From ABC7
May 3, 2023

For the first time, drone technology is taking off to combat mosquitos in the South Bay after an unprecedented rainy winter.

Mosquito season just started and this week the Santa Clara Vector Control District will begin using drones to reduce the mosquito population.

Nayer Zahiri, the county’s Vector Control District manager, said other districts in the state are using it.

“As you see a lot of standing water, a lot of waters around and we want to make sure we are able to control the stages we can control before they become adults,” Zahiri said.

Read more

From Times of San Diego
April 20, 2023

San Diego County will conduct its first larvicide drop of the year on up to 51 local waterways as part of a campaign to combat diseases spread by mosquitoes such as West Nile virus, it was announced Wednesday.

Aerial larvicide drops are carried out once a month between April and October each year, covering around 1,300 acres of mosquito breeding areas.

The routine helicopter drops will be conducted next Wednesday, and Thursday if necessary, according to a news release from the county.

County officials say the larvicide does not hurt people or pets.

Read more

Posted by Vector and Vector-borne Disease Committee
April 19, 2023

Leslie Foss*, Tina Feiszli, Vicki L. Kramer, William K. Reisen, Kerry Padgett.

*Leslie.Foss@cdph.ca.gov

PLoS ONE April 6, 2023 https://doi.org/10.1371/journal.pone.0284039

Abstract [condensed]

Since 2003, the California West Nile virus (WNV) dead bird surveillance program (DBSP) has monitored publicly reported dead birds for WNV surveillance and response. We examined DBSP data from the early epidemic years (2004–2006) with recent endemic years (2018–2020) to characterize changes in program operations, patterns of dead bird reports, and WNV prevalence among dead birds and their utility as early indicators of WNV activity. In recent years fewer agencies collected dead birds for testing, but updated protocols enhanced the efficiency of the program. The number of dead bird reports was approximately ten times lower during 2018–2020 compared to 2004–2006; reports from the Central Valley and parts of Southern California decreased the most. Dead corvid, sparrow, and quail reports decreased the most compared to other bird species reports. In the early years, WNV positive dead birds were the most frequent first indicators of WNV activity; in contrast, during 2018–2020 mosquitoes were the most frequent first indicators. Evidence for WNV impacts on avian populations and susceptibility are also discussed.

Note: Despite declines in the number of birds reported by the public, dead bird surveillance remains important to better understand changes in WNV ecology and adds critical data to a comprehensive environmental surveillance program.

From ABC 7
April 12, 2023

ORANGE COUNTY (KABC) — Southern California is still a couple months away from mosquito season, but this season could potentially be one of the worst because of all the rain to start the year.

However, the Orange County Mosquito and Vector Control District is being proactive.

Heather Hyland, director of communications for OC Vector, said spots that didn’t have standing water before may have some now.

“There’s areas due to the rain that are filling up that are producing more egg laying sites for mosquitos per usual,” Hyland said.

She said they’re seeing more mosquitoes in traps laid out to monitor their population.

Read more

Mosquito Awareness Week, observed April 16 – 22, 2023, educates California residents about mosquitoes and how to help prevent the spread of mosquito-transmitted diseases

Press Release

• Record Amounts of Rainfall Create Perfect Conditions for Mosquitoes

Social Media Graphics:

Invasive Aedes Toolkit

This invasive Aedes toolkit is designed to assist MVCAC members in their public education and outreach efforts.

Communities with Invasive AedesCommunities without Invasive Aedes

• Factsheet: English, Spanish
• Quickbites: English PDF, English PNG, Spanish PDF, Spanish PNG
• Social Media Graphics: English, Spanish
• Videos: English, Spanish

Communities without Invasive Aedes

• Factsheet: English, Spanish
• Quickbites: English PDF, English PNG, Spanish PDF, Spanish PNG
• Social Media Graphics: English, Spanish
• Videos: English, Spanish

Posted by Vector and Vector-borne Disease Committee
April 5, 2023

Vindhya S. Aryaprema, Madeline R. Steck, Steven T. Peper, Rui-de Xue, Whitney A. Qualls*

*wqualls@amcdfl.org

PLoS Neglected Tropical Diseases 2023.  https://doi.org/10.1371/journal.pntd.0011173

