Mosquito & Vector News

CDPR has approved WB1 Males for use in California

Following the U.S. Environmental Protection Agency’s registration of Mosquito Mate’s Aedes aegypti WB1 male mosquitoes, the California Department of Pesticide Regulation approved the use of WB1 males in California. For information about plans to use Wolbachia in California please contact Stephen Dobson with Mosquito Mate at sdobson@mosquitomate.com.

May is Lyme Disease Awareness Month

Nymphal Ixodes pacificus are most active in the spring and early summer in California. These tiny ticks pose a greater risk of transmitting Lyme disease.\

Messaging and resources to share in May:

  • Weblinks:

MVCAC- California Air Resources Board Fact Sheet

Beginning in 2024, the California Air Resources Board (CARB) is implementing new equipment and vehicle regulations to limit the purchase of gasoline powered equipment and promote the use of electric instead. The MVCAC Regulatory Affairs and IVM Committees have created a fact sheet to guide the membership through these changes.

VIEW FACT SHEET.

Want insecticide resistance training and testing in your area?

If you would like to collect and test mosquito (Aedes or Culex) samples for insecticide resistance, PacVec provides training and testing services at no charge. Michael Bollinger in Dr. Anton Cornel’s laboratory is leading this activity and is available to discuss testing strategies or to provide on-site training on bottle bioassay testing in your area. We offer three options for testing or training:

1. Partnering with a local agency to host a resistance testing workshop that includes the host agency and neighboring agencies in a single event.

2. Partnering with a local agency to perform mosquito collection and testing with the agency’s staff.

3.Collecting and testing mosquitoes from areas where data are lacking with/without involvement of local agency staff.

Any of the above activities will yield immediate data to guide your control decisions. Involvement of local agency staff is ideal to provide a learning experience. If a single agency would like to host a training that can involve neighboring agencies, that is also very helpful to increase the value of each workshop. If larval bioassays are wanted in addition to CDC bottle bioassays, please let us know that as well.

Contact us as soon as possible at bioassays@pacvec.us to make plans for summer testing and training.

 

West Nile Virus and Dead Bird Call Center Now Live

The California WNV and Dead Bird Call Center opened for the season on Monday, April 8, 2024. Now through mid-October, members of the public can report a dead bird by calling 1-877-WNV-BIRD (1-877-968-2473). Online reporting continues to be available year-round at: https://westnile.ca.gov/report. 

For questions about Call Center operations, please contact: Marie.Cerda@cdph.ca.gov.

As you plan for the upcoming WNV season, CDPH has resources available to assist your communication and outreach efforts:

Roaming Dogs, Intense Brown Dog Tick Infestation, and Emerging Rocky Mountain Spotted Fever in Tijuana, Mexico.

Foley J., et al. Am. J. Trop. Med. Hyg., 00(00), 2024, pp. 1–16 doi:10.4269/ajtmh.23-0410

Abstract. A two decades–long epidemic of Rocky Mountain spotted fever in northern Mexico reached the U.S. border city of Tijuana in 2021. Cases were near the city periphery in marginalized areas, some lacking infrastructure such as streets or utilities. We worked in the three census areas where human cases were reported and in 12 additional control Areas Geoestadisticas Basicas. Of 191 examined dogs, 61.8% were tick-infested, with 6-fold increased odds if they were allowed to roam. Although no dogs were Rickettsia polymerase chain reaction–positive, we found one R. rickettsii and 11 Rickettsia massiliae–infected ticks. The rickettsial IgG seroprevalence by immunofluorescence antibody assay was 76.4%, associated with unhealthy body condition, adults, dogs with> 10 ticks, more dogs being seen in the area, and dogs being permitted in the street. Insufficient medical and canine management resources have contributed to a case fatality rate of RMSF that has exceeded 50% in areas. High canine seroprevalence suggests risks to people and dogs; unfortunately, herd immunity is impeded by high turnover in the canine population owing to the birth of puppies and high death rates. Binational One Health workers should monitor disease spread, enact canine population management and tick eradication, and provide prevention, diagnostic, and treatment support.

Note: Abandoning dogs in Mexico by legal and illegal immigrants may only add to this public health issue and perhaps provide some risk for border communities.

Female Aedes aegypti mosquitoes use communal cues to manage population density at breeding sites.

Costa-da-Silva AL, et al.

