San Mateo County: Lyme Disease

Entomology Report April 2008, San Mateo County Mosquito and Vector Control District

The district continues to survey for Lyme disease in San Mateo County recreational parks. Disease-causing spirochetes have been detected for the first time in ticks at two additional parks this year: Water Dog Lake in Belmont and Huddart Park in Woodside (refer to table). The average prevalence of infection for San Mateo County is between 1 and 3% for adults and nymphs.

Park/Trail     Tick Stage  # Collected  Positive  Prevalence
Huddart Park
Bay Tree       Nymph            91          0         0
Richards Rd    Nymph            21          0         0
Chickadee      Nymph            84          3         3.6%*
Waterdog Lake
Lake           Adults          114          1         0.8%

*Prevalence at this site is preliminary due to small sample size.

San Mateo County: Photomicroscopy – Borrelia burgdorferi (the Lyme disease spirochete)

Entomology Report January 2008, San Mateo County Mosquito Abatement District

District staff collect and test Ixodes pacificus ticks annually to detect the presence of the Lyme disease bacterium, Borrelia burgdorferi (Bb). Ticks are dissected and their guts are split in half to perform two tests on each tick. Each tick is tested by direct fluorescent antibody (DFA) technique which involves staining tick guts with a fluorescent antibody specific to Borrelia burgdorferi. If Bb is present, the stained bacteria will appear green when viewed through a fluorescent microscope. The other half of the tick gut is placed in a culture medium that supports growth of Bb. These cultures are viewed weekly to look for live bacteria. Under dark field microscopy the otherwise clear bacteria appear white against a black background.

Lyme Disease in Santa Clara County: Tick Infection Rates

Source: Lyme Disease in Santa Clara County, Santa Clara County Vector Control District

Location of tick sampling    % positive to Borrelia burgdorferi
Freemont Older                     3.85
Foothills Open Space Dist.         2.86
Sierra Azul                        2.86
Sanborn Skyline                    2.78
Alum Rock Park                     2.75
Uvas County Park                   2.39
Duveneck Windmill OSD              2.27
Villa Montalvo                     2.22
Almaden Quicksilver                1.72
Los Trancos                        1.26

Tick Surveillance in California, 2005

Vector-Borne Diseases in California, Annual Report 2005, California Department of Health Services, Vector-Borne Disease Section

Tick surveillance

CDHS Vector-Borne Disease Section (VBDS) and collaborating agencies conducted tick surveillance in 17 California counties in 2005. Totals of 1,965 Ixodes pacificus (1,797 adults and 168 nymphs), 782 Dermacentor occidentalis, and 38 Dermacentor variabilis were collected. Nineteen hundred I. pacificus (1,736 adults and 164 nymphs) from 16 counties were tested for Borrelia burgdorferi in two laboratories. Ticks were tested by indirect fluorescent antibody (IFA) and/or polymerase chain reaction (PCR). Evidence of Borrelia sp. was identified in ticks collected from six counties. Borrelia burgdorferi was detected in 4 of 33 pools by IFA and 12 of 192 pools by PCR.

The U.S. Army Center for Health Promotion and Preventive Medicine tested by PCR 1,618 I. pacificus. Any ticks initially positive for the genus Borrelia were tested by an additional PCR assay using primers specific to B. burgdorferi. Borrelia sp. spirochetes detected in tick pools from Placer (1), Shasta (1), Trinity (1), Tuolumne (1) Counties did not match the genetic sequence for B. burgdorferi. These isolates most closely resembled B. miyamotoi, a Borrelia species in the RF genetic complex. Borrelia miyamotoi is not known to be pathogenic to humans.

A study of the ecology of I. pacificus in southern California, initiated in 2001, continued in 2005. VBDS and collaborating agencies (Los Angeles County Department of Health Services, Los Angeles West Vector Control District, and Riverside County Department of Health) monitored tick populations and collected questing ticks from six sites at three different geographic locales (Griffith Park, Santa Monica Mountains, and San Jacinto Mountains). Meterological factors, including rainfall and humidity, were simultaneously monitored. These data on tick populations, meterological factors, infections with B. burgdorferi, and molecular characterization of Borrelia spp. from ticks will continue to be collected to gain a better understanding of the ecology of I. pacificus ticks and B. burgdorferi in southern California.

