Laboratory Updates

Overview

Laboratory Updates

The District laboratory staff maintains this section monthly with updates on disease surveillance, research, and other laboratory projects.

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West Nile Virus Update – November 2019

San Mateo County

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.

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West Nile Virus Update – Ocotober 2019

San Mateo County

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.

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West Nile Virus Update – September 2019

San Mateo County

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.

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Catch Basin Treatment Evaluation

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

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Eastern Equine Encephalitis Virus (EEEV) making you EEEk this Halloween?

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.

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Tick Testing Results for August 2019

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.

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West Nile Virus Update – August 2019

San Mateo County

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.

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Tick Surveillance at Pacifica Schools

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. 

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West Nile Virus Update – July 2019

San Mateo County

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.

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Tick Surveillance Update for Water Year 2018-2019
June 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.

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West Nile Virus Update – June 2019

San Mateo County

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.

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Tick Surveillance Update for Water Year 2018-2019

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.

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West Nile Virus Update – May 2018

San Mateo County

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.

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Tick Surveillance Update for April 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.

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West Nile Virus Season Begins

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:

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Tick Surveillance for Water Year 2018-2019

During March, laboratory staff continued surveillance for adult Ixodes pacificus (Western black-legged ticks). The continuous on-and-off rainfall continued into March and greatly limited the number of tick-flagging opportunities this winter. The weather reduces the questing activity of the ticks and moisture saturates the tick flag, making it less effective as a collecting tool.

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Newcastle Disease in Chickens

In January of 2019 an alert went out from the California Department of Food and Agriculture warning people about an outbreak of Newcastle disease in domestic poultry in southern California.

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Tick Surveillance Update for February 2019
Water Year 2018-2019

During February, laboratory staff continued surveillance for adult Ixodes pacificus (Western black-legged ticks). The continuous on-and-off rainfall greatly limited the number of tick flagging opportunities in February, which is typically a peak month for collecting adult Ixodes pacificus. The weather reduces the questing activity of the ticks and moisture saturates the tick flag, making it less effective as a collecting tool. Parks that were surveyed in February were Ano Nuevo State Park, south of Pescadero and Sweeney Ridge in San Bruno.

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Tick Surveillance for Water Year 2018-2019

During January, laboratory staff began winter surveillance for adult Ixodes pacificus (Western black-legged ticks). 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, Borrelia miyamotoi and Anaplasma phagocytophilum.

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Laboratory Year in Review

The lab wraps up another busy year providing scientific support for our vector control programs.

We analyzed 479 field-collected larval and 1,206 adult mosquito collections, enabling quick and appropriate integrated vector management responses by our operations staff.  We improved our primary adult mosquito trap (CO2 trap) with simple modifications based on scientific trials we conducted the previous year that compared the performance of different designs.

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