People warned to beware of West Nile

With about 1 in 10 local mosquitoes testing positive for West Nile virus, the Hill County Mosquito Control District supervisor is warning people to take care.

A species that carries the virus, Culex tarsalis, makes up 13 percent of the total mosquitoes trapped by the Hill County district, Hill County's weed and mosquito district supervisor Terry Turner said Monday. Recent testing shows that about 90 percent of tarsalis mosquitoes in the district are infected with West Nile, he said.

Tarsalis mosquitoes only fly at night, Turner added, coming out a half hour before sundown. Peak hours are between 8 p.m. and 1 a.m.

Lab tests, however, have shown that the species can transmit the virus to Aedes vexans, another local mosquito species that usually comes out during the day, Turner said. The Aedes vexans species makes up nearly a third of the mosquitoes that fly during the day, he said, which could cause a more serious problem for Hill County.

"Hopefully we don't have that happen," he said. " ... It's pretty scary stuff."

Most people infected by West Nile show no symptoms, but 1 in 5 develop a fever and other symptoms, and 1 infected person in 150 will develop a serious illness. That person has a 10 percent chance of dying from the severe illness, which affects the central nervous system.

"I know about a dozen people who've gotten it in Havre," Turner added. "Their biggest regret is, they wish they'd put some DEET or something on to protect them from getting that virus."

Montana's West Nile cases

Montana has documented two cases of West Nile virus in humans so far this summer, Turner said, recorded in the last couple weeks.

"Mid-July is when we start seeing the cases - this was about a week early," Turner said.

Montana had eight positive equine cases this summer, Turner said; three horses in Cascade County tested positive for West Nile, two in Lake, one in Fergus, one in Musselshell and one in Powder River.

In the two human cases of West Nile, both people learned they had the disease after their blood donations were rejected.

Identifying West Nile-carrying mosquitoes

A tool - a "radar gun" - to identify mosquito species is close to release in stores, Turner added, but until then people can still identify the virus-carrying mosquito.

Culex tarsalis mosquitoes are marked by a white band across the middle of the proboscis, the needle through which they drink blood; the white band is naked-eye visible for those with good eyesight, Turner added, or under a magnifying glass.

The spread of Zika

Pregnant women should particularly consider covering up - global mosquito-borne diseases, like the Zika virus, also pose a threat to Montanans, Turner said.

The "horror story" of Zika, Turner said, is palpable just from audio recordings of newborns affected by the disease.

Zika can cause severe birth defects in babies whose mothers are infected while pregnant.

Zika arrived in the U.S. three years earlier than predicted by The American Mosquito Control Association, whose meetings Turner attends. He added that the association is the global leader of mosquito control, with roughly 40 countries attending its meetings to share information.

"(Zika) got here within a year of when we talked about it at the meeting," Turner said, adding that the spread is due to the 4.5 million U.S. tourists who visit the tropics each year.

"All it takes is an insect bite over in the tropics and (U.S. tourists) bring back the disease," Turner said.

Contrary to Turner's expectations, the virus did not remain only on the coasts but also spread into the middle of the states.

The United States saw the greatest incidence of Zika infections in 2016, including nine cases in Montana. Florida and New York each reported more than a thousand

Reported cases have declined each year since that peak summer, however, a chart on the Center for Disease Control web page reads.

How to protect yourself

"At nighttime, make dang sure you got your protection on," Turner said. " ... It's critical to make sure (you) cover up a half-hour before ... sundown."

The Four Ds of Prevention, Kim Larson of the Hill County Health Department said Thursday, are Dress (in dark clothing with long sleeves and pants), DEET, Dusk and Dawn (stay indoors or protect yourself), and Drain (standing water, where mosquitoes breed).

Although Turner said DEET is a "pretty safe product," as he's learned from meetings and scientific evaluations, a lot of people dislike its "stinky smell."

Picaridin is a good alternative to DEET, Turner said.

"This other stuff is actually pretty pleasant smelling, almost like a deodorant," he said. "But the mosquitoes don't like it, so it deters them away from ya."

