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The Arizona Daily Star
Wednesday, 29 September 1999
Mosquitoes carry virus; prof wants swamp closed
By Jim Erickson
"We're too old to worry about encephalitis,'' says 71-year-old Marianne Sacia, who lives in the Prince of Tucson RV park. ``But we've never had mosquitoes like this. I sleep with a sheet over my head."
The potentially deadly encephalitis virus has been found again in mosquitoes at a city-operated wetland and at a nearby RV park.
The finding prompted a University of Arizona entomologist to call for closure of the man-made swamp.
Entomology professor Henry H. Hagedorn called the Sweetwater wetland, near Interstate 10 and West Prince Road, "a very serious disease threat.''
"The mosquitoes are being bred by the city in a facility that they designed poorly, making it impossible to control the mosquitoes,'' Hagedorn said.
"My own personal opinion is that Sweetwater wetlands should be closed, dried out and redesigned,'' he said. "It ought to be redone.''
The Sweetwater wetland is a water recharge and habitat restoration project created by Tucson Water. Two ponds are filled with backwash from filters in the city's reclaimed-water plant, which produces water for irrigation and effluent from the waste-water treatment plant.
Hagedorn said that if city officials move ahead with plans to install other artificial wetlands, they will increase the risk of encephalitis and other mosquito-borne diseases.
A hydrologist at Tucson Water, which maintains the Sweetwater wetland, said the city has made significant progress in reducing the number of mosquitoes there by spraying insecticide from a truck and dropping pellets from a remote-controlled helicopter.
Last month, two mosquito samples from Sweetwater tested positive for the Western equine encephalitis virus.
Now two more mosquito samples from the wetlands have tested positive for St. Louis encephalitis, a more virulent form of the disease, said Michael Fink of the Arizona Department of Health Services.
The St. Louis encephalitis virus was also detected in mosquitoes collected at the nearby Prince of Tucson RV park, 3501 N. Freeway Road, Hagedorn said yesterday.
Encephalitis is an inflammation of the brain. Many victims suffer only mild fever and headache for a few days. But encephalitis can cause convulsions, coma and death.
Western equine encephalitis has a mortality rate of about 3 percent, while St. Louis encephalitis kills 5 percent to 15 percent of its victims, according to the federal Centers for Disease Control and Prevention.
An 8-year-old girl from Queen Creek, southeast of Phoenix, died Thursday of encephalitis after falling into a coma for three days. Epidemiologists don't yet know which pathogen was responsible for the girl's death, Fink said yesterday.
In New York City, scientists have tossed out their original diagnosis of a mosquito-borne ailment that has killed four people. St. Louis encephalitis was suspected, but the CDC reclassified the cases as West Nile-like fever, which is usually found in Africa and Asia.
Encephalitis is spread by Culex mosquitoes, which become infected when they feed on birds.
In an average year, five Culex mosquito samples test positive for encephalitis in Arizona, Fink said. This year, 18 positive tests have been recorded, including 11 in Maricopa County.
Fink said the long monsoon season may have contributed to the high numbers. As the weather begins to dry out and cool off, the mosquitoes will retreat to over-wintering sites in sheltered places with year-round water.
At the Sweetwater wetland, the city is dropping larvae-killing pellets into the water from a remote-controlled helicopter, said Bruce Prior, a Tucson Water hydrologist. Since Aug. 30, the city has also used a truck-mounted sprayer every two weeks to kill adult mosquitoes at the wetland, he said.
Malathion was used during the first spraying, then Tucson Water switched to pyrethrums, insecticides made from dried flower heads of chrysanthemums, Prior said.
The wetlands cover 18 acres, and the entire area is sprayed, he said.
Several residents of Prince of Tucson RV park, where the encephalitis virus has been detected, say they're not worried about disease-carrying mosquitoes.
Marianne Sacia, 71, who was drinking a beer outside her trailer, said mosquitoes bother her whether or not they carry diseases. So she and her friend Nora Butler, 70, have their own way to deal with the insects.
"We're too old to worry about encephalitis,'' Sacia said. "But we've never had mosquitoes like this. I sleep with a sheet over my head.''
