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

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

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.

Posted by Vector and Vector-borne Disease Committee
December 13, 2022

HE Johnson1, M Clifton2, JE Harbison3, A Erkapic2, GA Barrett-Wilt4, S Paskewitz5, L Bartholomay1 [e-mail: lbartholomay@wisc.edu].   1Dept Pathobiological Sciences, Univ Wisconsin-Madison, Madison, WI, 2North Shore Mosq Abatement Dist, Northfield, IL, 3Loyola Univ Chicago, Maywood, IL, 4Biotech Center, Univ Wisconsin-Madison, Madison, WI, 5Dept Entomology, Univ Wisconsin-Madison, Madison, WI

J. Med. Entomol. 2022 https://doi.org/10.1093/jme/tjac170

Note:  This study revealed the impact of ULV truck-mounted Altosid SR-20 [20% s-methoprene] applications in an open field and a suburban neighborhood.  Using emergence assays, the open field applications indicated that methoprene was effective against Culex pipiens for up to 53 m from the truck route. The neighborhood applications appeared to reach the front and back yards; however, adult Culex pipiens and Cx. restuans abundance was not decreased based on the trap collections. This study highlighted the challenges of conducting a successful neighborhood application and the impact that lower susceptibility of wild strains may play in efficacy. 

Posted by Vector and Vector-borne Disease Committee
December 7, 2022

S Lozano [nkq3@cdc.gov] et al.  PLoS NTD Nov 14, 2022.  https://doi.org/10.1371/journal.pntd.0010907

Abstract [condensed].  We evaluated the effect of releases of Wolbachia infected Ae. aegypti males on populations of wild Ae. aegypti in the metropolitan area of Houston, TX.  Releases were conducted by the company MosquitoMate, Inc. To estimate mosquito population reduction, we used a mosquito abundance Bayesian hierarchical estimator that accounted for inefficient trapping.  In this experiment we found a reduction of 93% after six weeks of continual releases. A similar result was reported by Verily Life Sciences, 96%, in releases made in Fresno, CA.

Note:  This and similar evaluations continue to indicate that genetic methods can show a reduction in Ae. aegypti populations, although none have resulted in extinction.

Posted by Vector and Vector-borne Disease Committee
December 7, 2022

A McMahon, CMB Franca, MC Wimberly  [email: mcwimberly@ou.edu].  Journal of Medical Entomology 59: 1936–1946, https://doi.org/10.1093/jme/tjac145.

Abstract [condensed]

We investigated how land cover and climate influenced abundances of Ae. albopictus (Skuse)  and Cx. quinquefasciatus (Say) in Norman, Oklahoma. From June–October 2019 and May–October 2020 we sampled mosquitoes along an urban-rural gradient using CO2 baited BG Sentinel traps. We compared statistical models of abundance based on microclimate, satellite, weather station, and land cover data. Mosquitoes were more abundant on trap days with higher temperature and relative humidity. Rainfall 2 wk prior to the trap day negatively affected mosquito abundances. Impervious surface cover was positively associated with Cx. quinquefasciatus and tree cover was negatively associated with Ae. albopictus. Among the data sources, models based on satellite variables and land cover data had the best fits.  

Note:  Methods such as these may be useful for planning surveillance sampling and perhaps even control operations in urban areas.

Posted by Vector and Vector-borne Disease Committee
December 1, 2022

LH Backus, JE Foley et al.   Ticks and Tick-Borne Diseases 13(6):102020, https://doi.org/10.1016/j.ttbdis.2022.102020

Abstract [condensed]

Ixodes (Ixodes) mojavensis, n. sp. (Acari: Ixodidae), is described from all parasitic stages collected from the endangered vole Microtus californicus scirpensis Bailey, 1900 (Rodentia: Cricetidae), Mus musculus L. 1758 (Rodentia: Muridae), and Reithrodontomys megalotis (Baird; 1857) (Rodentia: Cricetidae) in the Amargosa Valley of California. When first collected in 2014, this tick was tentatively identified as Ixodes minor Neumann, 1902 because the nucleotide similarity between its 16S rDNA sequence and a homologous GenBank sequence from an I. minor from the eastern U.S. was 99.51%. Nevertheless, adults of I. mojavensis differ morphologically from I. minor by hypostomal dentition, absence of a spur on palpal segment I, and punctation patterns; nymphs by the shapes of basis capituli, auriculae, cervical grooves and external files of hypostomal denticles; and larvae by the length of idiosomal setae and hypostomal dentition. DNA sequencing of fragments of 4 different genes shows that the mitochondrial gene sequences are almost identical to the I. minor homologous genes. Phylogenetically, the two species do not cluster in mutually exclusive monophyletic clades.

