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.

Tick-Borne Disease Surveillance in California, 2005

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

Human disease surveillance

Lyme disease

A total of 94 cases of Lyme disease were reported to the California Department of Health Services (CDHS) in 2005. Case-patients were residents of 26 counties. Humboldt County reported the most cases (11). Reported incidence was highest in Trinity County at 23 cases per 100,000 residents. Of 44 cases for whom county of likely exposure was reported, 32 had exposure outside their county of residence; 28 of these reported exposure outside California. The most frequently reported location of exposure was Massachusetts (eight cases).

The median age of reported Lyme disease cases was 43 years (range, 3 to 78 years) and 51 (54%) were female. Of 79 cases for which race was reported, 74 (94%) were white, 3 were Native American, and 1 each was Asian and Black. Erythema migrans (EM) was identified in 59 (63%) cases. Of 51 cases with EM for which date of illness onset was reported, 36 (71%) occurred between May and August.

Tick-borne relapsing fever

Five cases of tick-borne relapsing fever (RF) were reported to CDHS in 2005. Case-patients were residents of three counties (El Dorado, Humboldt, Santa Cruz) and ranged from 6 to 58 years old. Four case-patients were likely infected in the greater Lake Tahoe area; one case-patient was likely infected while visiting a private cabin in Lassen County. One case had onset of illness in April, while the remaining four had onset in late July and August.

CDHS collaborated with the El Dorado County Departments of Health and Environmental Management, the Nevada State Health Division, and the Division of Vector-Borne Infectious Diseases (DVBID), U.S. Centers for Disease Control and Prevention (CDC), to investigate two cases of RF with unusually severe clinical courses. A 46-year-old woman from Nevada and a 43-year-old woman from El Dorado County both developed RF between February and April that progressed to severe respiratory distress and extended hospitalizations. Both patients eventually recovered. Both case-patients had a history of travel to or residence in the Lake Tahoe area. Preliminary investigation of the California case’s residence revealed live and dead mice in the garage, as well as live chipmunks in and around the house. One engorged Ornithodoros sp. tick was discovered in the bedroom. Several Ornithodoros ticks were also recovered from rodent and bird nests removed from underneath the building’s exterior siding.

