Mosquito egg rafts float among leaves in an apartment complex pool.
Institute of the Environment 2017

BRACE Yourself for Changing Mosquito Seasons

Tuesday, June 28, 2016

by Paulina Jenney, Institute of the Environment

The buzz around standing water in Arizona backyards could be hazardous to your health, and climate researchers at the University of Arizona are out to help state residents prepare for the threat.

Backed by a nationwide initiative from the Centers for Disease Control and Prevention, a team of scientists is out to quantify the health effects associated with climate change. Their project, Building Resilience Against Climate Effects, or BRACE, is creating a map that will help the public, health care professionals, and government agencies pinpoint locations around the state that are at high risk for disease in the face of rising temperatures.

“The goal of BRACE is building resilience,” said Heidi Brown, a nationally sought expert on vector-borne diseases who is leading the team. “So a big part of the project is translating the charts and projections into something the public can use. If we think it’s going to be a bad mosquito year, we want to get the message out so that people start thinking about disease prevention in time.”

West Nile Virus.

West Nile Virus. Credit: Wikicommons

Brown, an assistant professor in the UA’s Mel and Enid Zuckerman College of Public Health, is looking specifically at West Nile virus, a mosquito-borne illness that infected 640 people in the state between 2010 and 2015, according to the Arizona Department of Health Services. Though usually mild, West Nile can cause headaches, vomiting, and fatigue, especially in people with weakened immune systems and the elderly.

By paying particular attention to demographics that indicate a higher risk of contracting the disease, like age and socioeconomic status, and proximity to stagnant water—common mosquito breeding grounds—BRACE aims to protect Arizonans who might need extra help fending off the swarms this summer.

“We have people with certain social vulnerabilities, people who don’t have access to things like health care or air conditioning,” Brown said. “And then, because of standing water in a backyard next door, here’s an added vulnerability to West Nile. BRACE provides a way to think about areas that might be of more concern.”

In addition to studying social vulnerability, the team used a mosquito simulation model to estimate the number of adult mosquitos we might expect to see in five cities around Arizona given current and future climate projections.

“What we found is that, in certain locations during the hot summer, the simulated populations crash before coming back during the monsoon season,” Brown said. In the summer, she explained, the temperature becomes too hot for mosquitoes to survive. “To transmit West Nile virus to humans, a mosquito needs to take a blood meal from an infected bird, survive long enough for it itself to become infected, and then successfully bite a human. So if the whole system is cut in half in the middle of the summer, then the disease might not take hold.”

Culex mosquito lands on a human finger

The Culex mosquito is a prominent vector for disease. Credit: Wikimedia Creative Commons

Whether the mid-summer dip in populations will break the transmission cycle is an ongoing area of research. There is the chance, Brown said, that warmer temperatures in early spring could provide enough time for potentially infectious mosquitoes to proliferate before dying off in the summer. However, this effect would be applicable only in cities that are expected to rise above a certain temperature during the summer.  For cooler areas like Flagstaff, longer warm seasons might create a situation in which mosquito populations might be present from the late spring to early fall, without dying off mid-summer.

As the BRACE team solidifies these projections, it will provide these estimates to public health officials and the Centers for Disease Control and Prevention to craft adaptation plans and design public service announcements. These announcements remind residents to stay inside during dusk hours, rid backyards of standing water, and apply repellent. For socially vulnerable populations that often are balancing multiple stressors at once, the timing of these announcements can be crucial to preventing outbreaks of the disease.

The BRACE project in Arizona is a joint initiative between the Arizona Department of Public Health, the IE-based Climate Assessment for the Southwest program, and Arizona State University. The team expects to deliver predictions as early as August 2016.