Note: Ixodes mojavensis has only been collected from the Amargosa and Owens Valleys in California where it was found infected with a bacteria related to the non-pathogenic spirochete Borrelia carolinensis.  The vector potential of I.mojavensis for human disease is currently unknown.

Posted by Vector and Vector-borne Disease Committee
December 1, 2022

A Gloria-Soria. [email:andrea.gloria-soria@ct.gov].  Journal of Medical Entomology 59: 1853–1860, https://doi.org/10.1093/jme/tjac063

Abstract [condensed]. Here, I reflect on parallels between control of Covid-19 and vector-borne disease control, discuss the advantages and caveats of using new genotyping technologies for the study of invasive species, and proceed to highlight papers that were published between 2020 and 2021 with a focus on those related to mosquito surveillance and population genetics of mosquito vectors.

Note:  In the open access publication, the author thoroughly describes the evolution of genetic methods used to track invasive species and summarizes the immigration of new mosquito species into the USA during the previous few years. 

Posted by Vector and Vector-borne Disease Committee
November 15, 2022

Lanjiao Wang1|  Albin Fontaine2,3|  Pascal Gaborit1|  Amandine Guidez1|Jean Issaly1|  Romain Girod1|  Mirdad Kazanji4|  Dominique Rousset5|Marco Vignuzzi6|  Yanouk Epelboin1|  Isabelle Dusfour1

1Vectopôle Amazonien Emile Abonnenc, Unité de contrôle et adaptation des vecteurs, Institut Pasteur de la Guyane, Cayenne.  2 Unité de Parasitologie et Entomologie, Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, Marseille, France.  3Aix Marseille Université, IRD, AP-HM, SSA, UMR Vecteurs–Infections Tropicales et Méditerranéennes (VITROME), IHU–Méditerranée Infection, Marseille.   5Laboratoire de Virologie, Institut Pasteur de la Guyane, Cayenne cedex, France.  6Unité des Populations Virales et Pathogénèse, Institut Pasteur, Paris cedex 15, France

Medical and Veterinary Entomology 36: 486-495.   https://doi.org/10.1111/mve.12593 

Authors’ Abstract.  The urban mosquito species, Aedes aegypti, is the main vector of arboviruses worldwide. Mosquito control with insecticides is the most prevalent method for preventing transmission in the absence of effective vaccines and available treatments; however, the extensive use of insecticides has led to the development of resistance in mosquito populations throughout the world, and the number of epidemics caused by arboviruses has increased. Three mosquito lines with different resistance profiles to deltamethrin were isolated in French Guiana, including one with the I1016 knock-down resistant allele.  Significant differences were observed in the cumulative proportion of mosquitoes with a disseminated chikungunya virus infection over time across these lines. In addition, some genes related to resistance (CYP6BB2,CYP6N12,GST2,trypsin) were variably over expressed in the midgut at 7 days after an infectious bloodmeal in these three lines. Our work shows that vector competence for chikungunya virus varied between Ae. aegypti laboratory lines with different deltamethrin resistance profiles. More accurate verification of the functional association between insecticide resistance and vector competence remains to be demonstrated.

Note:  This  and  related studies provide some evidence that selection for insecticide resistance also may alter the vector competence of the mosquito.   Although California has been monitoring insecticide resistance, less research has been done on the consequences of this resistance on arbovirus transmission. 

From the Monterey Herald
November 14, 2022

PAJARO VALLEY – From the lip of an overturned bottle cap, an Aedes aegypti mosquito — striped like a zebra — deposits eggs into the tiny puddle within.

The eggs may dry out for up to eight months. They may weather winter nights in the meager shelter of a garage. And yet, as soon as water rehydrates them, they will hatch into adults capable of spreading dengue, Zika, chikungunya and yellow fever.

