West Nile Virus a public health crisis in the making?

SACRAMENTO - Public Health officials today warned that California counties could see a 200 percent increase in West Nile Virus (WNV) this year due to a warmer than usual winter combined with new reporting protocols causing significant delays in treating mosquito breeding grounds. WNV has been identified in dead birds and mosquitoes in 2012 two months earlier than in previous years. In addition to the early arrival of mosquito season, California counties have seen a 183 percent increase in the detection of WNV; a 413 percent increase in the number of dead birds due to the virus; and a 75 percent increase in the detection of WNV in mosquito samples.

"This is a public health crisis in the making," said Ken Bayless, President of the Mosquito and Vector Control Association of California. "We are facing one of harshest mosquito seasons in years, and we are seeing a dramatic increase in the number of mosquitoes carrying WNV."

For 2012, WNV has been found in 12 counties, including Contra Costa, Fresno, Kern, Los Angeles, Merced, Riverside, Sacramento, San Bernardino, San Joaquin, Santa Clara, Stanislaus and Yolo.
Year to date, 91 positive mosquito samples have been reported in six counties (compared to only five positive samples last year at this time.) During last week alone, there were 61 new WNV positive mosquito samples reported in the counties of Sacramento (40), Riverside (11), Kern (8) and Fresno (2).  Forty-nine dead birds have been found in eight counties and within the last week, 16 new WNV positive dead birds were found in the counties of Merced (1), Sacramento (12), San Joaquin (2) and Stanislaus (1).

The increase in mosquitoes and detection of WNV is hitting California at the same time new regulations are hampering efforts to combat the increase. New regulations effective January of this year require vector control officials to seek a National Pollutant Discharge Elimination System (NPDES) Permit before treating standing water infested with mosquito larvae. The new regulations require 24-hour background sampling prior to treatment of water bodies, including visual and physical monitoring (including turbidity, pH, temperature and emulsifiable concentrates) at 18 sites for each active ingredient of the pesticide being applied. Technicians must then re-sample the ponds within 24 hours and seven days after implementing the prevention measures. The lifecycle of a mosquito is extremely short; larval eggs become flying adults in just three to five days. Because of the extreme time sensitivity, targeted spraying of standing pools of water infested with mosquito larvae must take place within a 72 to 96-hour window to avoid the need for spraying adult pesticide over a much wider geographic area. Within five days, adult mosquitoes can emerge and fly over 10 miles where they can lay eggs on new standing water.

The new regulations require a control technician to spend on average 9.6 hours per month implementing the additional inspections and monitoring and reporting requirements at 34 sample sites. One control technician can treat 50 infested sites in 9.6 hours. It is estimated that each control technician in the field is able to treat 50 fewer sites as a result of the time spent implementing the new monitoring and reporting requirements. If only 100 pools of standing water in a district of 10,000 sites are left untreated before the larvae become flying adults, it results in the need to spray adult pesticide over 100,000 acres.

The new regulations are duplicative of monitoring and testing requirements under the current integrated approach. California mosquito and vector control districts perform ongoing surveillance and rely on Integrated Pest Management (IPM) as an effective, preventive approach to mosquito control. With a focus on prevention and larvicide use, which targets the larval stage of a mosquito and uses fewer chemicals, mosquito experts have been able to effectively inspect and eliminate mosquito breeding grounds. The new NPDES Permit requirements, which must be performed in addition to the current IPM protocols and reporting, shift the focus from preventive management targeting mosquito larvae using less pesticide to post-infestation spraying for adult mosquitoes over a wider area using more and harsher pesticides.

"We are doing our best to get in front of this exploding mosquito population," Bayless said, "but the NPDES Permit requirement is crippling us, resulting in more pesticide spraying and putting the health of Californians at risk." Legislation that would correct this problem, H.R.872, is on the Senate floor this week.