In Western Australia, more mosquitoes can be hotter and have longer summers

Elizabeth Dixtra, a public health entomologist in Washington State, said:State Ministry of Health doing Mosquito surveillance For over 10 years.

The hot summers of the past few years may foresee conditions that increase the number of these little blood-sucking flies with needle-like mouths that some of us who came to Washington from other parts of the country are not looking forward to. No-and also their ability to infect something like the West Nile virus. Washington detected the first mosquitoes to carry the West Nile virus in July. This is a little earlier than usual. So far, scientists are monitoring the situation, but don’t worry.

In the last 40 years, Seattle has seen some of the biggest growths in mosquito-friendly conditions in American cities, according to an analysis by the nonprofit science communication group Climate Central.

Moisture and heat are the keys to the mosquito’s life cycle. Cory Morin, a clinical assistant professor at the University of Washington’s School of Environmental and Occupational Health Sciences, states that changing one or both of these factors is likely to change the population and its vulnerability to it.

Climatologists, scholars, and public health employees like Dykstra and Morin are beginning to explore more about how climate change affects human health, including its effects on mosquito-borne viruses.

“There’s another virus that’s been getting a little more attention in the last few years, but the West Nile virus is invading the Pacific Northwest, including Washington, which we probably need to worry about and plan for. There is, “says state climatologist Nick Bond.

Give mosquitoes what they need

Not all mosquitoes are made the same — until 2019, there are at least 52 recorded species in Washington alone — but they all breed under certain conditions. They like a hot, sultry and wet life. Climate Central points out the study Mosquito population temperature Between 50 and 95 degrees Fahrenheit, and Relative humidity At least 42%. Mosquitoes lay eggs in ponds, puddles, and other standing water. Mosquitoes grow faster if their habitat is present with moist, hot air.

The Pacific Northwest is moist but temperate, and has historically escaped its sweet spot.of Especially in urban areas like SeattleThere are storm drains and tunnels for mosquitoes in urban areas, but there are not many wetlands where mosquitoes like to spawn. On the eastern side of the state, mosquitoes breed on water from the irrigation system.

Not only are some mosquito populations widespread in Washington, but climatic conditions are becoming more and more friendly to them.

Washington’s summers are generally hot and long, and winters are rainy. Both help mosquito populations grow and prosper for more months of the year.

according to Climate Central analysis released last summerIn Seattle, between 1980 and 2019, “mosquito days” (ideal temperature and humidity days) increased by about a month, increasing from 105 to 144 days. This is far from Miami’s almost year-round mosquito weather, but this increase has made Seattle the 19th fastest growing mosquito season of the 239 US cities analyzed. I got the distinction that I have.

Dykstra of the Ministry of Health says that some mosquito populations on her surveillance site peaked early in the season. Dykstra says that four species of mosquitoes in the state, especially Culex pipiens and Culex pipiens (common home mosquitoes found in urban areas), are of concern to humans.Dykstra, who is doing regular monitoring at Billie Franks Junior Nisquarie National Wildlife Sanctuary near Olympia She said she couldn’t or couldn’t make a big declaration about the health of these species throughout the state since 2007.

And Dykstra saw Culex pipiens’ Population peaks early on average, peaking between mid-July and mid-June between 2015 and 2020.

Dykstra believes from her observations, rather than rigorous data, that the cause of the shift may be related to rising temperatures at the beginning of the year.

The longer mosquitoes grow and the earlier introduction of viruses such as West Nile fever into the population can extend the season in which the disease can be transmitted to animals such as humans and horses. .. As a result, the virus can be a problem for longer, says Dykstra.

Thermal events such as those experienced in June can help accelerate the growth and reproduction of mosquitoes. In moderately warm weather, mosquitoes can grow from eggs to adults in a week instead of a few weeks.

On Dykstra’s site, it’s unclear if heat waves played a role. A week before the heat wave, Dykstra collected a little over 2,000 mosquitoes at the shelter. During the hot week, she collected about 3,500 animals, her largest collection in the summer. After that, the number decreased after a week and became shy to 1,700 mosquitoes.