Though none of these viruses are currently transmitted in California, the mosquito has arrived in Santa Cruz County. Officials still see a path to temporary eradication, but if the experiences of scientists and other counties hold any lessons, A. aegypti may prove impossible to keep out indefinitely.

The mosquito has yet to show up in Monterey County, which recorded its most recent dengue and Zika cases in 2019 and 2017, respectively. But with only four technicians, Monterey’s Mosquito Abatement District would have a tough time checking yards and setting traps for invasions across the county — making prevention paramount.

Read more

From Palo Alto Online
November 3, 2022

A Santa Clara County resident has died from West Nile virus after a long illness, public health officials said Wednesday.

The person lives in Santa Clara County but was infected by the virus elsewhere in the greater San Francisco Bay Area, according to the Santa Clara County Department of Public Health.

No other details about the death were released in a brief statement posted Wednesday on the Santa Clara County Department of Public Health website.

As of Oct. 27, seven deaths from West Nile virus had been reported in California this year, according to the California Department of Public Health.

Read more

From ABC News
November 1, 2022

LONDON — Scientists say an invasive mosquito species was likely responsible for a large malaria outbreak in Ethiopia earlier this year, a finding that experts called a worrying sign that progress against the disease is at risk of unraveling.

The mosquito species, known as Anopheles stephensi, has mostly been seen in India and the Persian Gulf. In 2012, it was discovered in Djibouti and it has since been found in Sudan, Somalia, Yemen and Nigeria. The mosquitoes are suspected to be behind a recent rise in malaria in Djibouti, prompting the World Health Organization to try to stop the insects from spreading further in Africa.

On Tuesday, malaria scientist Fitsum Tadesse presented research at a meeting of the American Society of Tropical Medicine in Seattle, suggesting that the invasive mosquitoes were also responsible for an outbreak in Ethiopia.

Read more

Posted by Vector and Vector-borne Disease Committee
November 1, 2022

Bird species define the relationship between West Nile viremia and infectiousness to Culex pipiens mosquitoes. 2022.  PLoS Negl Trop Dis 16(10): e0010835. https://doi.org/10.1371/journal.pntd.0010835

Vaughan JA, Newman RA, Turell MJ

Department of Biology, University of North Dakota, Grand Forks, North Dakota. and VectorID LLC, Frederick, Maryland

Author’s Abstract.    The transmission cycle of West Nile virus (WNV) involves multiple species of birds. The relative importance of various bird species to the overall transmission is often inferred from the level and duration of viremia that they experience upon infection. Reports utilizing in vitro feeding techniques suggest that the source and condition of blood in which arboviruses are fed to mosquitoes can significantly alter the infectiousness of arbovirus to mosquitoes. We confirmed this using live hosts. A series of mosquito feedings with Culex pipiens was conducted on WNV-infected American robins and common grackles over a range of viremias. Mosquitoes were assayed individually by plaque assay for WNV at 3 to 7 days after feeding. At equivalent viremia, robins always infected more mosquitoes than did grackles. We conclude that the infectiousness of viremic birds cannot always be deduced from viremia alone. If information concerning the infectiousness of a particular bird species is important, such information is best acquired by feeding mosquitoes directly on experimentally infected individuals of that species.

Note:  Although not presented here, the robins and grackles used in this study were infected by different blood parasites but these apparently did not result in differences in WNV dissemination in Culex pipiens (Vaughan et al. 2021. J. Med. Entoml. 58: 1389).   If confirmed and universal, the data presented here complicate the current models of arboviral host competence. 

Posted by Vector and Vector-borne Disease Committee
November 1, 2022

Host selection and forage ratio in West Nile virus–transmitting Culex mosquitoes: Challenges and knowledge gaps. 2022. PLoS Negl Trop Dis 16(10): e0010819. https://doi.org/10.1371/journal.pntd.0010819

Riccetti N, Fasano A, Ferraccioli F, Gomez-Ramirez J, Stilianakis NI

European Commission, Joint Research Centre (JRC), Ispra (VA), Italy, Department of Biometry and Epidemiology, University of Erlangen-Nuremberg, Erlangen, Germany

Author’s Abstract [Shortened]

Background.  Whereas mosquitoes’ intrinsic characteristics cause them to favour certain hosts (host preference), absolute selection is impossible in natural settings. Conversely, the selection carried out among available hosts and influenced from hosts’ availability and other ecological/environmental factors is defined as host selection.