Local surveillance was conducted in San Mateo County for Rickettsia rickettsii, the agent of Rocky Mountain spotted fever. In June, CDHS and San Mateo County Mosquito Abatement District personnel collected 320 D. occidentalis and 27 D. variabilis. All ticks were tested by PCR for R. rickettsii by CDHS, Viral and Rickettsial Disease Laboratory; all tested negative. In addition, 120 Rhipicephalus sanguineus were collected from Riverside County. Of 62 ticks tested by PCR at the Division of Viral and Rickettsial Diseases, CDC, R. rickettsii was detected in one adult male R. sanguineus.

In June, CDHS collected 362 D. occidentalis and 5 D. variabilis in Tilden Regional Park, located in Contra Costa and Alameda Counties, as part of a continuing investigation of two human cases of tularemia in 2004. Ticks were tested for Francisella tularensis in 39 pools by PCR at DVBID CDC; all pools tested negative.

San Mateo County: Lyme Disease Surveillance

Entomology Report November/December 2005, San Mateo County Mosquito Abatement District

Surveillance for the western black-legged tick, Ixodes pacificus, has commenced for the 2005-2006 season. Adults of this species are abundant along recreational trails from November through May. Surveillance is being conducted with the assistance of a number of other agencies to determine the risk of Lyme disease exposure in San Mateo County. Ticks are collected on trails commonly used by the public. They are dissected and tested in the District laboratory to determine the prevalence of infection with the Lyme disease bacteria, Borrelia burgdorferi. Agencies participating in this project include: 3 divisions of the San Mateo County Department of Public Health (Environmental Health, Communicable Disease Control, and the Public Health Laboratory), County Parks, and State Parks. Staff from the San Francisco Department of Public Utilities (the Water Department) are also assisting in collecting on Crystal Springs Watershed.

So far this season, collections have been made at 6 parks. Tick density was low on the trails sampled early in the season (November). Surveillance in December yielded a larger number of ticks, with the highest density in Big Canyon Park. The first positive ticks of the season were collected from the San Andreas Trail. This site has yielded positive ticks in the past. Parks with low tick density will be sampled again later in the season. Other parks that may be surveyed this season, include Mills Canyon Park in Burlingame, Spur Trail Park in Millbrae, Edgewood Park in Redwood City, Smith Field Park in Half Moon Bay, and Sawyer Camp Trail in San Mateo.

Previous related entries:

San Mateo County: Lyme Disease Surveillance, October 2005
San Mateo County: Lyme Disease Surveillance, January 2005

Tick Infection Rates in Marin County 2005

Laboratory Report 2005, Marin / Sonoma Mosquito and Vector Control District

% infection of I. pacificus with B. burgdorferi
China Camp State Park, Marin County, 2005
Female ticks   4.9%
All ticks      3.5%

Tick Collection and Tick-borne Disease Surveillance (by Kristen Holt).
The western deer tick, Ixodes pacificus, is the most important carrier of Lyme disease and other tick-borne disease agents in northern California. During 2005, we collected a total of 577 deer ticks from China Camp State Park near San Rafael, to test for the Lyme disease agent. Twenty ticks (3.5%) were carrying the Borrelia bacterium. The rate was higher in female (4.9%) than male ticks.

Ticks and Lyme Disease in Contra Costa County 2005

2005 Annual Report, Contra Costa County Mosquito And Vector Control District

Tick Testing

Bollinger Canyon Rd, San Ramon Site
A total of 670 adult Western black-legged ticks were collected from the Bollinger Canyon Road site 1A this season. Seventy four ticks were tested (45 females, 29 males) for the presence of Lyme disease, using an Indirect Fluorescent Antibody test (IFA). Two of the seventy-four ticks tested were found to be positive for the Lyme disease, yielding a 2.7 percent infection rate. This is the twelfth season for which ticks have been tested from this site. The average infection rate over the twelve year period is 3.71 percent, which is slightly higher than the Californian State average of 2.0 percent. The chart below shows the Lyme disease (B. burgdoferi) infection rate at the Bollinger Canyon Site between the 1993-94 to 2004-05 seasons.

