The mosquito that authorities say is most likely to transmit the Zika virus could see a notable population increase in the Columbia area by summer, a new study says.
Largely because of climate, Columbia could see a moderate-to-high abundance of the Aedes aegypti mosquito by mid-July, according to the study by the journal PLOS Currents, a California-based forum for the rapid dispersion of new research and analyses.
The Aedes aegypti species of mosquito is currently found only in small numbers in the Palmetto State, and only in the Lowcountry, according to the S.C. Department of Health and Environmental Control.
Another species, the Aedes albopictus mosquito, is abundant throughout South Carolina but is only a potential carrier of the Zika virus, DHEC says. No cases of Zika have been identified in South Carolina, nor is the virus currently found in mosquitoes in the United States, DHEC said.
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Authorities are concerned that may change.
The PLOS Currents study analyzed 50 cities near or within the known range of the Aedes aegypti mosquito. The cities selected were suited for the production of the Aedes aegypti mosquito because of weather, atmospheric and other conditions, including temperature and rainfall, the study indicated. The cities were studied regardless of whether the mosquito is currently found in them.
Charleston and Savannah, Ga., were among nine cities in the country that could have a high abundance of the mosquito by mid-July, according to the study. Augusta, Ga., could also have a moderate-to-high abundance of the Aedes aegypti mosquito by summer.
The increased possibility of mosquitoes capable of carrying the Zika virus does not mean there will be a corresponding increase of Zika transmissions to humans. However, PLOS examined conditions that could impact the the virus’ transmission, including poverty and socioeconomic factors.
“Poverty has been linked to a number of indicators of elevated exposure to mosquitoes such as lower usage rates of air conditioning and less efficient cooling options, poorer housing infrastructure such as screening of windows, as well as decreased access to safe water and sanitation,” the PLOS Currents study said.
All 50 U.S. states have summer weather and atmospheric conditions that are suitable to the Aedes aegypti mosquito from July to September, according to PLOS. However, the study helps put the focus on the local areas where the risk of transmission of the Zika virus may become heightened, it said, and assist the timing for local mosquito control activities.
In South Carolina, local governments are responsible for monitoring mosquito populations in their areas, DHEC said. The agency’s role is to identify and track the spread of mosquito-borne diseases, the agency said.
Roddie Burris: 803-771-8398
Mosquitoes in South Carolina
The State asked DHEC several questions about Zika and its potential threat to South Carolina.
The N.C. Department of Health and Human Services plans to hire two medical entomologists whose first order of business will be to determine where two types of mosquitoes capable of transmitting the Zika virus live. Does South Carolina have any similar plans?
DHEC has long had an entomologist on staff who has worked for years researching and characterizing mosquito populations in South Carolina. Our public health and environmental officials work together to help identify and track the spread of mosquito-borne diseases. This effort includes partnering with the CDC (federal Centers for Disease Control and Prevention) to ensure mosquito populations are tested for viruses.
Is DHEC trying to determine where mosquitoes that transmit the Zika virus live?
It's important to note that no cases of Zika have been identified in South Carolina at this time, and the virus is not currently found in mosquitoes in the United States.
The most likely carrier of the Zika virus, the Aedes aegypti mosquito, is found only in small numbers and only in the Lowcountry. However, one species, the Aedes albopictus mosquito, is abundant throughout South Carolina and is a potential carrier.
The type of mosquitoes that are potential carriers for Zika virus live in close association with humans, and occur in numerous types of water-holding containers such as buckets, plastic containers, discarded tires, and other items often found around dwellings. These mosquitoes do not immediately require water to lay their eggs. The eggs are laid on the sides of containers above the water line, where they lay dormant until they are covered by rising water in the container. They do not breed in standing water such as ditches, marshes, or other large bodies of water.
With the weather relatively mild since the October floods, but plenty of standing water in S.C., does DHEC expect mosquitoes to be more abundant than usual in South Carolina? If you don't know now, when would the agency know?
We will have a better idea about mosquito population levels when the weather stays consistently warm in the spring. However, recent flooding in South Carolina could lead to a greater mosquito population as warm weather returns. Species that use floodwater habitats can lay eggs on the sides of containers or in mud or damp soil. These eggs can lie dormant in dry conditions, awaiting more rain.
It’s important to note that the type of mosquitoes that are potential carriers for Zika virus do not breed in standing water such as ditches, marshes or other large bodies of water.
What conditions are ideal for an explosion of mosquitoes?
Rainfall that will raise the water level in containers or in muddy/damp soil has the potential to stimulate the desiccation-resistant (resistant to dry conditions) eggs of floodwater mosquitoes to hatch. In addition, a drought can also increase populations of some mosquitoes, such as the Southern house mosquito, that don’t get washed out of storm drains because of heavy rains.
South Carolinians can help reduce the mosquito population in their own yards since these mosquitoes typically fly only a few hundred feet from their breeding areas. The most important step in controlling mosquitoes is to find all of the places where water can accumulate. Drain, fill, or eliminate sites that have standing water and empty or throw away containers that have standing water.
For more information, visit scdhec.gov/mosquitoes.