Resistance and inhibitor testing on Aedes aegypti (Linnaeus) (Culicidae: Diptera) populations in the Florida Keys.

Aedes aegypti is the species of greatest concern for mosquito-borne disease in the Florida Keys. Previous locally transmitted dengue outbreaks in Key West (2009-2010) and Key Largo (2020) illustrate the need for an immediate and effective response plan to maintain Ae. aegypti populations below threshold levels. An important part of the Florida Keys Mosquito Control District's vector response plan is adulticide application because it can provide an immediate reduction in Ae. aegypti adults in the community. It has become apparent that in the Florida Keys, and throughout Florida, Ae. aegypti resistance to the adulticide permethrin is prevalent. This study uses the CDC bottle bioassay method to look at resistance in Ae. aegypti collected from Key Largo, Vaca Key, and Key West, FL. Resistance was found in all three populations when exposed to permethrin and Sumithrin® but not malathion. Inhibitor testing revealed that esterase and glutathione transferase activity is involved in resistance to permethrin in Key Largo and Key West Ae. aegypti populations while oxidase activity is involved in resistance to permethrin in Ae. aegypti from Vaca Key. Lack of knockdown at the diagnostic time and previous studies detecting the presence of kdr-associated allele mutations suggest knockdown resistance in all three populations. Results from this study show that there are multiple factors involved with resistance in the Ae. aegypti populations in the Florida Keys and that resistance mechanisms vary between islands. Continued surveillance will remain important so the most effective active ingredients can be used in response to future disease transmission.

Aedes pertinax, A Lost and Found New Species Record for Monroe County, Florida.

Aedes pertinax, a little-studied tropical mosquito that has found its way into the USA, has recently been discovered to have existed in the Florida Keys for almost 25 years. A 2021 collection of Ae. pertinax adult females in Key Largo, FL, sparked a retrospective search for stored specimens collected in 1998 on Big Pine Key, FL. Positive identification of the specimens from the 1998 collection confirmed the specimens to be Ae. pertinax, predating the first reported specimen in the USA by 13 years.

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.

Ground Applications of Vectobac® WDG with A1 Super-Duty Mist Sprayer® and Micronair® AU5000 Atomizer for Suppression of Aedes aegypti Populations in the Florida Keys.

Since 2011, the Florida Keys Mosquito Control District (FKMCD) has used the WALS® application strategy with VectoBac® WDG containing Bacillus thuringiensis israelensis via helicopter in Key West for the control of Aedes aegypti larval populations. In 2018, FKMCD conducted a study to determine the effectiveness of using a trailer-mounted A1 Super Duty Mist Sprayer® (A1 Mist Sprayers) with a Micronair® AU5000 (Micron Group) atomizer to apply VectoBac WDG by ground at the rate of 0.5 lb/acre (0.56 kg/ha). Bioassay cups were placed in a residential area encompassing open, moderate, and heavy cover scenarios between 0 and 300 ft (0-91.44 m) perpendicular to the spray line. An application rate of 0.5 lbs/acre (0.56 kg/ha) was used. Bioassay cups were collected after application and returned to the laboratory where 100 ml of distilled water and 10 F1 generation Ae. aegypti larvae were added. Laval mortality was monitored at 2, 4, and 24 h. Three separate runs were completed during the summer of 2018. Average larval mortality at 24 h was >90%. The field trial demonstrated sufficient efficacy to introduce this method of larviciding into operational use.

Characterization of Pyrethroid Resistance Mechanisms in Aedes aegypti from the Florida Keys.

The status of insecticide resistance in Aedes aegypti is of concern in areas where Aedes-borne arboviruses like chikungunya, dengue, and Zika occur. In recent years, outbreaks involving these arboviruses have occurred, for which vaccines do not exist; therefore, disease prevention is only through vector control and personal protection. Aedes aegypti are present on every inhabited island within the Florida Keys. The resistance status of Ae. aegypti in the Florida Keys was assessed to guide knowledge of the best choice of chemical for use during an outbreak. Mosquito eggs were collected using ovitraps placed on Key West, Stock Island, Vaca Key, Upper Matecumbe Key, Plantation Key, and Key Largo. Bottle bioassays were conducted at the Florida Keys Mosquito Control District using Biomist® 30+30 (Clarke Mosquito Control Products, Inc., Roselle, IL). Further bottle testing using malathion and permethrin occurred at the CDC, Fort Collins, CO, in addition to molecular and biochemical assays. Levels of resistance varied between islands with different underlying mechanisms present. Resistance was seen to Biomist® 30+30 but not to permethrin, indicating that piperonyl butoxide (PBO) or the inert ingredients may be involved in resistance. No study has been conducted to date examining the role of PBO in resistance. Key Largo was treated the most with adulticides and expressed the highest levels of alpha and beta esterases, oxidases, glutathione-S-transferases, and frequency of the V1016I knockdown mutation from all sites tested. Knowledge of localized resistance and underlying mechanisms helps in making rational decisions in selection of appropriate and effective insecticides.

