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.

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.

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.

Persistence of Mycobacterium avium subspecies paratuberculosis in endangered Florida Key deer and Key deer habitat.

Mycobacterium avium subsp. paratuberculosis (MAP) was first reported in the endangered Key deer (Odocoileus virginianus clavium) in 1996 on Big Pine Key, Florida, USA. By 2008, eight additional MAP-positive Key deer had been identified on Big Pine Key and the nearby Newfound Harbor Keys. This study was conducted to determine if MAP was still present in Key deer and whether natural or man-made freshwater sources were contaminated with MAP. Between November 2009 and September 2012, MAP was isolated from 36/369 (10%) fecal samples collected from the ground throughout the Key deer range on Big Pine Key and the Newfound Harbor Keys, but all 36 positive samples were from Little Palm Island (36/142 [25%]). Only 1/729 (0.1%) environmental samples was positive; this was from the garden fountain on Little Palm Island (1/81 [1%]). In addition, MAP was detected in 3/43 (7%) necropsied Key deer, all from Little Palm Island (3/3 [100%]). Of these three Key deer, pooled samples from the ileum, cecum, and ileocecal lymph node from two were MAP-culture positive and feces from one of these were culture-positive. The third deer was only PCR-positive. Evidence of MAP was only detected on Little Palm Island during this sampling period and environmental contamination was limited.