San Mateo County: New Repellent Discovery

Entomology Report February 2009, San Mateo County Mosquito and Vector Control District

Chemist Aijun Zhang, of the USDA, along with collaborators from Nanjing Foresty University in China and the US Army Medical Department Center and School, discovered a compound in the South American Tauroniro tree that is as effective as DEET at repelling mosquitoes and ticks.  Tests were performed on two mosquito species (Aedes aegypti, and Anopheles stephensi), and two ticks, (Ixodes scapularis and Amblyomma americanum). The new compound is more repellant than DEET to mosquitoes.  For ticks, the new compound’s repellency is equal to that of DEET.

The repellent compound, isoflongifolenone, is already a component of several commercial products, including cosmetics, fragrances, deodorants and some paper. Because of its widespread use, it is presumed to be safer than DEET, which is not recommended to be worn under clothes, around broken skin, near eyes or mouth, and should be used in lower concentrations on children. The study authors have devised a way of inexpensively synthesizing the compound from turpentine feed stock. Some previously discovered natural compounds with insect repellent qualities haven’t become widely available because of the high cost of producing them. The study is available in the January 2009 issue of the Journal of Medical Entomology.

Here is the journal article:

Isolongifolenone: A Novel Sesquiterpene Repellent of Ticks and Mosquitoes

Authors: Zhang, Aijun; Klun, Jerome A.; Wang, Shifa; Carroll, John F.; Debboun, Mustapha

Source: Journal of Medical Entomology, Volume 46, Number 1, January 2009 , pp. 100-106(7)

San Mateo County: Ticks and Lyme Disease

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

In November, district staff began annual surveillance activities for Lyme disease bacteria in ticks. This year, the program will focus on surveying sites of potential risk that have not been thoroughly evaluated in the past. Tick surveys were conducted this month in Portola Valley Ranch and on a previously unsurveyed trail in Laurelwood Park (San Mateo). The western black-legged tick is the primary vector of the Lyme disease spirochete in California. Adults of this tick begin appearing on trails in November, reach peak abundance in January-February and persist into early May. The immature stage (nymph) reaches peak abundance in April-May and is found in dense hardwood forest. Nymphs present a higher risk for transmitting Lyme disease to people because they are harder to see and a high proportion may be infected.

In San Mateo County, Lyme disease spirochetes have been found in 1-3% of both adult and nymphal western black-legged ticks. However, nymphal ticks are more difficult to collect than adult ticks and have only been evaluated from four sites. The lab will be working to expand collection and testing of nymphs this spring in a greater number of locations.

San Mateo County: Tularemia Survey

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

District laboratory and operational staff trapped ground squirrels at a rural site in Portola Valley this month to survey for tularemia. Tularemia is a disease carried by wild mammals including rabbits, squirrels and mice. It can be transmitted to humans through the bite of ticks, fleas, horse flies and other insects, as well as by direct contact with infected animals. Cases of tularemia have occurred in primates housed at a site north of Alpine Road for the past several years. District staff have been working with staff from Stanford University to identify the source of infection in these monkeys. Past investigations have included trapping for mosquitoes and biting flies, flagging vegetation for ticks, and trapping small mammals. Previous attempts to collect small mammals and arthropods yielded very little. Although numerous ground squirrel burrows were observed at the site, no rodents were present.

This year, ground squirrels have re-colonized the area, prompting renewed trapping efforts. Trapping on October 22 and 23 yielded 8 squirrels. Blood samples and fleas were collected from each animal. Blood samples from the squirrels will be tested by the Centers for Disease Control (CDC). Fleas were “cleared” and identified using a taxonomic key. Clearing is a chemical process that makes the body more transparent, so that internal structures are visible. Some features that are important for determining flea species are the position and presence of hairs on the body surface, the shape of reproductive structures, and the size of body segments. Two species of fleas were found on the squirrels, Hoplopsyllus anomalus and Oropsylla montanus. Both flea species are potential vectors of tularemia and plague.

Aside from spreading disease, fleas are insects worthy of our admiration. Relative to their size, they are spectacular jumpers, second in the animal kingdom only to another insect, the froghopper. Fossils of fleas suggest that fleas have been around
for about 100 million years. It is estimated that around 2,000 different flea species exist today. During the two or three month lifespan of most fleas, a female can lay 2,000 eggs, allowing fleas to persist as a problem for a variety of animal hosts.

San Mateo County: Tularemia Investigations

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

In response to a tularemia outbreak in primates housed in a facility in Portola Valley, the entomology staff have been investigating the role of possible vectors responsible for the disease transmission. Tularemia, also known as rabbit fever, is a potentially serious and highly infectious disease caused by a bacterium found in wild mammals, mainly rodents and rabbits. It can be transmitted to humans by a variety of means. Potential ways people can become infected include: ticks, biting flies, exposure to infected animal carcasses, eating or drinking contaminated food or water, or breathing in bacteria suspended in air. Symptoms of tularemia include: sudden fever, chills, headache, diarrhea, muscle aches, joint pain, dry cough, and weakness. This disease is treatable with antibiotics.

