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.

San Mateo County: Tick Surveillance

Entomology Report November/December 2007, San Mateo County Mosquito Abatement District

This year, the lab will be measuring relative density and seasonal distribution of western black-legged ticks at five parks: Costanoa Lodge, Huddart Park, Skyline Ridge Open Space, Pulgas Ridge Open Space, and San Pedro Valley County Park. These parks represent the varied climates of the north, south, mid-, and coastal areas of the county. The study is designed to look at differences in the timing of tick activity in different parts of the county.

Additional testing for Lyme disease spirochetes will be conducted on ticks from Water Dog Lake and Camp Jones Gulch.

Alameda County: Lyme Disease Surveillance 2006-2007

Annual Report 2006-2007, Alameda County Vector Control Services

As part of the Lyme disease surveillance program, our staff collects and identifies ticks, and recommends testing for tick borne disease when deemed appropriate. Our District provides consultations, educational resources, tick identification, and testing facilities for Lyme disease. Fifteen Ixodes pacificus ticks were submitted to the Sonoma County Public Health Laboratory for Lyme disease testing; all tested negative. The District now has the capability to perform Lyme disease indirect fluorescent antibody (IFA) tests. We hope to expand this capability when new staff is hired.

San Mateo County: Tick Flagging with Santa Clara County Vector Control District

Entomology Report April 2007, San Mateo County Mosquito Abatement District

In April, District staff focused on collection of nymphal ticks for Lyme disease testing. On April 18, District laboratory staff collaborated with Santa Clara County Vector Control to search for nymphal ticks in sites near the county border. Sampling was carried out on Old Spanish Trail in Los Trancos Woods and at Foothill Park in Los Altos. These ticks are in the process of being tested for Lyme disease. Ixodes pacificus nymphs are active during the spring and early summer and are easily overlooked due to their small size. Nymphs infected with the bacteria that causes Lyme disease have been found throughout San Mateo County.

A 6-Year Analysis of Tick Surveillance in San Mateo County

Entomology Report February 2007, San Mateo County Mosquito Abatement District

% Infection of I. pacificus in San Mateo County Parks
Location             # Ix. pacificus Tested  % Infection
Pulgas Ridge                    60                3.3
Los Trancos Woods              733                2.5
Huddart Park                   140                2.1
Big Canyon Park                507                1.8
Crystal Springs Trail          556                1.6
San Pedro Valley Park          333                0.9
Laurelwood Park                428                0.7
Edgewood Park                  195                0.5

An analysis of tick surveillance data from 2002 through February 2007 in San Mateo County was performed. Adult Ixodes pacificus ticks have been collected from 11 parks. Thus far Lyme disease spirochetes have been detected in ticks from 8 parks (Big Canyon Park, Crystal Springs Trail, Edgewood Park, Huddart Park, Laurelwood Park, Los Trancos Woods, Pulgas Ridge, and San Pedro Valley Park). The prevalence of infection in ticks at these parks ranged from 0.5% - 3.3%. Ticks collected from Costanoa, Sweeney Ridge, and Water Dog Lake have not yet tested positive for Lyme Disease spirochetes.

Previous related entries:

Tick Surveillance in San Mateo County, January 2007, January 2007
Tick Surveillance in San Mateo County, December 2006, December 2006
San Mateo County: Lyme Disease Surveillance Winter/Spring 2005-06, June 2006
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: Results of the Efficacy of Suspend on Density of Ticks Along a Recreational Trail

Entomology Report January 2007, San Mateo County Mosquito Abatement District

The insecticide Suspend (Deltamethrin) was evaluated for its ability to control Dermacentor ticks along a recreational trail in San Mateo County. Three days post treatment, showed a 98% decline in ticks. One week post treatment resulted in 100% control and after seven weeks the trail was still at a density of 0 ticks. This study showed that the material is very effective in controlling Dermacentors. In the future, another study will be performed to evaluate the efficacy of Suspend on Ixodes pacificus ticks.

