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West Nile Virus poses threat, preparedness encouraged

by Wyoming Livestock Roundup

Last year, the Southwest saw their highest incidence of West Nile Virus in recent years. In Wyoming, 2012 only resulted in seven human cases of West Nile Virus, four avian cases and five equine cases. They also found 13 positive mosquito pools.

“There are issues with West Nile Virus is the states surrounding us,” comments Wyoming Weed and Pest Director Slade Franklin. “The Midwest is still the hotbed for West Nile, so we are right on the edge of what is going on.”

“We saw a lot of impacts in Texas and Oklahoma, and North Dakota had the highest incidence per capita of West Nile Virus in the country,” continued Franklin. “When you look at the per capita occurrence, Wyoming is somewhere around number 15. We are still high in incidence of West Nile.”

As a result, Franklin notes that West Nile Virus is of top concern for public health officials.

Controlling mosquito 


To control mosquito populations, Franklin noted that the Wyoming Department of Agriculture works each year to distribute state funding to assist mosquito management programs.

“The funding is provided through the Emergency Insect Management Program,” says Franklin. “This program and funding was set up for municipalities and government entities needing assistance in implement management programs for cyclic insect outbreaks or insects that can transmit pathogens harmful to human health.” 

The program has been around since 2003 and is also utilized for Weed and Pest grasshopper management programs. 

“The grant emphasis the use of pre- and post-application mosquito monitoring in making local management decisions instead of the historic principle of routine fogging,” he continues. 

Though this year grants weren’t all fully funded because of state budget cuts, Franklin mentions that all programs that applied for assistance received funding.

The Emergency Insect Management fund allocated $1,328,000 in 2013 for mosquito management to a wide variety of municipalities, ranging from big cities to small towns.

Preventing West Nile Virus

The primary carrier of West Nile Virus is a mosquito species called Culex tarsalis

C. tarsalis has a tendency to breed in really dirty, stagnant water,” comments Franklin. “Water in old tires, for example, is a habitat that Culex tarsalis loves.”

While tires are some of the worst breeding grounds for the mosquito, Franklin notes that any stagnant waters, including animal watering bowls, are also breeding grounds. 

The Wyoming Department of Health (WDH) says the “Five Ds of West Nile prevention” include dusk, dawn, dress, drain and DEET.

“When possible, avoid spending time outside at dusk and dawn,” says the WDH. “Wear shoes, socks, long pants and a long-sleeved shirt when outdoors for long periods of time or when mosquitos are most active.”

Additionally, draining any standing water is important to prevent proliferation of mosquitos. 

Finally, insect repellents containing DEET are also effective in reducing exposure. Other insect repellents, says WDH, may be less effective than those with DEET or picaridin.

Human infection

West Nile Virus can infect humans, birds, horses and other mammals. It can lead to West Nile fever or West Nile encephalitis, which results in swelling of the brain tissue.

“People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands. This is called West Nile fever,” says WDH. “People with more severe infections may experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions and paralysis. This is called West Nile encephalitis.”

West Nile Virus can also result in neuroinvasive illness, with clinical syndromes ranging from febrile headaches to aseptic meningitis to encephalitis, adds WDH.

“At this time, no specific treatment of human West Nile Virus infections is available,” says WDH. “In severe cases, treatment consists of supportive care that often involves hospitalization, intravenous fluids, respiratory support and prevention of secondary infections.”

Livestock considerations

Wyoming Assistant State Veterinarian Bob Meyer notes that West Nile Virus cases in livestock seem to ebb and flow.

“Over time, people vaccinate like mad, and we don’t see very much West Nile Virus,” he explains. “Then, they let their guard down and don’t hear about West Nile Virus, so they neglect to vaccinate and immunity wanes.”

He continues that the virus is present throughout the U.S., so vaccinations are important.

“I encourage horse owners to get their horses boosted every year because of possible exposure,” Meyer continued, noting that people should be vigilant in continuing to vaccinate.

For more information on West Nile Virus, visit

Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to

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