Dataset for mosquitoes (Diptera: Culicidae) from Vaca Key, Monroe County, Florida USA.

BACKGROUND: The Florida Keys Mosquito Control District has used dry ice-baited light traps to monitor mosquito populations on Vaca Key since 1998. The first site sampled was monitored continuously for almost 20 years until all vegetation was removed. NEW INFORMATION: This paper describes a dataset compiled over almost 20 years of continuous trapping along Manor Lane on Vaca Key, Florida.

Florida Keys Mosquito Control District Comprehensive Hurricane Plan.

The hurricane plan developed by the Florida Keys Mosquito Control District and approved by vote of the Board of Commissioners is presented. The plan is intended to facilitate prompt resumption of services after a tropical cyclone (tropical storm or hurricane) and to give direction and instructions to District staff who evacuate before a storm makes landfall. Specific procedures are documented for before and after storms, including communication, preparation of buildings and vehicles, and evacuation. The need for food and water for staff immediately after a storm is specifically mentioned in the plan. The plan is composed of five main sections: general preparedness, Lower Keys procedures, Middle Keys procedures, Upper Keys procedures, and aerial operations procedures. Also included is a section covering satellite telephone operation and a list of telephone contacts for local government and law enforcement agencies. An addendum details the District's policy for compensation for public emergency response work so all employees are aware of how they will be paid during the storm recovery period.

Dataset for mosquito collections on Big Pine Key, Florida, USA.

The Florida Keys Mosquito Control District has deployed dry ice-baited light traps to monitor mosquito (Diptera: Culicidae) populations throughout the Florida Keys starting in 1998. American Biophysics Company traps were deployed throughout the year at the same collection point. Traps were placed in the late afternoon and collected the following morning. Common mosquitoes are the black salt marsh mosquito, Aedes taeniorhynchus (Wiedemann), the crabhole mosquito, Deinocerites cancer Theobald, the Bahamian Culex, Culex bahamensis Dyar and Knab, and Anopheles atropos Dyar and Knab.

Aedes aegypti Males as Vehicles for Insecticide Delivery.

Aedes aegypti continues to spread globally and remains a challenge to control, in part due to its 'cryptic behavior' in that it often deposits eggs (oviposits) in larval habitats that are difficult to find and treat using traditional methods. Auto-dissemination strategies target these cryptic breeding sites by employing mosquitoes to deliver lethal doses of insecticide. This report describes the initial field trials of an application known as Autodissemination Augmented by Males (ADAM), utilizing A. aegypti males dusted with pyriproxyfen (PPF). Findings presented here are drawn from both caged and field trial studies. Together, these trials examined for the ability of A. aegypti males to disseminate PPF and to impact field populations. PPF-dusted males were able to effectively deliver lethal doses of PPF to oviposition sites under the conditions tested. Results from field trials in Florida and California demonstrated reduced A. aegypti populations in treated areas, compared to areas where PPF-treated males were not released. These results indicate that the release of PPF-dusted A. aegypti males can impact A. aegypti populations as measured by both reduced larval survival and lower numbers of adult female A. aegypti. We propose the ADAM approach as an addition to existing mosquito control techniques targeting A. aegypti and other mosquitoes that utilize cryptic larval habitats.

Establishment of Aedes albopictus (Diptera: Culicidae) in the Florida Keys, 2001-2017.

The presence of Aedes albopictus (Skuse) was first reported in the Florida Keys in 1993. Despite extensive surveillance, the Florida Keys Mosquito Control District (FKMCD) only collected specimens occasionally on a few islands, some years finding no evidence of the invasive species. In 2013-2017, FKMCD witnessed a sudden increase in population size and geographic extent of Ae. albopictus. Samples of Ae. albopictus have now been identified on 30 different islands in the Florida Keys. Three islands in particular (Key Largo, Big Pine Key, and Stock Island) have produced multiple positive samples during at least 4 of the last 5 yr, suggesting establishment of the invasive species. FKMCD continues to monitor Ae. albopictus throughout the Keys and make extensive efforts to reduce population abundance and geographic extent of this disease vector.

Effects of Mosquito Control Adulticides on Sterile Cochliomyia hominivorax (Diptera: Calliphoridae).