“We brought habitat from June to January. [available],so I [heat wave] It really helped me a bit in terms of numbers, “she says.

However, this population data follows the same trends she has seen in the last six years. “The overall mosquito population … doesn’t look like it was affected by the extreme heat,” she says.

Compared to eastern Washington, which can collect 19,000 mosquitoes at a time, 3,500 doesn’t seem to be that bad. “It was awkward for the technicians who were organizing it,” Dykstra said.

West Nile factor

Human West Nile virus increases from late summer to autumn. This is because mosquito-feeding virus-carrying birds have begun to move elsewhere, encouraging mosquitoes to look for new food sources.

At this time, Dykstra does not believe that mosquitoes are more of a health problem than ever before. Data from the Centers for Disease Control and Prevention In 2018 In Washington State, there were 56 cases of human mosquito-borne disease. The annual case rate has fluctuated since 2004, from a minimum of 24 in 2004 to a maximum of 156 in 2016, at the peak of Zika concerns.Ministry of Public Health Presentation The first case of West Nile fever detected in a mosquito on July 1, this year.

“Maybe it was a little faster than before, but our earliest [previous] The detection was actually done in late May, so it’s not unheard of, “says Dykstra. To issue an alarm is to see more cases or cases in a new location. Further analysis is needed to link these cases to climate change.

Public Health — First Identified by Seattle and King County Local cases of West Nile infection In humans in 2018.

The conditions that support the growth of West Nile virus are in many ways the same as those that generally support mosquitoes — hot and moist climates. Some studies West Nile heat propagation is highest between 75.2 and 77 degrees Fahrenheit. Morin and co-workers at the University of Washington say they found that the minimum daily temperature was the number one factor associated with an increase in West Nile infections in Washington State.

According to Morin, higher temperatures not only allow mosquitoes to grow faster and survive longer, but also cultivate West Nile virus faster and live long enough for mosquitoes to infect other hosts. Increase the possibility.

Ryan HarriganA part-time assistant professor at the Institute of Environment and Sustainability at the University of California, Los Angeles Dry state Increases counterintuitively transmission Of the virus. This is because there are few drinking fountains for both mosquitoes and major hosts such as horses and birds to choose from, and they tend to end up in the same place, starting the viral cycle early in the season.

Future risk

Summers in Washington are expected to warm on average over the next few decades, but in places like Seattle, there’s a way to go before the temperature range that Climate Central has found to support mosquitoes. There are still. This can increase the “mosquito days”, “says Brady.

Bond, a state climatologist, says there is a fairly strong consensus among climate models that our summers will be drier. The model also suggests that there is a lot of rain in winter.

Changes in temperature can also affect mosquitoes in Washington.

Ministry of Public Health Detected Two major West Nile species of concern — Culex pipiens When Culex pipiens — As of 2019, almost everywhere in Washington County, the former is represented in all but three counties, and the latter in all counties.

Dykstra says there is no definitive data to support it, but the rise in temperature and the decrease in summer snow cover may allow species to move to higher altitudes.

“One really warm summer may do nothing, but if you have them many times … it may give mosquitoes the opportunity to expand their range,” Morin says.

Currently monitoring is not easy

After all, the future of Washington mosquitoes is now largely mysterious, as the resources needed to monitor and analyze population growth are not available. This is one of the causes of COVID-19. Absorbed time Of public health employees.

Monitoring of these types of viruses is difficult without a COVID. Not only are many players involved among mosquito species, birds, horses and humans, but they are also learning about the conditions under which mosquitoes breed and transmit. It is also labor intensive in collecting data. West Nile fever is a virus whose population is difficult to track in the first place. About 80% of infected people are asymptomatic.

“It’s hard to get a really clear snapshot of everything that’s happening,” Morin says. “Sometimes you can do the right thing for the wrong reason … You might get really good data … but it takes time and money to actually do it.”