COMMUNICATIONS BIOLOGY | (2024) 7:143 | https://doi.org/10.1038/s42003-024-05830-5 | www.nature.com/commsbio 1 1234567890

Abstract: Where a female mosquito lays her eggs creates the conditions for reproductive success. Here, we identify a communal behavior among ovipositing female mosquitoes. When choosing equal breeding sites, gravid Aedes aegypti aggregate more often than expected. This aggregation occurs when water contact is restricted and does not require the presence of eggs. Instead, the aggregation is regulated by the number of females present at the breeding site. Using assays with both occupied and empty oviposition sites, we show that the Orco olfactory co-receptor and a carbon dioxide receptor, Gr3, detect the presence of mosquitoes. Orco mutants aggregate more often in empty sites, suggesting attractive olfactory cues influence females to associate with one another. Gr3 mutant females do not prefer either site, suggesting that the CO2 receptor is necessary to evaluate mosquito population density at breeding sites. Further, raising CO2 levels is sufficient to cause wild-type mosquitoes to avoid empty oviposition sites. Our results demonstrate that female mosquitoes can regulate their own population density at breeding sites using attractive and repellent communal cues.

Note: These results are based on a series of well done laboratory choice experiments that begin to tease apart the patterns of oviposition site choice and therefore the distribution of this mosquito in nature — information useful for surveillance and control.

Emerging and lesser-known arboviruses impacting animal and human health

A Faraji1, G Molaei, T Andreadis. J Med Entomol, 60(6), 2023, 1139–1141.

https://doi.org/10.1093/jme/tjad140.

In an effort to address problems surrounding emerging vector-borne pathogens, we have dedicated a series of Forum Articles for a special issue of the Journal of Medical Entomology titled “Emerging and Lesser-Known Arboviruses Impacting Animal and Human Health”. It is our hope that this series will further contribute to our understanding of these lesser-known arboviruses for the benefit of vector control personnel, clinicians, and public health stewards within a One Health approach. This issue will encompass arboviruses transmitted by biting midges (Diptera: Ceratopogonidae), mosquitoes (Diptera: Culicidae), and hard ticks (Ixodida: Ixodidae).

Note: Included within this series are papers on Cache Valley, Jamestown Canyon and Snow shoe hare, viruses thought to occur in California [see Reeves’ Monograph published by the MVCAC], but not included within current molecular surveillance diagnostics.

The mosquito knows no borders: Regional challenges for global confrontation in the dengue battle

Barcante JMP, Cherem J (2024)

https://doi.org/10.1371/journal.pntd.0011830

Note: Paper reviews the increasing international public health importance of dengue and calls for improved prevention focusing on vector control. The remarkable increase in cases throughout Central and South America undoubtedly will increase the risk of cases imported into California. The expanding distribution and abundance of Aedes aegypti concurrently will increase the risk of local transmission.

Do it yourself: 3D-printed miniature CDC trap for adult mosquito (Diptera: Culicidae) surveillance

Bibbs CS, Reissen N, Dewsnup MA, Sorensen RB, Faraji A, White GS (2024)

https://doi.org/10.1371/journal.pntd.0011899

Abstract: 3D printing could improve the accessibility of the CDC trap by eliminating some of the supply chain variables. We present here several trials with the Salt Lake City (SLC) trap, a three-dimensional (3D) printed trap design. No statistically significant differences were found when comparing CO2 line height(above vs. below fan), battery types (sealed lead acid vs. USB battery pack), and trap body collection shape (funnel body vs. simple/straight body). The SLC trap was compared directly to a commercial equivalent, the Clarke ABC trap, with comparative assessment on species diversity and abundance and found to be statistically equivalent on all metrics. Our final design is presented here with the publicly published stereolithography (STL) files and a detailed outline of the transport container system.

Note: This trap design was presented at the Annual MVCAC conference and is cited here for reference.

Response to An Outbreak of Locally Transmitted Dengue in Key Largo, FL

The Florida Keys Mosquito Control District. J Am Mosq Control Assoc., 39 (4), 2023, pp. 251–257.

Doi: https://doi.org/10.2987/23-7145

ABSTRACT: Seventy-two cases of locally acquired dengue were contracted by residents and visitors of Key Largo, FL, in 2020. The primary vector, Aedes aegypti, has been a large focus of the Florida Keys Mosquito Control District’s (FKMCD) control measures for over a decade. This paper recounts the 2020 outbreak of DENV in Key Largo, FL, and the FKMCD’s Ae. aegypti operational response. The overall House Index (13.43%) during the outbreak was considered high (>5%) risk for local transmission. Larval habitat characterized from property inspections was similar to previous larval and pupal habitat studies. Adult surveillance of the active dengue transmission area provided 3 positive pools out of 1,518 mosquitoes tested resulting in a minimum infection rate of 1.976. Increased personnel response with long-term larvicide formulations and increased aerial, truck, and handheld ultra-low-volume adulticide control measures quickly reduced the Ae. aegypti surveillance numbers below the action threshold. No active cases of dengue have been reported since October 2020.