"We just kill the suckers and scratch,'' Butler said. "And they don't like beer, so we come out here and drink.''
"Do you have any symptoms of encephalitis?'' Sacia asked.
"I don't know,'' said Butler, who became well-acquainted with mosquitoes in Florida. ``What are the symptoms? I just wish they'd spray like they do everywhere else.''
Resident August Kauzlarich, 73, said mosquitoes rarely feast on him because he spends most of his day indoors. Anyway, he said, "if you're going to get it, you're going to get it.''
Star reporter Hanna Miller contributed to this story.
The Arizona Daily Star
Thursday, 30 September 1999
Encephalitis risk lurks far beyond Sweetwater area
By Joe Burchell
1998 Star photo
The city, which operates Sweetwater, plans to tear out plants that shelter mosquito larvae; that might happen this winter
Found in Pinal, Maricopa, too
The health threat from encephalitis-carrying mosquitoes isn't limited to the area around Sweetwater wetlands, a state official said yesterday.
The only Pima County mosquitoes found to be carrying the virus were from the wetlands near Interstate 10 and West Prince Road.
But Mike Fink of the Arizona Department of Health Services said a high number of mosquitoes infected with encephalitis were found this summer in a corridor running through Pima, Pinal and Maricopa counties.
That indicates, "The virus is well distributed throughout those counties, " he said.
University of Arizona entomology professor Henry H. Hagedorn, who's campaigning to shut Sweetwater down, agrees encephalitis-carrying mosquitoes are probably far more widespread.
He emphasizes, however, that Sweetwater represents the greatest threat to public health because it produces so many mosquitoes and attracts many birds. Birds carry the virus and transmit it to mosquitoes.
The city, which operates Sweetwater, plans to tear out plants that shelter mosquito larvae - perhaps this winter.
City officials are opposed to closing the wetlands but could shut it down for the worst three mosquito months of the year if state and county officials deem it a health risk, said Bruce Pryor, a Tucson Water hydrologist.
Hagedorn points out the mosquito threat could triple in coming years with the opening of two other wetlands, at Kino Sports Park at East Ajo Way and South Country Club Road, and Lincoln Park southeast of South Pantano and East Escalante roads.
Officials say both projects, scheduled for construction late next year, feature mosquito-discouraging designs.
But Fink said wetlands will always generate mosquitoes, no matter what's done to minimize them. If they also attract birds, the encephalitis virus eventually will show up, he said.
"We're seeing it with every wetlands built, " he said.
State and county health officials have trapped 18 mosquitoes carrying encephalitis: 12 in Maricopa County, four in Pima County and two in Pinal County. That's more than double the number normally found each year, Fink said.
Fink speculated one reason infected mosquitoes were found at Sweetwater is that it's tested far more often than any other Pima County location. So many mosquitoes and more frequent testing are bound to turn up more positive tests, he said.
Hagedorn said the county tests potential mosquito-problem areas once a month, if that often.
Tucson Water's Pryor said the county sets three mosquito traps a month at Sweetwater, and Hagedorn's UA classes set 10 more traps every week.
If other locations were tested nearly that often, Pryor said, he has no doubt they'd show positive findings for encephalitis, too.
"That's what they're finding in Maricopa County. The more they look, the more they find, " he said.
Fink said it's hard to speculate how far the mosquitoes might migrate from Sweetwater. The type of mosquito most commonly found this time of year will generally travel about a mile, he said. But he believes the extremely large numbers of mosquitoes at Sweetwater likely spread out over a much greater distance.
Hagedorn wanted to study how far mosquitoes were straying from Sweetwater last spring. The city turned him down because it was trying to kill off mosquitoes. Catching thousands and then releasing them didn't make much sense at the time, Pryor said.
Fink said mosquitoes are a natural byproduct of efforts by many communities to re-create wetlands. They once occurred naturally all over the state, before the growing population started depleting the ground-water table and drying them up.
"There was a tradeoff. When we lost the natural cienegas, we lost those mosquito breeding areas. Now we're reintroducing swamps," he said.
