NAMPA, Idaho (AP) — On a recent slightly chilly, sun-soaked morning, Canyon County Mosquito Abatement larvicide technicians Scott Arbon and Jaron Lakey suit up with long wader boots, small plastic sample baggies and long poles with ladles attached on one end.
They hop a fence surrounding Deer Flat Wildlife Refuge near Lake Lowell and begin scooping up marsh water.
Tiny worm-like creatures squirm in the murky water, along with small beetles and shrimp. But on this day, Arbon and Lakey found only a few samples of what they were looking for: mosquito larvae. For now, that’s good news.
But unfortunately, other areas in Canyon County may not be so clear of mosquito larvae. Due to flooding from the Boise River that have left pools of standing water, many tracts of the county have become prime habitat for mosquito larvae, and larvicide technicians like Arbon and Lakey are canvassing the county in hopes of keeping a looming mosquito threat at bay.
Ed Burnett, director of the Canyon County Mosquito Abatement District, said the high water this spring is creating perfect conditions for a big mosquito summer. Since taking over as director in 2005, Burnett says 2017 is setting up to be the worst year he has seen so far and he’s cautioning county residents to prepare for the potential of large swarms of the pesky bugs in coming months.
“We are treating areas now while the temperatures are low,” he said. “But if temperatures get warm quickly, we could have a problem.”
Burnett said eggs from mosquitoes laid in dirt as long as seven years ago have likely been activated by floodwaters and can thrive in stagnant water. Larvicide technicians have found such high numbers of mosquito larvae in spots along the Boise River and at Deer Flat Wildlife Refuge that in April, Burnett issued a press release warning of the threat.
“We are seeing extremely high concentrated numbers of mosquito larvae and as temperatures warm up, the mosquito larvae found in many of the flooded areas around the county may turn into swarms of adult biting mosquitoes,” he said.
Luckily, the mosquitoes that appear early in the spring and summer seasons don’t harbor West Nile Virus, but as Burnett said, they are “very aggressive and will swarm in very high numbers.”
BATTLING CANYON COUNTY’S MOSQUITOES
Mosquito abatement efforts in Canyon County first began in 1997. Those early efforts focused on controlling the mosquito population around the Deer Flat National Wildlife Refuge near Lake Lowell. Called the Lake Lowell Mosquito Abatement District, it had no funding and relied on the work of volunteers.
“Home and landowners near Lake Lowell got together to address the mosquito problem,” Burnett said.
That first year’s efforts were considered a success and showed area residents that mosquito abatement meant they could enjoy a backyard barbecue without being eaten alive by the winged pests.
Then the mosquito threat became more serious in 2000 after cattle grazing in private pastures adjacent to the wildlife refuge tested positive for Western Equine Encephalitis, a mosquito-borne virus that can affect the nervous systems of horses and humans.
Infants and small children are most vulnerable to infection and can suffer permanent brain damage or death.
Also, another mosquito-borne disease was looming on the horizon: West Nile Virus.
In 2005, the first mosquito in Idaho tested positive for the virus and 21 people in the state died from infection in 2006, prompting the Canyon County Mosquito Abatement District to expand its reach from 24 square miles around Deer Flat Refuge to 80 square miles. At the time, Nampa and Caldwell were annexed into the district.
Canyon County Commissioners issued emergency declarations due to West Nile Virus in 2006 and 2007, then signed a resolution to make mosquito abatement a county-wide effort after Canyon County residents overwhelmingly approved the measure at the polls.
According to the Center for Disease Control, the first West Nile Virus case in Idaho was reported in 2003. That number spiked to 996 in 2006 but then dropped significantly in following years with only 13 cases reported in 2015.
Between 1999 and 2015, roughly 44,000 cases of the virus have been reported nationwide with about 2,000 deaths.
FINDING BALANCE WITH NATURE
At Deer Flat Wildlife Preserve, Arbon said the county doesn’t use standard insecticides to combat mosquito larvae. Instead, they’re relying solely on the bacteria bacillus thuringiensis israelensis, or Bti, which only affects the pH levels in the gut of mosquito, black fly and midge larvae.
Once ingested, the bacteria kills the mosquito larvae by using toxins to break down cell walls in the larval gut. The bacteria, discovered in Israel in 1976, is considered safe for humans, animals and crops by the Environmental Protection Agency.
Arbon said Mother Nature helps kill off many mosquitoes before they reach maturity, as the larvae are an essential link in the food chain.
“We are trying to protect a lot of organisms here because it is a refuge,” he said. “There are helpful bugs that kill the mosquitoes. Damselflies, dragonflies, whirligig beetles, predaceous diving beetles and a lot of other organisms out there that help with integrated pest management.”
Arbon said he and fellow larvicide technicians spot-treat areas with Bti granules that they spray with a device that operates like a leaf blower.
“We come out as a team and treat the area,” Arbon said. “But if we find lots of mosquitoes in a large area, we’ll have a pilot come in and do a low passover.”
