Placer Mosquito District reports first West Nile–positive mosquito in West Placer; warns Roseville residents about invasive Aedes spread

Megan Lovano, public information officer for the Placer Mosquito & Vector Control District, told the Roseville City Council on June 18 that the district found its first West Nile virus–positive mosquito sample in the West Placer area earlier that day and that invasive Aedes mosquitoes continue to appear in several Roseville neighborhoods.

The district identified the positive sample in a Culex species; Lovano said Culex pipiens and Culex tarsalis both carry West Nile virus and that the detection is the district’s first indication of local circulation this season. She said neighboring Sacramento–Yolo districts have also reported positive mosquito samples in recent days, and that the pattern and the ongoing high temperatures make additional positive detections likely.

Why this matters: West Nile virus is spread locally by Culex mosquitoes; invasive Aedes aegypti and Aedes albopictus are aggressive daytime biters and can carry dengue, Zika and chikungunya if those viruses are introduced by an infected person. The district’s surveillance and control work aim to slow or prevent local transmission.

Lovano summarized the district’s integrated vector management programs, which include surveillance, biological and chemical control, community outreach, applied research and a drone program used to treat larval habitat in locations that are hard to reach on foot. She said the district operates about 500 trap sites and last year collected roughly 51,000 mosquitoes, including 692 Aedes aegypti.

The district recommended several residents’ actions: remove standing water on private property, keep screens in good repair, and use EPA‑registered repellents containing DEET, picaridin, IR3535 or oil of lemon eucalyptus. Lovano directed residents to the statewide dead‑bird reporting site (westnile.ca.gov) for instructions on reporting and preparing a found dead bird for pickup and testing.

Lovano also described the district’s mosquito fish program for ponds and water troughs and explained that technicians can place mosquito fish where appropriate. She said the district has begun aerial larval treatments in rice fields in the western part of the county and that more treatments are likely now that the county has a West Nile–positive sample.

On invasive Aedes, Lovano said the species has been detected in Placer County since 2019 and has shown expanding presence this year. She listed Roseville neighborhoods with recent findings, including Fields Manor and Cherry Glen, Foothills Junction, Sierra Gardens and Woodcreek Oaks, and noted the district had new detections last year in 15 of 19 neighborhoods where it found Aedes. She stressed that invasive Aedes need very small water volumes to breed and prefer cryptic containers that make control difficult.

The council asked procedural questions about how to report dead birds and other public‑report pathways; Lovano provided the district’s webpage and reporting guidance and invited residents to sign up for the district’s email notifications for treatment and surveillance updates.

The district’s contact details and surveillance dashboards were provided to the council and the public for follow‑up.

Provenance: Placer Mosquito & Vector Control District presentation to Roseville City Council, June 18, 2025. Excerpts of the district presentation and council questions appear in the meeting transcript (presentation began at the council’s start of agenda and concluded prior to consent calendar).