The District conducts intensive surveillance for invasive Aedes
mosquitoes during the summer months. The surveillance program
mainly targets two container-breeding species, Aedes aegypti and
Aedes albopictus, which have been increasing their range within
California over the last several years. This summer, Ae. aegypti
and Ae. albopictus were detected for the first time in Shasta
County. The presence of these mosquitoes is highly undesirable
because they are aggressive human biters and also transmit
diseases including dengue, chikungunya, yellow fever and Zika.
As of August 31, 2020, there have been 140 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 been confirmed positive
for West Nile virus in San Mateo County in 2020.
As of August 4, 2020, there have been 120 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). To date,
there have been no confirmed West Nile virus detections in
mosquitoes or sentinel chickens in San Mateo County in 2020.
As of June 30, 2020, there have been 95 dead birds reported in
San Mateo County. Of those, 29 have been suitable for testing and
all 29 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 2020.
Beaches are popular among San Mateo County residents this summer,
including our local bees. District staff responded to a request
in June to identify bees nesting on a beach in Pacifica that were
flying in and out of small holes in the sand.
The District works to control mosquitoes in our county because
they are disease vectors and aggressive biting pests. However,
there are several mosquito species that are not known to bite
people. One of these infrequently-encountered mosquitoes is
called Orthopodomyia signifera. It breeds in the holes
of trees that hold water year-round and feeds exclusively on
birds.
As of May 31, 2020, there have been 68 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 2020.
During early March, 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.
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.