Note: This article provides a case study of one district’s response to a local dengue outbreak. Here, two initial cases were reported on 3 Mar 2020 but subsequent suspect cases were not recognized until 17 Jun after considerable transmission. Two cases that occurred in Jan 2020 were not reported until late 2021. This cascade of events clearly shows the importance of case surveillance and reporting and fits well with our conference discussions as districts review existing response plans following California’s first two cases of locally transmitted dengue.

Tick Resources Reminder

Adult Ixodes pacificus ticks are most active in California from fall through early spring. Now is a great time to encourage repellent use and tick checks for tick bite prevention.

For sample messaging and educational materials about ticks and tick bite prevention, please visit go.cdph.ca.gov/ticks and the following resources:

2024 Sentinel Chicken Order Forms Available Now!

ORDER NOW!

Chickens are being supplied by Gemperle Family Farms in Turlock, CA

Please return order form by March 1, 2024 Via email or fax to 916-444-7462

Northern and Southern Region

Pick-up date: Mid-April. Specific date, and location TBD (Turlock/Hilmar area)

 

The address for the farm will be provided as soon as we have it.

Questions: please email or call R’Mani White in Membership at rwhite@amgroup.us or (916) 440-0826 ext 125.

Epidemiological Update — Western Equine Encephalitis in the Region of the Americas

January 10, 2024

Summary of the situation: On 19 Dec 2023, the Pan American Health Organization/World Health Organization (PAHO/WHO) warned about the risk to human health associated with the circulation of the western equine encephalitis virus (WEE). From that date until 9 Jan 2024, 374 additional outbreaks (equine outbreak: occurrence of one or more cases of WEE in equines) in animals were reported (338 in Argentina and 36 in Uruguay) and 21 human cases, all of them in Argentina. Note: Human cases of WEEV have been absent from Argentina for more than 2 decades, similar to the long time absence of WEEV from California. We should remember that the SLEV strains now circulating in the SW USA [including California] were most closely aligned with strains previously isolated from Argentina, perhaps establishing a route/corridor for introduction by migrant birds? Testing Culex mosquitoes by triplex during 2024 would again seem prudent.

Read full article here

Help Support the 2024 WNV Call Center

The WNV Call Center needs YOUR help meeting their 2024 funding goal!

The West Nile Virus Call Center helps keep California safe from disease outbreaks by allowing the public to report dead birds on their area.

If other agencies are interested in contributing, please email Vicki.Kramer@cdph.ca.gov

Surveillance of Flea-Borne Typhus in California, 2011–2019

Yomogida K, Kjemtrup A, et al. Am. J. Trop. Med. Hyg., 110(1), 2024, pp. 142–149.

doi:10.4269/ajtmh.23-0272.

Abstract. Flea-borne typhus (FBT) is an acute febrile disease in humans caused by the bacteria Rickettsia typhi. In California, healthcare providers and testing laboratories are mandated to report to their respective local public health jurisdictions whenever R. typhi or antibodies reactive to R. typhi are detected in a patient. This study characterized the epidemiology of 881 flea-borne typhus cases in California from 2011 to 2019, with most cases reported among residents of Los Angeles and Orange Counties (97%). Demographics, animal exposures, and clinical courses for case patients were summarized. Additionally, spatiotemporal cluster analyses pointed to five areas in southern California with persistent FBT transmission.

Note: Additional detailed information has been published in the Proceedings of the MVCAC Annual Conference.

Call for Volunteers

Are you attending MVCAC 2024 in Monterey, CA?!? 

We are hosting an AMCA YPs booth at the upcoming MVCAC annual meeting in Monterey, CA! To make this event a success, we are seeking enthusiastic volunteers to assist with the YPs booth and various conference logistics. If you are attending, volunteer at our AMCA YPs booth! Connect and engage with your fellow California YP peers and seasoned professionals. If you’re eager to be a part of this dynamic experience, please complete the volunteer form: bit.ly/24MVCAC_YPsBooth

CalSurv Seeking Examples of Visualizations and Data Summaries

The CalSurv development team is seeking examples of visualizations and data summaries your agency includes in reports. If you’re willing to submit examples of reports that are useful to you, we’ll do our best to incorporate some of the examples in our workshops and resources. Please upload any example reports here.

 

If you missed our October training on creating your own reports in R using the new VectorSurv API, it’s not too late! You can check out the video on our YouTube channel. To get periodic updates from our team, sign up for our newsletter here.

