Laboratory staff conducted two surveys of wild rodents in the month of June. The surveys took place in Water Dog Lake park in Belmont on June 14th and 15th and Eaton and Big Canyon parks in San Carlos on June 20th and 21st. Blood samples were taken from captured rodents by a subocular bleed with a microcapillary tube and ear punches were also taken from the rodents. The blood and ear tissue will be tested in our District laboratory for Borrelia bacteria that cause Lyme disease and other infection.
As of June 630, 2017, there have been 215 dead birds reported in San Mateo County. Of those, 45 have been suitable for testing and 1 has tested positive (2%) for West Nile Virus (WNV). No dead squirrels or mosquito pools have been tested for West Nile Virus in San Mateo County thus far this year.
Did you know that there are more stinging insects than just wasps and honey bees? Stinging insects are grouped into the family Hymenoptera and are distinguished by having 2 sets of wings, a cinched “wasp waist,” and an ovipositor that has been modified into a stinger. That is about where the comparisons end however. The following article covers the incredible diversity of stinging insects and even points out a couple of the “wanna-bees” that have evolved to mimic their much more aggressive cousins.
Snipe flies, from the Family: Rhagionidae, are 4.5 to 15 mm long stout bodied flies that can range in color from black to brown and yellow. Though most snipe flies are predators of other insects, one genus (Symphoromyia) has adapted to feeding on mammal blood.
As of June 6, 2017, there have been 134 dead birds reported in San Mateo County. Of those, 21 have been suitable for testing and 1 has tested positive (5%) for West Nile Virus (WNV). No dead squirrels or mosquito pools have been tested for West Nile Virus in San Mateo County thus far this year.
Laboratory staff conducted one survey of wild rodents in the month of May. The surveys took place in Montara. Blood samples were taken from captured rodents by a subocular bleed with a microcapillary tube and on nobuto paper strips. This blood was sent to the California Department of Public Health for testing of plague and hantavirus. All rodents tested negative for plague. Results of hantavirus testing are pending.
Starting this year our laboratory will simultaneously test for three encephalitis diseases carried by Culex mosquitoes: West Nile Virus (WNV), Saint Louis Encephalitis (SLEV) and Western Equine Encephalitis (WEEV).
On March 21, the laboratory staff did an annual rodent survey for hantavirus at San Bruno Mountain County Open Space Preserve and State Park. Out of the 43 rodents collected, 5 were positive for hantavirus for an infection prevalence of 11.6%. Results for plague are still pending. The laboratory will schedule a follow-up survey for hantavirus at San Bruno Mountain in the summer and are on-schedule to complete our annual survey for rodent-borne diseases at Montara Mountain in May.
Dr. Nayer Zahiri, laboratory director at the District since November 2012, will be returning to Santa Clara Vector Control as their new District Manager. Nayer’s final day at San Mateo County MVCD will be April 7. During her time with us, Nayer brought her expertise in resistance and molecular biology to develop new laboratory programs for our District, including Q-PCR testing of birds and mosquitoes for West Nile Virus, Q-PCR tick testing for tick-borne bacteria, a robust larval bioassay method for pesticide resistance, and invasive Aedes mosquito monitoring.
The District has been awarded a grant to assist in surveillance of invasive Aedes mosquito surveillance. The grant funding comes from the Center for Disease Control and is administered by the nonprofit corporation Public Health Foundation Enterprises on behalf of the California Department of Public Health. The District plans to use the funds to greatly expand our efforts to detect and control invasive mosquito species.
The Mosquito and Vector Control Association of California (MVCAC) annual conference was held in San Diego March 26 – March 29. District Manager Chindi Peavey, Assistant Manager Brian Weber, Public Health Education and Outreach Officer Megan Sebay, Vector Ecologists Cheryl Tina Sebay and Warren Macdonald, Laboratory Technician Theresa Shelton and Trustee Donna Rutherford attended. During the banquest, Chindi Peavey received an award for her work as a representative of the coastal region of California to the MVCAC.
The 2017 sentinel chickens are situated in their coops for the West Nile Virus season. The three coops are at Woodside, East Palo Alto and San Mateo and contain ten chickens each. Starting May 1, the chickens will be tested every two weeks for the mosquito-borne diseases West Nile Virus, Saint Louis Encephalitis, and Western Equine Encephalitis.
From February 13 – 17, Laboratory Director Nayer Zahiri, Operations Supervisor Casey Stevenson and Trustee Peter DeJarnatt attended the annual conference of the American Mosquito Control Association in San Diego. Dr. Zahiri gave two presentations at the conference: “Monitoring Susceptibility of Culex pipiens to Larvicide Products Currently in use in San Mateo County” and “Aedes aegypti Surveillance in San Mateo County from 2013-2016.” Both presentations were well-received by attending mosquito control professionals.
Tick collection continued through the month of February during periods of dry weather. Parks visited in February include Quarry Park in El Granada, Montara Mountain in San Pedro Valley Park near Montara, Eaton Park in San Carlos, Edgewood Park in Redwood City and Purisima Creek Redwoods Preserve near Woodside.
Winter 2017 Tick Collections through February 2017
It is unusual to detect West Nile Virus in dead birds during the winter months. West Nile Virus season begins mid-April, with most activity in the summer. However, residents can report some species of dead birds (crows, ravens, scrub-jays, finches, sparrows, hawks and owls) year-round online at westnile.ca.gov and the District laboratory will test fresh specimens without signs of trauma (roadkill or partially decomposed specimens cannot be tested).The first West Nile Virus positive bird of 2017 in San Mateo County was detected in Redwood City.
Tularemia, rabbit or deerfly fever, is a relatively rare bacterial disease transmitted to humans and animals by the bite of ticks. It is much less common that Lyme disease in California and is primarily transmitted by the American dog tick (Dermacentor variablis) and possibly by the Pacific Coast tick (Dermacentor occidentalis).
The District laboratory is taking advantage of breaks in rainy weather to collect ticks from parks and open space areas in San Mateo County. Ticks are collected by dragging a tick flag – a large white piece of flannel attached to a wooden rod – over the vegetation alongside trails. The main target species of tick is Ixodes pacificus, the western black-legged tick, which vectors Lyme disease, Borrelia miyamotoi infection, and anaplasmosis. The ticks collected will be tested for the presence of bacteria that cause these diseases. The Ixodes pacificus ticks are in
In addition to testing for Borrelia burgdorferi and Borrelia miyamotoi, the District tested ticks collected this year from four parks for another bacteria that causes the disease Anaplasmosis. This disease is less common than Lyme disease in California but is transmitted by the same tick, the western black-legged tick (Ixodes pacificus). The ticks from these four parks were all close to an area where Anaplasmosis has been detected in the past.
The laboratory has filled two open positions. The part-time Laboratory Technician position has been filled by Theresa Shelton, formerly a Vector Ecologist at the District. The open Vector Ecologist position has been accepted by Tara Roth. Tara recently completed a Ph.D. in Integrative Pathobiology from University of California, Davis, where she studied the disease Tularemia, an infection of a bacteria that can be transmitted by ticks. Tara will be joining the District on January 9, 2017.