Effects of mosquito control adulticides on sterile screwworm flies, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), were investigated via bottle bioassays, outdoor cage tests, and exposure to treated vegetation. In bottle bioassays, 43 µg of permethrin via dilution of Evoluer, 474.56 µg of malathion via dilution of Fyfanon, and 25 µg of naled via dilution of Dibrom Concentrate were used to challenge screwworm flies. Permethrin was more toxic to screwworm flies than was malathion, which was more toxic than naled. On succeeding days, permethrin was still lethal to the flies, whereas malathion and naled were less toxic. During outdoor cage trials, screwworm mortality declined as distance from the spray truck increased. Sterile screwworm flies were killed by lower concentrations of permethrin needed to kill black salt marsh mosquitoes, Aedes taeniorhynchus (Wiedemann) (Diptera: Culicidae). Flies exposed to treated vegetation taken from the path of the spray cloud died more quickly than did flies exposed to leaves taken 5 ft inside the canopy. Fly mortality increased as volume mean diameter of droplets increased. In spite of the toxicity of Evoluer to screwworm flies, aspects of their biology make it unlikely that mosquito control operations would affect released flies.

A Large Scale Biorational Approach Using Bacillus thuringiensis israeliensis (Strain AM65-52) for Managing Aedes aegypti Populations to Prevent Dengue, Chikungunya and Zika Transmission.

BACKGROUND: Aedes aegypti is a container-inhabiting mosquito and a vector of dengue, chikungunya, and Zika viruses. In 2009 several cases of autochthonous dengue transmission were reported in Key West, Florida, USA prompting a comprehensive response to control A. aegypti. In Key West, larvae of this mosquito develop in containers around human habitations which can be numerous and labor intensive to find and treat. Aerial applications of larvicide covering large areas in a short time can be an efficient and economical method to control A. aegypti. Bacillus thuringiensis israelensis (Bti) is a bacterial larvicide which is highly target specific and appropriate for wide area spraying over urban areas, but to date, there are no studies that evaluate aerial spraying of Bti to control container mosquitoes like A. aegypti. METHODOLOGY: This paper examines the effectiveness of aerial larvicide applications using VectoBac® WG, a commercially available Bti formulation, for A. aegypti control in an urban setting in the USA. Droplet characteristics and spray drop deposition were evaluated in Key West, Florida, USA. The mortality of A. aegypti in containers placed under canopy in an urban environment was also evaluated. Efficacy of multiple larvicide applications on adult female A. aegypti population reduction was compared between an untreated control and treatment site. CONCLUSIONS: Droplet characteristics showed that small droplets can penetrate through dense canopy to reach small containers. VectoBac WG droplets reached small containers under heavy canopy in sufficient amounts to cause > 55% mortality on all application days and >90% mortality on 3 of 5 application days while controls had <5% mortality. Aerial applications of VectoBac WG caused significant decrease in adult female populations throughout the summer and during the 38th week (last application) the difference in adult female numbers between untreated and treated sites was >50%. Aerial larvicide applications using VectoBac WG can cover wide areas in a short period of time and can be effective in controlling A. aegypti and reducing A. aegypti-borne transmission in urban areas similar to Key West, Florida, USA.

Description of a New Species of the Genus Psectrosciara and a New Record of Parascatopse sonorensis (Diptera: Scatopsidae) From Florida.

Psectrosciara floridensis sp. nov. belonging to the scatopsiformis group is described and illustrated. This species is closely related to Psectrosciara scatopsiformis Enderlein, 1912, Psectrosciara californica (Cole, 1912), Psectrosciara brevipennis Cook, 1958, and Psectrosciara serrata Cook, 1958. A new record of Parascatopse sonorensis Cook is reported from the state of Florida.

Larviciding offshore islands reduces adulticidal treatment of populated areas adjacent to national wildlife refuges.

The Florida Keys Mosquito Control District has conducted larvicide missions on uninhabited offshore islands of the Great White Heron National Wildlife Refuge and the National Key Deer Refuge since 2003. The objective of these missions is to reduce the need to apply adulticides on nearby populated islands where private lands are interspersed with refuge lands that support a diverse assemblage of native butterflies and insect-pollinated plants on Big Pine Key, No Name Key, Little Torch Key, Middle Torch Key, and Big Torch Key (the Torch Keys). More than 800 visits were made to refuge islands by Florida Keys Mosquito Control District personnel; 334 aerial larvicide missions were flown. From 2003 to 2010, a marked reduction in adult mosquito numbers was seen on Big Pine Key, and to a lesser extent on No Name Key. Seasonal distribution of mosquitoes was not different, however. Number of aerial adulticide missions flown on Big Pine Key, No Name Key, and the Torch Keys was 2, 1, and 2 in 2003; 9, 10, and 7 in 2004; 4, 4, and 2 in 2005; 6, 6, and 7 in 2006; 1, 0, and 0 in 2007; 3, 2, and 4 in 2008; 4, 3, and 4 in 2009; and 1, 1, and 3 in 2010, respectively. This is a dramatic reduction from prior years; from 1998 to 2002, 57 aerial adulticide missions were flown on Big Pine Key, 45 missions were flown on No Name Key, and 38 on the Torch Keys. Larviciding is an important component of an integrated approach to mosquito management that seeks to reduce environmental impacts on the national wildlife refuges.

