Spread of West Nile virus expected to worsen in the area


As concerns mount that the number of West Nile Virus cases will soar this summer, local officials are responding to the alert by preparing and educating.

Bruce Johnson, with Moffat County pest management and Moffat County extension agent John Balliette, are partnering with the Visiting Nurse Association and local veterinarians for a summer of testing and prevention education. Their first step is a community meeting at which a representative from the Colorado Department of Health and area veterinarians will speak. It's part of West Nile Virus awareness week scheduled for March 31 to April 4.

"Basically, we have had a positive case in Moffat County and it's a national health alert," Johnson said. "We don't want to panic people, we just want to make them aware that West Nile Virus is here and talk about some precautions we can take."

The meeting begins at 7 p.m. Thursday at Shadow Mountain Clubhouse.

Two horses were found to have contracted the virus in Moffat County last summer -- one case was fatal.

"We expect it to be much worse this year," Johnson said.

Moffat County was the first Western Slope county to have a confirmed case of the disease. Mesa County is the only other West Slope county where the virus has been confirmed.

Johnson has already found mosquito larva in the standing pools of water created by this month's warm weather. He said there's no need to panic at the early arrival of the bugs. They are mostly males, and males don't bite, therefore don't carry or spread the disease.

Both males and females eat algae and chlorophyll, but the females must have a "blood meal" in order to reproduce.

Johnson is stepping up the county's mosquito-abatement efforts this summer in the hope of curbing the spread of the disease locally.

He will treat about 20,000 acres between Craig and Maybell with larvicide -- irrigated hay fields and standing water where the bugs are bred. The county kills adults by fogging 20 to 30 hours a week and contracts for an aerial attack twice during the summer.

The city has doubled its contribution to the mosquito-abatement fund and the county has established a contingency should Johnson feel more is needed.

"There are still going to be mosquitoes," he said. "It doesn't matter how much we spray."

There are four types of mosquitoes in Moffat County -- all have which have been identified as carriers of West Nile Virus. The culex charchalis is the main carrier and it is also the most prolific mosquito in the area.

"Up until now, mosquitoes have been a nuisance, no they're definitely a health hazard," Johnson said.

Johnson has been helping other counties establish mosquito-control programs. Weld County had no program and the highest rate of West Nile Virus infections.

Mosquitoes pick up West Nile Virus from birds. There are 61 species of birds that can carry the virus. Humans and horses can contract WNV from the bite of an infected mosquito.

When mosquitoes bite, they inject saliva in order to prevent the blood from coagulating and transfer West Nile Virus to humans that way.

Recently two lab workers have contracted the virus from handling infected birds. It has also been found to transfer from infected mother to fetus and through breast milk.

In 2001, WNV was detected in 27 states. In 2002, it reached 44 states -- making it the fastest-moving virus the nation has ever seen.

"By the end of the summer, it will be in all the states," Johnson said.

There were 149 human cases accounted for by the Centers for Disease Control from 1999-2001. In 2002 the number of human cases spiked to 3,852. Of those, there were 232 fatalities.

"They're expecting it to spike in the near future," Balliette said. "They don't know if they've peaked yet or not."

The number of cases peaked in August.

People age 55 and over are in the highest risk group for contracting the virus.

Nearly 15,000 horses were reported with the disease last year -- 400 died.

The virus also caused the deaths of other mammals including reindeer, mountain goats and squirrels. Cattle can contract the virus, but never show symptoms. It is not fatal to them.

Nor is it fatal to chickens, which is why Johnson plans to keep a flock of chickens as a test group. He will send their blood to be tested twice a month.

The chickens will be located outside the abatement area so they get maximum exposure to mosquitoes.

"Chickens can be hosts, but they're not affected. They don't get symptomatic," Johnson said. "People can have it and not know and people can have it and die."

Incidents of people getting ill from the virus are rare, Balliette said.

Testing for a human West Nile Virus vaccine is underway, but Balliette said approval is at least two years away.

There is a vaccination for horses and if ranchers want it to be effective, they need to start horses on the two-dose shot now.

"If they start today, basically they're looking at two months before the horse is immune," Balliette said.

The vaccine is only available through veterinarians.

The vaccination costs $28, which veterinarian Wayne Davis said is a good investment.

"Twenty-eight dollars isn't anything to what it costs to replace a horse," he said.

The vaccination can be given at any time, but takes six weeks to become effective.

A shot is administered and a booster shot is given three weeks later. It takes about three weeks after that to develop a good immunity, Davis said.

As far has human prevention is concerned, the only options right now are to avoid contact with mosquitoes.

Johnson advises people to use mosquito repellant and to stay indoors or wear pants and long-sleeved shirts during peak

mosquito hours -- morning and evening.

He also suggests eliminating breeding grounds where possible. Old tires are ideal breeding

grounds, as are any other places where water stands stagnant -- in birdfeeders, buckets and divots in the driveway and lawn.

One 10-inch hole can produce 1,000 mosquitoes a week, Johnson said.

Balliette advises people to notify the extension office if they find several dead birds. Gather them with a trash bag, making sure your hands are completely covered and do not touch the bird, he said.

The birds will be sent to be tested for the virus.

"I don't know how long we'll do bird surveillance because we already know it's here," Balliette said.

Johnson will also be setting up live mosquito traps throughout the county to harvest mosquitoes and test them.

The main message, he said, is to not panic.

Christina M. Currie can be reached at 824-7031, Ext. 210 or by e-mail a ccurrie@craigdailypress.com.


West Nile virus (WNV) disease is a viral disease commonly found in Europe, Africa, Australia, and Asia. It was first identified in the United States during the summer of 1999 in New York City, spreading along the East Coast and into Massachusetts during 2000 and 2001.

The reservoir for WNV is birds. WNV is transmitted from birds to mosquitoes when a mosquito takes a blood meal from an infected bird. Infected mosquitoes can then transmit the disease to birds, humans, horses, and other animals. Horses can become sick after being bitten by mosquitoes carrying WNV. In many horses infected by the virus, the disease is associated with mild symptoms. In some, the disease can be serious, even fatal.

West Nile virus is spread by the bite of an infected mosquito, and can infect people, horses, many types of birds, and some other animals.

Most people who become infected with West Nile virus will have either no symptoms or only mild ones. However, on rare occasions, West Nile virus infection can result in severe and sometimes fatal illnesses.

There is no evidence to suggest that West Nile virus can be spread from person to person or from animal to person.

Most people who are infected with West Nile virus will not have any type of illness. It is estimated that 20 percent of the people who become infected will develop West Nile fever: mild symptoms, including fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands.

The symptoms of severe infection (West Nile encephalitis, meningitis, and meningoencephalitis) include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. It is estimated that one in 150 persons infected with West Nile virus will develop a more severe form of disease.

Symptoms of mild disease will generally last a few days. Symptoms of severe disease may last several weeks, although neurological effects may be permanent.

Clinical signs in horses with West Nile virus infection vary. Some horses may show few or no signs of illness. The most common signs include an unsteady gait, depression or apprehension, hind-limb weakness, difficulty in rising, and muscle tremors. A small number of horses may develop muscle weakness that progresses to paralysis of all four limbs, inability to rise and death within two to nine days. About one in four of the horses showing signs of illness developed fever.

Horses affected by WNV do not need to be euthanized. Many horses display mild clinical signs and can recover from the disease with supportive care. Horses are humanely euthanized only when they are suffering from illness from which they will not be able to recover. Horses with WNV do not need to be quarantined since infected horses cannot transmit the disease to other horses or humans.

Other than symptomatic and supportive veterinary care, there are no specific treatments for horses with WNV.

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