Methodology/Principal findings.  In July 2022, we searched PubMed database for original articles exploring host selection among WNV-transmitting Culex mosquitoes, the main WNV vector. We considered only original field studies estimating and reporting forage ratio. This index results from the ratio between the proportion of blood meals taken by mosquitoes on potential host species and the hosts’ relative abundance.  From the originally retrieved 585 articles, 9 matched the inclusion criteria and were included in this review. All but one of the included studies were conducted in the Americas, six in the United States, and one each in Mexico and Colombia. The remaining study was conducted in Italy.  American Robin, Northern Cardinal, and House Finch were the most significantly preferred birds in the Americas, Common Blackbird in Italy.

Conclusions/Significance.  Although ornithophilic, all observed WNV-transmitting mosquitoes presented opportunistic feeding behaviour. All the observed species showed potential to act as bridges for zoonotic diseases, feeding also on humans. All the observed mosquitoes presented host selection patterns and did not feed on hosts as expected by chance alone.   The articles observe different species of mosquitoes in different environments. In addition, the way the relative host abundance was determined differed. Finally, this review is not systematic. Therefore, the translation of our results to different settings should be conducted cautiously.

Note:  This paper reviewed many references on host selection by Culex but seemingly failed to extract any novel conclusions north discussed previously.   An important aspect not discussed here was the significance of female Culex ‘hunting strategies’ and the utilization of flight paths dictated by landscape features which seemed to determine female-host contact.  This concept was originally discussed by Bidlingmayer (Bidlingmayer and Hem 1981) and later investigated for Culex tarsalis (Lothrop and Reisen 2001; Meyer et al. 1989).   Theoretically, if substantiated these flight paths could be targets for control, but operationally difficult to recognize and target effectively.

Reference List

Bidlingmayer, W. L., and D. G. Hem. 1981. Mosquito flight paths in relation to the environment. Effect of the forest edge upon trap catches in the field.  Mosq. News 41: 55-59.

Lothrop, H. D., and W. K. Reisen. 2001. Landscape affects the host-seeking patterns of Culex tarsalis (Diptera: Culicidae) in the Coachella Valley of California.  J Med Entomol. 38: 325-332.

Meyer, R. P., W. K. Reisen, and M. M. Milby. 1989. The influence of vegetation on CO₂ trap effectiveness.  Proc. Calif. Mosq. Vector Control Assoc. , 57: 80

Posted by Vector and Vector-borne Disease Committee
October 27, 2022

Tara M Roth, Arielle Crews, Angie Nakano

San Mateo County Mosquito and Vector Control District

Journal of Medical Entomology 59: 1787–1792, https://doi.org/10.1093/jme/tjac096

Author’s Abstract

Tularemia is a highly infectious, potentially fatal disease of humans and animals caused by the gram negative, intracellular bacterium Francisella tularensis. The San Mateo County Mosquito and Vector Control District conducted surveillance for F. tularensis from 2017 to 2021 in Dermacentor occidentalis (Marx) (Ixodida: Ixodidae), D. variabilis (Say) (Ixodida: Ixodidae), and Haemaphysalis leporispalustris (Packard) (Ixodida: Ixodidae) ticks in coastal southwestern San Mateo County, California. A total of 3,021 D. occidentalis and 1,019 D. variabilis were collected. Of those, 25 positive pools of F. tularensis were detected (five ticks per pool, overall minimum infection prevalence: 0.62%). Twenty-two of the 25 positive pools (88%) contained D. occidentalis. Eighty-eight percent (88%) of all positive pools were collected from the western half of the site, nearest to the ocean. We did not detect a seasonal effect on the probability of detecting a positive tick pool. There were two human cases of tularemia during the summers of 2019 and 2021. We conducted rodent surveillance in June of 2019, before the human case report. Twenty-four small mammals were collected, but none of their sera tested positive for F. tularensis. It is clear that tularemia is endemic to this region of San Mateo County, but the extent of its range and its ecology is not currently well understood.

Note:  It is useful for MVCAC districts to remember that there are other tick species that transmit other pathogens of public health concern.  The above study was conducted along hiking trails within a coastal park.