Tucson officials say the Sweetwater wetlands provide many benefits, including wildlife habitat, ground-water recharge, sewer water treatment and recreation for bird watchers.
Martin M. Karpiscak, a research scientist with the UA Office of Arid Land Studies, said there are about six large wetlands projects and more than 40 smaller ones around the state.
Karpiscak is working with Pima County to design the Kino wetlands in ways that discourage mosquito reproduction.
Pryor said one notable design problem at Sweetwater has contributed significantly to the mosquito problem: the number, height and type of plants. The thick stands of tall bulrushes growing in the water provide shelter for mosquito larvae and make it hard to effectively apply pesticides. Pryor said the city will tear out the existing plants and replace them with shorter, more sparsely placed ones. Winter is the best time to replace the plants, but the timing remains uncertain because of funding, he said. No cost figures were available.
Hagedorn wants Sweetwater redesigned to provide faster water flows, to discourage mosquito breeding and allow insect poisons to spread more efficiently.
Karpiscak said he doesn't believe that degree of re-engineering is possible or necessary at Sweetwater.
He said the Tres Rios wetlands project in Phoenix, which had a design similar to Sweetwater's, went through a mosquito and encephalitis problem about three years ago.
The mosquito population there has diminished significantly since workers opened up areas that were once clogged with dense plants - similar to the thinning planned at Sweetwater. They also introduced mosquito-eating fish and increased deep-water areas.
Pima County Administrator Chuck Huckelberry said the design of the Kino Sports Park wetlands was heavily revised on Karpiscak's advice, in part because of the Sweetwater experience. Those changes include:
* More deep-water areas, which hold the temperature down, making it less favorable for breeding.
* A system to circulate water from the bottom of the wetlands to the top and between the wetlands and a planned lake.
* Eliminating much vegetation.
Karpiscak said eliminating vegetation and some other changes he recommended are easier to do at Kino than Sweetwater because of their different goals and water sources.
Sweetwater uses backwash from the Roger Road sewage treatment plant. Plants growing there are supposed to extract nitrates from the water as part of the treatment process.
The Kino wetlands area is primarily for habitat restoration and recharge, and will use reclaimed water and/or Central Arizona Project water, so the county isn't trying to achieve a high level of treatment.
Linda Smith, project manager for the Lincoln Park wetlands project, said the city has made adjustments there in response to the mosquito problem, including using different plants from Sweetwater's and including more deep-water areas.
The Arizona Daily Star
Thursday, 30 September 1999
By Jane Erikson
Experts say be wary of mosquitoes, but don't get hysterical
They're better off dead - besides being a pest, mosquitoes can carry encephalitis. But ``the risk is small,'' says the UA's Dr. Kent Campbell.
WHAT YOU SHOULD KNOW
Q. What is encephalitis?
A. An inflammation of the brain brought on by an infectious organism. It differs from meningitis, which is an inflammation of the outer covering of the brain.
Q. What causes encephalitis?
A. Mosquitoes can spread viral forms of it to humans. Other types of infection - such as herpes, chickenpox, valley fever and tuberculosis - can also be the cause.
Q. What are the symptoms?
A. They range from non-existent - a person can be infected but have no signs of illness - to severe. Headache, body ache and fever are common. In severe cases, encephalitis causes seizures, coma and death.
Q. Can encephalitis be treated?
A. Not if it's caused by a virus transmitted by mosquitoes. But if it's caused by a more common infection - including tuberculosis, valley fever and herpes simplex - treatment is available.
Q. Can infection be prevented?
A. To a large extent, yes. Health experts are asking the public to take several precautions to reduce risk of exposure to encephalitis-bearing mosquitoes:
* Eliminate sources of standing water outside the home. Plant saucers, birdbaths and pet dishes should be emptied and rinsed at least twice a week. Do not take water away from outdoor pets - that would be life-threatening to them, especially when it's hot. Also check rain gutters clogged with leaves and debris. And be on the lookout for unexpected water containers - a tossed soda can or a Frisbee filled with rainwater, for example.
