Marin‑Sonoma vector district briefs San Rafael on surveillance, dengue risk and services

Peter Bonkruid, district manager of the Marin‑Sonoma Mosquito & Vector Control District, delivered an overview of the district’s work and local disease risk to the San Rafael City Council on Jan. 21. “Good news, 2024, we had no West Nile virus in Marin and Sonoma County,” Bonkruid said, while warning staff and council to watch the statewide trends and the emergence of invasive Aedes mosquitoes that can transmit dengue.

The nut graf: The district, an independent special district headquartered in Cotati that serves Marin and Sonoma counties, manages surveillance at tens of thousands of mapped sites, runs a lab for mosquito and tick testing, provides school and community outreach programs, offers rodent‑reduction consulting and ground‑nesting yellow‑jacket removal, and employs integrated vector management to tailor responses to habitat and species.

Bonkruid explained the surveillance and response approach: technicians inspect mapped sites at intervals dictated by habitat, the lab tests both immature and adult mosquitoes and collected birds for pathogens, and disease risk drives which species receive heightened attention (Culex tarsalis, Culex erythothorax and Culex pipiens for West Nile virus; Aedes aegypti and Aedes albopictus are the invasive species of concern for dengue). Bonkruid said the district is monitoring dengue activity elsewhere in the state and maintains ties with county public health, the California Department of Public Health and national partners.

Council members asked about pesticide use, rodent management and interagency coordination. Bonkruid said the district does not apply rodent baits (rodent work is advisory and exclusion‑focused), that pesticide applications are limited to the mosquito program and are selected with environmental compatibility in mind, and that the district works closely with county health officers and CDPH for public‑health escalation and funding.

A resident raised concerns about apparent declines in frog populations near the marsh after recent marsh treatments. Bonkruid said natural yearly cycles are common and, absent further evidence, he would not ascribe the decline to district treatments; he invited residents to contact the district for location‑specific information and to request inspections.

The presentation ended with offers for follow‑up and the district’s website as a resource for residents seeking vector or rodent help.