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: Results of the Evaluation of Trailside Mowing as a Tick Control Method, January 2007
San Mateo County: Effects of Mowing on Summer Tick Populations, June 2006

Ticks and Lyme Disease in Contra Costa County 2006

2006 Annual Report, Contra Costa County Mosquito and Vector Control District

Lyme disease is a bacterial infection transmitted by the Western black-legged tick (Ixodes pacificus), also known as the deer tick. While Lyme disease is rare in Contra Costa County (on average there are two to four human cases reported per year), it can cause serious complications if not treated promptly. The District monitors the risk of Lyme disease by collecting and testing black-legged ticks from several locations that we have been monitoring for as long as 12 years. These include Bollinger Canyon Rd., San Ramon; Springhill Rd., Lafayette; and the Bear Creek area of Briones Regional Park. The adult Western black-legged tick population was below average for most of the season, except during the last half of March where counts slightly exceeded the average. An unusually high number of days with rainfall during the collecting season limited the number of possible collection days; thus reducing the numbers of ticks collected. The graph below shows the average number of ticks that were collected from these locations.

On average, only one or two in a hundred black-legged ticks test positive for Lyme disease, although we have found a few locations where the rate is higher, and these tend to change over time. In 2006, we collected and tested 132 ticks from three locations; the highest infection rate was in the Bollinger Canyon area in San Ramon where three out of 58 ticks tested positive (just over 5 percent).

We also identify and test ticks brought in by members of the public who have been bitten. If the ticks are reasonably intact and not dried out, we can test them in our own laboratory free of charge. If they are in poor condition or dead, a more sensitive test is required and county residents have the option of allowing us to send the tick to a private laboratory for a fee of $60 (our cost). Out of 54 ticks tested for residents in 2006, only one was positive for Lyme bacteria (just below 2 percent).

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 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: 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

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.

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.

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

Tick-Borne Disease Surveillance in California, 2004

Vector-Borne Diseases in California, Annual Report 2004, California Department of Health Services, Vector-Borne Disease Section

Human disease surveillance

Lyme disease

Fifty-two cases of Lyme disease were reported to the California Department of Health Services (CDHS) in 2004. Case-patients were residents of 24 counties. Humboldt County reported the most cases (8) and incidence was highest in Trinity County at 23 cases per 100,000 residents. Of 32 cases for whom site of likely exposure was reported, 12 (37.5%) had exposure outside of their county of residence; 7 (22%) of these reported exposure outside California. The most frequently reported location of exposure was Humboldt County (9 cases).

The median age of reported Lyme disease cases was 32 years (range, 3 to 80 years) and 31 (60%) were male. Race was reported as white for 47 (91%) cases, Asian for 3, black for 1, and unknown for 1 case. Erythema migrans (EM) was identified in 23 (44%) cases. Of 22 cases with EM for which date of illness onset was reported, 13 (59%) occurred between May and August.

Anaplasmosis

Two cases of human granulocytic anaplasmosis (HGA, formerly known as human granulocytic ehrlichiosis) were reported to CDHS in 2004. In June, a 53-year-old female resident of Alameda County developed high fever (104 degrees F), headache, malaise, and rash. The CDHS Viral and Rickettsial Disease Laboratory (VRDL) detected antibodies to Anaplasma phagocytophilum (IgM > 1:40, IgG > 1:1024) in a serum specimen collected approximately four weeks after onset. The patient recovered without specific treatment.

The patient reported removing an attached tick from her back at least 12 hours after hiking in Tilden Park, Alameda County. In July 2004, CDHS staff conducted surveillance for ticks at Tilden Park. One Ixodes pacificus adult female tick was recovered and tested negative by polymerase chain reaction (PCR) to A. phagocytophilum at the United States Army Center for Health Promotion and Preventive Medicine - West at Fort Lewis Washington (USACHPPM). Although A. phagocytophilum were detected by PCR in I. pacificus collected from Alameda County in 1996, this was the first HGA case reported from this county.

A second case of anaplasmosis was reported in a male resident of San Mateo County. The case-patient had onset of illness in December following a tick bite he received in New Jersey.