From ABC7 News
October 25, 2022

SAN JOSE, Calif. (KGO) — A non-native pest new to Santa Clara County was recently detected at the San Jose and Milpitas border. Traps set by the county’s Vector Control District uncovered two invasive day-biting mosquitoes on Thursday.

Now, an effort is underway to find out whether there are more in the area, and to figure out where they’re coming from.

For the very first time, Aedes aegypti mosquitoes have landed in Santa Clara County. The mosquitoes measure a quarter-inch in diameter with distinct black and white markings on their back and legs.

Aedes aegypti can transmit diseases like Chikungunya, Dengue, Yellow Fever and Zika. The county says none of these diseases are currently found in California.

Read more

From the Mountain View Voice
October 19, 2022

Mosquitoes have tested positive for West Nile virus in a small area of Palo Alto and Los Altos, the Santa Clara County Vector Control District said on Wednesday.

The areas, which include ZIP codes 94304, 94306 and 94022 will be treated on Thursday starting at 10 p.m. to reduce adult mosquito populations, weather permitting. Truck-mounted equipment will apply the treatment over the area for approximately four hours.

A notice is being sent directly to the public in the treatment ZIP codes through AlertSCC and to those who subscribe to Nextdoor neighborhood networks. A general notice is being provided on various social media platforms — including Facebook, Instagram and Twitter — and to those subscribed to the district’s mosquito treatment notifications.

Read more

From the Sacramento Bee
October 19, 2022

An invasive mosquito species has been newly detected in Sacramento County, local officials announced Wednesday, marking the second such species found in the area since 2019.

Aedes albopictus, commonly referred to as the Asian tiger mosquito, was recently located in the backyard of a Carmichael resident who reported being bitten, the Sacramento-Yolo Mosquito and Vector Control District said in a news release.

Field technicians with the district then conducted door-to-door inspections at other homes in the same neighborhood and found additional mosquitoes and larvae, according to the release.

Read more

From ABC10
October 18, 2022

From CBS Sacramento
October 12, 2022

MANTECA — Eggs of the Aedes aegypti mosquito, commonly known as the “yellow fever” mosquito, have been discovered in Manteca for the first time.

The pesky bloodsucker continues to grow in population across San Joaquin County, first detected in West Stockton, Ripon, Escalon, and South Stockton.

They aren’t your average mosquito, and the San Joaquin district says you should call them right away if one bites you.

“This is a very fearless mosquito, and they are very aggressive biters,” said Omar Khweiss, General Manager for San Joaquin County Mosquito and Vector Control District.

Read more

From the Argus Courier
October 12, 2022

This year’s first detection of West Nile virus was found last week in Petaluma.

The Marin/Sonoma Mosquito and Vector Control District confirmed the finding after collecting a dead American Crow infected with the virus near South McDowell Boulevard and Casa Grande Road.

District staff will continue trapping, testing and monitoring the adult mosquitoes around the area where the positive dead bird was found. Vector control technicians are inspecting and keeping track of all sources of mosquito production and performing control operations as needed, according to the district.

“This positive dead bird is a reminder that West Nile virus is endemic to our region,” Nizza Sequeira, public information officer for the district, said in a news release.

Read more

Posted by Vector and Vector-borne Disease Committee
October 11, 2022

Padukka Vidanelage Desha Dilani¹, Ranil Samantha Dassanayake¹, Brij Kishore Tyagi² and Yasanthi Illika Nilmini Silva Gunawardene³

1Department of Chemistry, Faculty of Science, University of Colombo, Colombo, Sri Lanka