Condensed abstract.   Many different methods are used and new methods are evolving to control nuisance and vector mosquito populations across the world. Implementation of such control methods at the optimal time has been identified as critical to maintaining the populations below unacceptable levels. The establishment of evidenced-based action thresholds is encouraged to achieve maximum results under available resources. This review identified 87 publications: 30 reported originally generated thresholds, 13 inclusions reported a statistical method with a computable action threshold model, and 44 inclusions mentioned only previously generated thresholds. Overall, the inclusions with thresholds that were directly related to disease transmission conditions (“epidemiological thresholds”) outnumbered the inclusions with thresholds that were directly related to mosquito abundance (“entomological thresholds”). The majority of the thresholds originated in Asia targeting dengue and dengue vectors. The review discusses the associated surveillance characteristics such as the possibility of using external data (previously recorded data), spatial and temporal variations in data, and the importance of an adequate lead time to initiate control interventions that would help guide to plan better surveillance programs for the development of action thresholds.

Note:  Paper could provide useful references for decisions on the control of invasive Aedes. 

From ABC7
March 29, 2023

DUARTE, Calif. (KABC) — With so much rain drenching Southern California this season, there is another pesky problem lurking around the corner: mosquitoes.

“It doesn’t take long for mosquitoes to go from the larva you see to full grown ones that’ll look for someone like you to sting,” said Pablo Cabrera with the San Gabriel Valley Mosquito & Vector Control District.

Dense vegetation and stagnant water allow mosquitoes to grow and hide. Just a small amount of water is all mosquito needs to lay their eggs and with the historic rainfall, residents are being asked to do three things: tip, toss and protect.

The San Gabriel Valley Vector Control District urges resident to tip out stagnant water weekly, toss any unused containers left outside that can collect stagnant water, and protect yourself with some sort of mosquito repellent.

Cabrera said the SGVMVCD hasn’t captured any adult mosquitoes at the moment, but once the dry, warmer weather hits, that will change.

Read more

From the San Francisco Gate
March 26, 2023

SACRAMENTO COUNTY, Calif. — It is that time of year: Mosquitoes are back.

From NBC Bay Area
March 24, 2023

As we just hit spring, experts say mosquitoes are already multiplying, taking advantage of all the recent flooding.

In Belmont, families can still see and smell the flood waters that have been inundating them all year.

The conditions and all the standing water found around the bay area are a concern for The San Mateo County Vector Control Department who said, they’ve had more mosquito related requests than usual in the past few months.

In a statement. they wrote they anticipate water will continue to stand in many locations into the warmer month, so their acting now, regularly checking 40,000 sites throughout the county to prevent a large mosquito population and the viruses that come with them.

The county added they’re also working closely with communities prone to flooding by checking their crawlspaces something they recommend all families should do in case of any standing water.

Read more

Posted by Vector and Vector-borne Disease Committee
March 22, 2023

Note:  The program is only available after registration for non-members.  

From KCRA 3
March 22, 2023

It is that time of year in the Sacramento Valley: mosquitoes are back.

The bad news? You’ll likely see more of them this season, and with more mosquitoes comes a higher risk of West Nile virus.

The Sacramento-Yolo Mosquito and Vector Control District says the ongoing wet winter storms across the region since New Year’s Eve weekend are to blame.

“I think the amount of water we’ve seen over the last month or so is definitely a big concern,” Gary Goodman, the district manager, told KCRA 3.

He says standing water is the issue, especially in many places that haven’t seen a lot of water over recent years due to the drought, and believes we will have higher mosquito populations by the summer.

“We are anticipating a much busier year from an abundance standpoint and a [West Nile] virus standpoint,” Goodman said.

The main places of concern are agricultural areas and around rivers, creeks, and streams.

Read more

Posted by Vector and Vector-borne Disease Committee
March 20, 2023

MMWR Morb Mortal Wkly Rep 2023;72:290–291. http://dx.doi.org/10.15585/mmwr.mm7211a5

A Maricopa County, Arizona resident was hospitalized with Dengue-like symptoms on October 19, 2022 after brief travel to Mexicali, Mexico 7 days prior. RT-PCR testing was positive for dengue virus (DENV). Twenty-one mosquito pools within 5 miles of patient’s residence were tested retrospectively. One pool collected on October 5 tested positive for DENV. Whole genome sequencing identified both to be a DENV-3 strain not closely related to known strains in the area of travel. Preexisting response plans were activated and residences within a 150-meter radius were canvassed and residents interviewed. Twelve residents reporting recent Dengue-like symptoms were tested, all of which were negative by RT-PCR. Antibody testing of one of 53 resident without travel history was positive for Dengue antibodies, which were confirmed as DENV-3 by plaque reduction neutralization assay. Retrospective testing of 4,299 mosquito pools were negative. Aedes aegypti collected in BG-Sentinel traps were negative for DENV. The outbreak (2 cases) was declared over on January 4, 2023, following >45 days without additional cases.

