January 20, 2022
Final Reports
San Mateo Courts - Civil Grand Jury

2002-2003 Report:

Review of Mosquito Control Measures

Summary | Background | Findings | Conclusions | Recommendations| Responses


The San Mateo County Grand Jury finds that to combat the threat of further cases of West Nile Virus, the San Mateo County Mosquito Abatement District should be permitted to expand its programs of vector control throughout the entire county. All cities in the county should cooperate with LAFCo in expediting the proposed annexation of all areas not currently with the District.

Issue: Have San Mateo County agencies, including the San Mateo County Mosquito Abatement District, County government, and individual cities adequately responded to the threat of West Nile Virus?


There have been several cases of West Nile Virus among County residents. While only twenty percent of those infected contract the disease, and less than one percent contract the severe form with development of aggravated meningitis or encephalitis type symptoms, it can be fatal to the elderly or those with compromised immune systems.

The San Mateo County Mosquito Abatement District (SMCMAD), formed by the merger of two small districts in 1953 and headquartered in Burlingame, is an independent special district set up and empowered under state law with one of its primary functions that of combating mosquitoes and mosquito-borne diseases. It provides safe, i.e., non-toxic to humans, methods of control. SMCMAD recently completed and updated a comprehensive Arbovirus Surveillance and Response Plan under which SMCMAD will continue to provide vector management services. A "vector" is an organism that transmits a disease.

In a comprehensive report to the Board of Supervisors on the West Nile Virus on September 18, 2002, the San Mateo County Health Services Agency recommended that the SMCMAD be expanded to include the entire County. Currently, only one-third of the geographic area of the County is within the District. Seven cities in the northern portion of the County (Daly City, Brisbane, South San Francisco, Colma, San Bruno, Pacifica and Half Moon Bay), the western coastal section of the County, and certain rural areas to the south are outside the District.

The Board of Supervisors endorsed the recommended plan to combat West Nile threat to San Mateo County by annexing to SMCMAD portions of the County that are not within the District. Annexation would enlarge the District from approximately 166 square miles to a total County area of 450 square miles.

SMCMAD submitted a formal application for the annexation to LAFCo on January 21, 2003. Negotiations took place involving SMCMAD, the cities, the County and LAFCO. Such negotiations considered tax consequences in the newly annexed areas which would involve 1) a $3.74 annual parcel tax, equal to that imposed on owners presently within the District, and 2) allocation to the District of a portion of the one percent assessed value (AV) tax. Both subventions would increase SMCMAD revenue by approximately $335,000 from parcel tax proceeds and $400,000 from the AV allocations. The increased tax revenue would fund the cost of six new employees required to service newly annexed areas.


SMCMAD has stated that the annexation needs to conclude quickly so that the new staff can be hired and trained to be ready for the mosquito breeding season beginning this spring. No city or other areas, including unincorporated areas in the County, has formally opposed annexation, with the sole exception of Daly City. However, several cities have raised questions as to costs that would result from inclusion in the annexed area.

Daly City has refused to approve annexation. Daly City in its Council resolution stated that the annual costs of annexation would involve the transfer of $91,000 of City property taxes to the District and a further payment of $120,000 in parcel taxes. Daly City has stated it does not intend to agree to any transfer of property taxes or imposition of assessments on its owners and residents and has asked SMCMAD to delete its name from the resolution requesting annexation and the LAFCo application.

In a letter dated January 22, 2003, SMCMAD's Manager stated that while SMCMAD has a contractual abatement agreement with Daly City for the Mussel Rock area expiring June 30, 2003, SMCMAD would be unable to provide further services to Daly City on a contractual basis after that date.

Daly City has previously contracted for SMCMAD services, including responding to residents' complaints, mosquito surveillance and preventative and control measures at catch basins, vaults, waste water facilities, freshwater and salt marshes and residences, as well as overall monitoring and disease control including the use of sentinel flocks of chickens and dissemination of public information. It is SMCMAD's position that many if not all of these programs will be discontinued if Daly City is not annexed to the District. SMCMAD has performed significant preventative measures in significant areas of mosquito infestation within Daly City, including coast side, lands adjacent to San Francisco Bay, near Lake Merced, golf courses and storm drainage from Junipero Serra Boulevard and in the vicinity of the Cow Palace.


San Mateo County does not have a comprehensive countywide vector control program. To mount an effective campaign against the outbreak of further cases of West Nile Virus within San Mateo County, SMCMAD needs to conduct county-wide monitoring, surveillance, and treatment; and to provide public information and education. To be successful, SMCMAD needs the full legal power and authority, financial capacity, staffing, and public support.


1. LAFCo should expedite the proposed annexation of the currently unannexed portions of the County by SMCMAD.

2. The City of Daly City must join SMCMAD before the expiration of its current contract for vector control to not only protect its residents but to enable SMCMAD to take effective countywide measures.

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