Weather increases West Nile threat

David Kihara

Wednesday, Feb. 23, 2005 | 9:21 a.m.

The recent heavy rains in Nevada could exacerbate the threat of West Nile virus in Southern Nevada by creating breeding grounds for certain types of mosquitoes that carry and transmit the virus, the Clark County Health District officials said Tuesday.

The intense rains this year have already increased the water level of some streams and ponds in Beatty and filled swimming pools that had been empty. All the water has created breeding grounds for mosquitoes in and around Clark County, and any standing water could turn into breeding areas for mosquitoes by spring and summer, said Daniel Maxson, environmental health supervisor for the Health District.

"If the weather sustains the rains through spring, we are going to be looking at a very different picture (than last year)," said Maxson in reference to the mosquito population in Clark County.

Neglected swimming pools, in particular, could become perfect for breeding areas for the Culex mosquito, the species of mosquitoes that transfer the West Nile Virus to humans, Maxson said.

Other areas of concern in the Las Vegas Valley include birdbaths, children's swimming pools, unused wheelbarrows, and old tires all of which could potentially fill with water, he said.

"Those are the ones we're worried about," he said, adding that it is highly unlikely that the water would evaporate on its own by the time the mosquitoes become active in early April.

The Culex mosquitoes do not begin to lay eggs until early summer and that activity usually peaks in July, said Richard Hicks, an entomologist and vector control supervisor for the Clark County Department of Public Works.

Although time may appear to be on the side of the health district officials, they are stepping up efforts now to monitor the mosquito populations in rural areas such as Nye and Lincoln counties, Maxson said.

On Feb. 15, officials with the health district went to Beatty to survey the mosquito populations at the Amargosa River to survey how many mosquitoes are currently hatching in order to get a better understanding of the issues they will face later, Maxson said.

The Health District will send another survey team to Lincoln County to assess the mosquito population in various areas on Feb. 25.

Although the number of mosquitoes in those areas is now very low and the type of mosquito found there currently -- the "floodwater mosquito" -- is not a carrier of West Nile Virus, the information the teams will bring to the health district will ultimately help health officials detect the mosquitoes before they reach the human population and verify whether preventative measures are working, Maxson said.

Last year approximately 23 people were diagnosed with the West Nile virus in Clark County, Hicks said. Only about 20 percent of individuals with West Nile show symptoms, and of that group only a small percentage come down with serious symptoms, he said.