San Mateo County: Lyme Disease Surveillance Winter/Spring 2005-06

Entomology Report June 2006, San Mateo County Mosquito Abatement District

This year over 1000 ticks were tested for the Lyme disease bacteria (twice the numbertested in previous years). The increase was due to assistance provided by District mosquito control technicians and staff from other agencies (County Health, County Parks, Public Utilities, and State Parks). The extra man power allowed for more extensive surveillance at sites throughout the county. Prevalence of infection averaged between 1% to 3%, which is consistent with data from previous years. However, the density of ticks varied greatly between parks and between trails within each park.

Park                    # Infected ticks (%)  # ticks / 100 ft
Big Canyon, San Carlos            9/504 (2%)         2.8
Crystal Springs Trail, Millbrae   5/172 (3%)         3.6
Edgewood Pk, Redwood City         0/ 87 (0%)        18.6
Huddart Pk, Woodside              3/ 98 (3%)         3.3
San Pedro Valley Pk, Pacifica     3/286 (1%)         4.7

Previous related entries:

San Mateo County: Lyme Disease Surveillance Winter/Spring 2005-06, April 2006
San Mateo County: Lyme Disease Surveillance Winter/Spring 2005-06, March 2006
San Mateo County: Lyme Disease Surveillance 2006, February 2006
San Mateo County: Lyme Disease Surveillance 2006, January 2006
San Mateo County: Lyme Disease Surveillance, November/December 2005
San Mateo County: Lyme Disease Surveillance, October 2005
San Mateo County: Lyme Disease Surveillance, January 2005

San Mateo County: Effects of Mowing on Summer Tick Populations

Entomology Report June 2006, San Mateo County Mosquito Abatement District

With the cooperation of the San Mateo County Parks and Recreation Division, the District began a project in late June to assess the effects of mowing on tick populations. The study site, Sawyer Camp Trail, spans six miles along Crystal Springs Reservoir from San Mateo to Millbrae. It is one of the county’s most popular trails for walkers, joggers, and bicyclists.

Ticks were surveyed in three half-mile segments of the trail in the days before and after mowing. Ticks were also surveyed at unmowed sites at Edgewood Park (near Redwood City) and an area south of the San Andreas Trail in Millbrae.

A preliminary comparison of tick density before mowing and one week after mowing suggests that mowing vegetation along trails does not have a significant effect on the numbers of ticks present. However, long term effects still need to be evaluated, and monitoring will continue at both the mowed and unmowed sites on a weekly basis throughout the summer.

Previous related entries:

San Mateo County: Trial Application of Suspend for Control of Ticks, May 2006
San Mateo County: Trial Application of Suspend for Control of Ticks, April 2006

San Mateo County: Trial Application of Suspend for Control of Ticks

Entomology Report May 2006, San Mateo County Mosquito Abatement District

On April 28, District staff conducted assessed the effectiveness of Suspend (a pyrethroid) for control of ticks along recreational trails. The material was applied in a 8 ft swath along the uphill side of a trail in San Pedro Valley Park, Pacifica. 90 ticks were collected in the 0.37 mi section before treatment (4.6 ticks/100 ft). Four days after treatment, only 1 tick was found in the same area (0.05 ticks/100 ft), Tick density in untreated areas was 9.3/100 ft. Two weeks post-treatment, no ticks remained in the treated area and it has remained free of ticks for 6 weeks. Insects and spiders continue to be present on the trail.

Results of this trial will allow the District to advise land owners on measures they can take to decrease the risk of exposure to tick-borne diseases.

Previous related entries:

San Mateo County: Trial Application of Suspend for Control of Ticks, April 2006