CS Masthead


Mosquitoes Test Positive For West Nile Virus In Six Montana Counties

The Montana Department of Public Health and Human Services, in collaboration with Carroll College and Montana State University, has confirmed this season’s first signs of West Nile Virus-positive mosquitoes in Cascade, Blaine, Prairie, Sheridan, Phillips and Teton counties. 

In addition, an American White Pelican near the Medicine Lake National Wildlife Refuge in Sheridan County tested positive.

Although no case of human infection has been reported in Montana, 174 cases of WNV have been reported to the Centers for Disease Control and Prevention from other states.  The highest rates reported this year have been in North and South Dakota.

“Montana has been fortunate in recent years with relatively few cases of WNV reported,” said DPHHS director Richard Opper. “However, recent activity in neighboring states is a concern. We want to remind everyone that WNV is preventable and taking simple precautions can make a big difference.”

In 2012, six human cases of WNV were reported in Montana, including one death. Nationwide, there were 5,674 cases of WNV in 2012 and, of those, 286 were fatal. 

According to Joel Merriman of the DPHHS Communicable Disease Control Bureau, a seemingly late summer has stalled the increase in numbers of C. tarsalis, Montana’s common mosquito WNV vector. “This may explain the absence of reported human disease, to date, this season,” Merriman said.

Mosquito trapping, sampling and testing began in mid-June and will continue until approximately the end of September.

Most people who become infected with WNV experience no symptoms. Some individuals may develop a mild illness, called West Nile fever, which may last for three to six days. Generally, no treatment is needed. Other individuals, fewer than one of 150, may become severely ill with West Nile encephalitis or meningitis. Symptoms of this disease include headache, rash, high fever, stiff neck, mental confusion, muscle weakness, tremors, convulsions, coma and paralysis. Individuals who develop any of these symptoms should see their health-care provider. 

DPHHS reminds Montanans to take precautions and protect against West Nile Virus by following the five Ds for WNV prevention.

•DUSK/DAWN - Mosquitoes are most active during this time. If possible, stay indoors during the early morning and evening hours.

•If you must be outdoors when mosquitoes are most active, DRESS in long sleeves and pants.

•Before going outdoors, remember to apply an insect repellent containing DEET (N, N-diethyl-m-toluamide). DEET is recommended by the CDC and is the most effective and best studied insect repellent available.  Use a repellent containing 25 percent to 35 percent DEET when it is necessary to be outdoors. Children ages two to 12 should use repellent with 10 percent DEET or less. Products containing picaridin and permethrin have also been found to be effective in repelling mosquitoes, as has oil of lemon eucalyptus.

•To keep the mosquito population at bay around your home, DRAIN standing water in old tires, barrels, buckets, cans, clogged rain gutters and other items that collect water.  Change water in pet bowls, flowerpots and birdbaths at least twice a week.

For more information about WNV protection and detection efforts, contact your local county health department or visit www.dphhs.mt.gov.