* Avoid mosquito bites by wearing pants and long sleeves outdoors, and spray yourself with a mosquito repellent that contains DEET. The chemical is safe for children 2 and older, but pediatricians recommend a repellent with a DEET strength of 10 percent or less.
* Be particularly careful after dark - the culex mosquito that carries encephalitis is active from dusk to dawn.
Public health experts are warning Tucsonans to take precautions but not to panic over the threat of becoming infected by mosquitoes carrying encephalitis.
People are urged to use mosquito repellent and wear protective clothing or stay indoors at night when the culprit culex mosquitoes are most active.
They also are being asked to be vigilant about standing water in their yards, where mosquitoes breed.
That means emptying and rinsing plant saucers, pet water dishes and other sources of standing water at least twice a week. And it means being on the lookout for other, less likely mosquito breeding grounds: old soda cans filled with water, for example, or a rain gutter stuffed with leaves.
The precautions are recommended after the recent discovery of two strains of encephalitis in mosquitoes at the Sweetwater wetland project and a nearby RV park near Interstate 10 and West Prince Road.
But despite a growing population of mosquitoes in Arizona over the last 25 to 30 years, county and state health department experts said they knew of no confirmed cases of mosquito-transmitted encephalitis in Arizona.
And despite a growing public concern, health experts yesterday were not urging drastic mosquito control measures.
"The risk (of becoming infected) is small," said Dr. Kent Campbell, director of the (University of) Arizona Prevention Center.
"Finding a couple of positive pools of mosquitoes is worse than finding no positive pools, but it doesn't tell you what the risk is of anyone coming down with the infection," Campbell said.
Others agreed.
"What is the percent chance that anyone will get this? That just can't be stated," said Michael Fink, epidemiologist with the Arizona Department of Health Services.
"We're not saying there's going to be an outbreak," Fink continued. "And we are telling people to lessen their chances of coming down with this disease."
But even if a person is bitten by a mosquito carrying an encephalitis virus, he or she may not get sick, experts said.
"And not everybody who gets sick gets real sick," Campbell said.
Often, people who contact encephalitis experience mild to severe headache, some body aches, mild fever to high fever and fatigue - or no symptoms at all, Campbell said.
But encephalitis - an inflammation of the brain - can be far more serious, as evidenced by the deaths last week of an 8-year-old girl in Queen Creek, southeast of Phoenix, and four other people in New York City.
The New York deaths have been tentatively blamed on the West Nile encephalitis virus, endemic to one of several viruses transmitted by mosquitoes.
But public health experts were still unsure yesterday of what caused the death of the Queen Creek girl.
Encephalitis can be brought on by a variety of infectious organisms. They include such common viruses as chickenpox and herpes simplex, which causes cold sores, to fungal infections such as valley fever, to intestinal amoebas and other parasites, and more common bacterial infections.
"And you can actually get it from certain drug reactions,'' said Dr. Eskild Petersen, professor of infectious diseases and public health. "The list of possible causes is tremendously long."
Before last week, the West Nile encephalitis virus had never been recognized in the United States or any area of the Western Hemisphere, according to the Centers for Disease Control and Prevention in Atlanta.
Much more common in this part of the country are the western equine encephalitis virus - which infects horses and humans - and the St. Louis encephalitis virus.
All three are "arboviruses,'' meaning they are transmitted by mosquitoes that contract the viruses by feeding on infected birds.
DEET - diethyltoluamide - is the only proven mosquito repellent, public health experts said.
DEET can be used with some precautions on children age 2 and older. Repellents with a DEET concentration of 6 percent to 10 percent can safely protect young children, according to the American Academy of Pediatrics.
DEET should not be applied to young children's hands, which they frequently put in their mouths. And the repellent should be kept well out of children's reach.
Although encephalitis is transmitted from birds to mosquitoes to humans, health experts are not urging people to stop feeding birds.
While mosquito-borne illnesses are rare in Arizonans, a mosquito-borne parasitic disease called heartworm is becoming more common here in dogs, said Tucson veterinarian Michael Lent.
