Aedes aegypti most likely originated in Africa; since then, the mosquito has been transported globally throughout the world, through global trade and shipping activities. It's a very good transmitter of Zika virus, along with dengue and Chikungunya virus.
Aedes aegypti most likely originated in Africa; since then, the mosquito has been transported globally throughout the world, through global trade and shipping activities. It's a very good transmitter of Zika virus, along with dengue and Chikungunya virus. Photo courtesy, CDC


North Carolina’s weather is finally warming. That means health officials will watch for increased mosquito activity and monitor whether Zika virus infections appear in the state.

By Rose Hoban

Earlier this month, federal officials announced their findings from research into the cause of brain damage in babies born in areas with widespread presence of Zika virus: Something about the virus is causing the problem, although scientists are still not sure of the mechanism of the injury.

So far, the number of North Carolinians affected by the disease is small and limited to people who have traveled to the Caribbean and Central and South America, where mosquitoes carry the disease.

New map from the Centers for Disease Control and Prevention showing the estimated extent of Aedes egypti mosquitoes. They are the main type of mosquito that spread Zika, dengue, chikungunya, and other viruses.
Because Aedes aegypti mosquitoes live near and prefer to feed on people, they are more likely to spread these viruses than other types of mosquitoes. Map courtesy CDC.

But as the weather warms up, the prospect of Zika-carrying mosquitoes is becoming more real, state epidemiologist Megan Davies told lawmakers last week.

“We’ve developed a plan in partnership with Western Carolina University and NC State University and East Carolina University for doing mosquito surveillance and being able to really identify what mosquitoes are where and in what abundance,” she told lawmakers at the Joint Legislative Emergency Management Oversight Committee.

New territories

Davies showed lawmakers new maps developed this spring by the Centers for Disease Control and Prevention that indicate the presence of Aedes egypti mosquitoes, which most commonly carry Zika.

The map, she said, was developed by CDC experts “using a range of sources including more sort of informal communication with entomologists and academic partners, and they included any place that had ever detected one Aedes aegypti, and also people’s expert opinion about where they might be.”

New maps from the Centers for Disease Control and Prevention showing the extent of Aedes albopictus, or Asian tiger, mosquitoes. According to the CDC, because these mosquitoes feed on animals as well as people, they are less likely to spread viruses like Zika, dengue, chikungunya and other viruses. Map courtesy CDC.

On the old maps, areas reliably hosting Aedes egypti mosquitoes stopped short of North Carolina’s southern border. But the new maps show the state squarely within the range of possibility.

“We appreciate that it’s an estimated range and that this might be possible,” Davies said. ”But this makes it all the more important that we actually define what our risk is in North Carolina and not just go by an estimate.”

Another set of maps shows the extent of Aedes albopictus, or Asian tiger mosquitoes, which have been shown to carry Zika, but is a less efficient vector for the disease, according to state public health veterinarian Carl Williams.

“We’re all familiar with that,” he said. “You’ve all seen it in your backyards.”

Keeping track

Davies told legislators that when infected, the human body can quickly process the virus. There are exceptions, it seems, for the fetuses of pregnant women and in the semen of infected men, where it can persist for some time. CDC officials are suggesting that men who may have acquired Zika during travel to affected areas use condoms for at least six months if they and their partners are thinking about getting pregnant.

Commonly known as the Asian Tiger mosquito, Aedes Albopictus is capable of transmitting dengue, Chikungunya and also Zika viruses. Photo courtesy Wikimedia creative commons

For women who contract Zika while pregnant, Davies said, North Carolina will participate in a national registry to track the women and their babies. The women will be followed while pregnant, and health officials will check in again at two and four months and one year to see what, if any, effects the babies have.

Not every baby born to a mother infected with Zika will have long-term effects, she said. “It’s not 100 percent, but it’s some percentage, and we need to know what that is.”

Early in the pregnancy is the most susceptible time for the most severe brain damage,” she said. “There is evidence that when infected later in pregnancy, there can be other kinds of bad outcomes, like miscarriage.”

Federal and state officials are also working with blood-collection centers to screen people donating blood and blood products.

“The FDA has provided blood establishments that collect whole blood and blood components recommendations for donor deferral and product management to reduce the risk of transmitted Zika,” Davies said.

She said her department is coordinating with blood suppliers throughout North Carolina to review the FDA guidance and make sure it’s consistent across the state.

“We were reaching out to them and they were reaching out to us simultaneously,” she said of many of the blood suppliers. “So I think that’s a good sign.”

Targeted spraying

Williams told lawmakers that the standard of preventing the spread of Zika-bearing mosquitoes will be to do targeted spraying, rather than using trucks to spray clouds of insecticide.

Aedes aegypti most likely originated in Africa; since then, the mosquito has been transported globally throughout the world, through global trade and shipping activities. It’s a very good transmitter of Zika virus, along with dengue and Chikungunya virus. Photo courtesy, CDC

This aroused the ire of some lawmakers, who pushed for more aggressive mosquito control.

“We didn’t learn anything by letting the Anopheles come back and kill over a million people in Africa once we took a ban on DDT?” asked Sen. Ron Rabin (R-Spring Lake). “We’re now going to take the same sort of passive way to try to treat it.”

Williams explained that both species of Aedes mosquito breed not in swamps or ditches but in small water containers, such as birdbaths and buckets and other places close to where humans live. These mosquitoes also bite at all hours of the day, making them additionally difficult to control.

“There’s the logistical aspect of it being very difficult to control those mosquitoes with the traditional methods,” Williams said in response.

He said that much of the available data indicates that traditional methods of mosquito control are “not as effective or are unproven with regards to these peri-domestic container-breeding mosquitoes.”

Williams said that in Brazil, where the widespread appearance of Zika first aroused attention, people with backpacks are going throughout the neighborhoods of people with diagnosed disease spraying for mosquitoes and draining small containers of water.

“It’s really difficult to get at them,” he said.

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