BLM Glasgow working to stop spread of West Nile Virus

West Nile Virus is a disease that has spread from Equatorial Africa to the far reaches of Montana.

The Bureau of Land Management Glasgow Field Office is in the second year of a West Nile Virus surveillance partnership with Montana State University.

The effort to stand watch against West Nile Virus is centered in the newly designated Sagebrush Focal Area, partially located in southern Valley County. Positive test results for West Nile Virus have proven this year’s monitoring efforts to be fruitful. According to Montana State University Professor of Veterinary Entomology Gregory Johnson, West Nile Virus surfaced in Lake, Phillips, Prairie and Valley Counties in 2016.

 “West Nile Virus is very deadly to Greater Sage-grouse and considered one of the greatest threats to the population in this area,” said BLM Glasgow Field Manager Pat Gunderson.

West Nile Virus was identified in birds in the Nile delta region in 1953. Birds are the natural hosts of West Nile Virus, which is mainly transmitted to people through mosquitoes. The virus can cause neurological disease and death in people, horses and other animals, according to the World Health Organization. While some people develop a life-threatening illness that includes inflammation of the spinal cord or brain, approximately 80 percent of people infected with West Nile Virus either do not develop symptoms or have only minor ones, such as fever and mild headache. Mild symptoms of a West Nile virus infection generally go away on their own, according to the Mayo Clinic’s

Mosquitoes bearing illnesses have been one of the few forces in history able to decimate populations and stop wars at the infirmary rather than the battlefield by crippling entire armies. Therefore, to protect the American people, livestock and wild animals like Greater Sage-grouse, the BLM staff monitoring for WNV stand guard, ready to sound the warning at the first sign of trouble.

The number of infected mosquitoes peaks around early fall, which translates to more people and animals contracting the disease in late August to early September. 

“We are able to take advantage of Seasonal BLM staff in trapping mosquitoes one night per week from mid-June to mid-September,” explained Gunderson.

Nate Wold is one of the BLM seasonal employees working on the monitoring project. Wold uses netted traps at five locations spread over an approximately 140-mile loop. “Traps can collect from as few as 20 to well over 1,000 insects per night at each location,” he said.

Each unsorted catch is sent to Johnson and his staff at Montana State University. The insects are then sorted by species and the Culex tarsalis mosquito samples, the primary carrier of West Nile Virus, are sent to Carroll College to test for the virus.

“The partnership is a very cost effective way to conduct this testing in northeastern Montana,” said Gunderson.

Although this effort is focused on Greater Sage-grouse, the information regarding West Nile Virus can then be shared with the American public, land owners, livestock producers and government agencies so they can take appropriate measures. 

 “Peak biting activity for this species and many others is between dusk and midnight,” Johnson said. “When outside during these hours and mosquito are noticeable, it is highly recommended to use an insect repellent that contains either DEET (Tradename OFF), picaridin (Cutters Advanced), oil of lemon eucalyptus (Repel Lemon Eucalyptus), or IR3535 (Avon Skin-so-soft Bug Guard). These products provide longer-lasting protection compared to other products. Wear long-sleeved shirts and pants to reduce the amount of exposed skin.”

Human West Nile Virus infections have been reported in a number of countries for over 50 years. According to the World Health Organization, West Nile Virus was first isolated in a woman in the West Nile district of Uganda in 1937. It is commonly found in Africa, Europe, the Middle East, North America and West Asia. The largest outbreaks occurred in Greece, Israel, Romania, Russia and the United States. West Nile Virus circulating in Tunisia was imported to New York, producing an outbreak that spread throughout the continental United States of America from 1999-2010. The virus is now widely established from Canada to Venezuela.

 “Horses and other equines are also greatly affected by West Nile Virus. There are insect repellents available that can be applied to horses as a spray or wipe-on. Vaccinating horses for West Nile Virus is recommended,” Johnson added.

Future plans for an expanded BLM and MSU partnership include increasing the surveillance area in Valley and Phillips Counties and investigating which water body-types in sagebrush habitat are more prone to produce the C. tarsalis mosquito. Since this species is dependent on more permanent water bodies for breeding, this information will potentially enable the BLM to take prescribed management actions that will limit their production.

For more information on mosquito pools that tested positive for West Nile Virus, go to



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