Jennifer A. Henke’s scientific contributions

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Publications (16)


EFFECT OF SEX AND AGE ON SURVIVAL OF ADULT CULEX TARSALIS FROM A SUSCEPTIBLE LABORATORY STRAIN EXPOSED TO PERMETHRIN IN THE CDC BOTTLE BIOASSAY
  • Article
  • Full-text available

November 2024

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8 Reads

Journal of the American Mosquito Control Association

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Kim Y Hung

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Jennifer A Henke

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This study investigates the effect of mosquito sex and age on the survival and resistance determination of adult Culex tarsalis exposed to permethrin, a pyrethroid commonly used for mosquito control, using the Centers for Disease Control and Prevention (CDC) bottle bioassay method. A permethrin-susceptible strain of Cx. tarsalis (Bakersfield strain) was used in this study. Survival was compared for young adult females (2–5 days old) relative to older adult females (7–10 days old) and separately for female and male mosquitoes of the same age (2–5 days old). Mortality was slightly higher for males than females during the first observation period (0–5 min) following permethrin exposure, and higher for older females relative to younger females from 5 to 10 min following permethrin exposure, with no differences in mortality by either sex or age for observation periods during the remainder of the diagnostic period. When evaluated over the full diagnostic period, survival varied with mosquito age but not sex. However, all mosquitoes, regardless of sex or age, died within the 30-min diagnostic period for this species, confirming their permethrin susceptibility per the CDC bottle bioassay. This research contributes valuable insight into the potential impact of sex and age on mosquito susceptibility to insecticides in the context of insecticide resistance determination.

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Figure 2 A) Cross-coalescent analysis of effective population size and migration using MSMC2. Effective population size plotted on log10 scale for representative populations as a function of years before present, also on a log10 scale, assuming 12 generations per year. The pink histogram shows the estimated number of slave vessel embarcations scaled by millions of enslaved people (Slave Voyages 2023) (33) on the alternative, pink y-axis at right. The green histogram shows precipitation levels in the Sahara (34) according to the green scale at right. Both histograms shown for approximate temporal reference. B) Cumulative migration plotted as a function of time on log10
Sequencing 1206 genomes reveals origin and movement of Aedes aegypti driving increased dengue risk

July 2024

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234 Reads

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Seth Redmond

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Bradley J White

The number of dengue cases worldwide has increased ten-fold over the past decade as Aedes aegypti, the primary vector of this disease, thrives and expands its distribution, revealing limitations to current control methods. To better understand how Ae. aegypti evolved from a forest dwelling, generalist species to a highly anthropophilic urban species and the impact of contemporary gene flow on the future of dengue control, we sequenced 1,206 genomes from mosquitoes collected at 74 locations around the globe. Here we show that after evolving a preference for humans in the Sahel region of West Africa, the origin of the fully domesticated, anthropophilic subspecies Ae. aegypti aegypti (Aaa) occurred in the Americas during the Atlantic Slave Trade era and was followed by its explosive expansion around the globe. In recent decades, Aaa has invaded coastal Africa, the ancestral home range, introducing insecticide resistance mutations and an affinity for human hosts. Evidence of back-to-Africa migration is found in regions with recent dengue outbreaks, raising concern that global movement of Aaa could increase transmission risk of arboviruses including dengue in urban Africa. These data provide a platform to further study this important mosquito vector species and underscore developing complexity in the fight to limit the spread of dengue, Zika, and chikungunya diseases.