Note: This outbreak provides a case study of a local DENV outbreak in a new area and shows the benefits of having a preexisting response plan in the event of local transmission of an Aedes aegypti transmitted virus.  

Posted by Vector and Vector-borne Disease Committee
March 20, 2023

Pascoe, EL et al.   

2023. Journal of Vector Ecology, https://doi.org/10.52707/1081-1710-48.1.19

Condensed abstract:

In 2018, the River Fire burned a forest in the far-western U.S.A. where the ecology of tick-borne pathogens had been studied for decades. Forest structure, avifauna, large and small mammals, lizards, ticks, and tick-borne pathogens were assessed after the wildfire in 2019 and 2020. Burning reduced canopy cover and eliminated the layer of thick leaf litter that hosted free-living ticks, which over time was replaced by forbs and grasses. Tick abundance and the vertebrate host community changed dramatically. Assays for pathogens found no B. miyamotoi in either questing or host-feeding ticks, A. phagocytophilum DNA in 4% (1/23) in 2019, and 17% (29/173) in 2020 for questing and host-feeding ticks combined, and B. burgdorferi DNA in just 1% of all ticks collected in 2020 (2/173).Authors concluded that a moderately severe wildfire can have dramatic impacts on the ecology of tick-borne pathogens, with changes posited to continue for multiple years.

Posted by Vector and Vector-borne Disease Committee
March 8, 2023

DR Abdel-Haleem, EE Badr, AM Samy, SA Baker

2023. Medical and Veterinary Entomology. https://doi.org/10.1111/mve.12645

Condensed Abstract:

Novel cationic gemini surfactants were synthesized to assess their insecticidal activities using laboratory and field strains larvae of Culex pipiens L. in comparison to clove oil and spinosad. The two surfactants G1 and G2 showed good insecticidal activities against the laboratory strain with LC₅₀ 0.013 and 0.054 ppm, respectively, relative to spinosad with LC₅₀ 0.027 ppm, 48 h posttreatment. Although spinosad showed high efficiency against lab strain, it exhibited a high resistance ratio (RR) of 15.1 and 13.1 toward the field strain at 24 and 48 h posttreatment, respectively. The two gemini surfactants have a good safety profile and low RR (RR <5). The results of this study are promising in terms of developing novel, effective, affordable, and safe approaches for mosquito control.

Notes:  Use of similar products is not new, but this work provides perhaps a useful alternative.

From the Sacramento Bee
March 7, 2023

As spring rolls in and temperatures warm, hiking one of Northern California’s many trails is an obvious activity to indulge, but it’s important to be wary of ticks.

The eight-legged arachnids are most active in warmer months, and the parasites thrive in humid and rainy environments, which increase tick populations and risk of Lyme disease.

The Sacramento-Yolo Mosquito and Vector Control District performs routine tests at Sacramento and Yolo county hiking trails. In Sacramento County, it has 15 testing sites. The Vector Control District has been testing along the American River, starting at Ancil Hoffman to Folsom Zoo.

Read more

From the Capitol Weekly
February 24, 2023

BY BY WAKOLI WEKESA, PhD 

POSTED 02.24.2023

OPINION – Mosquito and vector control districts are on the front lines each day working to protect Californians from debilitating and deadly mosquito-transmitted diseases.

Invasive Aedes mosquitoes, which can transmit viruses that cause Zika, dengue, chikungunya, and yellow fever, pose significant challenges. First detected in California in 2013, these invasive mosquitoes are now in 25 counties throughout the state from San Diego to Shasta and are very hard to control. Districts urgently need new tools that can help them immediately fight back.