District staff have been examining the wildlife in the area to determine the cause of the outbreak. Burrowing ground squirrels are abundant near the facility and serve as a reservoir of infection. One group of vectors under investigation are horse flies in the family Tabanidae. These are large flies with a vicious and painful bite. They mainly feed on the blood of cattle and horses but will also attack humans and presumably other primates.

Two types of traps, a box trap and a malaise trap, were set out in the field to assess fly populations. Ground squirrels were trapped and blood samples were obtained to test for tularemia.

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: Physician Lyme Disease Survey Follow-Up

Entomology Report March 2008, San Mateo County Mosquito Abatement District

Follow-up on the physician survey on Lyme disease continued in March. Based on survey results, the district mailed educational materials to over 200 primary care physicians in San Mateo County. The mailing consisted of a letter about infection in local ticks, instructions on disease reporting, brochures, and tick identification cards.

Results of the survey were presented to the California Lyme Disease Advisory committee in Sacramento on March 12. On March 20, the district discussed the survey in a teleconference of the Communicable Disease Exchange, a forum of health departments from counties throughout California. Two counties in the coastal region have expressed interest in conducting similar surveys or using the results of the present survey to guide physician education.

San Mateo County: Surveying for Tularemia on the Coast

Entomology Report Frebruary 2008, San Mateo County Mosquito Abatement District

On February 27, the district trapped rodents south of Pescadero to test for tularemia. Tularemia is a bacterial disease of wildlife (primarily rodents and rabbits) that can sometimes be transmitted to people. Symptoms include abrupt onset of fever, chills, muscle aches and progressive weakness. When a person is infected by a tick bite, there is often a skin ulcer at the site of the bite and the local lymph nodes are swollen. The disease can be acquired from ticks or exposure to the tissues of infected animals, such as rabbits. Tularemia is not passed from one person to another and is treatable with antibiotics.

There have been two cases of tularemia in children in San Mateo County in the past 3 years. Both cases appear to have been caused by exposure to infected ticks at a location south of Pescadero along the coast highway. Tularemia has been detected in ticks collected at this site. In 2007, the bacteria was detected in 3 out of 102 adult American dog ticks (Dermacentor variabilis) and in 5 pools out of 128 adult Pacific coast ticks (D. occidentalis). The prevalence of infection in these ticks was 3 and 4%, respectively.

The survey conducted this month was aimed at assessing the level of infection in reservoir hosts. A total of 150 live traps were set and 12 animals were collected. Collections included 5 deer mice (Peromyscus maniculatus), 4 harvest mice (Reithrodonomys megalotis) and 3 California meadow voles (Microtus californicus). Blood samples obtained from these animals will be tested for serological evidence of exposure to tularemia by scientists at the Centers for Disease Control (CDC). Ultimately, the district plans to conduct monthly trapping and collect samples from at least 50 mice.

This project is a collaboration between the district, the San Mateo County Health Department, the California State Department of Public Health, and the CDC.

San Mateo County: Mosquito and Vector Control Association of California Annual Conference (Physician Survey on Lyme Disease)

Entomology Report January 2008, San Mateo County Mosquito Abatement District

Two laboratory staff presented research in the tick-borne disease symposium at the 2007 annual meeting of the Mosquito and Vector Control Association of California. Chindi Peavey, Vector Ecologist, spoke about tularemia, a disease of rabbits and rodents that can sometimes be transmitted to people. There have been 2 cases of tularemia in children in the past 3 years that have been traced to tick exposure on the coast near Pescadero. The District conducted follow-up investigations of these cases with the California department of Public Health in 2004 and 2006.

Assistant Vector Ecologist Lauren Marcus presented the findings of a physician survey performed in San Mateo County, in conjunction with the San Mateo County Health Department. Physicians were asked about their beliefs about Lyme Disease (LD). 86% of respondents believe that LD can be acquired locally. 73% of physicians note that 1 to 5 patients seek medical attention due to a tick bite annually and diagnose an average of 1.4 LD cases in 5 years. Of those who have diagnosed a patient with LD, 40% observed an erythma migrans (EM) rash and 52% stated that the patient had recalled a tick bite within three months of symptom onset. Physicians were asked what types of public education materials would be most useful. A resounding 80% wanted data on tick infection prevalence in the County, followed by 78% who wanted fact sheets on tick ecology, risk exposure, and prevention information. Finally, 73% wanted tick ID cards. Overall, the physician survey was successful in determining beliefs towards LD and what forms of educational materials were desired.