Large-scalereleases and establishment of wMel Wolbachia in Aedes aegypti mosquitoes throughout the Cities of Bello, Medellı´n and Itagu¨ı´, Colombia. PLoS Negl

Velez ID, Uribe A, Barajas J, Uribe S, A´ ngel S, Suaza-Vasco JD, et al. (2023)

Trop Dis 17(11): e0011642.

https://doi.org/10.1371/journal.pntd.0011642

The introduction of the naturally occurring wMel Wolbachia strain into Aedes aegypti mosquitoes has been shown to reduce the ability of the mosquitoes to transmit dengue and other viruses. Following engagement with communities to gain acceptance and support, a series of large-scale releases of Ae. aegypti mosquitoes that contained wMel Wolbachia, were undertaken across the cities of Bello, Medellı´n and Itagu¨ı´ in Colombia. These releases were undertaken under operational conditions with the aim of rapidly scaling the intervention in response to the Zika virus crisis. Mosquito populations were monitored during and after releases to determine the levels of Wolbachia and whether it persisted in the local mosquitoes. Wolbachia was found to be stable and established at consistent levels in local mosquito populations in the majority of areas. On-going monitoring in these areas will determine whether Wolbachia persists and also whether it establishes at a high level in the remaining areas. This intervention forms the basis of an epidemiological study to assess the impact of operational deployment of wMel Wolbachia on the reduction of the incidence of notified dengue cases and virologically-confirmed dengue.

Note: This important study shows the establishment of the wMel Wolbachia and the companion paper shows the reduction of dengue in the treated cities. However, this method does not reduce the biting pressure of Aedes aegypti and insecticide applications would be counter intuitive to this public health response.

Fitness costs in the presence and absence of insecticide use explains abundance of two common Aedes aegypti kdr resistance alleles found in the Americas.

Silva JJ, Fisher CR, Dressel AE, Scott JG (2023) 

PLoS Negl Trop Dis 17(11): e0011741

https://doi.org/10.1371/journal.pntd.0011741 

Resistance to widely used pyrethroid insecticides can occur by mutations in the voltage gated sodium channel (Vgsc) and alleles with these mutations are collectively known as knockdown resistance (kdr). The frequency of resistance alleles is driven by selection with pyrethroid insecticides, but kdr alleles decrease in frequency in the absence of insecticide. The relative fitness of different kdr alleles to each other is largely unknown. We show through cage experiments that the 1534C allele is favored in the absence of pyrethroid applications, but that the 410L+1016I+1534C allele is favored when deltamethrin selection occurs. These results help to explain the relative frequency of these alleles that have been detected in field collections.

Q&A: New York Times Reporter Reflects on Global Malaria Fight

November 28, 2023

From Pest Control Technology

New York Times Global Health Reporter Stephanie Nolen traveled to five countries in Africa and Latin America to crack the code on what’s being done to control mosquito-borne diseases. Here’s what she found.

Read full article

Special Collection: Emerging and Lesser-Known Arboviruses Impacting Animal and Human Health: Emerging and lesser-known arboviruses impacting animal and human health.

A Faraji, G Molaei, T Andreadis. Special Collection: Emerging and Lesser-Known Arboviruses Impacting Animal and Human Health: Emerging and lesser-known arboviruses impacting animal and human health. J Medical Entomol, 60(6), 2023, 1139–1141.

https://doi.org/10.1093/jme/tjad140

This paper is the introduction to Special Collection of 10 papers on the epidemiology and ecology of emerging and lesser-known viruses of public and veterinary importance within the United States. Included within the series are papers on orbiviruses transmitted by Culicoides, lesser known viruses transmitted by mosquitoes including Cache Valley, Everglades, Jamestown Canyon, and LaCrosse, and recently discovered viruses transmitted by ticks including Bourbon, Heartland, Colorado tick fever, and Powassan.

FDA Approves First Vaccine Against Mosquito-Borne Virus Chikungunya

November 10, 2023

From The Washington Post

The Food and Drug Administration has approved the world’s first vaccine to prevent chikungunya, a mosquito-borne illness that can cause debilitating joint pain for months to years.

Read more here

Aedes Aegypti Oviposition-Sites Choice Under Semi-Field Conditions

David,M.R.,Maciel-de-Freitas,R., Petersen,M.T.,Bray,D.,Hawkes,F.M.,Fernández-Grandon, G.M.etal.(2023)

Aedes aegypti oviposition-sites choice under semi-field conditions. Medical and Veterinary Entomology, 37(4),683–692.