The association between meteorological variables and the abundance of Aedes taeniorhynchus in the Florida Keys.

The black salt marsh mosquito, Aedes taeniorhynchus, is a serious nuisance pest and a potential vector of a number of arboviruses. This study examined the effect of wind direction, wind speed, temperature, and time of year on the abundance of Ae. taeniorhynchus collected in CO2 -baited light traps at 12 sites in the Florida Keys during 2004. The dependent variable analyzed was the natural log of weekly mosquito abundance. The previous week's wind speed and wind direction, and the current week's temperature were used as independent variables. Simple and multiple linear regression models were used to assess the significance and nature of association between the meteorological variables and the natural log of mosquito abundance, and to determine whether the meteorological variables had significant associations with mosquito abundance after also controlling for time of year. Week of year was treated as a circular independent variable in the regression models, using the sine and cosine of week in radians to model the periodic seasonal fluctuation in mosquito abundance. Mosquito abundance was significantly associated with all meteorological variables and with week of year. Individually, previous week's wind speed and wind direction, and current week's temperature were able to explain respectively 24.5%, 24.5%, and 52.1% of the variation in mosquito abundance observed over the year. Week of year had the strongest individual association with mosquito abundance, explaining 65.7% of the variation in mosquito abundance. The meteorological variables were still significantly associated with mosquito abundance, after controlling for week of year. Week and the meteorological variables together explained 79.2% of the variation in mosquito abundance. The regression models fit to the data from this study suggest a strong periodic seasonal variation in mosquito abundance, with meteorological conditions explaining a significant portion of the variation beyond the seasonal trend.

Mosquito fauna of wilderness islands within the National Key Deer Refuge and the Great White Heron National Wildlife Refuge, Monroe County, Florida.

Dry ice-baited light traps, counts of mosquitoes biting and landing on technicians, and larval surveillance were used to determine mosquito species abundance on Annette Key, Little Knockem-down Key, Little Pine Key, Raccoon Key, and the Water Keys, all of which are located offshore, within the National Key Deer Refuge and Great White Heron National Wildlife Refuge in Monroe County, FL. Due to the close proximity of these wilderness islands to the inhabited islands of the Florida Keys, it is important to understand the abundance and composition of the mosquitoes and the effects they may have on populations on inhabited islands. Thirty different species were collected during 2004-2008. Aedes taeniorhynchus, the black salt-marsh mosquito, was the most abundant mosquito species collected at all locations. Other mosquitoes collected in large numbers at all locations were Anopheles atropos, Culex bahamensis, Cx. nigripalpus, and Deinocerites cancer. Because these wilderness islands are difficult to traverse due to vegetative growth, the placement of mosquito traps close to the perimeter of the islands may influence assessment of the abundance and diversity of mosquito species collected on each island.

Mosquito fauna of Key Largo, Florida.

A total of 28 species of mosquitoes was collected in dry-ice-baited light traps on Key Largo, Florida during 2002-2004. Total number of mosquitoes increased each year during the study.

Potential for North American mosquitoes to transmit Rift Valley fever virus.

The rapid spread of West Nile viral activity across North America since its discovery in 1999 illustrates the potential for an exotic arbovirus to be introduced and widely established across North America. Rift Valley fever virus (RVFV) has been responsible for large outbreaks in Africa that have resulted in hundreds of thousands of human infections and major economic disruption due to loss of livestock and to trade restrictions. However, little is known about the potential for North American mosquitoes to transmit this virus should it be introduced into North America. Therefore, we evaluated selected mosquito species from the southeastern United States for their ability to serve as potential vectors for RVFV. Mosquitoes were fed on adult hamsters inoculated 1 day previously with RVFV. These mosquitoes were tested for infection and ability to transmit RVFV after incubation at 26 degrees C for 7-21 days. None of the species tested (Aedes taeniorhynchus, Ae. vexans, Culex erraticus, Cx. nigripalpus, Cx. quinquefasciatus, and Cx. salinarius) were efficient vectors after they fed on hamsters with viremias ranging from 10(4.1) to 10(6.9) plaque-forming units (PFU)/ml. However, Ae. taeniorhynchus, Ae. vexans, and Cx. erraticus all developed disseminated infections after they fed on hamsters with viremias between 10(8.5) and 10(10.2) PFU/ml, and both Ae. vexans and Cx. erraticus transmitted RVFV by bite. These studies illustrate the need to identify the ability of individual mosquito species to transmit RVFV so that appropriate decisions can be made concerning the application of control measures during an outbreak.