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: Tularemia Surveillance 2006-2007

Annual Report 2006-2007, Alameda County Vector Control Services

Tularemia is caused by the bacterium Francisella tularensis that infects a variety of arthropods and vertebrates. Symptoms of human tularemia may include fever, chills, malaise, and fatigue. The disease is commonly transmitted by contacts with rabbits, insects, or tick bites. In Alameda County, a confirmed human case, transmitted by an American dog tick, Dermacentor variabilis was reported by CDHS in 2004. Since tularemia is classified as a bio-terrorism agent, the CDHS requested blood samples from various animals for testing. In 2006, 12 rodent samples were submitted; results are still pending.

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: Population Dynamics of the American Dog Tick and Pacific Coast Tick

Entomology Report June 2007, San Mateo County Mosquito Abatement District

District staff have been monitoring the seasonal population dynamics of the American Dog tick (Dermacentor variabilis) and the Pacific Coast tick (Dermacentor occidentalis) along the coast this year. These ticks are potential vectors of tularemia and Rocky Mountain Spotted Fever in California. Human cases of these diseases appear to have been acquired in San Mateo County during the past 3 years. Cases of tularemia have occurred in children camping south of Pescadero in 2004 and 2006. In 2004, a tick removed from a patient tested positive and in 2006, infection was detected in local ticks collected in the same area.

Adults of these ticks appear during spring and summer months. Because they are not vectors of Lyme disease, they have not been surveyed by District staff as extensively as the Western black-legged tick. The District is now sampling for these ticks on a weekly basis to further characterize their seasonal population trends. This information will be incorporated into public education campaigns that teach people to avoid tick-borne diseases.

Previous related entries:

San Mateo County: Tularemia Detected in Coastal Ticks, September 2006

San Mateo County: Physician Survey on Lyme Disease

Entomology Report June 2007, San Mateo County Mosquito Abatement District

In conjunction with the San Mateo County Public Health Department, laboratory staff have surveyed over 100 physicians throughout the county to assess physician beliefs and awareness about Lyme Disease. So far, 9% of the surveys have been completed and returned. This survey will be used to develop educational materials, geared towards physicians, informing them of the risk of acquiring Lyme Disease in the county.

Previous related entries:

Survey of San Mateo County Physicians on Lyme Disease, March 2007
San Mateo County Physician Survey on Lyme Disease, November/December 2006

San Mateo County: Nymphal Tick Surveillance

Entomology Report May 2007, San Mateo County Mosquito Abatement District

Testing nymphs, the juvenile stage, is an integral part of the Lyme disease surveillance program. Their extremely small, hard to see, size of this stage contributes to their role in transmission of Lyme disease. Nymphs are collected by dragging white flannel sheets over forest floors with dense leaf litter, the preferred habitat of nymphal ticks. Lab and field staff regularly monitor, collect, and test ticks in these areas to determine prevalence of Lyme disease in nymphal ticks. So far, surveys for nymphs have been carried out in Los Trancos Woods, Costanoa Resort in Pescadero, Skyline Ridge Open Space, Edgewood Park in Redwood City and Laurelwood Park in San Mateo.

Previous related entries:

San Mateo County: Tick Flagging with Santa Clara County Vector Control District, April 2007

Orange County: Rocky Mountain Spotted Fever Confirmed in County Park

Rocky Mountain Spotted Fever confirmed in County park, Orange County Vector Control District

Rocky Mountain Spotted Fever confirmed in County park. A Pacific Coast Tick, Dermacentor occidentalis that was collected in Aliso and Wood Canyons Wilderness Park tested positive for Rocky Mountain Spotted Fever (RMSF). Orange County Vector Control District (OCVCD) collected the tick on January 29, 2007 as part of an ongoing surveillance program. Samples were submitted to the California Department of Health Services (DHS), although the actual testing was done by The Centers for Disease Control and Prevention (CDC). The District received confirmation on the positive tick from DHS on, March 30, 2007.

Los Angeles County West: Locations of Lyme Positive Ticks

Locations of Lyme Positive Ticks, Los Angeles County West Vector Control District

Map:
Sites where ticks positive for Lyme disease bacterium have been found in the district

Charmlee Park
Malibu Creek State Park
Tapia State Park
Topanga State Park
Will Rogers State Park
Palos Verdes Estates - Bluff Cove
Rolling Hills - Purple Canyon Trail

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

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.

San Mateo County: Public Education and Other Activities: Lyme Disease and Ticks

Entomology Report March 2007, San Mateo County Mosquito Abatement District

• Dr. Chindi Peavey, the District Vector Ecologist, gave a presentation on Lyme Disease Ecology and Surveillance at El Camino Hospital on March 17 in conjunction with Dr. Anne Kjemtrup, from the California Department of Health Services, and Victor Romano, from Santa Clara County Vector Control.
• Laboratory staff distributed a press release on the presence of vector ticks in vacant lots in a well-developed residential area in Pacifica. This story was picked up and published in an article by the Pacifica Tribune. The article has generated a number of calls from residents on the coast. Laboratory staff visited additional sites and spoke with residents about ways to reduce the risk of acquiring Lyme Disease.
• Legislation declaring May as Lyme Disease Awareness Month is currently going through the state legislature.