In the past 10 years, no new tools have been approved in our state to assist mosquito control districts in fighting the spread of invasive Aedes mosquitoes. Unfortunately, the California Department of Pesticide Regulation (DPR) is not demonstrating a sense of urgency to support research necessary to develop new tools to fight this difficult and expensive uphill battle. The timeframe it takes for disease-spreading mosquitoes to invade new regions is not in line with current regulatory standards for approval and such delays put our state very far behind.

While there has not yet been local transmission of Zika, dengue, chikungunya, and yellow fever in California, the question is not if, but when. Looking at last year alone, the border state of Sonora, Mexico had more than 9,000 cases with 91 people dying from dengue in 2022 and while 750 Floridians acquired dengue while traveling, 57 people were infected at home because the mosquitoes that can transmit the virus are in their neighborhoods.

Read more

Posted by Vector and Vector-borne Disease Committee
February 22, 2023

Wilke, Andre B.B., et al. Email: andwilke@iu.edu

2023. Acta Tropica, https://doi.org/10.1016/j.actatropica.2023.106833

Condensed abstract:

This study determined the spatiotemporal distribution of vector mosquito species abundance in Maricopa County, AZ from 2011 to 2021, and identified ‘hotspot’ areas for West Nile virus (WNV) and St. Louis Encephalitis virus (SLEV) transmission during the epidemic of 2021. High levels of heterogeneity were detected in the risk of WNV and SLEV transmission to humans disregarding trap geographical proximity. The authors did not relate their analyses to epidemiological data, but the vector index as well as abundance patterns showed overlap with human population density.  The authors concluded that the well-defined species-specific spatiotemporal and geographical patterns could be used to inform vector control operations.

Note: This study analyzed the patterns of mosquito and virus distribution during the extremely high West Nile season of 2021 and placed these results into historical context of previous surveillance. An earlier version of this publication can be read free of cost: https://www.biorxiv.org/content/biorxiv/early/2022/12/05/2022.07.28.501907.full.pdf.

From CBS 8
February 13, 2023

Posted by Vector and Vector-borne Disease Committee
February 8, 2023

Field, E.N., Shepard, J.J., Clifton, M.E. et al. Semi-field and surveillance data define the natural diapause timeline for Culex pipiens across the United States. Commun Biol 5, 1300 (2022). https://doi.org/10.1038/s42003-022-04276-x 

Abstract:

Reproductive diapause serves as biological mechanism for many insects, including the mosquito Culex pipiens, to overwinter in temperate climates. While Cx. pipiens diapause has been well-studied in the laboratory, the timing and environmental signals that promote diapause under natural conditions are less understood. In this study, we examine laboratory, semi-field, and mosquito surveillance data to define the approximate timeline and seasonal conditions that contribute to Cx. pipiens diapause across the United States. While confirming integral roles of temperature and photoperiod in diapause induction, we also demonstrate the influence of latitude, elevation, and mosquito population genetics in shaping Cx. pipiens diapause incidence across the country. Coinciding with the cessation of WNV activity, these data can have important implications for mosquito control, where targeted efforts prior to diapause induction can decrease mosquito populations and WNV overwintering to reduce mosquito-borne disease incidence the following season.

Note: This article highlights the importance of the roles of both short day lengths as well as temperature in inducing diapause in Culex pipiens.  Comparisons were also made between the diapause timelines of Cx. pipiens in different geographical locations throughout the US and the influence of contributing variables such as latitude, elevation, and population genetics.

Posted by Vector and Vector-borne Disease Committee
February 8, 2023

Wilke ABB, Mhlanga A, Kummer AG, Vasquez C, Moreno M, Petrie WD, et al. (2023) PLoS Negl Trop Dis 17(1): e0011074. https://doi.org/10.1371/journal.pntd.0011074

Abstract:

Mathematical models have been widely used to study vector mosquitoes as well as to test the effectiveness of arbovirus outbreak response and mosquito control strategies. However, due to the lack of empirical data, there are no studies focusing on the effectiveness of adulticide applications at different hours of the day to control different mosquito populations. This study leveraged a unique dataset in which approximately 25,000 mosquitoes comprising 19 species were collected hourly in Miami-Dade County, Florida, and Brownsville, Texas. We then developed a mathematical model to simulate the population dynamics of five mosquito vector species to evaluate the effectiveness of adulticide spraying at different times of the day and at different frequencies. Mosquito community composition and abundance varied significantly throughout the day in both Brownsville and Miami-Dade County with more than 10-fold differences during the day. Depending on the target vector species, the application of adulticides at a given hour of the day may lead to drastically different results, although we found some common patterns such as the remarkable effectiveness of interventions performed at 9 PM.

