes are able to breed in the water filling a bottle cap or a crushed can.

However, exactly why the mosquitoes are larger in lower income neighborhoods requires more research.

Next steps

"There is so much we don't yet understand about how ecological and social structures interact to influence ecosystem function or human disease risk in this case," said LaDeau. "And what we don't know is then magnified by ongoing changes in climate."

Responsible garbage management and improved maintenance in lower income neighborhoods may play a pivotal role in helping to curb the population of tiger mosquitoes.

Tiger mosquitoesare already established across much of the southeastern United States and they are continually moving northward, LaDeau says.

As the eggs are able to persist even when dry for months, rubber tires are seen as the favorite habitat for the species in moving them long distances. Managing the persistence of eggs in tires and motivating responsible garbage management are important steps moving forward, according to LaDeau.

"There are environmental justice and equity implications at play," LaDeau said. "Residents of less affluent neighborhoods are exposed to more mosquitoes. If those mosquitoes have greater longevity or fitness, as previous studies on body size suggest, then residents may be at a greater risk of contracting mosquito-borne illnesses. There's a pressing need to address infrastructure abandonment and waste management to protect all residents."