This bites: Summer storms could mean ‘extreme mosquito activity’ for Greenville

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The Aedes albopictus, or Asian tiger mosquito, is one of the three prevalent species in South Carolina. Photo: iStock

If you’ve been swatting at the air above your head or sprinting indoors to escape a large swarm of bloodsucking pests, you’re not alone. The mosquitoes really are terrible this year, and they’re only expected to become more active in the coming weeks.

Quoting pest-management professionals, AccuWeather.com experts estimate that mosquito activity along the East Coast is two to three times higher this summer.

The website, which produces a forecast specifically focused on the pesky insects, predicts “extreme mosquito activity” in Greenville for much of the next two weeks.

“It makes sense considering the recent weather patterns we’ve seen across the Piedmont,” said Dr. Elmer Gray, a Clemson graduate and entomologist with the University of Georgia Cooperative Extension, who conducts research throughout parts of the Upstate.

Gray said this year’s mosquito season experienced a slow start in the Southeast due to a dry winter and cooler spring. But above-average rainfall totals and high temperatures during the months of May, June, and July left many states, including South Carolina, with standing pools of water that provide ideal breeding grounds for mosquitoes to lay their eggs and develop larvae.

The bad news: It only takes about two weeks for mosquitoes to fully develop and hatch in standing water. And last week’s rains likely left behind a lot of water that, combined with the heat and humidity, could speed up the maturation process of larvae and provide additional breeding locations for mosquitoes throughout the Upstate, Gray said.

He added that mosquito activity could remain elevated even if standing water evaporates.

“There are other sources of water that have built up during the wet period that mosquitoes can use for breeding,” Gray said. “They often concentrate near bird baths and other structures that are capable of holding moisture.”

The bloodsucking pests also tend to concentrate in neighborhoods when people water their plants or let their kids play with the water hose or sprinkler in the yard, activities that can leave standing water on the ground for breeding mosquitoes, he added.

“Attack of the Killer Mosquitoes.” Illustration by Timothy Banks.

While it’s hard to know exactly how long mosquito activity will remain elevated throughout the Piedmont, Gray said he expects “pretty high levels” into autumn as the temperatures continue to rise and rains keep falling.

Dr. Chris Evans, an entomologist with the state Department of Health and Environmental Control, said South Carolina’s mosquito season is “generally unpredictable” but typically runs from March to November. “Mosquitoes are most active when temperatures are above 60 degrees,” Evans wrote in an email to the Greenville Journal. “Two to three freezes are generally required to force mosquitoes into winter hibernation.”

Mosquito season, however, is growing longer for many cities across the country.

Rising temperatures and humidity since the 1980s have driven an increase in the number of days each year with ideal conditions for mosquitoes, according to a recent analysis from Climate Central, a nonprofit news organization that reports on climate change.

As temperatures slowly increase across the country, the number of days above 50 degrees grows, according to the analysis. And as things get warmer, more moisture is evaporated into the air, which increases the humidity.

“Mosquitoes love hot and humid days,” Gray said.

Dozens of cities throughout the country have seen their mosquito seasons grow by at least 20 days over the past 35 years. In Greenville, the mosquito season has increased from 113 days to 137 days since 1989, an increase of 24 days. Spartanburg’s season, on the other hand, has increased from 105 days to 125 days since 1989, an increase of 20 days.

As warming continues, the areas favorable for mosquitoes will continue to shift and grow, likely increasing the risk of disease, according to Dr. Michael Reiskind, an assistant professor of entomology at North Carolina State University.

“Higher temperatures can cause some mosquitoes to feed more frequently, which increases their chances of acquiring a virus,” Reiskind explained.

Reiskind added that a virus has to reproduce in a mosquito for a certain period of time before it can be transmitted through a subsequent bite. 

Warmer temperatures, however, allow mosquitoes to develop faster and the viruses they carry to replicate faster, meaning an infected mosquito is able to transmit whatever disease they have to more animals and humans before their life cycle ends.

Mosquitoes aren’t hatched carrying malaria or any other disease but can become carriers if they bite an infected human or animal, according to Reiskind. The bloodsucking insects transmit the disease to the next victim they bite.

In many tropical and subtropical countries, mosquitoes carry and transmit diseases like malaria, yellow fever, dengue, and chikungunya, which together result in more than 1 million deaths each year, according to the Centers for Disease Control.

Mosquito-borne illnesses are most prevalent in central Africa, India, and South and Central America along with much of Asia. But a number of illnesses, including the Zika virus and West Nile virus, are on the rise across the U.S. thanks to increased migration — including by refugees created directly by climate change — trade, and international travel.

Nationally, illnesses from insects like mosquitoes, ticks, and fleas tripled from 2004 to 2016, according to a new report by the CDC. In that time, nine new germs spread by mosquitoes and ticks were found or introduced into the U.S.