Springhill Rd, Lafayette Sites
In addition to our regular Lyme disease IFA testing, a total of 374 adult Western black-legged ticks were collected from five sites near Springhill Road, Lafayette, and were tested using real-time PCR by Dr. Alan Barbour of University of California, Irvine, for the presence of two species of Lyme disease causing bacterium, Borrelia burgdorferi and Borrelia miyamotoi. Borrelia miyamotoi is closely related to B. burgdoferi, but at this time has not been shown to cause disease in humans. This location was chosen as it was an area previously known to have had high Lyme disease infection rates in Western black-legged ticks that were collected by both Contra Costa Mosquito & Vector Control staff and those submitted by the public to our office for testing. The infection rates have varied yearly from 0-14 percent.

San Mateo County: Lyme Disease Surveillance

Entomology Report October 2005, San Mateo County Mosquito Abatement District

Surveillance for the western black-legged ticks (Ixodes pacificus) will commence in November. This tick is a vector of the Lyme disease spirochete, Borrelia burgdorferi. Adults of this species feed on large mammals such as deer, humans, horses and dogs. They are the primary tick found along recreational trails from November through May. Surveys in past years have detected Lyme disease spirochetes in 2% of adult and nymphal ticks in San Mateo County. The prevalence of infection has not differed significantly between years, sites or life history stage of ticks.

Laboratory staff will test ticks submitted by residents free of charge and provide information on Lyme disease and ways to minimize exposure to it.

This year, the district hopes to expand the surveillance program to include more parks, and estimate relative public health risk at different recreational sites based on degree of public use, tick density, and prevalence of infection in ticks.

Protect Yourself

People who frequent high risk areas can protect themselves from ticks by tucking their pants into their socks and thoroughly checking skin, hair, clothing and pets for ticks before returning home. Light colored clothing helps make ticks more visible so that they can be removed before attaching. Permethrin can be applied to the outside of your clothes to repel ticks. Products labeled for use on clothing can be obtained at stores that sell recreational equipment. Always read and follow the directions on the label of any pesticide before using it. Permethrin should never applied directly to bare skin.

Removal of ticks: With tweezers, firmly grasp the tick as close to the skin as possible and pull tick straight up and out.

Symptoms of Lyme Disease: Fatigue, chills, fever, headache, muscle and joint aches, swollen lymph nodes, and other neurological symptoms. This disease is caused by a bacteria and therefore can be treated with antibiotics.

Previous related entries:

San Mateo County: Lyme Disease Surveillance, January 2005

Sacramento-Yolo Counties Lyme Disease Surveillance 2005

Annual Report 2005, Sacramento-Yolo Mosquito and Vector Control District

Summary of Sacramento-Yolo MVCD 2004—2005 Tick Surveillance Data

Location          Total   Pools    Positive   Estimated Minimum
                  Ticks   Tested   Pools      Infection Rate
Yolo
Cache Creek        257      23         3              1.2%
Sacramento
Ancil Hoffman        0       0         0              N/A
Mississippi Bar     66      12         1              1.5%
Negro Bar           19      13         0              0.0%
Nimbus Dam          38       9         2              2.7%
Snipes Park         68      13         0              0.0%
Willow Creek        46      10         0              0.0%
Total              494      80         8

The bacterium that causes Lyme disease is called Borrelia burgdorferi. The primary vector for Lyme disease for Sacramento and Yolo Counties is Ixodes pacificus, also known as the western black—legged tick. The table... summarizes the Lyme disease surveillance data of Ixodes pacificus ticks collected from November 2004 through May 2005.

Tick specimens were collected by dragging a flannel sheet along the side of a trail, a technique called flagging. The ticks were pooled and tested by indirect immunofluorescence assay (IFA). A sample was considered positive by IFA if one or more fluorescently stained spiral—shaped bacteria were present. Some positive samples were confirmed using a polymerase chain reaction assay and by culture in liquid media.

