No, this bug doesn't prefer farmers to city folks, but there are some issues you might consider.
This virus is a close relative of some heavy-hitters responsible for thousands of deaths over the years: Yellow Fever, Dengue and Japanese Encephalitis, just to mention a few.
All of these diseases are spread by the bite of infected mosquitoes, only now the mosquitoes infected with West Nile virus are right here in Yuma County.
The standard scenario for virus transmission is for the mosquito to acquire
an infective dose of virus in a blood meal taken from a bird. The threshold
for a mosquito to be infected from a blood meal is 100,000 virus particles
per ml of blood. Many bird species do not produce a sufficiently high
a level of circulating virus. Some do however, and some of the best virus
producers are abundant in the desert southwest, and include finches and
US Army researchers at USAMRIID have looked at what kinds of mosquitoes are efficient vectors of West Nile virus, and found some very disturbing facts. The most efficient vector evaluated so far appears to be one of the most abundant species along the Colorado and Gila rivers; Culex tarsalis.
Infection and dissemination rates for mosquitoes that ingested 107.0 +0.5 PFU/ml of West Nile virus
Department of Vector Assessment, Virology Division, USAMRIID
Feel free to call either the Yuma County Pest Abatement District at 726-1030 or Yuma County Health Department at 317-4584 for advice and treatment options.
If you have livestock, dump the water at least every week or stock the troughs with mosquito fish also available from YCPAD at no cost.
Remember, you as a landowner are responsible for mosquitoes breeding on your property. Please take the time to check for mosquito breeding sites, and feel free to ask for assistance from the above agencies.
The West Nile infection in horses is deadly. About 1/3 of infected horses will die or have to be euthenised. This can be avoided with a vaccination available from local large animal veterinarians.
West Nile infection in humans is reported as either West Nile fever, which is the more common mild set of symptoms, which includes fever, headache, body ache, occasionally rash on the body trunk and swollen lymph glands, or as the more severe West Nile Meningo-Encephalitis (WNME). The latter occurs in less than 1% of infected people but includes severe head and neck pain, meningitis, encephalitis, tremors, flaccid paralysis, coma and death. Older people are at increased risk from the more severe form of the disease as shown below:
Human WNV Disease Incidence, by Age Group and Clinical Category, United States, 2002*
West Nile Cases Reported by Week (2002)*
In summary, here are some things you should do:
For more information call YCPAD at 726-1030. On-line information on West
Nile surveillance in Arizona is available at:
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director Cooperative Extension, College of Agriculture and Life Sciences, The University of Arizona.
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Information provided by:
Barry Bequette, email@example.com Extension Agent, Urban Horticulture
Barry Tickes, firstname.lastname@example.org Extension Agent, Yuma County
Mohammed Zerkoune, email@example.com Extension Agent, Agriculture
University of Arizona, Tucson, Arizona.
Material written September 2003.
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