Fig. 1. Field sites in southern California where Culex tarsalis were captured. Inland Valley sites (IV1 and IV2) are wetland habitats in western Riverside County, while Coachella Valley sites (COA1, COA2, and COA3) are desert habitats near agricultural production north of the Salton Sea in eastern Riverside County.
Fig. 2. Mosquito survival rate by Kaplan-Meier survival analysis. Vertical dashed line at 20 min indicates the diagnostic exposure time with mosquitoes surviving beyond this time considered resistant to permethrin according to CDC bottle bioassay procedures.
Test for hypothesis of equal frequency of per- methrin resistance in mosquito populations from different field sites (Fisher's exact test).
Prevalence of Permethrin Resistance in Culex Tarsalis Populations in Southern California

December 2023

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61 Reads

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1 Citation

Journal of the American Mosquito Control Association

In the western United States, Culex tarsalis is the most important vector of West Nile virus. Insecticides containing permethrin or other pyrethroid compounds are commonly used to control these mosquitoes. Because of the range of environments where Cx. tarsalis are found, this species is under insecticide pressure from both vector control and agricultural spraying. Mosquito populations may evolve resistance through mechanisms such as target site insensitivity, including the frequently identified knockdown resistance (kdr) mutations. Prevalence of permethrin resistance was determined for Cx. tarsalis from 5 southern California field sites representing 2 distinct valley regions (Coachella Valley and Inland Valley), which are geographically separated by the north-south-running Peninsular Mountain Ranges. These two valley regions are >100 km apart and vary considerably in their environmental and habitat characteristics. Permethrin resistance in mosquito populations was determined by the Centers for Disease Control and Prevention (CDC) bottle bioassay, using glass bottles coated with permethrin at 0.19 μg/cm2 of internal surface. Permethrin resistance was evident in Cx. tarsalis populations from the Coachella Valley field sites with all sites showing similar mortality in the bottle bioassay, while Cx. tarsalis from the Inland Valley field sites were largely susceptible to permethrin, with mortality rates that were similar to a susceptible lab strain of Cx. tarsalis.


A Spatially Resolved and Environmentally Informed Forecast Model of West Nile Virus in Coachella Valley, California

December 2023

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66 Reads

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5 Citations

West Nile virus (WNV) is the most significant arbovirus in the United States in terms of both morbidity and mortality. West Nile exists in a complex transmission cycle between avian hosts and the arthropod vector, Culex spp. mosquitoes. Human spillover events occur when humans are bitten by an infected mosquito and predicting these rates of infection and therefore the risk to humans may be associated with fluctuations in environmental conditions. In this study, we evaluate the hydrological and meteorological drivers associated with mosquito biology and viral development to determine if these associations can be used to forecast seasonal mosquito infection rates with WNV in the Coachella Valley of California. We developed and tested a spatially resolved ensemble forecast model of the WNV mosquito infection rate in the Coachella Valley using 17 years of mosquito surveillance data and North American Land Data Assimilation System‐2 environmental data. Our multi‐model inference system indicated that the combination of a cooler and dryer winter, followed by a wetter and warmer spring, and a cooler than normal summer was most predictive of the prevalence of West Nile positive mosquitoes in the Coachella Valley. The ability to make accurate early season predictions of West Nile risk has the potential to allow local abatement districts and public health entities to implement early season interventions such as targeted adulticiding and public health messaging before human transmission occurs. Such early and targeted interventions could better mitigate the risk of WNV to humans.