KEEPING FLYING INSECTS AT BAY
Frankie’s Aerial Application is one of the two air service companies that help with mosquito mitigation in Canyon County.
Frank Amen, the company’s owner, has been distributing Bti larvicide over waterways in Canyon County in his 1100 horsepower M-18 Dromader turboprop plane for a decade. He is a crucial component of Canyon County’s mosquito abatement program because he can cover large, hard-to-reach areas of shallow larvae infested water.
He spreads 8 to 10 pounds of dry Bti material per acre. His plane, used for agricultural application of pesticides and fertilizers, is already equipped with a dry spreader, which is controlled by the pilot and monitored by electronic equipment.
Using a GPS system, he programs the coordinates of application areas, which are determined in the field by technicians like Arbon and Lakey.
“Ed (Burnett) gives us a Google map with the coordinates, and the boundaries are outlined so the pilot knows where to spread the granules,” he said.
Amen has been flying for 36 years, since he was 17 years old. He said spreading Bti on problem areas is much like crop dusting dry fertilizer.
“The hazards for the pilot are still significant because obstacles such as towers and guy wires penetrate the airspace he flies in,” Amen said. “There are also large birds like pelicans and eagles to avoid around the waterways.”
Clear, sunny weather is ideal for flying, Amen said, but he can also apply Bti granules in a light rain. He said his company is on call with the Mosquito Abatement District from March through November.
Amen said he is thankful to be able to serve the people in his community by helping keep mosquito-caused infections like West Nile Virus to a minimum.
“My wife is a nurse and has taken care of people who were sickened by West Nile virus. It can be a very mild or very devastating illness,” he said. “So when Ed tells us that the application was effective, we are happy.”
HOW WEST NILE WORKS
The virus was first identified in the West Nile subregion in Uganda in 1937. Birds are the most commonly infected animal and generally serve as the virus’ main host.
When a female mosquito of the Culex genus lands on a human or animal, it draws blood from its host while injecting some of its saliva. If the mosquito is infected with West Nile virus, the saliva can transmit a virus to the host it feeds on. When a human is infected with West Nile virus, the virus enters an incubation period of up to two weeks, during which it replicates.
Humans are considered “accidental hosts,” since they can’t transmit the virus to other humans or animals.
About 75 percent of people infected with West Nile virus do not exhibit any symptoms. According to the Centers for Disease Control and Prevention, one in five people infected with West Nile virus experiences headaches, body aches, vomiting, diarrhea or rashes. Those who experience these symptoms often recover completely, but can experience fatigue and weakness for weeks or months.
But for less than 1 percent of the human population, West Nile virus can pose more significant health threats, including neurological illnesses like inflammation of brain tissue. Some never fully recover. About 10 percent of those who experience neurological symptoms die. Currently, there is no vaccine for West Nile virus.
Female Culex mosquitoes are considered the prime transmitter of West Nile virus. Culex mosquitoes are common and can be found all over the globe. But those types of mosquitoes are active only in the late summer when temperatures reach the 90s.
In 2016, Culex mosquitoes made up 44 percent of those sampled by Canyon County Mosquito Abatement. The good news is that most of the mosquito larvae that the Canyon County Mosquito Abatement District is working to eradicate now don’t carry the virus.
HOW THE COUNTY FINDS THE VIRUS
Burnett said that mosquito abatement employees place mosquito traps filled with 2 to 3 pounds of dry ice in areas throughout the county. The carbon dioxide released by the dry ice attracts mosquitoes, as does a light in the traps. Once mosquitoes are drawn into the trap, a small fan keeps them from escaping.
Those trapped mosquitoes are then collected by county employees and separated by species. About 50 mosquitoes of each variety are crushed, then tested for West Nile virus at a lab at the Canyon County Mosquito Abatement headquarters on Booker Lane in Nampa.
“We can set traps in the evening, retrieve them in the morning, and we can know if we have West Nile virus by that evening,” Burnett said.
If West Nile is detected in mosquitoes, the district immediately issues a press release informing the public of the infected area. Officials also create a Facebook post informing county residents where night spraying will occur.
Burnett said the “fogging trucks,” used to spray, are calibrated by a private company to ensure they are putting out a safe amount of the insecticide as required by federal law, which for the trucks is about three-quarters of an ounce per acre.
He said roughly 313 acres of the Boise River in Canyon County has been treated with Bti via airplane this year. He said another 264 acres of the Boise River, between south Notus and Highway 95, was scheduled for treatment at the end of April.
In 2016, 2,725 acres of Deer Flat Wildlife Refuge were treated with Bti, with most of that area treated by air. The total cost of mosquito abatement efforts last year was roughly $136,000.
Burnett said that even though the mosquito problem is especially bad this year, the abatement district should still be on track with its budget.
“We are prepared to handle an above normal outbreak,” he said.