The often fatal infection is easily prevented with a once-a-month tablet, Lent said.
Dr. Elizabeth MacNeill, chief medical officer for the Pima County Health Department, said yesterday that she is less worried about mosquito-borne encephalitis than the possibility of widespread, serious consequences from the upcoming influenza season, which usually starts in November and lasts through March or April.
Although annual injections of flu vaccine offer good protection from flu viruses, influenza will kill 20,000 Americans this winter, MacNeill said.
In addition, she noted, Pima County is in the second year of an outbreak of pertussis - whooping cough - that has killed two infants in the last year.
"Your chances of catching pertussis or having serious problems with the flu are much greater than your risk of becoming seriously ill with encephalitis," MacNeill said.
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E-bug.net has tips on how to control mosquitos.
The Arizona Daily Star
Tuesday, 5 October 1999
Drain wetland if it's needed, candidates say
By Thomas Stauffer
Both major-party mayoral candidates said yesterday that the city must stamp out encephalitis-carrying mosquitoes at the Sweetwater wetland, even if it means closing the facility.
"My opinion is that not one person should be exposed to that risk," Republican mayoral candidate Bob Walkup said at a press conference. "If that means we have to drain the wetland, then drain the wetland."
Democratic candidate Molly McKasson said she supported the closing of the facility "if there's no other way to wipe these things out, and there doesn't seem to be."
UA entomology professor Henry H. Hagedorn raised the issue of the wetland last week, branding it a "very serious health threat'' because it attracts so many birds, which carry the deadly virus, and so many mosquitoes, which transmit the virus to humans.
Two mosquito samples gathered last month from Sweetwater tested positive for the Western equine encephalitis virus.
Mike Witte, chairman and CEO of Alphagraphics, called the press conference with the candidates because of concerns among the 1,700 employees who work at the Tucson Commerce Business Park. The park is just 100 yards from the wetland, near Interstate 10 and West Prince Road.
"Our building grounds are infested with mosquitoes and the University of Arizona has confirmed that over 40 percent of the mosquitoes on my property are the type that causes encephalitis," Witte said. "What's it going to take, someone getting killed?"
Witte said he called the city last week to ask what he could do to protect his employees. "Their best answer was 'have your employees wear lots of OFF!(mosquito repellent)',"
he said.
A spokesman for Tucson Water said spraying pesticides has reduced the mosquito count at the wetland this year. Future modifications at the facility would reduce the amount even further, said Mitch Basefsky. "We've got less mosquitoes there now than last year or before there even was a plant, " Basefsky said. ``We're concerned about public safety, and we're working with the state and the county to make sure there's not a problem, but we don't feel that the facility should be closed."
Having fewer mosquitoes this year is no consolation if deadly ones remain, Witte said. "That's like saying we've got 50 percent less vagrants on the streets, but the ones that are left are all carrying high-powered weapons," Witte said.
City Manager Luis Gutierez said the city is doing the best job it can of getting rid of the pests. "I know they're going to cut back some plants where there was a problem, and make some other changes," Gutierez said.
Basefsky said one method of reducing the mosquitoes would be to drain one side of the wetland, dry it out to kill the mosquitoes and then do the same with the other side. "Those larva have to stay wet, so you can reduce the amount even more by using a wet cycle/dry cycle method," Basefsky said.
Nothing short of closure of Sweetwater would suffice for Witte. He said that beyond the health concerns, there is also a business concern for vendors and customers who visit his work place. "What do I say when customers ask why they have to wear Deep Woods OFF! in your building? 'Well, I don't want you to be alarmed, but you may get killed'," Witte said.
McKasson said she tried to get the city to do more about mosquitoes when she was on the council. She said the idea of a wetland is "a wonderful thing, but it's not working." "This is not the end of this wetland, but they need to make it so it functions properly." she said. "I hope we can salvage it and just redo it."
Walkup knows how severe a case of encephalitis can be. He contracted the virus as a junior in high school in 1953. "I was running around on the football field one day and bam, I just went down, " he said. ``I don't think it was the treatment that got me through it, I was just young enough and healthy enough to get over it."