Available from:https://doi.org/10.1111/mve.12670

Aedes aegypti in Brazil were offered a variety of oviposition containers within a semi-field cage. Gravid females preferred to oviposit close to the ground and in open water containers with organic compounds from plant watering. Domestic large artificial containers containing tap water received significantly fewer eggs, except for car tires, which received as many eggs as potted plants. Visual (potted plant shape) and olfactory clues (odor of the plant or from water containing organic matter) were equally attractive separately as they were together. These data may be useful in surveillance and control operations searching for larval sources.

First locally acquired case of dengue virus discovered in Pasadena

From CBS Los Angeles

October 20, 2023

Public health officials confirmed Friday the first locally acquired case of dengue virus in a Pasadena resident. This case is the first in California that is not associated with travel, according to Manuel Carmona, acting director of Public Health for the City of Pasadena. 

Read More

Rodent-targeted approaches to reduce acarological risk of human exposure to pathogen-infected Ixodes ticks.

Lars Eisen

Ticks Tick Borne Dis. 2023 Mar;14(2):102119, https://doi.org/10.1016/j.ttbdis.2023.102119

Condensed abstract: In the United States, rodents serve as important hosts of medically important Ixodes ticks, including Ixodes scapularis and Ixodes pacificus, as well as reservoirs for human pathogens, including Anaplasma phagocytophilum, Borrelia burgdorferi sensu stricto (s.s.), and Babesia microti. Over the last four decades, different methods to disrupt enzootic transmission of these pathogens between tick vectors and rodent reservoirs have been developed and evaluated. These techniques include the application of topical acaricides, antibiotics, or a vaccine against Bo. burgdorferi s.s., delivered orally via rodent food baits. This review outlines the general benefits and drawbacks of rodent-targeted tick and pathogen control methods, and then describes the empirical evidence for different approaches to impact enzootic pathogen transmission and acarological risk of human exposure to pathogen-infected Ixodes ticks. Note: This review paper describes various rodent-targeted tick management techniques, summarizing results of experiments and compiling the benefits and drawbacks.

MVCAC’s Response to Dengue Case in Pasadena

In response to the locally acquired dengue case recently reported in Pasadena, MVCAC drafted a statement to assist with your outreach efforts and if you receive questions from residents and stakeholders.

Podcast Episode: The Mosquitoes Are Winning

From The Daily

For decades, the world seemed to be winning the war against mosquitoes and tamping down the deadly diseases they carried. But in the past few years, progress has not only stalled, it has reversed. Stephanie Nolen, who covers global health for The Times, explains how the mosquito has once again gained the upper hand in the fight.

Listen Now

CA West Nile Virus & Dead Bird Call Center closes for the season on October 13, 2023

This season, the California Department of Public Health received over 5,900 dead bird reports to the CA West Nile Virus & Dead Bird Call Center (1-877-WNV-BIRD) and website. Over 1,700 dead birds were collected for testing, with 773 birds testing positive for West Nile virus (WNV). On October 13, the Call Center will transition to internet-only reporting at https://westnile.ca.gov/. WNV testing is limited in the fall and winter as WNV activity decreases, but dead bird reports are appreciated all year round.

 

Dengue Will ‘Take Off’ in Southern Europe, US, Africa This Decade, WHO Scientist Says

October 9, 2023

From MedScape

Dengue fever will become a major threat in the southern United States, southern Europe and new parts of Africa this decade, the WHO’s chief scientist said, as warmer temperatures create the conditions for the mosquitoes carrying the infection to spread.

Read more

AMCA Research Fund Day of Contributing: October 10, 2023

Date: Tuesday, October 10th, 2023

What Is It? It’s a day for everyone in the AMCA community to come together and support mosquito control research. Your contribution, no matter the amount, can make a significant impact.

How Can You Participate?

  1. Mark Your Calendar: Set a reminder for October 10th.
  2. Donate: We’ll provide a donation link on the day.
  3. Spread the Word: Share our social media posts to encourage your community to contribute too.

Why Do We Need Your Support? Your involvement can help us advance research, nurture young scientists, and protect public health. We are hoping our community can gather together to help us support one additional project each year!

Donate Today!

Convergent Trends and Spatiotemporal Patterns of Aedes-Borne Arboviruses in Mexico and Central America

Bernardo Gutierrez ,Darlan da Silva Candido,Sumali Bajaj,Abril Paulina Rodriguez Maldonado,Fabiola Garces Ayala,María de la Luz Torre Rodriguez,Adnan Araiza Rodriguez,Claudia Wong Arámbula,Ernesto Ramírez González,Irma López Martínez,José Alberto Díaz-Quiñónez,Mauricio Vázquez Pichardo,Sarah C. Hill, [ … ],Marina Escalera-Zamudio [ view all ]

Published: Plos Neglected Tropical Diseases, September 6, 2023

https://doi.org/10.1371/journal.pntd.0011169

Results indicate that CHIKV, DENV-1 and DENV-2 in Mexico share evolutionary and epidemiological trajectories. The southwest region of the country was determined to be the most likely location for viral introductions from abroad, with a subsequent spread into the Pacific coast towards the north of Mexico. Virus diffusion patterns observed across the country are likely driven by multiple factors, including mobility linked to human migration from Central towards North America. Considering Mexico’s geographic positioning displaying a high human mobility across borders, our results prompt the need to better understand the role of anthropogenic factors in the transmission dynamics of Aedes-borne arboviruses, particularly linked to land-based human migration.

