Mosquito outbreak causes new public health concerns

A fogger sprays in the back of a Division of Fish and Wildlife – Mosquito Control truck in Milford. Delaware State News/Marc Clery

MILFORD — Concern shifted soon after an unprecedented recent mosquito outbreak was thankfully over.

This week, state officials announced 2018’s first case of a West Nile virus-carrying bird found in southwestern Sussex County. The mosquito-generated disease was located on June 29 and tested positive on July 5 by the Public Health Laboratory, the Delaware Department of Natural Resources and Environmental Control said.

In most years, the state said, the first West Nile detection usually comes upstate and later in the season. The early case follows a historic period that has now fueled potential public health issues ahead.

The state’s Fish & Wildlife Mosquito Control Section was overwhelmed during a five-week stretch of rain between mid-May and mid-June that prompted Delawareans to flood help phone lines with requested service.

The section took over 3,700 calls in a period that could compare to no other. Program Administrator William Meredith said the most calls taken for an entire year (registered as May to October) before were 2,800 in 2009.

“People were begging for relief, pleading with us to come out and spray, to come out and help us,” said Mr. Meredith, with 38 years experience (18 as administrator) in the Mosquito Control Section.

“In terms of the intensity, I’ve never seen anything like this.”

Another crow was found with the virus four days after the first, DNREC said.

“Heavy rainfall amounts three times above normal from mid-May to mid-June caused a serious irruption of adult mosquitoes statewide, with conditions worse downstate than upstate,” according to Mr. Meredith in a public statement issued by the state.

“But with extensive aerial spraying, we have now knocked back mosquito numbers in Delaware. We are hoping this early virus detection does not foreshadow abnormal mosquito-borne disease activity later in the year.”

To deal with the massive amount of adult mosquitoes who thrived in the rainy season, the state had two contracted airplanes cover “thousands and thousands” of acres during 20 separate air missions, Mr. Meredith said. The ground strategy involved 100 night time fog missions, sometimes involving five trucks at a time.

Paul Zarebicki, Environmental Scientist with the Division of Fish and Wildlife – Mosquito Control Section inspects a fogger. Delaware State News/Marc Clery

With a wide coverage area from the air, planes could quickly cut down on mosquito population, Mr. Meredith said. Ground trucks covered less area and the opportunity for mosquitoes to repopulate a fogged area were quicker.

Flood and standing water patches allowed species to breed and hatch in optimal conditions and thwarted attempts to spray larvicide to kill the life cycle before hatching. By July 1, the mosquito “eruption” was pretty much “knocked down,” Mr. Meredith said.

The response was costly but ultimately successful, officials concluded.

“It’s taxing on the budget but the state has always come through and never said not to (do whatever is necessary to address the issue),” Mr. Meredith said. “They have always put public safety and public comfort first.”

Early this week, Mosquito Control said only 27 complaints awaited response. During the siege of complaints, the section had three people taking phone calls in Milford and three entering the data of location, time, intensity, etc. Some responses came a week or two after initial call due to the backlog, Mr. Meredith said.

The section conducted tests, finding rates of 70 to 100 bites per minute in some areas of southwest Sussex County, which Mr. Meredith described as “third world numbers.” Bites of 30 to 50 per minute were not uncommon and five to 10 were routine, he said.

“Normally the calls will naturally wane, but this time they just kept coming,” Mr. Meredith said.

According to DNREC mid-August to mid-October is the top time for transmission of West Nile Virus and Eastern equine encephalitis, another mosquito-bourne disease.

Tips, contact information

DNREC issued tips to limit concerns about mosquito bites, including:

• Wearing long-sleeved shirts and long pants when outdoors in mosquito-prone areas.

• Applying insect repellent containing 10-30 percent DEET in accordance with all label instructions.

• Avoiding mosquito-infested areas or times of peak mosquito activity around dusk, dawn or throughout the night.

“The possibility of mosquito-borne disease transmissions will not subside until cooler autumn temperatures set in, usually in mid-October and sometimes later,” a news release stated.

DNREC said more information is available through phone calls and online, including:

• Mosquito biology/ecology and control – Contact the Mosquito Control Section’s Dover office at 739-9917.

• Reporting WNV-suspect wild birds, or for requests for mosquito relief – For upstate areas from Dover north, contact Mosquito Control’s Glasgow field office at 836-2555; for downstate areas south of Dover, contact Mosquito Control’s Milford field office at 422-1512.

• WNV or EEE in humans and related medical issues – Contact the Delaware Division of Public Health at 888-295-5156.

• WNV or EEE in horses and equine vaccines – Contact the Department of Agriculture’s Poultry and Animal Health Section at 698-4500 or 800-282-8685 (Delaware only).

• For more information on West Nile virus or Eastern equine encephalitis – Visit the CDC website,

Facebook Comment