Rocky Mountain Spotted Fever

One case of Rocky Mountain Spotted Fever (RMSF) was reported to CDHS in 2004. In June, a 52-year-old male resident of San Mateo County presented to an emergency room with fever (101 degrees F - 104 degrees F), lethargy, altered consciousness, and hallucinations. The patient was hospitalized and three days later developed a macular rash that began on the palms and soles and expanded to the upper limbs and trunk. Despite initiation of antibiotic treatment, the patient remained comatose with encephalitis for four days. The patient eventually improved and was discharged from the hospital 13 days after admission. The VRDL detected a significant rise in IgG titer to Rickettsia rickettsii between acute (1:4096) and convalescent (1:16,384) sera collected approximately seven and seventeen days after onset, respectively. The patient reported travel and camping in Marin and San Mateo Counties in May and June; he had observed ticks but did not recall a specific bite. Staff of Marin-Sonoma Mosquito and Vector Control District and the CDHS Vector-Borne Disease Section (VBDS) collected three male and one female Dermacentor occidentalis ticks from the Marin County site in July. VBDS and staff from the San Mateo County Mosquito Abatement District collected four male and two female D. occidentalis, three male, six female, and one nymphal D. variabilis, and one female and five nymphal I. pacificus from two sites in San Mateo County in July. The USACHPPM reported detecting by PCR Spotted Fever Group Rickettsia in two D. occidentalis from Marin County and one D. variabilis from San Mateo County.

Tularemia

Three cases of tularemia were reported to CDHS in 2004, two of which were likely acquired through a tick bite. In late May, a ten-year-old male resident of Contra Costa County developed cervical lymphadenitis. He was initially treated as an outpatient but did not improve. The CDHS Microbial Disease Laboratory (MDL) cultured Francisella tularensis (Type A) from a lymph node aspirate obtained approximately five weeks after onset. In late June, a five-year-old male resident of Alameda County had similar onset of fever and cevical lymphadenitis. The MDL isolated F. tularensis (Type B) from a lymph node culture in July from the Alameda patient. Both patients recovered following short hospitalizations.

The Alameda case-patient had camped in San Mateo County about five days prior to oneset and had visited Tilden Park in Alameda County about 10 days earlier. The Contra Costa case-patient also walked trails in Tilden Park in the week prior to onset. Neither patient had any contact with rabbits or other wild animals. Both case-patients reported tick bites to their face or head about three days prior to onset of illness. The tick from the Alameda case was retained and later identified by CDHS staff as an adult D. variabilis.

In July, CDHS conducted surveillance for ticks at the Tilden Park and San Mateo locations. Forty D. occidentalis were collected from Tilden Park and 16 D. occidentalis and 87 D. variabilis from the San Mateo location. Ticks were submitted to the Division of Vector-Borne Infectious Diseases, U.S. Centers for Disease Control and Prevention, for culture and PCR. F. tularensis (Type B) was identified in the tick recovered from the Alameda patient; all ticks collected in the field were negative.

Tick-borne relapsing fever

Six cases of tick-borne relapsing fever were reported to CDHS in 2004. Case-patients were residents of five counties (Contra Costa, El Dorado, Madera, San Mateo, and Santa Clara) and ranged from 8 to 49-years-old. Five case-patients were likely infected while visiting the western Sierra Nevada; exposure information was unavailable for one case.

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.

Tick-Borne Diseases in Santa Cruz County 2003-2004

Annual Report 2003-2004, Santa Cruz County Mosquito and Vector Control District

The County had 8 reported cases of Lyme disease, and one reported case of Rocky Mountain spotted fever in 2003, and 3 reported cases of Lyme disease in 2004 from tick bites. Lyme disease continues to be the most important vector-borne disease in the State, with an average of 200-300 reported cases per year. A recent study by San Jose State University suggested that the infection rate of Ixodes pacificus ticks with Lyme disease in our County may be higher than in other parts of the state, with the number infected averaging 5-6%. This finding was notably higher than previously reported prevalence estimates, although the infection rate in this area is still relatively low compared to that of some east coast states.... Prevention of bites and recognition of symptoms by the public and physicians are the recommended methods of dealing with tick-borne disease.

Alameda County Lyme Disease Surveillance, 2003-2004

Annual Report FY 2003-2004, 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 collection of 1,175 questing ticks of which 651 were Ixodes pacificus, the Lyme disease vector. Three of these ticks were confirmed to be Lyme disease positive by direct immuno-fluorescence (IFA). The three positive ticks represented about 0.046% positive for Lyme disease from the samples taken so far. This number is far 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. Thirty-seven residents or pets from Alameda County were bitten by ticks. These were submitted to the Sonoma County Public Health Laboratory for Lyme disease testing. All local ticks which bit Alameda County Residents tested negative 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.

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.