2Sponsored Research & Industrial Centre, VIT University, Vellore (TN), India

3Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka

REVIEW article.  Front. Insect Sci., 30 September 2022.  Sec. Insect Physiology

https://doi.org/10.3389/finsc.2022.957570 

Author’s abstract.  Transgenic mosquitoes developed by genetic manipulation, offer a promising strategy for the sustainable and effective control of mosquito-borne diseases. This strategy relies on the mass release of transgenic mosquitoes into the wild, where their transgene is expected to persist in the natural environment, either permanently or transiently, within the mosquito population. In such circumstances, the fitness of transgenic mosquitoes is an important factor in determining their survival in the wild. The impact of transgene expression, insertional mutagenesis, inbreeding depression related to laboratory adaptation, and the hitchhiking effect involved in developing homozygous mosquito lines can all have an effect on the fitness of transgenic mosquitoes. Therefore, real-time estimation of transgene-associated fitness cost is imperative for modeling and planning transgenic mosquito release programs. This can be achieved by directly comparing fitness parameters in individuals homozygous or hemizygous for the transgene and their wild-type counterparts, or by cage invasion experiments to monitor the frequency of the transgenic allele over multiple generations. Recent advancements such as site-specific integration systems and gene drives, provide platforms to address fitness issues in transgenic mosquitoes. More research on the fitness of transgenic individuals is required to develop transgenic mosquitoes with a low fitness cost.

Note:  This review paper addresses the fitness of released mosquitoes and should be of interest to those agencies that are using releases for invasive Aedes control, even though some of the genetic methods may not be similar to what is being used locally.

From The Horse
October 10, 2022

On Oct. 6 the California Department of Food and Agriculture confirmed a 6-year-old Quarter Horse mare in Sacramento County tested positive for West Nile virus (WNV). She began falling and was acutely unable to move beginning Sept. 28 and is currently alive. 

This is the 14th confirmed case of equine WNV in California in 2022. 

Read more

From North Bay News
October 7, 2022

PETALUMA — The first dead bird in the North Bay infected with the West Nile Virus this year was found in Sonoma County, officials said Friday.

The dead American crow was found in the area of South McDowell Blvd. and Casa Grande Rd. in Petaluma, according to the Marin/Sonoma Mosquito and Vector Control District.

“This positive dead bird is a reminder that West Nile virus is endemic to our region,” said district spokesperson Nizza Sequeira in a press statement. “As we head into fall, we urge the public to continue to look for and eliminate standing water in their yards, stock permanent ponds with mosquitofish, and protect themselves from mosquito bites.”

The district said staffers will continue to trap, test, and monitor the abundance of adult mosquitoes in the area where the positive dead bird was found. The district is also reviewing all documented sources of mosquito production and searching for new sources.

Read more

Posted by Vector and Vector-borne Disease Committee
October 1, 2022

Chase L. Ridenour 1,2, Jill Cocking 1,2, Samuel Poidmore 2, Daryn Erickson 2, Breezy Brock 2, Michael Valentine 3, Chandler C. Roe 1,2, Steven J. Young 4, Jennifer A. Henke 5, Kim Y. Hung 5, Jeremy Wittie 5, Elene Stefanakos 6, Chris Sumner 6, Martha Ruedas 6, Vivek Raman 7, Nicole Seaton 7, William Bendik 7, Heidie M. Hornstra O’Neill 2, Krystal Sheridan 2,3, Heather Centner 3, Darrin Lemmer 3, Viacheslav Fofanov 1,2, Kirk Smith 4, James Will 4, John Townsend 4, Jeffrey T. Foster 2, Paul S. Keim 2,3, David M. Engelthaler 3 and Crystal M. Hepp 1,2*

1 School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ, United States, 2 The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ, United States, 3 Translational Genomics Research Institute, Flagstaff, AZ, United States, 4 Vector Control Division, Maricopa County Environmental Services Department, Phoenix, AZ, United States, 5 Coachella Valley Mosquito and Vector Control District, Indio, CA, United States, 6 Yuma County Pest Abatement District, Yuma, AZ, United States, 7 Southern Nevada Health District, Las Vegas, NV, United States

2021. Frontiers in Genetics. 12: 667805 [doi: 10.3389/fgene.2021.667895]

Author’s abstract.  Since the reemergence of St. Louis Encephalitis (SLE) Virus (SLEV) in the Southwest United States, identified during the 2015 outbreak in Arizona, SLEV has been seasonally detected within Culex spp. populations throughout the Southwest United States. Previous work revealed the 2015 outbreak was caused by an importation of SLEV genotype III, which had only been detected previously in Argentina. However, little is known about when the importation occurred or the transmission and genetic dynamics since its arrival into the Southwest. In this study, we sought to determine whether the annual detection of SLEV in the Southwest is due to enzootic cycling or new importations. To address this question, we analyzed 174 SLEV genomes (142 sequenced as part of this study) using Bayesian phylogenetic analyses to estimate the date of arrival into the American Southwest and characterize the underlying population structure of SLEV. Phylogenetic clustering showed that SLEV variants circulating in Maricopa and Riverside counties form two distinct populations with little evidence of inter-county transmission since the onset of the outbreak. Alternatively, it appears that in 2019, Yuma and Clark counties experienced annual importations of SLEV that originated in Riverside and Maricopa counties. Finally, the earliest representatives of SLEV genotype III in the Southwest form a polytomy that includes both California and Arizona samples. We propose that the initial outbreak most likely resulted from the importation of a population of SLEV genotype III variants, perhaps in multiple birds, possibly multiple species, migrating north in 2013, rather than a single variant introduced by one bird.