Reported Lyme Disease Cases by County of Residence, California, 1996-2005

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

Reported Lyme disease cases by county of residence,
California, 1996-2005.
                                                      Incidence/
                                                      100,000
County        '96 '97 '98 '99 '00 '01 '02 '03 '04 '05 person-yrs
Alameda         2   3   6   3   4   3   5   1   0   5   0.22
Alpine          0   0   0   0   0   0   0   0   0   0   0.00
Amador          0   0   0   1   0   1   0   0   0   0   0.57
Butte           4  53  13  18   3   1   3   2   2   0   4.84
Calaveras       0   0   0   0   1   0   0   0   0   0   0.25
Colusa          0   0   0   0   0   0   0   0   0   0   0.00
Contra Costa    1   6   2   1   1   5   3   4   0   4   0.28
Del Norte       0   1   0   1   0   0   2   0   0   0   1.44
El Dorado       0   3   2   1   0   0   0   0   3   3   0.75
Fresno          1   0   0   0   1   0   0   0   0   0   0.02
Glenn           0   2   0   1   1   0   0   0   0   0   1.50
Humboldt        5  19  20  14  10   4   4   5   7  11   7.80
Imperial        0   1   0   0   0   0   0   0   0   0   0.07
Inyo            0   0   0   0   0   1   0   0   0   0   0.55
Kern            1   2   2   2   2   0   2   1   0   2   0.21
Kings           0   0   0   0   0   0   0   0   0   0   0.00
Lake            0   1   2   1   0   1   0   1   1   1   1.36
Lassen          0   2   1   2   0   0   2   0   0   0   2.04
Los Angeles     2   6   3   7   2   9   6   7   2   9   0.05
Madera          0   0   0   1   0   0   0   0   0   0   0.08
Marin           0   4   8   4   3   1   4   4   0   1   1.25
Mariposa        0   0   0   0   0   0   1   0   1   0   1.17
Mendocino       3   2  16   8   7   4  11   6   2   0   6.90
Merced          0   2   0   1   1   0   0   0   0   0   0.19
Modoc           0   0   0   0   0   0   0   0   0   0   0.00
Mono            1   0   0   1   0   0   0   3   1   0   4.67
Monterey        0   2   1   2   1   0   5   1   1   0   0.32
Napa            1   3   0   2   2   3   3   0   1   1   1.28
Nevada          2   1   4   5   9   6   3   4   1   3   4.12
Orange          0   0   1   2   3   0   3   2   0   1   0.04
Placer          0   5   4   2   1   4   3   0   2   2   0.92
Plumas          3   0   2   1   0   1   0   0   0   0   3.37
Riverside       1   0   0   0   3   2   1   2   1   4   0.09
Sacramento      0   5   1   1   3   4   1   4   2   6   0.22
San Benito      0   0   0   0   0   1   1   0   0   0   0.37
San Bernardino  0   0   0   1   1   0   0   2   0   0   0.02
San Diego       5   4   0  16   9   3   7   2   4   8   0.20
San Francisco   4   1   7   1   2   3   3   3   1   7   0.42
San Joaquin     1   2   0   0   0   0   0   0   0   0   0.05
San Luis Obispo 1   0   1   1   1   0   0   0   0   1   0.20
San Mateo       2   3   4   4   2   4   4   5   1   4   0.46
Santa Barbara   1   1   3   0   0   1   2   2   2   0   0.30
Santa Clara     2   4   6   2   2   2   6   4   0   2   0.18
Santa Cruz      2   2   2   2   5   9   1   8   3   0   1.32
Shasta          1   0   2   0   0   2   1   0   2   2   0.61
Sierra          0   0   0   0   0   0   0   0   0   0   0.00
Siskiyou        0   1   1   0   0   1   1   0   0   0   0.89
Solano          0   0   0   0   1   1   0   0   0   0   0.05
Sonoma         13  10  15  14   8   6   4   9   2   9   1.95
Stanislaus      3   1   0   0   1   1   0   0   0   1   0.16
Sutter          0   1   0   0   1   1   0   0   0   0   0.38
Tehama          0   1   1   0   2   0   0   0   0   0   0.72
Trinity         1   0   1  13   1   1   1   1   3   3  19.23
Tulare          1   0   1   1   0   2   0   2   0   0   0.19
Tuolumne        1   0   0   0   0   2   1   0   0   1   0.91
Vetura          0   0   2   1   2   2   1   1   2   1   0.16
Yolo            0   0   0   0   0   0   2   0   1   0   0.18
Yuba            0   0   1   1   0   0   0   0   0   0   0.33
Total          65 154 135 139  96  92  97  86  48  94   0.30

San Mateo County: Tularemia Detected in Coastal Ticks

Entomology Report September 2006, San Mateo County Mosquito Abatement District

Tularemia has been detected in ticks collected south of Pescadero this summer. The ticks were collected in July. Results of testing (conducted at the Centers for Disease Control) were received this month. This survey was conducted along with staff from the California Dept. of Health Services in response to a human case of tularemia. The patient had exposure to ticks in coastal San Mateo County, as well as locations in Marin and Alameda Counties. Tularemia was detected by PCR in 1 of 6 pools of Dermacentor occidentalis (totaling 43 ticks) and 1 of 17 pools of D. variabilis (211 ticks). The minimum infection rate for these ticks was 1 out of 43 or 2.8% for D. occidentalis, 1 out of 211 or 0.5% for D. variabilis and 2 out of 247 or 0.8% overall. This is somewhat lower than the prevalence of Lyme disease spirochetes in western black-legged ticks (1-3% countywide). The MIR calculated for D. occidentalis is probably not an accurate estimate for that species because the number tested was small.