San Mateo County: Lyme Disease Surveillance

Entomology Report January 2005, San Mateo County Mosquito Abatement District

Surveys for western black-legged tick, Ixodes pacificus, continued through January. This tick is a vector of the Lyme disease bacteria, Borrelia burgdorferi. Adults of this species feed on large mammals such as deer, humans and dogs. They are abundant along recreational trails from November through May. Ticks have been collected at 6 sites thus far. Two out of 147 ticks collected in Los Trancos Woods this year (1%) tested positive for the bacteria.

Sacramento-Yolo Counties Lyme Disease Surveillance 2004

Annual Report 2004, Sacramento-Yolo Mosquito and Vector Control District

Summary of Sacramento-Yolo MVCD 2003-2004 Tick Surveillance

Location          Total   Pools    Positive   Estimated Minimum
                  Ticks   Tested   Pools (b)  Infection Rate (a)
Yolo
Cache Creek        368      42         5              1.4%
Sacramento
Ancil Hoffman        0       0         0              N/A
Mississippi Bar     83      11         1              1.2%
Negro Bar          189      22         0              0.0%
Nimbus Dam          74      11         2              2.7%
Snipes Park         64      11         0              0.0%
Willow Creek        69      12         0              0.0%
Totals             847     109         3

a IFA-positive samples were tested by a PCR assay targeting the 5S(rrf)-23S(rrl) intergenic spacer region of B. burgdorferi.
b Minimum infection rate (%) = (#positive pools/#ticks tested) x (100). Assume a positive pool contains a minimum of one infected tick.

The bacterium that causes Lyme disease is called Borrelia burgdorferi. The primary vector for Lyme disease for Sacramento and Yolo Counties is Ixodes pacificus, also known as the western black-legged tick. The table (above) summarizes the Lyme disease surveillance data from Ixodes pacificus ticks collected from November 2003 through May 2004.

Tick specimens were collected by dragging a flannel sheet along the side of a trail, a technique called flagging. The ticks were pooled and tested by indirect immunofluorescence assay (IFA). A sample was considered positive by IFA if one or more fluorescently stained spiral-shaped bacteria were present. Some positive samples were confirmed using a polymerase chain reaction assay and by culture in liquid media.

Alameda County Lyme Disease Surveillance, 2002-2003

Annual Report FY 2002-2003, Alameda County Vector Control Services

As part of the Lyme disease surveillance program, staff collect and identify ticks, and may recommend testing for tick borne disease when appropriate. Seventeen field surveys were conducted at nine locations, which resulted in the capture of 182 adult Ixodes pacificus ticks. Three of these ticks were confirmed to be Lyme disease positive by direct immuno-fluorescence (IFA). The three positive ticks represented about 1.6% positive for Lyme disease from the samples taken so far. This number is slightly below the two percent figure, which is the typical average for endemic Lyme disease areas in California. Alameda County continues to have a low incidence of locally acquired Lyme disease, mainly due to its’ isolated number of suitable habitats for the reservoir and vector.

Twenty-seven residents of Alameda County were bitten by ticks, and submitted them to the Sonoma County Public Health Laboratory for Lyme disease testing. All of the twenty-seven ticks acquired in Alameda County tested negative for the Lyme disease spirochete. Two Lyme disease case histories from the previous year were completed in 2002. The areas where these victims had frequented were surveyed several times, but none of the tick samples yielded positive results for the Lyme disease spirochete, Borrelia burgdorferi.