Az Daily Star,
Wednesday, 6 October 1999
Mosquito virus didn't kill girl, tests suggest
QUEEN CREEK (AP) - Tests on a Queen Creek girl who died of encephalitis last month have come back negative for mosquito-borne strains of the virus.
But Arizona Department of Health Services officials said they can't totally rule out insect bites as the cause.
Alexandra Ashcroft, 8, died Sept. 23 with mosquito bites on her skin. Authorities speculated the third-grader - the first person from Arizona to die from encephalitis this summer - was infected by a mosquito.
But tests last week for the mosquito-born St. Louis and Western equine viruses came back negative, sources familiar with the girl's case said.
Limitations in testing methods so far have prevented mosquitoes from being eliminated as a cause.
State health department officials would not comment specifically on Alexandra's case, except to say that none of the four cases of encephalitis in Arizona has tested positive for the mosquito-born viruses.
While some laboratory testing is pending, mosquitoes cannot yet be blamed or ruled out in the four encephalitis cases, said Craig Levy, an epidemiologist for the Department of Health Services.
Two tests are needed to confirm the mosquito-borne version of the virus: one in the early stages of the disease and a subsequent measurement of the gradual rise in antibodies.
In Alexandra's case, investigators say she may have died too quickly for a conclusive antibody test.
The Arizona Daily Star
Thursday, 7 October 1999
No need to drain wetland, health chief says
By Jim Erickson
The city's mosquito-infested Sweetwater wetland is not a public health threat, and there is no need to drain it, the county health director said yesterday.
"It is not a threat to public health at this juncture," said Dennis Douglas, director of the Pima County Health Department. "The number of mosquitoes being trapped there is low."
Last week a University of Arizona entomologist called for closure of the man-made swamp near Interstate 10 and West Prince Road after a second strain of encephalitis virus was found in mosquitoes trapped there.
Potentially deadly St. Louis encephalitis virus was found in Sweetwater mosquitoes several weeks after Western equine encephalitis virus was detected in some of the insects.
UA entomology Professor Henry Hagedorn called Sweetwater "a very serious disease threat."
Monday, both major-party mayoral candidates said the disease-carrying pests at Sweetwater must be eradicated, even if it means closing the facility.
Douglas and other county health officials visited the 18-acre artificial wetland yesterday and met with Tucson Water officials. Sweetwater is a water recharge and habitat restoration project created and managed by Tucson Water.
Tucson Water uses insecticides to kill mosquito larvae and adult mosquitoes at Sweetwater. Larvae-killing pellets are dropped from a small, remote-control helicopter, and insecticide is sprayed from a truck to kill adults.
Douglas said he sees no reason for drastic change in the mosquito abatement program at Sweetwater.
"We're working with Tucson Water to ensure that they are getting sufficient quantities of larvicide and adulticide, and we talked about some of the challenges of getting complete coverage on the water surface," he said.
"But we did not ask them to drain the wetlands or any of those kinds of things."
Arizona Daily Star Comment,
Sunday, 10 October 1999
It came from the wetlands
By Henry Hagedorn
Bring on the water!
Make the streams run again! Let's all have a neighborhood swamp!
The fascination Tucson residents have with restoring water to this desert community is phenomenal. Tucsonans love the idea.
There is a problem, however: Water is also a dangerous fascination for Tucsonans, because mosquitoes like water, too, and each of Tucson's grandiose water plans seems highly likely to increase the problems we have with mosquitoes and the diseases they carry.
Indeed, I have become increasingly alarmed that, as these various water schemes develop, officials in Tucson seem not to want to be bothered by such small details as your health.
Witness the county health director's refusal Wednesday to close and drain the city's Sweetwater wetlands, where in recent weeks two strains of the potentially deadly encephalitis virus have been found in trapped mosquitoes. Does someone have to die before officials will start thinking seriously about the problem?
Or take County Administrator Chuck Huckelberry's recent view that the benefits of having wetlands outweigh the risk of getting sick from a mosquito bite. Really? Try telling that to New York City public health officials as they grapple with an outbreak of encephalitis there that has now infected more than 40 people and killed several.