Note:  In this open access publication, the authors showed the activity of different urban mosquito species in a 24-hour period and used mathematical models to determine the best time for conducting adulticide applications for each species.  The authors noted an overlap in activity between invasive Aedes spp. and Culex spp. at 9 PM, suggesting this as the most effective time for adulticide treatments targeting both invasive Aedes spp. and WNV vectors.

From the Mercury News
February 3, 2023

With Marin residents taking advantage of the clear weather following recent storms, so are the ticks that carry bacteria that can cause Lyme disease and other illnesses.

Marin is among the counties in California with the highest prevalence of ticks carrying Lyme disease, said Linda Giampa, executive director of the Bay Area Lyme Foundation. The small, blood-sucking arachnids prefer moist, foggy areas in the grasslands and chaparral.

Tick season is basically year-round in Marin, but the most activity occurs from October through July, according to the Marin/Sonoma Mosquito and Vector Control District. It is around February and March that young ticks, known as nymphs, are beginning to come out — especially after rain — and search for an animal or human leg to hop on for a meal.

Read more

From Phys.org
January 25, 2023

Using machine learning techniques to predict the age of mosquitoes from different populations could reduce turnaround time for malaria research and improve surveillance programs, says a new study published in BMC Bioinformatics.

Knowledge of a mosquito’s age helps scientists to understand its potential to spread malaria, but the existing tools used for predicting this are costly, labor-intensive and often prone to human errors, the researchers say.

According to the World Health Organization, the African region accounted for about 95 percent of the 247 million cases of malaria globally in 2021, and scientists say the adoption of innovative tools to control mosquitoes and prevent the spread of malaria is key to eliminating the disease.

Read more

Posted by Vector and Vector-borne Disease Committee
January 19, 2023

Evaluation of an open forecasting challenge to assess skill of West Nile virus neuroinvasive disease prediction.

Holcomb, Karen M., et al. Centers for Disease Control, Email: kholcolb@cdc.gov

2023. Parasites & Vectors https://doi.org/10.1186/s13071-022-05630-y

Condensed abstract:

This study used forecasting models submitted to the 2020 WNV Forecasting Challenge, an open challenge organized by the Centers for Disease Control and Prevention, to assess the status of WNV neuroinvasive disease (WNND) prediction and identify avenues for improvement. Researchers performed a multi-model comparative assessment of probabilistic forecasts submitted by 15 teams for annual WNND cases in US counties for 2020 and assessed forecast accuracy, calibration, and discriminatory power. Results showed that simple models based on historical WNND cases generally scored better than more complex models and combined higher discriminatory power with better calibration of uncertainty. Among models using additional data, inclusion of climate or human demographic data was associated with higher skill, while inclusion of mosquito or land use data was associated with lower skill. Although opportunities might exist to specifically improve predictions for areas with large populations and low or high winter temperatures, areas with high case-count variability are intrinsically more difficult to predict. Further improvements to prediction could be obtained with improved calibration of forecast uncertainty and access to real-time data streams (e.g., current weather and preliminary human cases).

Note: This study presents an analysis of a challenge to predict the number of cases of WNV neuroinvasive disease in 2020 across all US counties and discusses the difficulties of creating a nationwide model.

Posted by Vector and Vector-borne Disease Committee
January 17, 2023

From:  American Society of Tropical Medicine and Hygiene News

CDC Division of Vector-borne Diseases

https://sherwood-astmh.informz.net/sherwood-astmh/data/images/2023%20CDC%20Mosquito%20Tick%20survey.pdf

Note:  These two pages summarize surveys of the behaviors of 7 at-risk audiences focusing on which Personal Protective Behaviors they would likely use.   It also ranked the Communication and Media Channel preferences. 