Note:  This interesting study explored several hypotheses concerning the persistence and movement of SLEV in the SW.  Interestingly all recent isolates have been Lineage III previously only known from South America, whereas the historically endemic lineages I and II found only in North America have not been detected since their extinction in 2003 when WNV invaded the SW. 

From CBS Los Angeles
September 29, 2022

An invasive genus of mosquitos have made their way to Southern California, leaving a trail of irritation and itchy bites in their wake. 

The Aedes mosquito, originally located in tropical climates, have been found on nearly every continent in the world, and are believed to have arrived in California more than 10 years ago via cargo ship. 

This summer, it appears they’ve migrated in mass to the Southland, spreading throughout the San Fernando Valley, Inland Empire and Greater San Diego. 

They’re small and black, covered with white stripes on their legs and body.

Read more

From NBC Palm Springs
September 27, 2022

“West Nile virus is and can be a very dangerous disease so we’re telling people right now, just be careful when you go outside,” said Tammy Gordon, Public Information Manager for Coachella Valley Mosquito and Vector Control District. 

At least 100 positive samples of the West Nile virus have been detected in the Coachella Valley so far this year. 

“The current samples that we have are showing the Mecca area, so downtown Mecca. However, we have found samples in La Quinta, South La Quinta,” said Gordon. 

West Nile virus is the leading cause of mosquito-borne disease in the United States, according to the CDC. 

No human cases of the illness have been reported in the Coachella Valley, however, the state of california reports 69 positive cases of the virus this year. 

The virus spreads when a female mosquito bites an infected bird. The carrier mosquito can then transmit the virus to humans. 

Read more

From The University of Idaho (UI) IHHE

Dear members of the Institute for Health in the Human Ecosystem (IHHE),  

The University of Idaho (UI) IHHE is hosting its annual Biology of Vector-borne Diseases six-day course, Monday through Saturday, June 12-17, 2023, on the UI campus in Moscow, Idaho. This course provides accessible, condensed training and “knowledge networking” for advanced graduate students, postdoctoral fellows, new faculty, and current professionals to ensure competency in basic biology and cutting-edge knowledge for U.S. and global vector-borne diseases of plants, animals, and humans.  

With the support of 30+ internationally recognized faculty, we seek to train the next generation of scientists and professionals to think about vector-borne diseases as interconnected pathosystems and help them to develop effective solutions to current and emerging vector-borne disease threats in complex human ecosystems. 

Applications will be reviewed starting December 1, 2022, and applicants will be notified of their acceptance for the course in spring 2023. Please email chhe@uidaho.edu with any questions 

Please would you/your organization to share our event information 

A link to our event is:  https://www.uidaho.edu/research/entities/ihhe/education/vector-borne-diseases  

Apply here: https://www.uidaho.edu/research/entities/ihhe/education/vector-borne-diseases/application 

Posted by Vector and Vector-borne Disease Committee
September 25, 2022

Rebecca Trout Fryxell

Associate Professor of Medical and Veterinary Entomology, University of Tennessee

9 Sep 2022.  The Conversation.  https://theconversation.com/la-crosse-virus-is-the-second-most-common-virus-in-the-us-spread-by-mosquitoes-and-can-cause-severe-neurological-damage-in-rare-cases-184412.

