Melissa
Kaplan's
Herp Care Collection
Last updated
April 19, 2007
West Nile Virus and Mosquito Control
Overview, Suggestions, and Resources
©2002 Melissa Kaplan
What
do WNV and Lyme Disease and related tickborne infections have in common?
Ticks!
Transstadial
transfer of West Nile virus by three species of ixodid ticks.
West
Nile virus Web site promoted
Carol
Benfell, Press Democrat,
08/17/2004
SANTA ROSA - A state West Nile virus hotline for reporting dead birds is being inundated with calls, and officials are asking the public to respond by Internet instead. Thousands of calls a week have been pouring into the state health department as West Nile virus spreads across California. Waiting times have become so long that callers are hanging up, health officials said. The state tracks the progress of West Nile through necropsies of dead birds; birds are often the first to succumb to the disease. West Nile virus is a mosquito-borne disease that can sicken humans and, in rare instances, kill. The first birds in Sonoma County felled by West Nile virus were reported earlier this month. Authorities fear there may be human cases before fall, when mosquito season ends. The Internet address to report a dead bird with no visible injuries is westnile.ca.gov/deadbird.cfm. The hotline number is 1-800-WNV-BIRD. As of Friday, 169 human cases of West Nile disease had been reported statewide, including one in Yolo County, near Sacramento. Five people in Southern California have died of the disease so far this year.
Medical Diagnostics Laboratories now has WNV detection by PCR.
The West Nile Virus (WNV), a mosquito-borne virus, has now been detected in most of the states in the United States, in Canda and Mexico. Dozens of dead and infected birds and mammals have been tested across the US and Canada, both wild and domestic Zoo animals are getting it. Many people are surprised that reptiles are susceptible, as well. WNV is spreading far more rapidly than projections originally estimated and is being transmitted in ways unforeseen by the federal and state public health agencies.
The USGS maintains detailed WNV maps on on reported and confirmed cases across the U.S. The Centers for Disease Control maintains a list of states and confirmed cases.
Of
Special Note:
2004:
What is more pervasive than WNV, grossly
underdiagnosed, and disabling thousands of people a year?
WNV
Drawing Closer to California's North Coast
2003:
California Predicted to be Epicenter of 2004
WNV Season
DHHS
Warns WNV Could Hit Hard (2003)
2002:
WNV Transmitted
through Blood, Organ Donation
WNV Transmitted
through Breast Milk
Neurological
Symptoms Alert
Updated Case Count
(CDC)
|
Got blood? The West Nile Virus (WNV) is spread through mosquito bites. As with tickborne diseases, mosquitoes inject the infectious organism, along with an anticoagulant, into other animals when they settle for a blood meal. |
 The treehole mosquito (Aedes triseriatus) transmits the virus that causes La Crosse encephalitis. Photo: CDCVBID |
The
mosquitoes
Only the female mosquitoes bite, needing the protein in the blood for
use in producing her 150 or so eggs. She deposits the eggs in water or
damp place. (Male mosquitoes feed on the sugars from flower nectar and
fruit.)
Humans are not the only animals the female mosquitoes look to for their blood meals. Other mammals, as well as birds and even reptiles provide the concentrations of the amino acids needed for the eggs.
One square foot of shallow water, under the right conditions, can produce 100,000 mosquitoes. That is more than 1,000,000 mosquitoes per square meter!
While most of the 1,500 species of mosquitoes worldwide are crepuscular (dawn and dusk), they won't pass up an opportunity to feed if they come across a potential blood meal.
Avoiding Bites
Since mosquitoes
are most active at dawn and dusk, try to avoid being outdoors during those
hours. If you must, cover up: long pants, long sleeved shirts, and a mosquito
repellent on exposed areas. There is a wide range of repellents, from
the highly to non-toxic.
If babies are outside during the peak hours or near suitable mosquito habitat, keep them covered up. Mosquito netting can be draped across strollers and playpens outside, and bassinet and play areas inside.
As with other infectious organisms, those in the high risk category are at higher risk from getting ill from mosquito borne disease. Infants and toddlers, the elderly, and anyone with an already compromised or suppressed immune system are at highest risk.
Reducing or Eliminating
Mosquito Populations
The biggest
impact is to eliminate all nonessential standing water and damp areas.
Empty containers, flower pots, saucers should be emptied and turned over
so that they cannot collect water.
Depressions or hollows that stay damp or wet for long periods of time should be leveled or permanent drainage established.
If you are being bothered by mosquitoes but cannot figure out where they are coming from, some species use seeps under buildings, around septic tanks and other hard-to-find areas. If you have dealt with all standing water you can find, contacts your local Mosquito & Vector Control agency to ask about their coming out to inspect the area to try to locate the source.
The mosquito larvae (small black "wrigglers" that can be seen floating, swimming and flipping around in standing water) do have some natural predators: mosquito fish (Gambusia affinis) eat the larvae, while a bacterium, Bacillus thuringiensis israeliensis, parasitizes them. Dragonflies are one of the mosquitoes daytime predators, as are many birds. Contrary to popular notion, while bats and purple martins do eat mosquitoes, they don't eat enough to be relied upon to control the astounding numbers of mosquitoes that can reach adulthood from very small bodies of water.