Ticks and Lyme Disease in Contra Costa County 2002

2002 Annual Report, Contra Costa County Mosquito and Vector Control District

Adult Ixodes pacificus Surveillance Summary
Location                            # tested  # pos.  % Infected
Bollinger Cyn. Rd, San Ramon             100      1      1%
Springhill Rd (End), Lafayette           100      1      1%
Briones RP, Bear Creek Staging            40      2      5%
Springhill Rd. (middle), Lafayette        24      3     13%
Donald Rheem Elementary, Moraga           13      0      0%
Brookside Rd., Orinda                      8      0      0%
Alameda Diablo, Diablo                    54      0      0%
Contra Costa County 2001-02 season       339      7      2%

IFA Testing Results

During the 2001-02 tick season, adult I. pacificus (Western Black-legged tick) that were collected from Bollinger Canyon Rd., San Ramon; Springhill Rd. in Lafayette; and at the Bear Creek Staging area of Briones Regional Park were tested for the presence of the Lyme disease spirochete, Borrelia burgdorferi. Ticks were also collected and tested from other miscellaneous locations within the County in order to continue to expand on the current picture of the average Borrelia burgdorferi infection rate in Contra Costa County. Details are summarized below.

Springhill Rd, Lafayette Site
A total of 204 adult I. pacificus were collected from the Springhill Rd. site during the 2001-02 season, 36 percent females and 64 percent males. One hundred individuals were tested (40 females, 60 males) for the presence of Borrelia burgdorferi and a single tick was found positive. The infection rate at this location has been as high as six percent with an average infection rate of 1.38 percent over the nine year period that we have been collecting data from this site.

Bollinger Canyon Rd, San Ramon Site
Five hundred thirty-seven I. pacificus adults were collected from the Bollinger Canyon Rd. site, 47 percent females and 53 percent males. One hundred ticks were tested and one was found positive for B. burgdorferi. This site has had a history of higher-than-average infection rates. Over the last five years however, infection rates have been in the 0-2 percent range. The average infection rate for this location over the last nine years is 3.28 percent.

Briones Regional Park Site
The Briones Regional Park site typically has a low I. pacificus population. During the 2001-02 season only 53 individuals were collected, 40 of which were tested. The table (above) is a summary of all sites surveyed this season and includes four additional locations within the County where ticks were collected and tested for B. burgdorferi infection. Also included are the overall totals and average infection rate for Contra Costa County.

Alameda County Lyme Disease Surveillance, 2001-2002

Annual Report 2001-2002, Alameda County Vector Control Services

As part of the Lyme disease surveillance program, District Staff identify ticks and mites, and will authorize testing for tick borne disease when appropriate. The District is currently investigating two human Lyme disease, case histories, from victims who are believed to have acquired the disease in Alameda County. The collections and surveillance will occur in the spring of 2002, when the adult and nymphal Ixodes pacificus ticks are most numerous. As part of the general tick borne disease surveillance program, 49 Western Black Legged Ticks were tested and none were positive for Borrelia burgdorferi. Vector control officers are being trained in tick surveillance techniques and equipment, and plans are in place to increase tick surveillance. Sixty-Five residents of Alameda County were bitten by ticks, and submitted them to the Alameda County Public Health Laboratory for Lyme disease testing. Some additional samples were sent to IgeneX, a private laboratory for PCR Testing. All of the twenty-four ticks acquired in Alameda County tested negative for the Lyme disease spirochete. Additional ticks, one from France and another from the east coast, tested positive for Borrelia burgdorferi, the bacteria responsible for Lyme disease.

Alameda County Lyme Disease Surveillance, 2000-2001

Annual Report FY 2000-2001, Alameda County Vector Control Services

The district will identify ticks and mites, and will authorize testing for tick borne disease when appropriate. Fifty-seven residents of Alameda County were bitten by ticks, and submitted them to the Alameda County Public Health Laboratory for Lyme disease testing. Some additional samples were sent to IgeneX, a private laboratory for PCR Testing. One of the Ixodes pacificus ticks tested positive for Borrelia burgdorferi, the bacteria responsible for Lyme disease.

Sunol / Ohlone Regional Park
Staff conducted a tick survey at Sunol/Ohlone Regional Park in April of 2000, in response to a report of a confirmed case of Lyme disease by a visitor to the park. Twenty-five Western Black Legged Ticks, Ixodes pacificus, were collected and submitted to the Alameda County Public Health laboratory for testing. One of the tick pools, containing about 5 ticks, tested positive for Borrelia burgdorferi, the spirochete responsible for Lyme Disease.