Such carelessness is disturbing, because some of the problems we are having with mosquitoes result from poor planning, lack of foresight and poor management on the part of Tucson Water and other government departments. Moreover, these problems will get worse - much worse - if current plans for a wetter Tucson continue without considering the consequences.
Mosquito bites are a nuisance, but as we are all learning from recent national news, as well as from the disovery of encephalitis near the city's Sweetwater wetlands, mosquitoes can transmit diseases. This is another matter entirely, and it requires that we, as a community, think carefully about the decisions we make now about our use of water.
The problems here are complex because we are dealing with three different mosquitoes and three different disease threats.
The first of those problems involves the construction of artificial wetlands, especially involving wastewater. Currently, the only functioning wastewater wetlands we have near Tucson are the ones currently in the news: the euphemistically named "Sweetwater wetlands" near Prince and I-10.
The water in the wetlands comes from the sewage treatment plant across the street and is not secondary water, but rather backwash water from cleaning filters that remove particulate matter from the sewage during treatment.
The title ``Sweetwater'' could not be more inappropriate; the low quality of the water makes Sweetwater wetlands a health hazard without the mosquitoes. Still, the city decided to build the facility to purify this water and to create a site that would attract birds and therefore be recreational.
The problem with this site, and with wetlands in general, is that they attract both birds and mosquitoes - in particular, a mosquito called Culex tarsalis. The birds are often infected by a virus that can cause a disease in humans called encephalitis. This virus is transmitted by Culex tarsalis, meaning that the mosquito can pick up the virus from one bird and transmit it to another.
Further, this mosquito sometimes bites humans and horses and can therefore transmit the virus to them. Viral encephalitis is a sometimes fatal disease that affects the nervous system. There are several types of viruses that cause encephalitis in the Western states, the most dangerous of which is called St. Louis encephalitis.
St. Louis encephalitis virus has been detected in mosquitoes collected at the Sweetwater wetlands and at a nearby recreational vehicle park, as well as near Phoenix and other places around the state. How much of a threat is this to the people in Tucson? We do not believe mosquitoes at Sweetwater fly far enough to be a threat to most of the people in the city, but they certainly are for the people living and working in the area around thewetlands.
What is irritating in this, meanwhile, is that it is a problem that didn't have to happen. The design of Sweetwater was decided on despite the expert advice of environmental consultants who warned of the danger of mosquitoes. Further, the design made it impossible to attempt mosquito control once the predictions proved true.
In addition, Sweetwater is being touted as an educational site to which you can bring children to show them what this area was like years ago.
Do we really want our children running around this cesspool? There is not even a working sink on site at which they can wash their hands with soap if they are contaminated.
This is mismanagement on a large, and rather expensive, scale. Wetlands are complex ecosystems involving, in part, water, plants, mosquitoes and a host of other invertebrates, birds and other animals, as well as a wide range of microbial inhabitants. Managing such a site requires a professional staff, which has been sadly missing.
My concern, beyond that, is that the city of Tucson and Pima County have plans to build several other wetlands in and around Tucson. The largest of these will be in the detention basin near Tucson Electric Park. This site is also being designed to attract birds. As it is near the ballpark, the mosquitoes bred there will have easy access to people to bite in the stadium; how convenient for the mosquitoes.
Historically, Culex tarsalis has been a mosquito that was more typical of rural areas of Arizona. Now that these wetlands are being built, or planned, nearer to population centers, the threat of outbreaks of mosquito-borne encephalitis of the type that occurred recently in New York City are much more likely to occur in Tucson. In fact, there has been a threefold increase in the number of mosquitoes testing positive for encephalitis in the last year, most of which were collected from urban areas.
Can wetlands be built that will not breed thousands of mosquitoes? This is an active area of research and a definitive answer is not available.
The Tres Rios wetlands near Phoenix offer an instructive example. These wetlands are larger than the ones at Sweetwater and had similar problems with the triad of birds, mosquitoes and encephalitis.