Note:  This recent review describes the impact of La Cross virus (LACV) on human health east of the Mississippi where it is transmitted mostly by Aedes triseriatus and Ae. albopictus.  Unlike West Nile virus this neuroinvasive virus affects children more frequently than the elderly and can result in long lasting sequellae.  LACV is one of several arboviruses within the California encephalitis virus (CEV) serogroup within the family Peribunyaviridae.  Although few cases have been diagnosed and surveillance programs no longer test mosquitoes for these viruses, the type virus for this group, CEV, is endemic to California where it is maintained vertically within Aedes melanimon and Ae. dorsalis populations and amplified by horizontal transmission to rabbits.   Another virus within this serogroup, Jamestown Canyon virus, has been isolated from Culiseta inornata collected in California, but seems to be a human health problem mostly in the upper Midwest. 

From Pasadena NOW
September 25, 2022

The dangerous West Nile virus (WNV) continues to be detected in mosquito and bird populations in the San  Gabriel Valley and one Pasadena resident is known to have contracted the virus this tear, a city health official said.

Manuel Carmona, Acting Director of the Pasadena Public Health Department, said that as of September 9,  there have been 11 human West Nile vims cases reported in Los Angeles County, including one in  Pasadena. 

Mosquito control experts are advising residents to remove stagnant water due to the early  September rain. The stagnant rainwater sitting in containers can result in a risk of mosquito-borne diseases in the community. 

City officials said that if residents notice any stagnant water issues in their community, they can submit a tip online or call 626-814-9466.  

Read more

From Fox 40
September 20, 2022

(KTXL) — The Sacramento-Yolo Mosquito and Vector Control District are reminding residents to “drain after the rain” in order to prevent mosquitoes.

According to the Sacramento-Yolo Mosquito and Vector Control District, warm temperatures after rain will create ideal breeding conditions for mosquitoes.

The Sacramento-Yolo Mosquito and Vector Control District said in a news release that mosquito season is not over and the threat of West Nile virus is still being seen in dead birds and mosquito samples across the county. There are 3 confirmed cases of West Nile virus in humans in Yolo County.

Read more

From the County of Santa Clara
September 20, 2022

SANTA CLARA COUNTY, CALIF. – The County of Santa Clara Vector Control District has confirmed the presence of West Nile virus-positive mosquitoes in a small area that includes Mountain View, Los Altos Hills and Sunnyvale (ZIP codes 94024, 94040 and 94087). Weather permitting, this area will be treated to reduce adult mosquito populations with the use of truck-mounted equipment on Thursday, Sept. 22, starting around 10 p.m. and concluding a few hours later.
 
The District’s mosquito management program largely focuses on preventing mosquitoes from reaching the adult biting stage by proactively targeting immature stages of mosquitoes found in standing water. When a mosquito with West Nile Virus (WNV) is detected, however, the District takes the added step of conducting adult mosquito control treatment to reduce the mosquito population in the area, which decreases the risk of a WNV-human infection.
 
It is normal to see an increase in West Nile virus during the summer and early fall because mosquitoes thrive in warm weather. Although mosquitoes need water at each stage of life, they are still able to thrive during the drought conditions the state and county are seeing now.

Read more

From the County of Santa Clara
September 19, 2022

SANTA CLARA COUNTY, CALIF. – The County of Santa Clara Vector Control District has confirmed the presence of West Nile virus-positive mosquitoes in a small area of Milpitas (ZIP code 95035). Weather permitting, this area will be treated to reduce adult mosquito populations with the use of truck-mounted equipment on Wednesday, Sept. 21, starting around 10 p.m. and concluding a few hours later.
 
The District’s mosquito management program largely focuses on preventing mosquitoes from reaching the adult biting stage by proactively targeting immature stages of mosquitoes found in standing water. When a mosquito with West Nile Virus (WNV) is detected, however, the District takes the added step of conducting adult mosquito control treatment to reduce the mosquito population in the area, which decreases the risk of a WNV-human infection.
 
It is normal to see an increase in West Nile virus during the summer and early fall because mosquitoes thrive in warm weather. Although mosquitoes need water at each stage of life, they are still able to thrive during the drought conditions the state and county are seeing now.

Read more

From MSN
September 14, 2022

REDONDO BEACH, CA — Residents of Redondo Beach have been pestered by relentless, and frankly annoying, bites from the invasive Aedes mosquito that has made a new home in Southern California.

Atypical to other mosquitos that usually go for just one bite at dawn or dusk, Aedes mosquitos are aggressive and love to bite people during the day according to Aaron Arugay, Executive Director of Los Angeles County West Vector Control.

Read more