Direct Mosquito Feedings on Dengue-2 Virus-Infected People Reveal Dynamics of Human Infectiousness

Louis Lambrechts, Robert C. Reiner et.al.

Plos Neglected Tropical Diseases Sept 2023

https://doi.org/10.1371/journal.pntd.0011593

This study in Iquitos, Peru, showed that dengue patients with mild disease were most infectious to Aedes aegypti mosquitoes 2 d after the onset of symptoms and that these mosquitoes were able to transmit their infection 7 – 16 d after blood feeding.  This empirical study provided a timeline for when secondary dengue cases could be expected following the onset of symptoms in an imported dengue case, thereby providing a timeline for preventive control operations.    

Article Series: Mosquitoes Are a Growing Public Health Threat, Reversing Years of Progress

September 29, 2023

From New York Times

Climate change and the rapid evolution of the insect have helped drive up malaria deaths and brought dengue and other mosquito-borne viruses to places that never had to worry about them.

Read more here

The late-summer itch: Ankle-biting mosquitoes are in extra full force in L.A. Why?

From LA Times

September 21, 2023

When you think “so L.A.,” Erewhon smoothies, Barbie-pink sunsets and baristas with IMDB credits might come to mind. Now you can add mosquitoes to the list.

Read more here

 

CA Endures Worst Mosquito Season In Years. When Will It End?

From Patch

September 16, 2023

As the blood-sucking ankle-biters take bite out of the Golden State, human West Nile Virus cases are spiking.

Read Here

First West Nile Virus Death Reported in LA County

September 7. 2023

From the County of Los Angeles Public Health

First death of 2023 reinforces need for all residents to take precautions against mosquitoes

Read More 

The biting rate of Aedes aegypti and its variability: A systematic review(1970–2022).

:ZahidMH, VanWykH, MorrisonAC, ColomaJ, LeeGO, CevallosV, etal.(2023)

https://doi.org/10.1371/journal.pntd.0010831

Author summary: Half of the world’s population is now at risk of dengue infection, which transmits to humans mostly through the bite of an infected female Aedes aegypti mosquito. Disease transmission models have played an important role in understanding the dynamics of dengue transmission and helping to develop control measures. The mosquito biting rate is one of the central parameters used in these models. Mosquito biting rates used in existing works are taken from a variety of studies, each with its strengths and limitations. To understand how existing study designs are used to estimate biting rate and how these estimates may vary over time, space, and environmental factors, we perform a systematic review of biting rate studies. We identify three study designs (human landing catch, marked-release-recapture, and histological) that play an important role in estimating per mosquito biting rates and capturing variability across a number of environmental factors. In particular, human landing catch studies can capture the variability of biting rates and marked-released-recapture studies along with histological studies can quantify the multiple feeding that occurs between ovipositions. Transmission modeling studies should be more informed by the biology of mosquito behavior. By understanding the biology of blood-feeding and context-specific factors, we can arrive at more informed per mosquito biting rate estimates for site-specific transmission model analysis.

[Submitted by the Vector and Vector-Borne Disease Committee]

West Nile virus is a growing threat this summer in California. What you need to know

August 30, 2023

From Los Angeles Times

West Nile virus infections are on the rise this year in California after a particularly wet winter led to more mosquito reproduction, according to health experts.

Read More

In the US, West Nile virus is leading cause of viral disease spread by insects, CDC study says

August 24, 2023

From CNN

The United States has seen a flurry of West Nile virus deaths reported in the last few days, including most recently in Illinois, Nebraska and Colorado.