Because of these problems, it was shut down and drained. Under the capable direction of Roland Wass, it was redesigned, using several of the more recent concepts for preventing mosquito breeding, including changing the shape of the wetlands and using different arrangements and types of plants.
But the fact is that these are experiments, and we don't yet know how to create wetlands that will not produce mosquitoes. It would be wise for us to put plans for wetlands on hold until an effective design has been designed and tested. It is also reasonable for us to ask whether wetlands are, in fact, an effective way to recover water.
And so, because Sweetwater presents such a clear health danger to the people who live and work in its vicinity, I maintain that it should be closed, drained and not reopened until we can be more confident about wetlands design and operation. Wetlands are complex ecosystems involving water, plants, mosquitoes, birds, microbes and animals. Managing such a facility requires a professional staff. Until Tucson Water hires professional people
to deal with such complex issues it should dry out its swamp.
Other water schemes also deserve a more careful look. The concept of revitalizing our streams, having water flow through them again, for example, is being actively planned by many groups within the area, including those who are interested in reclaiming CAP water, as well as those who want to restore the mesquite bosques and cottonwoods that once lined the Santa Cruz many years ago.
Stories of what these rivers were once like are very attractive, but these stories fail to feature malaria. Malaria is caused by a protozoan that is also transmitted by a mosquito, in this region one called Anopheles freeborni.
Malaria was a serious problem in this area 130 years ago. Records kept at Fort Lowell indicate that between 1868 and 1874, the number of cases of malaria in the soldiers ranged from 70 to 210 per year, about 50 percent of the cases of all illnesses reported.
Mosquitoes have different preferences for water conditions. Anopheles freeborni prefers clean running water of the type that is found at edges of streams or in wetlands that have cleaner water than is found at Sweetwater.
It is likely populations of this mosquito will increase as streams are revitalized, and creating conditions in the streams that prevent mosquito growth may be very difficult. Various plans to reduce the growth of mosquitoes in these streams have been proposed, such as filling and drying them out on a periodic basis. This may work, but experiments need to be done to prove it.
Malaria is one of the most severe diseases transmitted by insects in the world. It is estimated that 110 million new cases of malaria occur every year, most of them in Africa. It is not uncommon for tourists to return home with malaria. Such an event could re-establish the disease in Tucson if the population of Anopheles freeborni increases.
The city should therefore proceed with the utmost caution as it weighs putting water back into its streambeds. Limiting the water available for sustaining larvae and life cycles of mosquitoes must become an urgent public health priority.
One clarification is in order, meanwhile. This concerns the mosquito that bothers us most in Tucson: Aedes aegypti - the one that is a vector of dengue, another serious viral disease that has not reached Tucson as yet.
Aedes aegypti, it should be understood, differs from the other mosquitoes we have been discussing in that it prefers to live in the small amounts of water that are common in our back yards. Because it lives in our yards, its control requires a different response than improved city management: namely, the creation of citizen-run mosquito control districts in the city. A drive to organize such districts is being spearheaded by Sam Hughes resident Sarah Palmer.
It is important, however, that people not confuse this common backyard mosquito with the mosquito breeding in the wetlands. They represent two very different problems, both of which need to be controlled.
As to where we should go from here, the first stop should be dialogue. Should we panic about these situations? No. Should we be concerned? Definitely. And disturbingly, the problems we are having with mosquitoes in large part result from poor planning, lack of foresight and poor management. Solving these problems will take some effort by the whole community.
I don't think most people in the area are aware of the plans the city and county government have to build wetlands around the city and to make our desert streams run again. Most of the time, these plans are being made and embraced in blithe ignorance of the disease problems such projects might bring.
It is vital to the future health of this community that we have an open and honest discussion of these problems before new wetlands are created or water is released into our riverbeds for whatever good and noble purposes.
Perhaps it is time for us to realize it may not be in our best interests to recreate the mosquito-friendly conditions that existed here hundreds of years ago, now that we are a sprawling metropolis.
Henry Hagedorn is a professor of entomology at the University of Arizona. He leads the Mosquito Busters working group at the university.
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