In bodies of water that cannot be eliminated, such as ponds and water features, use mosquito fish or Bacillus thuringiensis israeliensis. The latter comes in compressed disks called dunks, as well as in loose and pelleted forms. Placed in the water (the amount depends upon the volume of water), the organisms go to work on the larvae. Remember to put in fresh Bt israeliensis every 30 days or as directed on the package.
Mosquitoes don't like moving water, so water features with active fountains or bubblers kept on all the time will dissuade any mosquitoes from settling to lay their eggs. Some mosquito species lay their eggs on algal mats that grow on the surface of still water or along the still shore water of large ponds. These mats can be broken up and mosquito fish used to eliminate any larvae.
Bt israeliensis are useful both in water in which fish cannot be kept, as well as in water that has fish, as the organisms will not harm fish, including fish sensitive to pesticides. (Bt israeliensis may clog up very small pumps in small water features, however, so read the pump literature carefully.)
Why
You Should Care
Mosquito-borne diseases are like any other viral and bacterial infection:
some people are more susceptible than others when it comes to their immune
system being able to fight off the infection. The people most susceptible
to infection are the very young (children under 5 years of age, due to
their immature immune system), the elderly, those with compromised immune
systems (cancer patients, those with HIV/AIDS and other autoimmune diseases,
blood and organ recipients). Pregnant women and their fetuses may also
be at risk: there simply is not enough known at this point to say for
sure.
Many animal species are highly susceptible, too. That is why the states' surveillance system involves certain bird species, as well as horses. Some other animals are very susceptible too, such as emus. In September, the WNV was confirmed for the first time in an Illinois dog.
Why Everyone Needs
to Take Action
Don't rely on your city or county mosquito vector control staff to find
and deal with all the standing water in public and private areas. If you
see standing water that no one seems to be paying attention to, call them!
Look in the county or city pages of your phone book, in the department
of health listings. Vector control may be listed on its own or under the
environmental health subsection.
Some mosquito vector control departments give out mosquito fish and instructions on using them to help control mosquito larvae. In California's Sonoma and Marin counties, contact:
Marin-Sonoma
Mosquito & Vector Control District (MS/MVCD)
595 Helman Lane (Hwys 116 x 101)
Cotati 94931-9736
800-231-3236
707-285-2200
If you find finches crows, ravens, red-tailed hawks or sparrows within 24 hours of death, contact the California Department of Health Services WNV dead bird line at 877-WNV-BIRD (877-968-2473).
Information
on WNV and other Arboviruses
West
Nile Virus: Avoid Mosquito Bites to Avoid Infection
States Known To Have WNV
USGS
WNV Maps
West
Nile Virus Will Sweep Across U.S. (NewScientist.com)
Links
to State and Local Government Sites (May not be complete)
International
Society of Infectious Diseases Bulletins (ProMED)
MedlinePLUS:
West Nile Virus
West
Nile Virus and Weather
CDC:
Statistics, Surveillance and Control
CDC Div. of
Vector-Borne Infectious Diseases: Arboviruses Encephalitides
National Biological
Information Infrastructure: WNV
Mosquito
Control
Mosquito & Vector
Control Association of California
Marin-Sonoma Mosquito & Vector
Control District
Shasta Moquito Vector Control
District
Moquito Control & Research
Links
Biological
Control Application to Mosquito Abatement (Orange County, CA)
Natural Pest Control (online sources
for Bt israeliensis)
Products and
Promotions That Have Limited Value for Mosquito Control
US
Department of Agriculture:
Mosquito &
Fly Research Institute
How
Attractive Are You?
WNV
in Canada
Health
Canada | Santé
Canada
Other sources used
for this article:
Marin-Sonoma Mosquito & Vector
Control District (pers. comm.)
El
Dorado County Environmental Management Department
Everglades National
Park
Find out about activities in your city, county and state
To find your state's
health departments listing:
www.state.xx.us (replace the xx with
your state's two letter abbreviation) or use the CDC's Public Health Department
option on its search page.
Find your city's departments
listing
www.ci.city-name.xx.us or
www.ci.yyy.xx.us where city-name
is the city full name, yyy is the city's standard abbreviation for its
name , and xx is your state's two letter abbreviation. For example: www.ci.santa-rosa.ca.us
= Santa Rosa, CA; www.ci.la.ca.us = Los Angeles, CA; www.ci.ssf.ca.us
= South San Francisco, CA; www.ci.dallas.tx.us = Dallas, TX.
Reptiles
& WNV
West
Nile Virus, Reptiles, Alligators, USA (FL)
West
Nile Virus, Reptiles, Alligators, USA (FL) 02
West
Nile Virus, Reptiles, Alligators, USA (FL) 03
West
Nile Virus, Reptiles, Alligators, USA (FL) 04
West
Nile Virus, Reptiles, Alligators, USA (FL) 05