The Center for Disease Control has approved picaridin as one of only a few effective mosquito repellants. Turner said he plans to approach local stores to carry Moskito Care, a picaridin insect repellent, because people who've tried his samples prefer the smell to DEET's.

"Gotta get something that people wanna wear," Turner said. "It seemed pretty doggone effective when we put it on."

A 4 ounce bottle costs $10, he said, adding, "It'll last quite a long time."

The Picaridin lotion is water resistant, Turner said. A representative of the company told him an application is effective for nine hours and added that the 14 hours advertised on the bottles is pushing it.

Home prevention

People can also protect their homes using natural methods, Turner said.

"I encourage everybody to check the rain gutters," he said. "Put a couple drops of canola oil or some cooking oil and put it up there. Keeps the larvae from breeding. Just takes a thin micron of oil to stop them breathing - stop their breathing, you kill 'em."

Draining standing water in the yard is important.

"We do have little shaker pellets you can put right in the water to take care of the mosquito larvae, and those are safe for pets," he said, adding that Havre Hardware has the shakers.

The insecticide is nontoxic to humans and is approved for use for pest control in organic farming operations, the CDC web page says.

Altosid pellets are another nontoxic option avaialble in Havre, Turner said. The pellets don't kill the mosquito larvae but instead prevent them from going into the adult stage.

"So, in the meantime, the dragonfly larvae can eat the mosquito larvae that's swimming around in the water," Turner said.

District test for West Nile

"Last week they tested about 10 (district pools)," Turner said.

These are not swimming pools, he clarified, but groups of trapped mosquitoes.

"We collect the mosquitoes in what we call a light trap and then they're separated out (under a microscope) according to species," he said. "We did get up to about 500 or 600 in the trap. We used to get about 4,000 ... ," he said. "We've cut the population down pretty good, so that reduces your risk of getting it."

Tests of mosquitoes came back positive from Hill, Blaine, Cascade, Gallatin, Lewis and Clark and Valley counties.

At least half of Montana's counties are infected with West Nile, Turner said he estimates. Turner believes many other counties in Montana are probably also positive but do not have the technology to take samples, he said, so a 50 percent estimate is probably on the very low end.

Districtwide protection

The mosquito district also works to kill the mosquitoes.

In the early mornings there are fewer mosquitoes flying, Turner said, so the Hill County district does its drive-by fogging treatments from 8 to 11 p.m. each night and sometimes a bit later.

Turner said he gets a lot of help with his work, and that everyone who drives the fogging machine trucks earns a mosquito abatement license and a completes a full week of training before they are sent into the field. The fogging machines, which spray about a shot glass of chemical per acre, automatically stop spraying if the truck exceeds 20 miles per hour, he added. The machines are annually calibrated to get the droplet size to 17 microns - basically smaller than a needlepoint, Turner said.

Mosquitoes have to be airborne to be killed by the insecticide, Turner added.

"Disturb the vegetation in your yard," he said, adding that people can shake their trees' branches. "Get the mosquitoes airborne so we can kill 'em."

People do not need to worry about being accidentally sprayed, Turner said.

"You'd have to stand in the fogger for 11 hours at 15 feet away to have any health risk," he said. "If it was any hazard to humans, I sure wouldn't be using it."

Permanone is the insecticide used by the Hill County district, Turner said. Its active ingredient is pyrethrin, a derivative of chrysanthemum flowers that is synthetically reproduced.

"Actually the real chrysanthemum flowers are stronger than the synthetic," Turner added. "I try to use the safest product that's out there."

The district also protects the "good insects" that pollinate during the day.

"We make sure we don't do any spraying during the daytime," Turner said. "We do the treatment after the bees go into their hives."

Worldwide prevention

Countries around the world are battling mosquito-borne diseases.

"They've been mass-releasing sterilized males," Turner said, "and then the females turn around and produce sterile babies."

China has four or five factories that release about 40,000 sterile mosquitoes a day, he added.

"We have the technology to eliminate the mosquito," Turner said. "It's just a matter of getting it to certain species."

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Online: Centers for Disease Control map of the United States' West Nile virus status and information on West Nile: https://www.cdc.gov/westnile/.