Dermacentor ticks reach their peak numbers in the summer (June-July). They are found in drier areas and later in the year than the western black-legged tick which transmits Lyme disease.

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

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

Entomology Report April 2006, San Mateo County Mosquito Abatement District

The season for adult western black-legged ticks (vector of Lyme disease) is coming to a close. A total of 1,065 ticks were collected in 2005-06. This is twice the number collected in previous years. Participation by staff from the San Mateo County Health Department, the San Francisco Water Department and the California State Parks Department greatly increased the number of sites surveyed. Most collections were made in January and February. Frequent rains limited the number of days in March that surveys could be conducted. Ixodes pacificus ticks do not quest actively during heavy rains.

Park                              # Infected
Big Canyon, San Carlos            5/219  (2%)
Crystal Springs Trail, Millbrae   3/108  (3%)
Edgewood Pk, Redwood City         0/ 41  (0%)
Huddart Pk, Woodside              2/ 21 (10%)
San Pedro Valley Pk, Pacifica     3/252  (1%)

Previous related entries:

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: Trial Application of Suspend for Control of Ticks

Entomology Report April 2006, San Mateo County Mosquito Abatement District

In May, the District conducted a small trial on the effectiveness of Suspend for control of ticks along recreational trails. The material was applied in a 8 ft swath along the uphill side of a 0.37 mi stretch of trail. 90 ticks were collected before treatment. Sampling was conducted three days and one week after treatment. 1 male tick was collected after three days and 0 ticks were collected at one week. In contrast, a segment of the trail immediately adjacent to the treated area contained 131 ticks per 0.27 mi. This data suggests that the control work was effective. The District will determine the feasibility of different control methods and make it available to the public. Assistance will be given to other agencies seeking methods to control ticks in high risk areas.

Reported Cases of Lyme Disease in Sonoma County

Lyme Disease Cases Up in County, Marin / Sonoma Mosquito and Vector Control District

Fifteen cases were reported through April, according to county health officials, who said May and June tend to be the months in which the tick-borne disease is worst.

There were 16 cases all of last year in Sonoma County.

Lyme Disease Cases:
2003       Sonoma County - 11
2004       Sonoma County -  4
2005       Sonoma County - 16
2006*      Sonoma County - 15
*As of April 30, 2006

Meeting of the Lyme Disease Support Group of San Mateo County

Entomology Report March 2006, San Mateo County Mosquito Abatement District

Vector Ecologist, Chindi Peavey, Assistant Vector Ecologist, Angie Nakano, and Trustee, Valentina Cogoni (Menlo Park), represented the district at a meeting of the San Mateo County Lyme Disease Support Group on March 14 at El Camino Hospital in Mountain View. This support group provides guest speakers, education, medical information and moral support to those who are affected by Lyme disease. District staff gave an overview of district activities to protect and inform the public about Lyme disease and other tick-borne diseases in the area. The patient group voiced questions and concerns on a number of related topics from tick research and the functions of Mosquito Abatement and other County Health organizations to their frustrations in obtaining medical care for various Lyme Disease symptoms. From this lively discussion, the patient group came to a clearer understanding of the Mosquito Abatement District’s role in monitoring disease risks. District representatives gained more insight into the disease from the perspective of the patients, as well as new ideas on how to more effectively educate the public.

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

Entomology Report March 2006, San Mateo County Mosquito Abatement District

Laboratory testing revealed ticks positive for the Lyme disease agent at 5 parks this year. Prevalence rates are similar to other parts of Northern California. Tick density varies widely between parks as shown in the map. The prevalence of infection at Huddart Park and Edgewood Parks is inaccurately low due to the small number of ticks tested to date. Further testing is needed at these sites.