Read More 

Mosquito Hearing Could Be New Target for Mating Disruption, Study Shows

From Entomological Society of America

August 23, 2023

Read more

August is peak mosquito season, and California’s in a fight against disease some carry

From the Orange County Register

August 11, 2023

Read more here

Community-based Integrated Tick Management Programs: Cost and Feasibility Scenarios

TL Schulze, L Eisen, K Russell, RA Jordan
Journal of Medical Entomology, tjad093, https://doi.org/10.1093/jme/tjad093
 
Abstract: Numerous studies have assessed the efficacy of environmentally based control methods to suppress populations of the blacklegged tick (Ixodes scapularis Say), but few of these estimated the cost of control. We estimated costs for a range of tick control methods (including habitat management, deer exclusion or population reduction, broadcast of acaricides, and use of host-targeted acaricides) implemented singly or in combination and applied to a model community comprising 320 residential properties and parklands. Using the high end for cost ranges, tick control based on a single method was estimated to have mean annual costs per household ranging from $132 for treating only forest ecotone with a broadcast synthetic acaricide to kill host-seeking ticks (or $404 for treating all residential forested habitat) to >$2,000 for deployment of bait boxes (SELECT TCS) across all residential tick habitat to treat rodents topically with acaricide to kill infesting ticks. Combining different sets of multiple methods in an integrated tick management program placed the annual cost between $508 and 3,192 annually per household, underscoring the disconnect between what people in Lyme disease endemic areas say they are willing to pay for tick control (not more than $100–150 annually) and the actual costs for tick control. Additional barriers to implementing community-based tick management programs within residential communities are discussed.
 
Notes: Surveillance and determination of pathogen risk provide a basis for public health messaging to warn the public in affected areas, but do little to actually mitigate the problem. As risk elevates so does the mandate for a coordinated response. Schulze et al. provide estimates of mitigation costs to residents residing within Lyme disease endemic areas in the Eastern USA. These data are useful for MVCAC agencies considering mitigation in response to increasing threats of tick-borne diseases. 
 
[Submitted by the Vector and Vector-Borne Disease Committee]
 
 

Delftia Tsuruhatensis TC1 Symbiont Suppresses Malaria Transmission by Anopheline Mosquitoes

Huang, W., J. Rodrigues, E. Bilgo, J. R. Tormo, J. D. Challenger, C. De Cozar-Gallardo, I. Pérez-Victoria, F. Reyes, P. Castañeda-Casado, E. J. Gnambani, D. F. Hien, M. Konkobo, B. Urones, I. Coppens, A. Mendoza-Losana, L. Ballell, A. Diabate, T. S. Churcher, and M. Jacobs-Lorena. 2023. delftia tsuruhatensis TC1 symbiont suppresses malaria transmission by Anopheline Mosquitoes. Science. 381: 533–540. DOI: https://doi.org/10.1126/science.adf8141
 
Abstract: Malaria control demands the development of a wide range of complementary strategies. We describe the properties of a naturally occurring, non–genetically modified symbiotic bacterium, Delftia tsuruhatensis TC1, which was isolated from mosquitoes incapable of sustaining the development of Plasmodium falciparum parasites. D. tsuruhatensis TC1 inhibits early stages of Plasmodium development and subsequent transmission by the Anopheles mosquito through secretion of a small-molecule inhibitor. We have identified this inhibitor to be the hydrophobic molecule harmane. We also found that, on mosquito contact, harmane penetrates the cuticle, inhibiting Plasmodium development. D. tsuruhatensis TC1 stably populates the mosquito gut, does not impose a fitness cost on the mosquito, and inhibits Plasmodium development for the mosquito’s life. Contained field studies in Burkina Faso and modeling showed that D. tsuruhatensis TC1 has the potential to complement mosquito-targeted malaria transmission control.
 
Notes: This article describes the findings of a study investigating the role of harmane, a compound secreted by Delftia tsuruhatensis TC1 bacteria, in the disruption of Plasmodium development in the midgut and the reduction of sporozoite prevalence in salivary glands of anopheline mosquitoes. The authors also describe the efficacious delivery of D. tsuruhatensis TC1 to larvae and adult mosquitoes in laboratory and field settings, indicating the versatility of potential deployment in the field.  Studies like this show the importance of understanding the mosquito microbiome in variability seen in pathogen transmission in the laboratory and field. 
 
[submitted by the Vector and Vector-Borne Disease Committee]
 
 
 

Near Tulare Lake, State Disaster Relief Includes Millions for Mosquito Abatement

From KVPR

August 7, 2023

One mosquito abatement district in Tulare County has reportedly purchased its first-ever drone, amphibious vehicle and airboat.

