Point Reyes Light - October 7, 2004
Coast to vote on joining mosquito district
By Jim Kravets
Marin-Sonoma Mosquito & Vector Control District this Thursday, Oct. 7, is scheduled to mail ballots to all West Marin residents, asking if they want to be annexed into the district. Residents will have 45 days to mail back their votes.
The only towns in West Marin that won’t be voting are in the San Geronimo Valley, which is already part of the district.
In order for the district to expand, the measure needs 50 percent of the vote (plus one). By voting to be annexed into the district, voters will also agree to a $19 per year assessment for a single family.
The district already serves more than 600,000 residents in a 960-square-mile area. The annexation would add 42,000 parcels of land to the district: 7,000 in Marin County and the remainder in Sonoma County.
With the recent spread of West Nile Virus to West Marin, the vote has taken on new significance. Last week state health officials confirmed that a fox sparrow found dead in Bolinas in September tested positive for the virus. To date, including the one in Bolinas, nine West Marin birds have tested positive for West Nile Virus, including seven finches in Tomales last August and one Western scrub jay in Woodacre whose test results were announced Sept. 10.
Mosquitoes carry the disease, which can afflict humans, horses, and birds. District officials on Monday told The Light that mosquitoes trapped on Irwin Lane in Santa Rosa have just now been found to be carrying the virus – the first confirmation of infected mosquitoes in Marin or Sonoma Counties. No human cases have yet been reported in either county.
In addition to mosquito monitoring and control, the district deals with other types of pestilence including yellow jackets. It also educates residents about tick-borne diseases and about controlling rodents, along with providing inspection services. Fire ants, which have now spread to the Sacramento area from the Southwest, would also fall under the district’s purview.
Any form of organized mosquito abatement has proven controversial in Marin County. West Marin residents have had relatively little experience dealing with the mosquito control issues, but last summer Fairfax residents debated the topic before the Town Council.
The first bird in Marin County found to have been carrying the virus was a crow that died in Fairfax, but residents and some council members were skeptical about calls for mosquito control. Their skepticism notwithstanding, Fairfax is within the Mosquito & Vector Control District, so it, not the town, decides what needs to be done.
Nonetheless, the district is not indifferent to public opinion. In Fairfax, the public objections to mosquito control mainly concerned the use of pesticides, which is only one of several controls the district uses, depending upon the situation. Concerns raised:
• Could the pesticide used by mosquito officials prove toxic to humans?
• Might pesticides be a greater risk to the public than the West Nile Virus?
• Would the public get advance notice whenever pesticides were deemed necessary?
• What would be the effect of anti-mosquito pesticides on plants and wildlife?
West Marin, meanwhile, with its remote open spaces, agriculture land, and vast wetlands would present special challenges for mosquito control officials.
Mosquito district’s answers
Responding to these concerns, which were also raised by The Light, district manager Jim Wanderscheid and district spokesman Chris Canterbury on Monday said:
Anti-mosquito pesticide is dispersed by technicians using hand-held equipment. The truck-mounted machines that emit a fog to kill adult mosquitoes while they fly are rarely, if ever, used. Spraying from aircraft would never occur, Wanderscheid promised.
The pesticide used by the district is pyrethrin, a naturally occurring chemical derived from the chrysanthemum plant; it has long been known toxic specifically to insects. "We choose pyrethrins because they’re the absolute lowest in the toxicity range." Amphibians, like frogs, which depend on insects would not be severely impacted from the spraying, Canterbury added. "We’re good at our job, but we’re not that good," he said. "There will still be ample food for amphibians."
Going after the source
The district’s primary work is eliminating the sources of mosquitoes. "There are 7,000 known sources in Marin that we regularly check every 14 to 28 days," Wanderscheid said. These sites include holes in trees, which collect water, and seasonal ponds.
If voters here agree to join the district, it would catalog breeding sites in West Marin. Fish and bacteria that target mosquito larva would be used to control the number of mosquitoes. Helicopters are sometimes used to drop the bacteria in remote locations.
The district also fills cavities in tree trunks and limbs with a plastic polymer that turns to jelly when wet, eliminating places where mosquito eggs can hatch.
In the event that spraying is necessary, Canterbury said, "we would always notify residents via newspapers, public posting and other media. As in Fairfax, if there is a resident that doesn’t want to be part of the program we’ll put them on a ‘no spray’ list."
Epidemics change all rules
However, the officials noted, if Marin Public Health Officer Dr. Fred Schwartz were to declare an epidemic, the district’s jurisdiction supersedes any local ordinance or no-spray list. "The general public health takes precedence," Wanderscheid said. And even if West Marin voters decide not to be annexed, the district could still act here were there to be a public health crisis.
A worrisome component with West Nile Virus, said Wanderscheid, is its ability to be "vectored" or carried by different species of mosquitoes – unlike malaria or dengue fever, each of which is carried by only one type of mosquito.
"In three months, we’ve discovered that two more local species of mosquito can carry the virus for a total of nine species." This makes controlling the spread of the virus challenging, Wanderscheid said. Of particular concern for West Marin with its many marshes, is Ochlerotatus squamiger, a species of mosquito that breeds in brackish water.
Wanderscheid said the district will hire six additional staff to service the newly annexed areas of West Marin and Sonoma County if voters approve the measure.
Background of district
Marin-Sonoma Mosquito & Vector Control District has been providing mosquito-control for more than 85 years in Marin County and for more than 25 years in Sonoma County. The Marin district was the first such district to be established in California following the state’s 1914 Mosquito Abatement Act.
"At the time," Wanderscheid said with amusement, "the San Rafael Women’s Club wanted to encourage visitors." The club found that San Francisco were loathe to visit Marin because of all the mosquitoes here.
Supervisors in both Marin and Sonoma counties, as well as Marin’s Local Agency Formation Commission, have endorsed expansion of the district. Manager Wanderscheid said that anyone with questions about the district can call its office at 707 285-2200.