Bird Tests Positive for St. Louis Encephalitis in Clark County

Health District Stresses Need for Preventative Steps to Avoid Mosquito Bites


28 June, 2005

(Las Vegas, Nev., – June 28, 2005) – The health district has received confirmation from the Nevada Department of Agriculture Animal Disease Laboratory that a migratory mallard has tested positive for St. Louis Encephalitis. Blood from the mallard was collected earlier this month as part of a cooperative agreement between Clark County and the U.S. Department of Agriculture that provides for the periodic sampling of bird populations for disease.

The virus that causes St. Louis Encephalitis is spread in the same manner as West Nile virus — through the bite of infected mosquitoes. The insects acquire the virus by feeding on infected birds. According to the U.S. Centers for Disease Control and Prevention (CDC), only three human cases of St. Louis Encephalitis have been reported in Nevada since 1964. No West Nile virus activity has been detected in Clark County this year.

“Though human cases of St. Louis Encephalitis are rare, this detection, along with the upcoming West Nile virus season, underscores the importance of protecting yourself from mosquito bites,” said Dr. Donald Kwalick, chief health officer.

The following actions can help prevent mosquito bites:

  • Apply an insect repellent containing DEET (N, N-diethyl-meta-toluamide) according to manufacturer’s directions. Repellants containing Picaradin or oil of lemon eucalyptus can also be effective in preventing mosquito bites.
  • Wear pants and long-sleeved shirts, when outdoors.
  • Avoid spending time outside when mosquitoes are most active, notably at dusk (the first two hours after sunset) and dawn.
  • Eliminate areas of standing water, including bird baths, un-maintained swimming pools and sprinkler runoff, which support mosquito breeding.
  • Make sure doors and windows have tight-fitting screens without tears or holes.

For additional information, visit the health district website at or call the district’s West Nile virus telephone information line at (702) 759-1220. The public may call the line for basic information and to report dead birds, mosquitoes, standing water or improperly maintained swimming pools (which support mosquito breeding).

For more information on the laboratory results, contact Ed Foster with the Nevada Department of Agriculture at (775) 688-1182.

Visit the Media Contacts webpage for media related inquiries.


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