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Fleaborne Typhus–Associated Deaths

Los Angeles County, California, 2022

Alarcón J, Sanosyan A, Contreras ZA, et al. MMWR Morb Mortal Wkly Rep 2023;72:838–843. DOI: http://dx.doi.org/10.15585/mmwr.mm7231a1
 
Abstract. Fleaborne typhus (also known as murine typhus), a widely distributed vectorborne zoonosis caused by Rickettsia typhi, is a moderately severe, but infrequently fatal illness; among patients who receive doxycycline, the case-fatality rate is <1%. Fleaborne typhus is a mandated reportable condition in California. Reported fleaborne typhus cases in Los Angeles County have been increasing since 2010, with the highest number (171) reported during 2022. During June–October 2022, Los Angeles County Department of Public Health learned of three fleaborne typhus–associated deaths. This report describes the clinical presentation, illness course, and methods used to diagnose fleaborne typhus in these three cases. Increased health care provider and public health awareness of the prevalence and severity of fleaborne typhus and of the importance of early doxycycline therapy is essential for prevention and treaogy oftment efforts.
Comment.  For detailed accounts on the evolution and extent of this problem in Los Angeles and Orange Counties see Cummings et al. (2022: PMVCAC 90: 33-42).  As reviewed, the epidemiology and etiology of typhus has been somewhat confounded by the occurrence of two rickettsia with differing life cycles and transmission patterns. However, the expansion of urban rodent, opossum and feral cat populations clearly have exacerbated the problem. The spread of homeless encampments is a related issue. Clinical research is needed to identify which rickettsia are involved in human disease, to delineate the extent of human infection in California, and to identify risk factors that may be targets for public health/vector control district intervention. Although human cases mostly seem confined to southern California, Rickettsia felis most likely is present wherever cat flea populations are found.  
 
[Submitted by the Vector and Vectorborne Disease Committee]    
 

Statement on Locally Acquired Malaria Cases in Florida and Texas

August 1, 2023

Recently, locally acquired cases of malaria in Florida and Texas have received national media attention. MVCAC has developed the below statement for member agencies to use when responding to questions regarding these detections and the risk of locally acquired cases in California. MVCDs are encouraged to tailor this statement with information specific to their district.

Despite reports of recent malaria cases in Florida and Texas, local transmission of malaria in the U.S. is very rare. Most malaria cases are acquired when people travel outside of the U.S. where malaria transmission occurs. Anopheles mosquitoes that can spread malaria are present in California, but the parasites that cause malaria are not currently found in these mosquitoes in California. The last cases of local transmission of malaria in California were reported in 1990. About 100 cases of malaria are reported each year in California from people who were infected while traveling in other countries. Since malaria is a reportable disease, all diagnosed imported cases are tracked by the state and local public health departments. The patient’s history and potential for exposure to local malaria vectors are evaluated and if need be, actions are made to prevent possible transmission within the local community.

Mosquito and vector control agencies in California monitor many species of mosquitoes including those that carry West Nile Virus, invasive mosquitoes, and those that have the ability to carry malaria. Mosquito and vector control agencies do this to protect public health and quickly respond when mosquito-borne diseases threaten residents.

Residents are encouraged to wear EPA-registered insect repellent and dump and drain all standing water in and around their homes to prevent mosquito bites. To learn more about mosquito prevention please visit mvcac.org. To learn more about malaria please visit the CDC and the California Department of Public Health.

West Nile Virus Strikes Again: Mosquito Spraying Ramps Up in San Jose, Milpitas

From Hoodline

August 1, 2023

In response to the discovery of West Nile virus-positive mosquitoes in San Jose and Milpitas, the Santa Clara County Vector Control District has initiated truck-mounted insecticide treatments to control and kill adult mosquitoes in the affected areas. 

 

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Dangerous virus detected in mosquitoes in New Hampshire

From WMUR9

July 26, 2023

Health officials urge residents to take precautions. The mosquito-borne Jamestown Canyon virus has been detected in seven batches of mosquitoes in New Hampshire this year but has so far not been found in people.

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New Process for Submitting Updated NOIs and PAPs to the State Water Board

June 2023

For vector control districts that wish to use pyriproxyfen in WOTUS, an updated Notice of Intent form and Pesticide Application Plan needs to be submitted to the State Water Board. Examples of completed documents can be found on the Water Board NPDES Vector Control Permit website. Due to web accessibility requirements, the State Water Board is no longer allowed to post 3rd party documents unless they are ADA-compliant. Therefore, the Water Board requests applicants post documents on their webpage and provide a link which will then be used to post on the State Water Board website for 30-day public comment as required per the permit.

Email Gurgagn Chand, Gurgagn.Chand@waterboards.ca.gov, your website link for the document. After the application link is posted for 30-day public comment, Water Board staff will notify you of any items that need to be addressed within the amended application package as well as any public comments received. If everything checks out, generally an amended Notice of Applicability approving the revisions will be issued by the Deputy Director of Water Quality within 1-2 weeks. 

Email MVCAC Regulatory Affairs Committee Chair (Erika Castillo, erika@mosquitoes.org) if you have any additional questions.