Park                              # Infected
Big Canyon, San Carlos            5/219  (2%)
Crystal Springs Trail, Millbrae   3/108  (3%)
Edgewood Pk, Redwood City         0/ 41  (0%)
Huddart Pk, Woodside              2/ 21 (10%)
San Pedro Valley Pk, Pacifica     3/252  (1%)

Previous related entries:

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: Lyme Disease Surveillance 2006

Entomology Report February 2006, San Mateo County Mosquito Abatement District

Tick surveys have yielded total of 1,091 western black-legged ticks (Ixodes pacificus) thus far this season. Parks with the highest density of I. pacificus adults per mile included San Pedro Valley, Edgewood, and Huddart County Parks, and municipal parks at Water Dog Lake in Belmont and Big Canyon Park in San Carlos. The prevalence of infection county-wide remains at 3%.

Park                           Ticks/Mile
San Pedro Valley County Park       83
Water Dog Lake Park                20
Big Canyon Park                    74
Edgewood County Park               53
Huddart County Park                23

Previous related entries:

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: Lyme Disease Surveillance 2006

Entomology Report January 2006, San Mateo County Mosquito Abatement District

Location            # Ticks   Ticks/  Female/   # Positive/
                  collected    mile     mile    # tested
Big Canyon Park         316    1.40     0.6     Results Pending
Crystal Springs Trail   118    0.30     0.2     3+/118
Edgewood Park            41    0.9      0.4     Results Pending
Huddart Park             50    0.4      0.2     Results Pending
Junipero Serra            0    0        0       Results Pending
Laurelwood Park          14    0.2      0.04    Results Pending
San Pedro Valley        174    1.2      0.7     Results Pending
Water Dog Lake           36    0.4      0.2     Results Pending
Grand Total             749    0.6      0.3     Results Pending

Previous related entries:

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

Tick-Borne Diseases in Santa Cruz County 2005

Annual Report 2005, Santa Cruz County Mosquito and Vector Control District

The County had six reported cases of Lyme disease, and one reported case of relapsing fever in 2005 from tick bites. Lyme disease continues to be the most important vector-borne disease in the State, with 94 reported cases in 2005. As part of an effort to enhance services, MVC now accepts, identifies, and submits ticks for Lyme disease testing for persons who have been bitten. Prevention of bites and recognition of symptoms by the public and physicians are the most recommended methods of dealing with tick-borne disease. There is currently no efficient means to control ticks other than clearing brush.

Reported Cases of Tularemia in California 2004

Annual Report 2005, Alameda County Vector Control Services

Tularemia, a diseased caused by strains of Francisella tularensis, is not commonly transmitted by contacting rodents or tick bites. However, three human cases of tularemia were reported to CDHS in 2004; two of which were likely acquired through a tick bite: one from Alameda County and one from Contra Costa County. The adult American dog tick (Dermacentor variabilis) removed from the Alameda case was tested positive by culture and PCR for F. tularensis (type B) by Center for Disease Control and Prevention (CDC). Because of the human cases and also its importance as a bioterrorism agent, the CDHS requested blood samples from various animals for testing. Blood samples from twenty-three rodents from various locations in Alameda County were submitted for testing. None of these samples showed infection with F. tularensis. United State Department of Agriculture (USDA) – Animal and Plant Health Inspection Service (APHIS) submitted additional twenty-eight blood samples of feral cats, skunks, Norway rats, jackrabbits and red foxes. Of these, one striped skunk tested positive for the tularemia pathogen.

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.

Alameda County Lyme Disease Surveillance, 2004-2005

Annual Report FY 2004-2005, 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. Field surveys were conducted at seven locations, which resulted in the collection of 446 questing ticks of which 439 were Ixodes pacificus, the Lyme disease vector. None of these ticks were confirmed to be Lyme disease positive by direct immunofluorescence (IFA). Forty four residents or pets from Alameda County were bitten by ticks. These were submitted to the Sonoma County Public Health Laboratory for Lyme disease testing. One local ticks which bit Alameda County Residents tested positive for the Lyme disease spirochete. The District now has the capability of conducting Lyme disease IFA Tests. We hope to expand this capability when new staff are hired.