This month: Trustee Field Day, hantavirus surveillance, the winter salt marsh mosquito, and more.
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District News

  • Laboratory staff conducted hantavirus surveillance on Nov. 14th at San Pedro Valley County Park. None of the 24 rodents tested were positive for hantavirus antibodies. Hantavirus surveillance will continue in January.
  • On Nov.16th, District staff presented on District Services at the Menlo Oaks District Association Annual Meeting.
  • Laboratory staff led six middle school science classes at two local schools in a mosquito lab activity on Dec. 8th-9th.
  • District trustees attended Trustee Field Day on Dec.10th, including governance training, updates from District staff, and presentations by vector control technicians. Trustees and visitors from several cities also attended a tour of District facilities held after Trustee Field Day.
  • On December 16th, District staff presented to the Half Moon Bay City Council on District Services.
  • A Resident Survey was implemented in December, with preliminary results showing a high levels of satisfaction with District services among residents.
  • Implementation of the District's new brand began in November, beginning with electronic resources. Rebranding will continue into early 2015.
  • Work on the District's new website continued in November and December. The new website will launch Jan. 2015.
  • Starting in November, the Resident Survey was sent to all residents who provided an email address when making a service request. Results to date have demonstrated a high level of resident satisfaction with District services.
  • In December, laboratory staff acquired an annual permit to collect ticks on local public lands, including county parks and Open Space preserves.
  • The District underwent a program review by CDPH in December. All feedback was positive.
The District asks residents to report dead birds or tree squirrels at Specimens that appear to have been dead for less than 24 hours and are in good condition will be tested for West Nile Virus.

Aedes squamiger, the Winter Salt Marsh Mosquito

Summer may be mosquito season, but here in San Mateo County, winter brings a new concern: the winter salt marsh mosquito, or Aedes squamiger, which breeds in the salt marshes along the edge of the Bay. These mosquitoes may fly up to 20 miles from their marsh breeding habitat, and often become a major pest when present in large numbers.

Above: Local marshes provide breeding habitat for Aedes squamiger.

Many of the salt marshes of San Mateo County were created by humans in order to harvest salt or to attract waterfowl for hunting. To make matters worse, human construction has altered the natural flow of water into and out of the tidal marsh, allowing water to stand and providing an ideal breeding habitat for winter salt marsh mosquitoes. Females use local creeks as highways as they travel between their marsh breeding habitat and inland areas where they seek a blood meal. In the spring, they lay their eggs. Aedes squamiger eggs remain dormant until the following winter, when marshes fill with rainwater again, but may be viable for more than 20 years, hatching only when conditions are right.

To control winter salt marsh mosquitoes in the ecologically sensitive habitats along the bay, San Mateo County Mosquito and Vector Control District technicians coordinate with other local agencies to restore normal water flow to the marshes and to treat breeding areas with bio-rational products. These control measures prevent Aedes squamiger, an aggressive day-biting mosquito, from becoming a nuisance to area residents.

Below, right: The Bair Island Restoration Project reduces mosquito breeding habitat by promoting proper tidal circulation in the marsh.  Below, left: Marshes are often found in close proximity to homes and businesses, but winter salt marsh mosquitoes will travel up to 20 miles to seek a blood meal.


District Balance Sheet

Consolidated Funds as of November 30th, 2014.

District Profit & Loss

Consolidated Funds for the Month Ending November 30th, 2014.

Service Requests

Acres and Sources Treated

Vector Ecologist Theresa Shelton demonstrates laboratory equipment to District trustees.

Trustee Field Day and Facility Tour
     On Dec. 10th, the District held its annual Trustee Field Day. Trustees from each city spent a day at the District office, receiving governance training, listening to presentations from department managers, and meeting with their respective technicians for an update on vector control activities in their cities.

     In addition to the usual Trustee Field Day activities, District staff planned an extensive facility tour for trustees and guests from their city governments. Tour highlights included the laboratory, where guests were invited to view mosquito larvae under the microscope and observe the District’s live mosquito colony, and the garages, where guests saw demonstrations of equipment such as catch basin jeeps, Argo amphibious vehicles,  and the airboat.

     An additional public open house and tour is planned for 2015.
Lab staff, with the assistance of with Melissa Yoshimizu, biologist from the California Department of Public Health, take a blood sample from a Peromyscus mouse.

Hantavirus Surveillance
     On November 14th, District staff, in conjunction with the California Department of Public Health, trapped and tested rodents for Sin Nombre hantavirus at San Pedro Valley County Park.  Staff set 100 traps and caught twenty six rodents in them.  Each rodent was anesthetized, then measured and checked for parasites.  Laboratory staff then drew blood for the hantavirus antibody test.  After recovering from anesthesia, each rodent was carefully released at the exact location where it was trapped.  Staff tested a total of twenty four mice.  Test results showed that none of the animals tested had antibodies to Sin Nombre Virus.

     Sin Nombre Virus is the strain of hantavirus that causes Hantavirus Pulmonary Syndrome (HPS) in California.  It is typically contracted through exposure to the dried urine of Peromyscus maniculatus (deer mice) in enclosed spaces.  One to five weeks after exposure, an individual may experience flu-like symptoms, followed by nausea and vomiting, then difficulty breathing.  Surveillance from 1975 to present day has shown a 7.5% infection rate of Peromyscus mice at trapping sites along the coast and at San Bruno Mountain in San Mateo County, but no human cases of HPS have been determined to be contracted within the county.  Counties in California where exposure to Sin Nombre Virus is highest are Mono, Inyo, Mariposa, Tuolumne, Nevada and Kern Counties.
San Mateo County Mosquito and Vector Control District
Protecting public health since 1916

1351 Rollins Rd. | Burlingame CA 94041
(650) 344—8592 |

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