Every summer, Mecklenburg County Health Department interns fan out across the county, inspecting creeks, ditches and backyard containers that provide breeding grounds for mosquitoes and the diseases they carry.
This year, the county has hired extra people for this work, as part of a pre-emptive strike in the fight against an advancing Zika virus.
North Carolina doesn’t yet have a single case of locally transmitted Zika infection – the state’s 33 victims contracted the virus while traveling. But with the country’s first locally transmitted cases now reported in Florida, the threat has state and local health officials on alert.
“We’re not just sitting around waiting for something to happen,” said Mecklenburg health director Dr. Marcus Plescia.
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With extra money from state and federal governments, the county hired four extra interns, for a total of 14, and temporarily brought back two former employees who are longtime experts in mosquito control.
Since May, they’ve been monitoring about 1,200 mosquito breeding sites. You might see them, in bright yellow “mosquito control” T-shirts, heads down, searching for tiny mosquito larvae. When they find it, they treat the water to kill the babies before they mature. They spray with mineral oil, which forms a film on the surface and keeps the larvae from getting oxygen, and they drop in Mosquito Briquets, a non-chemical larvicide.
They also respond to complaints, advising residents to “tip and toss” any containers with standing water, such as buckets, flower pots and bird baths.
Even the smallest container can hold enough water for mosquitoes to lay their eggs, said James Bjorneboe, mosquito control coordinator for Mecklenburg. “I’ve seen them breed in little bottle caps.”
Birth defect worries
Because of Zika, concern about mosquitoes is much higher this year than last, when the department got only 199 mosquito-related complaints. So far in 2016, there have been about 340. “There was a time in May or April when it seemed like I talked to every pregnant woman in Charlotte,” Bjornboe said.
That was after concern about Zika’s effects on pregnant women became starkly apparent during the outbreak in South America.
While the Zika virus doesn’t make most people sick, an infected pregnant woman can pass the virus to her unborn baby, and it can cause a serious birth defect of the brain called microcephaly. Overall, about one in five people infected with the Zika virus will show flu-like symptoms. Some have developed a more serious autoimmune disease called Guillain-Barré syndrome.
Zika virus is primarily transmitted through the bite of an infectious Aedes aegypti mosquito, but sexual transmission between humans is also possible.
The Aedes aegypti mosquito hasn’t been found in North Carolina for about 25 years. The state’s most prevalent type – Aedes albopictus – doesn’t commonly transmit Zika. But state and local health officials are monitoring mosquitoes closely so they’ll be aware if Aedes aegypti shows up.
In the state’s first formal survey of mosquito types since 1994, about 20 counties, including Mecklenburg, are collecting mosquitoes and sending them to university research labs at East Carolina, N.C. State and Western Carolina.
In Mecklenburg, health officials have set out 12 ovitraps – “That’s a twenty dollar word for a plastic cup,” Bjornboe said. One of the water-filled cups sits in the grass under the trees behind the county’s vector control center, a corrugated metal building off North Graham Street near the North Carolina Music Factory.
The water, shade and humidity provide a perfect breeding place. “If I were a mosquito, I’d hang out here,” Bjornboe joked.
Each week, his staff collects eggs from the cups and sends them to Western Carolina, where they’re allowed to hatch. This will allow the state to know “exactly what container-breeding species we have,” Bjornboe said.
Eliminate standing water
As part of this year’s mosquito control efforts, the interns and other health department staffers are also visiting homes in 25 neighborhoods to identify areas of concern.
They leave behind orange paper door hangers explaining what, if any, problems they detected. The door hangers also give homeowners suggestions: Dump or store kiddie pools, empty wheelbarrows and flower pots, clean gutters, change water in bird baths weekly.
Inspectors return four to six weeks later to see if things have improved. Bjorneboe said residents should take responsibility for eliminating standing water on their property. “I can tip over your bird bath for you,” he said, “but then I’m gone.”
Some residents hire private mosquito control services to spray their yards, and Bjornboe said that can work, but it kills only adult mosquitoes. “It’s all what people want to spend their money on. There’s no magic cure-all,” he said. “We’re trying to kill them before they emerge into adulthood.”
Now that local transmission has reached the United States, health officials say it’s just a matter of time until Zika reaches North Carolina. They can’t predict when, but they’re trying to be ready. As Bjornboe said: “We’re out here trying to be as proactive as we can.”
▪ North Carolina Department of Health and Human Services: http://epi.publichealth.nc.gov/cd/diseases/zika.html
▪ U.S. Centers for Disease Control and Prevention: www.cdc.gov/zika.
▪ Prevent mosquito bites by: Wearing insect repellent as well as long-sleeved shirts and pants when outdoors, avoiding outdoor activity in early evening hours when mosquitoes are most active, using air conditioning or making sure window and door screens are in place.
▪ Prevent mosquito breeding by: Dumping water from containers, such as flower pots and buckets, storing or flipping kiddie pools, cleaning gutters, changing water in bird baths weekly.