Posted by Vector and Vector-borne Disease Committee
January 13, 2023

Lee,X., et al.  2023.  J. Med. Entomol. 60: 22.  https://doi.org/10.1093/jme/tjac164

Department of Entomology, College of Agricultural and Life Sciences, University of Wisconsin – Madison, WI 53706.  Email: xlee1@wisc.edu

Abstract [condensed]:   Mowing vegetation is a recommended method to control ticks, but few studies have evaluated the efficacy of this practice.  This study determined if a single mowing event could reduce the abundance of host-seeking ticks on recreational trails. The authors encountered a total of 3,456 ticks (2,459 Ixodes scapularis Say and 997 Dermacentor variabilis L.) during the 7-week study period. There were no significant differences in the abundance of I. scapularis (adults) or D. variabilis (adults only) between control and mown trail sections. Mowing was a significant predictor of nymphal I. scapularis abundance, but trended towards more ticks in mown sections compared to controls. These results suggest that a single mowing intervention during early June is likely to be ineffective as a strategy to reduce the risk of human contacts with ticks on trails.

Note:  Vegetation was mowed to a height of 8 cm, but this did not appear to reduce the numbers of ticks that could be sampled by dragging, indicating there potentially was no impact on the risk of tick attachment. 

Posted by Vector and Vector-borne Disease Committee
January 10, 2023

Tian,Y., et al.  University of Florida.  Email: yuexun1220@gmail.com

2022. Journal of Medical Entomology https://doi.org/10.1093/jme/tjac185 

Abstract [condensed]:

Three Ripicephalus sanguineus s.l. (brown dog tick) strains, one from a laboratory colony (NC) and two from colonies originally collected from Florida (FL) and California (CA), were evaluated for resistance against permethrin and fipronil. Metabolic detoxification mechanisms were evaluated in the FL strain using three synergists, and a polymerase chain reaction assay was used to detect a resistance mutation in all strains. The NC strain was susceptible to both permethrin and fipronil, whereas both the FL and CA strains exhibited high resistance to permethrin and tolerance to fipronil. The synergist tests and PCR results indicated that the FL strain utilized both metabolic resistance and target site insensitivity against permethrin, whereas the CA strain was documented to have the target-site insensitivity resistant allele. Fipronil resistance was not detected suggesting this acaricide may provide suitable tick control.

Note: This study provides evidence of permethrin resistance in Rhipicephalus sanguineus ticks, including a colony originating from Imperial County, CA. Results indicated that fibronil would be a more effective treatment for these populations.

From UC Riverside News
January 9, 2023

Mosquitoes spread several diseases, such as malaria and dengue. In 2020 about 241 million cases of malaria occurred worldwide, with a few more million cases occurring in 2021. Nearly half the world’s population lives in regions where contracting dengue virus is a risk. Insects also destroy a third of agriculture. 

New research by scientists at the University of California, Riverside, has potential in insect control through volatile repellents that could be applied on surfaces such as windowsills, eaves of huts, house entryways, backyards, outside produce storage areas, entryways of livestock shelters, and next to crops in a field.

The researchers focused on ammonia, a basic volatile compound found in insect environments. At low concentrations, such as in human sweat, ammonia is an attractant for mosquitoes and other insects. At high concentrations, however, for example the concentrations found in household cleaners, ammonia is no longer attractive to insects. The researchers inquired into what happens to the olfactory (smell) system and gustatory (taste) system of fruit flies and mosquitoes in the presence of ammonia.

Read m0re

Posted by Vector and Vector-borne Disease Committee
December 21, 2022

Shelomi, M.  [email: mshelomi@ntus.edu.tw].   Bull. Entomol. Res.

Summary: Entomol. Today.   https://entomologytoday.org/2022/11/21/vitamin-b1-not-mosquito-repellent/

Note:  After reviewing over 100 papers written over 80 years, the authors concludes:  “oral mosquito repellents do not work”.   His paper addresses two questions:  “So, where did this idea come from, and why won’t it go away?”.   Seems this paper would be useful information to answer constituent inquiries about alternatives to DEET and other surface repellents to prevent mosquito bites. 

In 2020, the Centers for Disease Control and Prevention circulated the National Public Health Framework for the Prevention and Control of Vector-Borne Diseases in Humans. Using the five goals and 19 strategic priorities developed using the framework, on November 21 the Department of Health and Human Services (HHS) released a request for information soliciting comments and suggestions from stakeholders for the development of a new National Strategy for the Prevention and Control of Vector-Borne Diseases. The proposed strategy details the federal government’s priorities for addressing both current and potential future vector-borne disease threats. Submit comments and suggestions electronically by December 21.