Virus detection using small RNA libraries. (a) Schematic representation of the experimental protocol. RNA was extracted from mosquito pools, reverse transcribed, PCR amplified, size selected for small RNA, and sequenced. Pool sizes are listed in Supplementary Table S1. (b) Schematic representation of virus detection including VirusDetect. Reads were assembled into contigs in two ways and compared to a viral genome database by BLAST. (c) Number of known mosquito viruses detected in a sample vs. number of sequenced for that sample (Spearman’s R = 0.569 for all samples). (d) High nucleotide identity (> 90%) virus detections in Cx. quinquefasciatus samples by taxonomic group. Hepe-Virga supergroup and Toti-chryso are loose classifications of related virus families.
Clustering and correlation of mosquito pools by virus small RNA quantities. (a) Clustering of mosquito pool samples by virus small RNA quantities using the dimension reduction method UMAP. The three plots differ only by the sample property used to color the data points. (b) Pearson correlation matrix of mosquito pool samples by virus small RNA quantities. Sample properties are labeled to the left and below the matrix, and regions of high correlation are denoted. (c) Pearson correlation matrix of detected viruses by reads mapped from all samples. Regions of low and high correlation are denoted.
Analysis of small RNA derived from the Culex genome. (a) Percentages of small RNA reads from all Cx. quinquefasciatus field samples mapping to each type of genomic feature in the mosquito genome. (b) Numbers of miRNA genes determined as differentially expressed for each comparison of field Cx. quinquefasciatus samples, with field vs. lab as a point of reference for these comparisons. (c–e) Comparison of miRNA expression in samples with higher abundance of (c) viruses, (d) Wolbachia, or (e) CxNV1 against those with lower abundance. Volcano significance plots have adjusted P-value cutoff of 0.05 and log2fold change cutoff of 1. NS: not significant. Log2 FC: significant by log2fold change only (threshold ± 1). P: significant by adjusted P-value only (threshold 0.05). P & Log2 FC: significant by both adjusted P-value and log2fold change.
Small RNA responses of field Culex mosquitoes against specific viruses. (a) Examples of small RNA size profiles showing percentages of mapped reads of each size. HCLV1 displays a strong siRNA response (21-nt peaks), while CbunLV and CphasLV display both siRNA and piRNA responses (24–29 nt enrichment). Percent values are averages across all samples in which the virus was detected. Error bars show the average ± standard error for that small RNA size across all samples. (b) Sequence logo plots showing nucleotide bias for 24–29 nt reads mapping to individual viruses. Bias is indicative of piRNA generation by the ping-pong cycle. (c) Likely siRNAs and piRNAs mapped to Culex phasma-like virus segment S. Only 24–29 nt reads with 1U (for antisense reads) or 10A (for sense reads) are included in the piRNA track.
Virus coverage plots showing evidence of siRNAs and/or piRNAs in three viruses. (a) Sense-mapped reads are shown in the upper half of each track in blue, while antisense-mapped reads are shown in the bottom half in red. Reads shown are from all pools in which the virus was detected by VirusDetect. (a) The presence of antisense 21-nt reads but not antisense 24–29 nt reads, as well as lack of nucleotide bias in 24–29 nt reads, suggest siRNA but not piRNA generation against WNV. (b) Both sense and antisense reads for both size ranges are generated in abundance against the Culex bunya-like virus genomic region shown, and the 24–29 nt reads include a high percentage with the piRNA nucleotide bias. (c) Antisense 21-nt reads are abundant against the entire Culex narnavirus 1 genome, while antisense 24–29 nt reads are confined to a strong peak upstream of the coding region and many possess the piRNA nucleotide bias. This suggests generation of viral piRNAs without a detectable ping-pong signature.
Small RNA sequencing of field Culex mosquitoes identifies patterns of viral infection and the mosquito immune response

June 2023

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98 Reads

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5 Citations

Mosquito-borne disease remains a significant burden on global health. In the United States, the major threat posed by mosquitoes is transmission of arboviruses, including West Nile virus by mosquitoes of the Culex genus. Virus metagenomic analysis of mosquito small RNA using deep sequencing and advanced bioinformatic tools enables the rapid detection of viruses and other infecting organisms, both pathogenic and non-pathogenic to humans, without any precedent knowledge. In this study, we sequenced small RNA samples from over 60 pools of Culex mosquitoes from two major areas of Southern California from 2017 to 2019 to elucidate the virome and immune responses of Culex. Our results demonstrated that small RNAs not only allowed the detection of viruses but also revealed distinct patterns of viral infection based on location, Culex species, and time. We also identified miRNAs that are most likely involved in Culex immune responses to viruses and Wolbachia bacteria, and show the utility of using small RNA to detect antiviral immune pathways including piRNAs against some pathogens. Collectively, these findings show that deep sequencing of small RNA can be used for virus discovery and surveillance. One could also conceive that such work could be accomplished in various locations across the world and over time to better understand patterns of mosquito infection and immune response to many vector-borne diseases in field samples.


A spatially resolved and environmentally informed forecast model of West Nile virus in Coachella Valley, California.

