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Tick Surveillance Updates

July 2021 update

During June, laboratory staff conducted tick surveillance at Stulsaft Park, Edgewood County Park, Los Trancos Open Space Preserve (OSP), Coal Creek OSP, Skyline Ridge OSP, Costanoa, and Butano State Park. In addition to normal surveillance, some of these collections were part of research collaborations.

Habitat Fragmentation Study

Ticks were collected for the Swei Laboratory from areas of high habitat connectivity (Coal Creek, Los Trancos, Skyline), as well as in more fragmented habitats (Edgewood, Stulsaft).

The District is collaborating with San Francisco State University’s tick borne disease specialist Dr. Andrea Swei.  Dr. Swei’s research focuses on the ecology of Borreliae (including Borrelia burgdorferi, the bacteria that causes Lyme disease). The Swei lab (with the support of the District) was awarded a 2021-2022 Pacific Southwest Center of Excellence in Vector-Borne Diseases Training Grant for a graduate-led project titled “Habitat connectivity and transmission dynamics of tick-borne diseases.”

Habitat fragmentation can occur when an open space is divided by roads, railways, dams, and other infrastructure that may prevent animals from moving around freely. This fragmentation can also affect waterways, sedimentation, and nutrient availability, all of which could impact the distribution of animals, ticks, and tick-borne diseases.  San Mateo County is an ideal location for this research because it has both connected open space and smaller, fragmented parks surrounded by housing. As part of this project, District lab staff sampled five county locations for nymphal ticks (see map). A total of 1,570 ticks were collected. This is the District’s third collaboration with the Swei Laboratory on grant-funded projects.

Haemaphysalis Research

In June, District staff also collected and contributed ticks for a project led by by Dr. Andrea Egizi, a Research Scientist with the Monmouth County Mosquito Control Division/Tick-borne Disease Laboratory at Rutgers University in New Jersey. Dr. Egizi is examining the morphology and genetics of North American Haemaphysalis ticks. One species of Haemaphysalis, the rabbit tick (H. leporispalustris) is found in parts of San Mateo County.

Rabbit ticks rarely bite humans and do not transmit Lyme disease, but are occasionally collected in District tick surveys. Rabbit ticks have been found to carry Rocky Mountain spotted fever and tularemia but, due to the strong preference to feed on rabbits, the risk of disease transmission to humans from this tick is very low. The District’s laboratory contributed 93 rabbit ticks from three life stages (larvae, nymph, adult) for this project.


June 2021 update

During May, laboratory staff focused on surveillance of nymphal Ixodes pacificus, Western black-legged ticks. Tick nymphs are more difficult to collect than adults because they don’t quest on vegetation along trails. Instead, they are found on tree stumps, downed longs, rocks, and in leaf litter. Areas that were surveyed in May include Edgewood County Park and Stulsaft Park in Redwood City, Hidden Canyon Park in Belmont, Los Trancos Open Space and Coal Creek Preserve near Portola Valley, Skyline Ridge Preserve near La Honda, and Costanoa and Año Nuevo State Park near Pescadero.


May 2021 update

During April, laboratory staff focused on surveillance of nymphal Ixodes pacificus, Western black-legged ticks. Tick nymphs are more difficult to collect than adults because they don’t quest on vegetation along trails. Instead, they are found on tree stumps, downed longs, rocks, and in leaf litter. Nymphal ticks are considered more dangerous than adult ticks because in some regions of California they have been found to be more likely to be carrying Borrelia burgdorferi bacteria, which causes Lyme disease. Areas that were surveyed in April include Edgewood park and Stuflsaft park in Redwood City, Laurelwood park in San Mateo, Hallmark park in Belmont, Costanoa and Año Nuevo state park near Pescadero and several schools in Pacifica and Hillsborough.


April 2021 update

During early March 2021, laboratory staff continued surveillance for adult Ixodes pacificus (Western black-legged ticks). Ticks are collected by dragging a 1 meter square sheet of white flannel over the vegetation alongside trails. Ixodes pacificus ticks will be tested for the presence of bacteria Borrelia burgdorferi, the causative agent of Lyme disease, as well as Borrelia miyamotoi and Anaplasma phagocytophilum. Areas that were surveyed in March were trails in the north part of Año Nuevo State Park and trails near the Costanoa resort near Pescadero. Tick surveillance activities were halted midway through the month.

Park/NeighborhoodNearest City/TownNumber of Ixodes pacificus
Año Nuevo State ParkPescadero687
Butano State ParkPescadero226
Junipero Serra ParkSan Bruno20
La Honda Open Space PreserveLa Honda37
Lakeview neighborhoodHillsborough273
Los Trancos WoodsPortola Valley300
Spencer Lake AreaHillsborough153
Wunderlich County ParkWoodside100

Tick Surveillance at Schools

During the 2019-2020 water year, the District initiated a pilot program to assist area schools located in tick-endemic areas of the county in assessing their risk of tick exposure on campus.  Lab staff conducted tick surveys at 15 area schools.  Each school was sent a detailed report with the number and location of any ticks collected, as well as an evaluation of tick disease risk and recommendations on environmental modifications to reduce risk to students, faculty, and staff.  Each school was also offered customized tick-safety materials to send to students and parents, in multiple languages. 

Some schools reported performing significant landscaping and grounds maintenance work on their campuses in response to the initial assessment.  Return trips to these schools by lab staff found dramatic reductions in the number of ticks present in student-accessible areas. 

The District looks forward to continuing to work with schools and expanding efforts in the future to proactively reduce the risk of tick-borne disease for residents of all ages in San Mateo County.

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