West Nile Virus: A Bite Out of Summer
The mosquito-borne West Nile Virus, threatening human and equine health, may now stop sport-hunting on a wild bird, too.
Source: Centers for Disease Control
One summer pest, health and wildlife officials now know, can’t be batted away. It’s going to take chemistry, public education, and even changes in the law to combat Culex tarsalis, the mosquito that carries West Nile Virus.
North Dakota is taking an especially aggressive approach. This state had the highest per capita rate of reported West Nile Virus infections last year, 369 confirmed human cases and three deaths (in 2003 there was even greater incidence of WNV ““ five deaths and 617 documented human cases in North Dakota). Though infection from the virus in this region usually peaks in August, the state has already begun a surveillance program. It involves monitoring residents who show West Nile’s flu-like symptoms, trapping and testing mosquitoes, testing sick horses, and reporting and testing dead birds.
This fall for the first time in 45 years, North Dakota has suspended its hunting season on the sage grouse. A count in April showed male populations of this species in Golden Valley, Slope and Bowman counties were less than half of last year’s numbers, down from 159 in 2007 to only 77 this year, the lowest number ever on record.
Photo: Washington State University, Wildlife Extension
Stan Kohn, a bird biologist with the state Game and Fish Department, told the AP, “We’re not sure of the true cause but we’re guessing it may be due to the West Nile Virus.”
Montana, with sage grouse numbers also declining, is weighing whether to shorten its sage grouse season from two months to only one.
Ten years ago, West Nile Virus was unknown in the U.S. It first appeared in New York State in 1999 and has now spread all the way to the Pacific. Typically the virus causes mild flu-like symptoms, but in some cases, most often among the elderly, it can be serious, leading to fever and deadly brain diseases — encephalitis and meningitis.
The Centers for Disease Control report that the virus “has caused more than 19,000 cases of human illness including more than 750 deaths in the United States.” Though the Culex tarsalis hatches in late summer, there have already been cases of West Nile Virus reported this year. (Check the CDC's 2008 map.)
Who knows how many thousands more cases go unreported? Margaret Adie of Austin, Texas, was diagnosed with West Nile Virus only after suffering through six weeks of illness, once her health began to improve. A physician made the diagnosis based on Adie’s symptoms without ordering the costly blood test. So her case wasn't registered among the 257 that CDC reported for Texas last year.
Margaret Adie of Austin, Texas, contracted West Nile Virus from a mosquito bite last October. She is likely immune from the disease now but still takes precautions when outside.
Photo: Julie Ardery
“It was a bit confusing at first,” Adie says. “I had received a flu shot on a Monday (in early October) and by Tuesday evening was feeling like I was getting sick. By Wednesday, I was certain I was having a reaction to the flu shot, because I felt just like I had the flu."
After about six days of aches and fatigue, she began feeling better; then the disease took a turn. “I felt almost normal for about a day and a half,” she recounts, “but on the morning of the second day that second week, I awoke with a rash all over — on my arms, trunk, legs, face, even the palms of my hands and the soles of my feet. I had to remove the rings on my fingers.”
The rash disappeared after several days, Adie says, “and I felt fine for a week. Then it really hit me hard. I woke up with a high fever — 102.5 — and a very bad headache. I went to my regular physician and she checked me out to make sure I didn’t have meningitis. After a series of tests, she told me I had a virus and to go home and rest. Boy, did I rest! I think I slept for about two weeks. Absolutely no energy at all. I would start to feel a bit better and then another wave of flu-like symptoms would come on me and I would sleep some more.”
After five weeks of illness, she returned to her doctor, who then diagnosed the problem as West Nile Virus. “The test is expensive,” Adie says, “and by this time my health was improving. The doctor said there had been a lot of cases in Austin last summer, probably lots more than we knew because most people had very mild cases. Mine was pretty severe.”
Bamboo multiplies and collects moisture, nice for mosquito larvae
Photo: Margaret Adie
Adie feels certain that she was infected by an insect. “The mosquitoes are terrible where I live. There is so much bamboo growing around my house, and in the neighbors’ yards on both sides. I have been told that the brackets where the leaves sprout on bamboo hold enough water for mosquitoes to hatch!
“Also there has been construction two houses from me, where they dug a hole for a swimming pool and stopped work. It would be full of stagnant water for weeks, even had tadpoles in it.”
Now fully recovered, Adie is back at her work making bows for musical instruments, creating assemblage art, and taking photographs. “I have always been careful about standing water around my house and try to keep the bamboo at bay,” she says. “I spray myself with repellant when I go outside and come back inside when there are a lot of mosquitos around. Evenings are the worst time.”
Her practice about sums up what the Centers for Disease Control advises. The CDC also recommends protective clothing.
In Colorado, Wyoming, and the Dakotas, where West Nile Virus has been most prevalent, health officials say the biggest obstacle they face is human complacency.
Mike Hildreth, a professor and researcher at South Dakota State University, explains, "Last year, with the dry summer, what we were hearing from people is, 'There's no mosquito problem, why are you spraying?', and yet the tarsalis, which handles the drier conditions much, much better, was in plentiful numbers."
South Dakota had 208 human WNV infections and six deaths last year. Since the disease first appeared in this state (2002), over 300 people have developed the serious neuroinvasive diseases of encephalitis and meningitis from West Nile Virus. Twenty-six South Dakotans have died of it.