May 2023

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23 Reads

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1 Citation

West Nile virus is the most significant arbovirus in the United States in terms of both morbidity and mortality. West Nile exists in a complex transmission cycle between avian hosts and the arthropod vector, Culex spp. mosquitoes. Human spillover events occur when humans are in close proximity to vector populations with high rates of infection. Predicting these rates of infection and therefore the risk to humans is not straightforward. In this study, we evaluate the hydrological and meteorological drivers associated with mosquito biology and viral development to determine if these associations can be used to forecast seasonal West Nile risk in the Coachella Valley of California. To test this, we developed and tested a spatially-resolved ensemble forecast model of West Nile virus transmission in the Coachella Valley using 17 years of mosquito surveillance data and NLDAS-2 environmental data. Our multi-model inference system indicated that the combination of a cooler and dryer winter followed by a wetter and warmer spring and a cooler than normal summer was most predictive of West Nile positive mosquitoes in the Coachella Valley. The ability to make accurate early season predictions of West Nile risk could allow local abatement districts and public health entities to implement early season interventions such as targeted adulticiding and public messaging before human transmission occurs. Such early and targeted interventions could better mitigate the risk of West Nile virus to humans in the Coachella Valley.


Satellite Rearing of Aedes Mosquito Eggs: Synchronized Empirical Test of a Novel Mass Rearing Model

March 2023

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41 Reads

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2 Citations

Journal of the American Mosquito Control Association

Mosquito suppression strategies based on "rear and release" of male mosquitoes are attracting renewed interest from governments, municipalities, and private businesses. These include irradiation-based sterile insect technique, Wolbachia-based technologies, and genetic modification. Each of these approaches requires the mass rearing and release of adult male mosquitoes, which typically is accomplished via a rearing facility near the release site. Although some release programs have relied on centralized rearing and shipment of adult males, adult male mosquitoes are relatively fragile, and their fitness can be diminished by temperature fluctuations, humidity, nutritional deficiencies, and other stresses that occur during shipment. Furthermore, expensive, expedited shipment is typically used to maximize the amount of adult lifetime in the field following the release. In contrast, Aedes aegypti and Ae. albopictus eggs can be desiccated and stored for long periods. They are small, and many millions of eggs can be shipped without specialized environmental conditions and using less expensive means. Here we examine a model in which mosquito eggs are centrally produced and then mailed to satellite rearing facilities. As a control, a replicate set of eggs was reared at the factory of origin. At each of the rearing sites, cloud-based software was used to track and compare rearing at the different locations. The results demonstrate similar rearing outcomes (i.e., egg hatch, immature development, and number of adult males) at each of the different sites for both species. We discuss the outcome in relation to downstream applications and potential future studies.


The maximum clade credibility phylogenetic tree reconstructed using 174 genotype III St. Louis Encephalitis Virus (SLEV) genomes throughout the Southwest. The tip colors distinguish the sampling location of each sample Arizona Counties, Maricopa (Blue), and Yuma (Gray); California Counties, Imperial (Green), Riverside (Teal), and Others (Brown); Nevada, Clark (Pink); Texas, El Paso (Yellow); Oregon, Malheur (Dark Blue); and Idaho, Gem (Purple). Posterior values for branches above 0.50 are written above their corresponding branch. Branches with posterior values below 0.5 were collapsed into polytomies (Supplementary Figure S3 contains the BEAST tree prior to collapsing and contains the 95% HPD CI for each node). After correcting for low confidence branches, the phylogeny clusters into three distinct clades. Clade 1 consists of all the 2015–2016 California and 2015 Arizona samples. Clade 2 consists of the 2017–2018 California samples and the 2017–2019 Arizona samples. Clade 2 is further divided into two subclades 2A and 2B. Subclade 2A comprises Coachella Valley, California; Yuma County, Arizona, and Clark County, Nevada; subclade 2B comprises 2017–2019 Arizona samples, with two Yuma County and three Clark County samples.
The United States map colors counties where SLEV positive mosquitoes or human cases were observed between 2015 and 2019. Sampling locations for the genomes sequenced in this study are indicated by the numbered black stars. Star 1 is Coachella Valley, Star 2 is Yuma County, Star 3 is Maricopa County, and Star 4 is Clark County. Heat map of densities of positive mosquito traps found within Coachella Valley from 2015 to 2018 and Maricopa County from 2015 to 2019. The black points represent the individual mosquito trap locations. Two-dimensional kernel density estimation with axis-aligned bivariate normal kernel was used to estimate the density of positive mosquito traps within each year. Red indicates a higher density of positive traps.
The results from the four test statistics used by bayesian tip-association significance testing (BaTS) to determine if there were phylogenetic-trait associations between SLEV and its mosquito vectors Culex quinquefasciatus and Cx. tarsalis.
St. Louis Encephalitis Virus in the Southwestern United States: A Phylogeographic Case for a Multi-Variant Introduction Event

June 2021

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134 Reads

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8 Citations

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.



Sunshine versus gold: The effect of population age on genetic structure of an invasive mosquito

August 2020

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85 Reads

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4 Citations

The genetic diversity and structure of invasive species are affected by the time since invasion, but it is not well understood how. We compare likely the oldest populations of Aedes aegypti in continental North America with some of the newest to illuminate the range of genetic diversity and structure that can be found within the invasive range of this important disease vector. Aedes aegypti populations in Florida have probably persisted since the 1600‐1700s, while populations in southern California derive from new invasions that occurred in the last 10 years. For this comparison, we genotyped 1,193 individuals from 28 sites at 12 highly variable microsatellites and a subset of these individuals at 23,961 single nucleotide polymorphisms (SNPs). This is the largest sample analyzed for genetic structure for either region, and it doubles the number of southern California populations previously analyzed. As predicted, the older populations (Florida) showed fewer indicators of recent founder effect and bottlenecks; in particular, these populations have dramatically higher genetic diversity and lower genetic structure. Geographic distance and driving distance were not good predictors of genetic distance in either region, especially southern California. Additionally, southern California had higher levels of genetic differentiation than any comparably sized documented region throughout the worldwide distribution of the species. Although population age and demographic history are likely driving these differences, differences in climate and transportation practices could also play a role.


Citations (9)


... To help reduce the risk of mosquito-borne illnesses of humans and domestic animals, mosquito control programs often target adult mosquitoes using insecticides to reduce adult abundance (Richards et al. 2017). However, resistance of Cx. tarsalis to insecticides, including permethrin, is widespread, having been reported from Colorado and South Dakota (Strong et al. 2008, Vincent et al. 2018) and throughout California (Choi 2016;Hughes 2017;Hung et al. , 2022Tsecouras et al. 2023). ...

Reference:

EFFECT OF SEX AND AGE ON SURVIVAL OF ADULT CULEX TARSALIS FROM A SUSCEPTIBLE LABORATORY STRAIN EXPOSED TO PERMETHRIN IN THE CDC BOTTLE BIOASSAY
Prevalence of Permethrin Resistance in Culex Tarsalis Populations in Southern California

Journal of the American Mosquito Control Association

... Although West Nile virus (WNV) is also an important zoonosis and transmitted by arthropods, the virus is caused by a favivirus in the family Flaviviridae [13][14][15]. It was frst isolated in 1937 from the blood of a woman in the West Nile province of Uganda who had a mild febrile illness [16]. ...

A Spatially Resolved and Environmentally Informed Forecast Model of West Nile Virus in Coachella Valley, California

... In the mosquito Aedes albopictus, piRNA expression has been identified in somatic cells in response to viral infection [63]. Indeed, there are numerous reports of the antiviral role of piRNAs in multiple mosquito species including Aedes aegypti, Aedes vexans, Anopheles gambiae, and Culex quinquefasciatus [64][65][66][67][68][69]. The antiviral role of piRNAs in mosquitoes has previously been reviewed by other authors [70]. ...

Small RNA sequencing of field Culex mosquitoes identifies patterns of viral infection and the mosquito immune response

... In recent years, there has been renewed interest in the SIT for mosquitoes, particularly for Aedes species, due to increased arbovirus outbreaks and the rapid spread of Aedes mosquitoes into new territories 5-7 . While the SIT programs and technical components are still under development for mosquitoes [8][9][10][11] , and are still relatively small compared to programs for plant pests, significant progress has been made more recently as reviewed in Vreysen et al. 12 . This progress is crucial for the integrated management of Aedes-borne viral diseases 13,14 . ...

Satellite Rearing of Aedes Mosquito Eggs: Synchronized Empirical Test of a Novel Mass Rearing Model
  • Citing Article
  • March 2023

Journal of the American Mosquito Control Association

... This virus is maintained in nature by enzootic transmission networks between several species of Culex ssp mosquitoes and avian species. 1,2 The re-emergence of the infection throughout America and geographical expansion, evidenced by its emergence in previously unaffected areas, have raised significant concerns. Since vector species distribution determines the geographic distribution of SLEV, 3,4 the significance of the changes in geographic ranges of arthropods for public health has been studied. ...

St. Louis Encephalitis Virus in the Southwestern United States: A Phylogeographic Case for a Multi-Variant Introduction Event

... Mosquito species are composed of an array of locally adapted populations across their respective ranges. Substantial genetic variation exists in mosquito species (Fouet et al., 2017;Holt et al., 2002;Kang et al., 2021;Maffey et al., 2020;Pless et al., 2020;Yurchenko et al., 2020) and at fine-spatial scales (Ayala et al., 2020;Carvajal et al., 2020;Gutiérrez et al., 2010;Jasper et al., 2019;Matowo et al., 2019), with significant consequences for transmission potential (Azar et al., 2017;Palmer et al., 2018;Vega-Rúa et al., 2020). This genetic variation can interact with local environmental conditions to impact the capacity of mosquito vectors to transmit human pathogens (e.g., dengue; Gloria-Soria et al. (2017) and chikungunya; Zouache et al. (2014)). ...

Sunshine versus gold: The effect of population age on genetic structure of an invasive mosquito

... Prior work on spatial repellents, including flunothrin, metofluthrin, and transfluthrin have shown promise in controlling mosquito vectors and some filth fly vectors. For example, Britch et al. [7] demonstrated that selected mosquito species could be repelled from entering treated enclosures. House flies were significantly repelled from pyrethroid-treated (including transfluthrin) tiles in Scrivener et al. [8]. ...

Transfluthrin Spatial Repellent on US Military Materials Reduces Culex tarsalis Incursion in a Desert Environment

Journal of the American Mosquito Control Association

... Due to the time it takes for a person to become sick enough to seek treatment, as well as the reporting delays of cases to the state health department, we assumed that meteorological conditions and reported case counts are not directly related in time. Given that substantial lags between case onset and case reporting-an average of 5 weeks-have been found in other WNV outbreaks, temperature and rainfall were both lagged one month, so that the variables prior month temperature and prior month rainfall would better reflect the current month's cases [12]. As the reporting of vector data are also subject to delays in reporting and biological processes, it was assumed that the mosquito pool positivity rate and dead bird count follow similar delays as cases and therefore were not lagged [12]. ...

Modeling and Surveillance of Reporting Delays of Mosquitoes and Humans Infected With West Nile Virus and Associations With Accuracy of West Nile Virus Forecasts

JAMA Network Open

... larvae for a period of 7-35 days. [18,19] Spinosad acts like a contact poison and affects the nervous system causing paralysis and death. Natular™, a larvicide product, being marketed in the USA and Mexico uses spinosad at concentrations up to 1.6 ppm for community control of mosquito-borne illnesses. ...

Ultra-Low Volume Application of Spinosad (Natular 2EC) as a Residual in a Hot-Arid Environment Against Aedes aegypti

Journal of the American Mosquito Control Association