“Zika, West Nile, Lyme, and chikungunya — a growing list of diseases caused by the bite of an infected mosquito, tick, or flea — have confronted the U.S. in recent years, making a lot of people sick,” CDC Director Dr. Robert R. Redfield said in the report. “And we don’t know what will threaten Americans next.”

Currently, the Zika virus is widespread throughout Central and South America as well as the Caribbean, according to the CDC. But there have been no local transmissions of the virus, and all South Carolina cases have been travel-related.

The Zika virus is spread to people by the Aedes aegypti and Aedes albopictus mosquitoes, both of which are found in South Carolina, according to DHEC.

About 80 percent of people who contract the virus don’t experience any symptoms, which can range from mild flu-like symptoms to serious neurologic conditions in adults.

In pregnant mothers, however, Zika can cause microcephaly, a condition where a newborn baby has an abnormally small head and developmental problems.

Swarm of mosquitoes. Photo: iStock.

“When traveling to any country with active Zika transmission, travelers should proactively take steps to prevent mosquito bites, such as using insect repellent, wearing long sleeves and pants, and staying in places with air conditioning or that use window and door screens,” Dr. Linda Bell, an epidemiologist with DHEC, said in a statement.

While local transmission of Zika hasn’t been observed in South Carolina, the risk of being exposed to the West Nile virus continues to pose a real threat. Peak transmission of the virus occurs between Aug. 15 and Sept. 15 annually.

Earlier this month, DHEC officials announced that an individual from the Pee Dee region had contracted South Carolina’s first case of West Nile virus in 2018. A bird infected with the virus was previously found at a home near Broadway Lake in Anderson County.

West Nile virus can cause inflammation of the brain and spinal cord, according to DHEC, but the risk of serious illness or death from the virus is low.

“Most people infected with West Nile virus have no symptoms,” Bell said. “The risk of serious illness is low as less than one percent of people infected develop a potentially fatal inflammation of the brain, known as encephalitis.”

Bell added that about one in five people infected becomes ill within two to 14 days with symptoms that may include fever, headache, joint pain, muscle pain, and occasionally nausea and vomiting. Symptoms of the more severe form of illness include headache, high fever, neck stiffness, disorientation, coma, seizures, or paralysis.

“If you develop fever or other symptoms after being bitten by a mosquito, you should contact your health care provider,” Bell said.

A few ways to help protect yourself from the bloodsuckers:

Source: S.C. Department of Health and Environmental Control

  • Call the Greenville County “mosquito hotline” at 864-467-5988. The free spraying program is available from June 1 to Sept. 31 for residents in the nonincorporated areas of the county and in the cities of Greenville, Greer, Simpsonville, and Travelers Rest.
  • Apply insect repellent containing DEET, picaridin, oil of lemon eucalyptus, or IR 3535 according to label instructions. Repellents help keep mosquitoes from biting.
  • Wear clothing that reduces the risk of skin exposure.
  • Exposure to mosquitoes is most common at night and during the early morning. Some species bite during the day, especially in wooded or other shaded areas. Avoid exposure during these times and in these areas.
  • Make sure that your doors and windows have tight-fitting screens to keep out mosquitoes.
  • Eliminate all sources of standing water on your property, including flowerpots, gutters, buckets, pool covers, birdbaths, old car tires, rain gutters, and pet bowls.

Which mosquitoes are most dangerous in South Carolina? 

Source: S.C. Department of Health and Environmental Control

At least 61 species of mosquitoes exist in the Palmetto State. Here is a list of some of the most prevalent species that can transmit a variety of viruses and parasites to humans:

Aedes albopictus, or Asian tiger mosquito: This species of mosquito can transmit several diseases, including Zika virus and West Nile virus. The Asian tiger mosquito is found abundantly throughout South Carolina, including the Upstate. It can be identified by the bright white or silver stripes on its abdomen, thorax, and legs.

Aedes aegypti, or yellow fever mosquito: This species of mosquito is a known carrier of several viruses, including yellow fever, dengue, chikungunya, and Zika. It prefers biting people and tends to cluster near neighborhoods. However, it is currently found only in small numbers in South Carolina, and mainly in the Lowcountry.

Culex quinquefasciatus, or Southern house mosquito: This species of mosquito is most common in tropic and subtropic regions. It is the primary carrier of the St. Louis encephalitis virus and can also transmit West Nile virus.

Did you know? 

The Greenville-Spartanburg area ranked No. 31 on pest control company Orkin’s Top 50 Mosquito Cities list, which ranks metro areas by the number of new mosquito customers served from April 1, 2017, to March 31, 2018.

For more information, visit scdhec.gov.

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