During February, 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.
District staff are assisting in a collaborative study on a
mosquito parasite that is spearheaded by researchers from
Stanford University and the University of Innsbruck in Austria.
The parasite is a ciliate type of protozoa, Lambornella
clarki, which is a single-celled animal that lives in water.
Lambornella clarki is found in water that collects in
tree holes, and can enter the body of the mosquito larvae of
Aedes sierrensis, the western tree-hole mosquito. Inside
the mosquito larvae, it multiplies and kills the hosts.
On January 26-29, the Mosquito and Vector Control Association of
California (MVCAC) held their annual meeting in San Diego.
District laboratory staff presented on some of the projects they
conducted during the previous year.
The SMCMVCD Laboratory presented three scientific posters at
MVCAC:
Laboratory staff began winter surveillance for adult Ixodes
pacificus (Western black-legged ticks) in December. Ticks
are collected by dragging a 1 meter square piece 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.
In the 2019 calendar year, the District closed out one of its
lowest seasons for West Nile virus activity since the virus first
appeared in San Mateo County in 2004. No virus was detected
in the county this year in any of the standard WNV surveillance
indicators.
As of December 1, 2019, there have been 231 dead birds reported
in San Mateo County. Of those, 57 have been suitable for testing
and all have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of November 1, 2019, there have been 215 dead birds reported
in San Mateo County. Of those, 53 have been suitable for testing
and all 53 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of October 2, 2019, there have been 191 dead birds reported in
San Mateo County. Of those, 44 have been suitable for testing and
all 44 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
This summer, the District participated in a
collaborative study to evaluate a new formulation of methoprene,
a biorational mosquito larvicide, in catch basins. While
District mosquito control operations has used methoprene products
for many years as part of its Integrated Pest Management program
(IPM), this collaborative effort introduced our staff to new
sampling and testing methods specific to catch basin/storm drain
applications. Instead of using traditional cup-shaped
dippers to collect water samples, District staff used fish nets
attached to long poles to sampl
Eastern equine encephalitis virus, often termed EEEV or Triple-E,
has been making headlines lately in the United States. This
mosquito-borne virus can cause a sometimes-fatal brain infection.
With 31 cases and 9 deaths this year to date, this is the worst
outbreak of EEEV disease since the US began monitoring the
disease 15 years ago. While those numbers sound scary, EEEV
disease is relatively rare. An average of 7 human cases of
EEEV disease are diagnosed in the United States annually.
Every year the District collects ticks from recreational areas in the county to assess the risk of tick-borne disease. One way to measure this is by determining the minimum infection prevalence (MIP), which estimates what percentage of these ticks are expected to be carrying a given disease agent in a population.
As of September 3, 2019, there have been 179 dead birds reported
in San Mateo County. Of those, 38 have been suitable for testing
and all 38 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
In response to parental concerns about the possibility of
children picking up ticks on athletic fields, the District
recently conducted tick surveys at seven elementary and middle
schools in the Pacifica School District (PSD). Many schools in
Pacifica border open spaces that host wildlife and large areas of
tick habitat, and are near parks and other outdoor recreation
areas where tick exposures are common. All athletic fields
and grassy areas were sampled at each school, as well as any
bordering natural habitat that could present a hospitable
environment for ticks.
As of August 1, 2019, there have been 155 dead birds reported in
San Mateo County. Of those, 31 have been suitable for testing and
all 31 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
Laboratory staff continued collecting Ixodes pacificus
ticks in the nymph life stage and adult Dermacentor
ticks during the month of June. Collections in June occurred at
Año Nuevo and the nearby Costanoa campground. A very high number
of Dermacentor ticks have been collected from this
location because District staff have made multiple collecting
trips as part of a study on Tularemia.
As of June 28, 2019, there have been 120 dead birds reported in
San Mateo County. Of those, 23 have been suitable for testing and
all 23 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
Laboratory staff continued collecting Ixodes pacificus
ticks in the nymph life stage and adult Dermacentor
ticks during the month of May. Collections in May occurred at
Thornewood Open Space Preserve near Woodside, Wunderlich County
Park in Woodside, Water Dog Lake Park in Belmont, Big Canyon Park
and Eaton Park in San Carlos, Edgewood Park in Redwood City,
Costanoa campground near Año Nuevo, and Laurelwood Park in San
Mateo.
As of June 3, 2019, there have been 86 dead birds reported in San
Mateo County. Of those, sixteen have been suitable for testing
and all sixteen have tested negative for West Nile virus (WNV).
No mosquito pools or sentinel chickens have tested positive for
West Nile virus in San Mateo County in 2019.
During April, laboratory staff shifted focus from collecting
adult stage to nymphal stage 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.
Surveillance for West Nile virus began in California in
mid-April. The District protects residents from this
mosquito-borne disease with control methods that target
mosquitoes in the larval stage, as well as mosquito population
monitoring, disease surveillance and public education. The
laboratory staff conducts disease surveillance in three main
ways:
