Evaluation of Freezanz automated misting system against mosquitoes.

Automated misting systems are a convenient way for homeowners or small businesses to control adult mosquitoes. One such system was presented to the Anastasia Mosquito Control District (AMCD) for evaluation to control caged Aedes aegypti. The system consisted of 3 spray tanks, 2 pumps, water level sensors, and flow meters, and was controlled through an Android tablet loaded with dedicated control software. The evaluation of the system included calibration tests, droplet characterization, spray dispersion in the open field, and effectiveness testing using bio-assay cages for mortality assessment. For these tests, a loop of 14 nozzles 4 m apart was connected and held at 1 m height utilizing a total of 120 m tube. All nozzles were arranged in a 16 × 12 m rectangle laid in the East-West direction. Water was sprayed for calibration and droplet size measurements at pressures of 13.0, 15.5, and 18 bar; water and 10% red dye solution for spray dispersion at 18 bar pressure, and 0.17% solution of equalizer 20-20 was sprayed at 18 bar pressure for mortality tests. All 3 replicated tests were conducted in the morning between 9:00 and 11:30 am. During this time, temperature ranged from 21-26°C, relative humidity from 54-95 %, and wind speed from 0 - 2 km/hr. The combined flow rate from all 14 nozzles was significantly affected by pressure and was in agreement with the machine-calculated flow rate. There was a similar flow rate from all nozzles, indicated by a standard error of 0.82 mL/min. The droplet characteristics represented by DV0.1, DV0.5, and DV0.9 were not affected by nozzles but decreased with an increase in pressure as expected. The percentage of coverage on the cards, an indicator of spray dispersion, ranged from 20 -100 %, and it was found to increase in the direction of the wind. Mosquito mortality showed a similar trend of increasing in the wind direction and ranged from 30 to 100%. There was no effect of the location of cages on mosquito mortality. These results indicate that the effectiveness of this spray depends upon wind direction. The results, however, may be different when there is no wind, which may be the case during the times these applications are made.

Ground-Based Pyrethroid Adulticides Reduce Mosquitoes But Not Nontarget Insects in Central Florida.

As stewards of public and environmental health, mosquito control agencies are rightfully concerned about impacts on nontarget organisms. This study examined the impact of a modern, pyrethroid based ground adulticide program using ultra-low volume applications in a metropolitan county in central Florida. Nontarget insects and mosquitoes were collected in a before-after control-impact design at 21 sites over 1.5 years. While mosquitoes were reduced, we found no evidence for reduction of nontarget insects, regardless of taxon. Night-flying Lepidoptera may experience greater risk than other nontarget taxa, but overall effects of adulticide missions on this group were low and inconsistent. Instead, meteorology, habitat, and phenology dominate patterns of nontarget abundance. Mosquito reduction was more clearly observed and corrected post-mission reduction was consistent with results expected in complex urban and suburban treatment zones.

Improving access to melarsomine therapy: treating canine heartworm infection in a high-volume, outpatient community clinic setting.

BACKGROUND: Models that provide high-quality veterinary care for more affordable prices are emerging, but not well documented outside of wellness and preventative care. Effective treatment guidelines for heartworm disease have been developed by the American Heartworm Society; however, not all owners are able to access treatment due to the high costs associated with sick and emergency care services. METHODS: To increase access to high-quality adulticidal treatment of canine heartworm disease, we developed and implemented a technician-leveraged heartworm treatment protocol for high-volume, outpatient community clinic settings based on the American Heartworm Society guidelines. Modifications were few and included limited pre-treatment blood work, pre-injection sedation, post-injection pain medication, and a reduced exercise restriction period. We monitored retention rates for 556 dogs throughout treatment, evaluated treatment success (defined as no antigen detection 9 months post treatment) for patients that returned for post-treatment antigen testing, and reported on adverse reactions and therapy adherence throughout treatment. RESULTS: Of the patients that began adulticide therapy, 539/556 (97%) successfully completed the three-injection series. No microfilariae were detected in 99% (428/433) of those who returned for post-injection microfilaria testing. Among those that returned for or reported the results of post-injection antigen testing, no antigen was detected for 99% (245/248) and no microfilariae were detected for 99.5% (200/201). During the course of treatment, 483/539 (90%) of patients experienced at least one adverse reaction, with the most frequently reported types being behavioral and injection site reactions. 25/539 (4.6%) of owners sought additional medical care for adverse reactions at some point during the treatment course. The overall mortality rate was 1.3% (7/556). CONCLUSIONS: This study represents the first evaluation of a heartworm treatment protocol optimized for implementation in a high-volume, outpatient community clinic setting. Our findings align with those previously reported in private practice or tertiary referral centers, illustrating that through the inclusion of pre-treatment blood work, employing short-acting or reversible sedatives, ensuring proper analgesia, minimizing the use of ancillary diagnostics, reducing the duration of in-clinic monitoring while focusing on outpatient care, and maximizing technician involvement, we can deliver effective and safe melarsomine therapy at a more affordable cost to pet owners.

Fecundity decline is male derived following transfluthrin exposures in a field strain of Aedes albopictus (Diptera: Culicidae).

Volatile pyrethroids are effective in reducing mosquito populations and repelling vectors away from hosts. However, many gaps in knowledge exist for the sublethal impacts of volatile pyrethroids on mosquitoes. To that end, transfluthrin exposures were conducted on a field strain of Aedes albopictus (Skuse) held as a laboratory colony. Dose-response analysis was conducted on both sexes at either 1-4 days old or 5-10 days old. Resultant concentration data were used to evaluate the LC20 and LC50 values in various mate pairings of treatments and controls in which either the male or female was from a selectively treated group and mated with a counterpart that was treated independently. Blood feeding proportion, delayed mortality after a 24-h recovery period, egg collection totals, and F1 larval survival were determined following transfluthrin treatment in the F0, but outcomes were not significant. In contrast, sterility was predicated on male treatment, with treated females resulting in higher overall egg viability. Treated males in the mating pair resulted in significantly lower egg viability and accelerated larval hatch in the F1. Additionally, the presence of sperm in female spermathecae was significantly diminished in test groups containing treated male mosquitoes. Male sublethal effects may be a critical determinant of a mixed population's reproductive success.

Evaluation of ultra-low volume treatments on Culex quinquefasciatus (Diptera: Culicidae) abundance and relative age by parity dissection.

St. Tammany Parish Mosquito Abatement District relies on ultra-low volume (ULV) insecticides to manage adult Culex quinquefasciatus (Say 1823), the primary vector of West Nile virus in Louisiana, but abundance rarely declines post-treatment. Three field ULV applications each of adulticides containing deltamethrin, naled, or resmethrin were conducted from May through October 2022 to measure efficacy against free-flying Cx. quinquefasciatus. Female mosquitoes trapped before and after treatment were identified, counted, and age-graded by parity dissection. No insecticide applications reduced Cx. quinquefasciatus abundance, but trials with deltamethrin and naled significantly lowered average mosquito age in the area post-treatment. No trials with resmethrin reduced mosquito age, which corroborates laboratory susceptibility data indicating local resistance toward the pyrethroid. These trials establish parity dissections and relative age gradation as a means of measuring treatment success against Cx. quinquefasciatus.

Field Evaluation of Fyfanon Ew Against Aedes Aegypti: A Low Odor Ultra-Low Volume Formulation of Malathion.

A low odor formulation of ultra-low volume (ULV) malathion (Fyfanon EW®) mosquito adulticide was evaluated in the field for its efficacy using caged female Aedes aegypti. Cages were placed in three rows, 30 m apart at 30, 60, and 90 m from the spray line. The product was applied at the manufacturer's suggested operational rate of 0.28 liter/min (9.5 fl oz/min) and at the maximum label rate of 0.37 liter/min (12.6 fl oz/min) with a Guardian 190ES truck mounted ULV sprayer. At 1 h post-treatment for the manufacturer's suggested operational rate, adult mortality ranged from 85% at 30 m to 46% at 90 m (overall average 65.5%). At 24 h post-treatment, mortality was significantly greater at each distance with complete control of caged mosquitoes at 30 m and >95% at 90 m. Overall, 24-h average mortality at this rate was 96.8%. At the maximum label rate, mosquito mortality at 1 h was considerably greater at all distances and ranged from about 89% to 75% with an overall average of 84.3%. At 24 h post-treatment, complete mortality was recorded at all transect distances at this higher rate. In conclusion, our results showed that at 24 h, Fyfanon EW® was considered very effective when applied by ULV truck mounted ground equipment for area-wide control of mosquitoes.

Uncrewed Aerial Spray Systems For Mosquito Control: Efficacy Studies For Space Sprays.

Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASSs). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASSs. The alternative is a lightweight rotary atomizer, which when run at a maximum rpm with a minimal flow rate can achieve the appropriate droplet size distribution. For this study a UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 of 48 µm and Dv0.9 of 76 µm). Spray was released from an altitude of 23 m (75 ft). The spray plume was shown to effectively disperse through the sampling zone. To achieve the appropriate application rate, the flight speed was 3 m/sec (6.7 mph) with an assumed swath of 150 m (500 ft). The objective of this project was not to conduct an operational application; instead only 1 flight line was used so that the effective swath width could be confirmed and the appropriate flightline separation defined. This study showed that control was achieved across distances of 100-150 m. Considering a swath width of 150 m (500 ft), ground deposition was 13-36% of applied material. Spray deposition corresponded well with the mortality data, which helped improve confidence in the data. The overall conclusion from this study is that aerial adulticiding is feasible with the system presented here. Further work is required to improve the atomization system to allow operational flight speeds and to determine the interaction between release altitude and droplet size in order to minimize ground deposition of application material.

Response to An Outbreak of Locally Transmitted Dengue in Key Largo, FL, by The Florida Keys Mosquito Control District.

Dengue virus (DENV) is an ever-increasing threat to the residents of South Florida. 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 (τ = 0.78, P < 0.005) and pupal (τ = 0.745, P < 0.005) 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.

UNCREWED AERIAL SPRAY SYSTEMS FOR MOSQUITO CONTROL: EFFICACY STUDIES FOR SPACE SPRAYS.

Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASSs). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASSs. The alternative is a lightweight rotary atomizer, which when run at a maximum rpm with a minimal flow rate can achieve the appropriate droplet size distribution. For this study a UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 of 48 µm and Dv0.9 of 76 µm). Spray was released from an altitude of 23 m (75 ft). The spray plume was shown to effectively disperse through the sampling zone. To achieve the appropriate application rate, the flight speed was 3 m/sec (6.7 mph) with an assumed swath of 150 m (500 ft). The objective of this project was not to conduct an operational application; instead only 1 flight line was used so that the effective swath width could be confirmed and the appropriate flightline separation defined. This study showed that control was achieved across distances of 100-150 m. Considering a swath width of 150 m (500 ft), ground deposition was 13-36% of applied material. Spray deposition corresponded well with the mortality data, which helped improve confidence in the data. The overall conclusion from this study is that aerial adulticiding is feasible with the system presented here. Further work is required to improve the atomization system to allow operational flight speeds and to determine the interaction between release altitude and droplet size in order to minimize ground deposition of application material.

Evaluation of An Aerial Application of Duet Hd® Against Aedes Dorsalis and Culex Tarsalis in Rural Habitats of the Great Salt Lake, Utah.

The Salt Lake City Mosquito Abatement District (SLCMAD) has been conducting aerial applications using an organophosphate insecticide against adult mosquitoes for several decades. In order to evaluate a potential rotation product, aerial applications of Duet HD™, a pyrethroid, were conducted under operational conditions against wild populations of Aedes dorsalis and Culex tarsalis and against colony strains of Cx. pipiens and Cx. quinquefasciatus. The erratic wind patterns of the greater Salt Lake area did not prevent sufficient droplet deposition flux at 9 monitoring locations spread across a 5,120-acre (2,072 ha) spray block within rural habitats. Three separate aerial application trials showed great efficacy against Ae. dorsalis. In contrast, Cx. tarsalis exhibited inconsistent treatment-associated mortalities, suggesting the presence of less susceptible or resistant field populations as a result of spillover from agricultural or residential pyrethroid usage. Bottle bioassays to diagnose pyrethroid resistance using field-collected Cx. tarsalis indicated that some populations of this species, especially those closest to urban edges, failed to show adequate mortality in resistance assays. Despite challenging weather conditions, Duet HD worked reasonably well against susceptible mosquito species, and it may provide a crucial role as an alternative for organophosphate applications within specific and sensitive areas. However, its area-wide adoption into control applications by the SLCMAD could be problematic due to reduced impacts on the most important arboviral vector species, Cx. tarsalis, in this area. This study demonstrates the importance of testing mosquito control products under different operational environments and against potentially resistant mosquito populations by municipal mosquito control districts.

Effects of doxycycline dose rate and pre-adulticide wait period on heartworm-associated pathology and adult worm mass.

BACKGROUND: The American Heartworm Society canine guidelines recommend treatment with doxycycline prior to adulticide administration to reduce levels of Wolbachia and its associated metabolites, which are known to be a leading cause of pulmonary pathology. Studies have determined that doxycycline administered at 10 mg/kg BID for 28 days is an effective dose for eliminating Wolbachia, but what has not been determined is the clinical relevance of this elimination. The current guidelines also recommend a 30-day wait period following administration of doxycycline to allow for clearance of metabolites, such as Wolbachia surface protein, and for further reduction in heartworm biomass before administration of adulticide. Reducing the doxycycline dose and eliminating the wait period may carry practical benefits for the animal, client, and practitioner. METHODS: To investigate these treatment practices, Dirofilaria immitis adults were surgically transplanted into each of 45 dogs, which were divided into nine study groups of five dogs each. Seventy-five days after transplantation, two groups each were administered 5, 7.5, or 10 mg/kg BID doxycycline orally for 28 days and 6 µg/kg ivermectin monthly, with three untreated groups serving as controls. Study animals were necropsied and examined prior to treatment as well as 30 and 60 days post-treatment. RESULTS: Mean worm weight was unaffected by dosage but exhibited a significant increase at 30 days and significant decrease at 60 days post-treatment, including in control groups. Histopathology lesion scores did not significantly differ among groups, with the exception of the lung composite score for one untreated group. Liver enzymes, the levels of which are a concern in doxycycline treatment, were also examined, with no abnormalities in alanine aminotransferase or alkaline phosphatase observed. CONCLUSIONS: No consistent worsening of tissue lesions was observed with or without the AHS-recommended 30-day wait period, nor did reduced dosages of doxycycline lead to worsening of pathology or any change in efficacy in depleting worm weight. Mean worm weight did significantly increase prior to, and decrease following, the wait period. Future work that also includes adulticide treatment (i.e. melarsomine) will study treatment recommendations that may improve both animal health and owner compliance.

Evaluation of field resistance in field-collected mosquito Culex quinquefasciatus Say through quantification of ULV permethrin/PBO formulation in field bioassays.

BACKGROUND: Pyrethroids are among the most applied adulticides worldwide to control mosquito vectors for prevention of arboviral diseases transmission. However, pesticide resistance development in a mosquito population could lead to decreased control efficacy. While most studies investigate the resistant genotype (i.e. kdr, CYP450, etc.) as explanatory variables, few field efficacy studies have measured pesticide quantities deposited at different distances from the sprayer in association with observed mosquito mortality. The current study determined field delivered amounts of an applied ULV permethrin/PBO formulation (31% permethrin + 66% piperonyl butoxide) by GC/MS and estimated practical resistance ratios using caged mosquito females. RESULTS: For field samples, the extraction method recovered 78 ± 3.92-108 ± 8.97% of the permethrin/PBO formulation when utilizing the peaks of PBO from GC/MS to estimate the concentrations of adulticide deposited near the mosquito cages. The field bioassay showed that the spatial distribution of permethrin/PBO formulation was heterogeneous among three pseudo-replicates within the same distance. Within the quantifiable permethrin/PBO range of 15.7-51.4 ng/cm2 , field-collected mosquito mortalities started at 64% and linearly increased reaching 100% only in two areas, while all Sebring susceptible mosquitoes died. The field LC95 resistance ratio (RR) of F0 Cx. quinquefasciatus ranged from 2.65-3.51, falling within the 95% CI of RR95 estimated by laboratory vial assays. Tests with and without PBO indicated P450's enzymes contributed to field resistance. CONCLUSION: Results showed the suitability of the collection and quantification method to estimate the field resistance ratio at the applied pesticide rate. Pesticide quantification would also allow the association of the known frequencies of resistance mechanisms (e.g. kdr, CYP450) with field mortalities to estimate the resistance level conferred by such mechanisms. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Further variation of the adulticide protocol for the treatment of canine heartworm infection: can it be even shorter and cost less?

BACKGROUND: This retrospective study evaluated modified three-dose melarsomine treatment protocols in a shelter setting and compared them to the American Heartworm Society (AHS)-recommended protocol. METHODS: As compared with the AHS protocol, the shelter protocols utilized doxycycline 10 mg/kg once daily (SID) or twice daily (BID), and varied the time from initiation of doxycycline (day 1) to the first melarsomine injection (M1). Dogs were retrospectively grouped based on the shelter's current protocol (M1 on day 14; Group A) and the AHS protocol (M1 on day 60; Group C), allowing a week on either side of the target M1 day. Treatments that fell outside these ranges formed two additional treatment groups (Groups B and D). Respiratory complications were defined as respiratory signs requiring additional treatment, and were statistically compared for Groups A and C. New respiratory signs and gastrointestinal (GI) signs were compared between dogs receiving SID or BID doxycycline. RESULTS: One hundred fifty-seven dogs with asymptomatic or mild heartworm disease at presentation were included. All dogs survived to discharge. There was no statistically significant difference between Groups A (n = 79) and C (n = 27) for new respiratory signs post-melarsomine (P = 0.73). The time to M1 for 14 dogs that developed new respiratory signs was a median of 19 days, compared with 22 days for 143 dogs without new respiratory signs (P = 0.2). Respiratory complications post-melarsomine were uncommon. New respiratory signs post-melarsomine occurred in 10/109 (9.2%) dogs receiving SID doxycycline and 4/48 (8.3%) dogs receiving BID doxycycline (P > 0.999). GI signs prior to M1 were recorded for 40/109 (36.7%) dogs receiving SID doxycycline and 25/48 (52.1%) receiving BID doxycycline (P = 0.08). Forty-four follow-up antigen test results were available; all tests performed > 3 months after the third melarsomine injection were negative. CONCLUSIONS: This study provided support for initiating melarsomine after 14 days of doxycycline and for a lower doxycycline dose. Shorter and less expensive treatment protocols can increase lifesaving capacity and improve quality of life for shelter dogs by reducing the duration of exercise restriction and length of stay.

Case report: Disseminated intravascular coagulation in a dog following treatment with melarsomine for Dirofilaria immitis.

Disseminated intravascular coagulation following melarsomine therapy for Dirofilaria immitis (D. immitis) is reported in a 9-year-old female intact pit bull-type dog. The dog had been diagnosed with D. immitis (antigen and microfilaria positive) and treated with imidacloprid, moxidectin, doxycycline and 3 doses of melarsomine over a 92-day period. Seven days after the third melarsomine injection, the patient was presented to her family veterinarian due to right pelvic limb swelling. Prothrombin and activated partial thromboplastin times were prolonged beyond the detectable range. Treatment included vitamin K1 and fresh frozen plasma (FFP) prior to referral to the authors' institution. At this time the patient remained coagulopathic. Further investigations included thoracic radiographs, abdominal ultrasound and an echocardiogram. The patient was administered multiple units of packed red blood cells and FFP, sildenafil, dexamethasone SP, aminocaproic acid and vitamin K1. Repeat CBC approximately 20 h after admission showed persistent anemia and thrombocytopenia. Despite ongoing administration of FFP, a repeat coagulation panel showed worsening of the coagulopathy with prothrombin time of 84.2s [reference interval (RI) 7.0-9.3s], activated partial thromboplastin time >140s (RI 10.4-12.9s) and fibrinogen <50 mg/dL (RI 109-311 mg/dL). Following discussion with the owners, the patient was euthanized. Necropsy was performed and confirmed heartworm infection with severe pulmonary arterial thrombosis, vascular remodeling, and intraluminal degenerate nematodes. Multifocal subcutaneous and organ hemorrhage was apparent. Although coagulopathy has been described in caval syndrome associated with heartworm disease and is listed as a potential side effect of melarsomine administration, this is the first report of documented disseminated intravascular coagulation following melarsomine treatment for D. immitis. Potential mechanisms for the coagulopathy are discussed and the case report highlights a rare, but serious complication of adulticide therapy.

Mosquito Surveillance and Insecticide Resistance Monitoring Conducted by the Florida Keys Mosquito Control District, Monroe County, Florida, USA.

Mosquito control programs in the State of Florida are charged with protecting human and animal health, fostering economic development of the State, permitting enjoyment of the natural attractions in Florida, and improving the quality of life of citizens. Mosquito control programs must accomplish these tasks in such a manner as will protect the environment and terrestrial, marine, and freshwater ecosystems. The Florida Keys Mosquito Control District provides a science-based Integrated Pest Management mosquito control program to the residents of the Florida Keys, Monroe County, Florida. Operational decisions are based on surveillance of adult and immature mosquitoes. Mosquito populations are monitored by means of carbon dioxide-baited light traps BG Sentinel traps, truck traps, gravid traps, oviposition traps, and human landing rate counts. Larvae and pupae are monitored by inspections of natural and human-made immature habitats. Due to past and current reliance on chemical pesticides for control of mosquitoes, the District maintains a pesticide resistance detection program consisting of CDC bottle bioassays and larval bioassays, challenging local mosquito species with currently used adulticides and larvicides.

Insecticidal effects of some selected plant extracts against Anopheles stephensi (Culicidae: Diptera).

BACKGROUND: The use of synthetic insecticides against mosquitoes may lead to resistance development and potential health hazards in humans and the environment. Consequently, a paradigm needs to shift towards the alternative use of botanical insecticides that could strengthen an insecticide resistance management programme. This study aimed to assess the insecticidal effects aqueous, hexane, and methanol crude leaf extracts of Calpurnia aurea, Momordica foetida, and Zehneria scabra on an insectary colony of Anopheles stephensi larvae and adults. METHODS: Fresh leaves of C. aurea, M. foetida and Z. scabra were collected and dried, then separately ground to powder. Powdered leaves of test plants were extracted using sonication with aqueous, hexane, and methanol solvents. The extracts were concentrated, and a stock solution was prepared. For comparison, Temephos (Abate®) and control solutions (a mixture of water and emulsifier) were used as the positive and negative controls, respectively. Different test concentrations for the larvae and the adults were prepared and tested according to WHO (2005) and CDC (2010) guidelines to determine lethal concentration (LC) values. Mortality was observed after 24 h exposure. The statistical analyses were performed using Statistical Package for the Social Sciences (SPSS) software (Kruskal-Wallis test) and R software (a generalized linear model was used to determine LC50 and LC90 values of the extracts). RESULTS: The lowest LC50 values were observed in aqueous extracts of M. foetida followed by Z. scabra extract and C. aurea leaves at 34.61, 35.85, and 38.69 ppm, respectively, against the larvae. Larval mortality was not observed from the hexane extracts and negative control, while the standard larvicide (temephos) achieved 100% mortality. Further, the adulticidal efficacy was greatest for aqueous extract of Z. scabra with LC50 = 176.20 ppm followed by aqueous extract of C. aurea (LC50 = 297.75 ppm). CONCLUSION: The results suggest that the leaf extracts of the three test plants have the potential of being used for the control of vector An. stephensi larvae and adult instead of synthetic mosquitocides. Further studies need to be conducted to identify the active ingredients and their mode of action.

Implicit versus explicit vector management strategies in models for vector-borne disease epidemiology.

Throughout the vector-borne disease modeling literature, there exist two general frameworks for incorporating vector management strategies (e.g. area-wide adulticide spraying and larval source reduction campaigns) into vector population models, namely, the "implicit" and "explicit" control frameworks. The more simplistic "implicit" framework facilitates derivation of mathematically rigorous results on disease suppression and optimal control, but the biological connection of these results to real-world "explicit" control actions that could guide specific management actions is vague at best. Here, we formally define a biological and mathematical relationship between implicit and explicit control, and we provide mathematical expressions relating the strength of implicit control to management-relevant properties of explicit control for four common intervention strategies. These expressions allow the optimal control and basic reproduction number analyses typically utilized in implicit control modeling to be interpreted directly in terms of real-world actions and real-world monetary costs. Our methods reveal that only certain sub-classes of explicit control protocols are able to be represented as implicit controls, and that implicit control is a meaningful approximation of explicit control only when resonance-like synergistic effects between multiple explicit controls have negligible effects on population reduction. When non-negligible synergy exists, implicit control results, despite their mathematical tidiness, fail to provide accurate predictions regarding vector control and disease spread. Collectively, these elements build an effective bridge between analytically interesting and mathematically tractable implicit control and the challenging, action-oriented explicit control.

Reduced Potential for Consecutive Truck-Mounted Ultra-Low Volume Mosquito Adulticide Applications in Chicago Metropolitan Area Due to Weather Conditions.

To increase the effectiveness of adult mosquito control, more frequent ultra-low volume (ULV) applications have been suggested. In the Chicago area, weather may be a limiting factor to more frequent applications. To investigate this, ULV adulticidal application dates from the Northwest Mosquito Abatement District during June 2011 to September 2020 were compared to historical weather data-wind and rain patterns to determine optimum conditions for conducting ULV treatments. During the 85 applications performed during 2011-20, there would have been an opportunity, based on weather conditions, for an additional consecutive night for about half (48.2%) of the time. These opportunities diminished with each additional application. The most intensive response possible would have been a spray of 5 consecutive nights, which occurred once in 3 of the 10 years investigated.

The Impact of Adulticide on Culex Abundance and Infection Rate in North Shore of Cook County, Illinois.

Mosquito surveillance is critical to reduce the risk of West Nile virus (WNV) transmission to humans. In response to surveillance indicators such as elevated mosquito abundance or increased WNV levels, many mosquito control programs will perform truck-mounted ultra-low volume (ULV) adulticide application to reduce the number of mosquitoes and associated virus transmission. Despite the common use of truck-based ULV adulticiding as a public health measure to reduce WNV prevalence, limited evidence exists to support a role in reducing viral transmission to humans. We use a generalized additive and fused ridge regression model to quantify the location-specific impact of truck-mounted ULV adulticide spray efforts from 2010 to 2018 in the North Shore Mosquito Abatement District (NSMAD) in metropolitan Chicago, IL, on commonly assessed risk factors from NSMAD surveillance gravid traps: Culex abundance, infection rate, and vector index. Our model also takes into account environmental variables commonly associated with WNV, including temperature, precipitation, wind speed, location, and week of year. Since it is unlikely ULV adulticide spraying will have the same impact at each trap location, we use a spatially varying spray effect with a fused ridge penalty to determine how the effect varies by trap location. We found that ULV adulticide spraying has an immediate temporary reduction in abundance followed by an increase after 5 days. It is estimated that mosquito abundance increased more in sprayed areas than if left unsprayed in all but 3 trap locations. The impact on infection rate and vector index were inconclusive due to the large error associated with estimating trap-specific infection rates.

A Broad-Based Mosquito Yeast Interfering RNA Pesticide Targeting Rbfox1 Represses Notch Signaling and Kills Both Larvae and Adult Mosquitoes.

Prevention of mosquito-borne infectious diseases will require new classes of environmentally safe insecticides and novel mosquito control technologies. Saccharomyces cerevisiae was engineered to express short hairpin RNA (shRNA) corresponding to mosquito Rbfox1 genes. The yeast induced target gene silencing, resulting in larval death that was observed in both laboratory and outdoor semi-field trials conducted on Aedes aegypti. High levels of mortality were also observed during simulated field trials in which adult females consumed yeast delivered through a sugar bait. Mortality correlated with defects in the mosquito brain, in which a role for Rbfox1 as a positive regulator of Notch signaling was identified. The larvicidal and adulticidal activities of the yeast were subsequently confirmed in trials conducted on Aedes albopictus, Anopheles gambiae, and Culex quinquefasciatus, yet the yeast had no impact on survival of select non-target arthropods. These studies indicate that yeast RNAi pesticides targeting Rbfox1 could be further developed as broad-based mosquito larvicides and adulticides for deployment in integrated biorational mosquito control programs. These findings also suggest that the species-specificity of attractive targeted sugar baits, a new paradigm for vector control, could potentially be enhanced through RNAi technology, and specifically through the use of yeast-based interfering RNA pesticides.