FDACS Project P0010729 Final Report: September 2017
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FDACS Project P0010729 Final Report: September 2017 1 Project Title: Toxicity of Vapor Active Insecticides for Multi-Vector Control 2 3 Principle Investigator: Phillip E. Kaufman, PhD 4 Co-Principle Investigator: Christopher S. Bibbs, PhD Student 5 6 Project Objectives: 7 1. Determine informative concentrations of active ingredient that include metofluthrin, 8 transfluthrin, prallethrin, and flumethrin to determine vapor toxicity against Aedes albopictus, an 9 initial screening species. 10 2. Utilize the informative concentration ranges determined in Objective 1 to replicate the vapor 11 activity bioassays using the four candidate insecticides against three additional vector-capable 12 mosquito species. 13 3. Replicate the vapor activity bioassays and analysis with a fifth candidate insecticide, 14 meperfluthrin, against all prior tested vector-capable mosquito species. 15 1 FDACS Project P0010729 Final Report: September 2017 16 ABSTRACT Objectives 1 and 2 were completed ahead of schedule, so an additional objective 17 was created in adding meperfluthrin to vapor bioassays. Volatile pyrethroid compounds are 18 among the tools commercially dubbed “spatial repellents.” Spatial repellents have been 19 advocated for urban vector management, and there is environmental overlap between mosquitoes 20 found in domestic settings and people that use spatial repellents for outdoor protection. Recent 21 research on several of these spatial repellents indicated considerable adulticidal action. With the 22 idea that these pyrethroid chemicals kill adult mosquitoes, metofluthrin, meperfluthrin, 23 transfluthrin, prallethrin, and flumethrin were evaluated against Aedes albopictus Skuse and 24 Aedes aegypti (L.), Culex pipiens quinquefasciatus Say, and Anopheles quadrimaculatus Say. 25 Dose response LC50 and LC90 data were obtained and analyzed for Ae. albopictus, Ae. aegypti, 26 Cx. quinquefasciatus, and Anopheles quadrimaculatus. It has been determined that transfluthrin 27 vapors had the highest overall toxicity against the four species. Meperfluthrin and metofluthrin 28 vapors demonstrated comparable toxicity. Prallethrin and metofluthrin vapors were similarly 29 toxic against Ae. albopictus, but prallethrin was less toxic than metofluthrin against the other 30 species. Flumethrin was the least toxic against all tested species. 31 32 This project is applicable to the following three Florida Coordinating Council on Mosquito 33 Control research 2016 priorities (rank): 34 1. Pesticide- Efficacy/ Resistance (1) 35 2. Domestic Mosquito Control (3) 36 3. Application- Adulticides (8) 37 2 FDACS Project P0010729 Final Report: September 2017 38 INTRODUCTION 39 Domestic mosquito species, particularly Aedes albopictus Skuse and Aedes aegypti (L.), 40 provoke high levels of nuisance due to their cryptic oviposition that limits mosquito control 41 district treatment options. This is compounded by short flight ranges increasing the localized 42 human contact with these mosquitoes, and low resource demand for these species to reach high 43 numbers, as evidenced by breeding in shallow containers common across domestic properties. 44 These mosquitoes are also the associated vectors for dengue, chikungunya, and Zika viruses 45 (Derraik and Slaney 2015, Ngoagouni et al. 2015, Wilson and Chen 2015). This elevates the risk 46 of emerging pathogen establishment. Domestic risks also extend to Culex pipiens 47 quinquefasciatus Say, which is a ubiquitous urban vector of St. Louis encephalitis virus and 48 West Nile virus, and whose immatures develop in ditches and urban drain infrastructure (Noori 49 et al. 2015). Recently, this species has been suspected to have compatibility with Zika virus in a 50 laboratory study (Ayres 2016). Due to expansive residential development into swampland and 51 estuarine habitat in Florida, Anopheles spp. mosquitoes also are common species of interest in 52 such landscapes, with Anopheles quadrimaculatus Say being the most important U. S. species 53 tied to malaria transmission (Rutledge et al. 2005). Local malaria transmission occasionally 54 occurs, with Palm Beach County, FL being a Florida example (CDC 2003). 55 These examples demonstrate the importance of citizen awareness of risk and the 56 recognition of their employing personal protective solutions to supplement existing mosquito 57 control operations. Mosquito control programs recruit the citizen base as part of this 58 supplementation to be involved in mosquito habitat identification and source reduction (Marciel- 59 de-Freitas and Lourenço-de-Oliveira 2011, Dowling et al. 2013, Fonesca et al. 2013). However, 60 the citizen base also can choose to supplement their vector prevention with over-the-counter 61 pesticides. Among those available tools, volatile pyrethroid compounds, or “spatial repellents,” 3 FDACS Project P0010729 Final Report: September 2017 62 have been advocated for urban vector management (Ritchie and Devine 2013). It is important to 63 evaluate the chemicals these consumers use for this supplemental effort. 64 Volatile pyrethroid compounds provide protection in an area well outside the source of 65 chemical dispersion (Achee et al. 2012, Kline and Strickman 2015) and are a marketing 66 alternative to topical repellents that garner favorable usage by citizens (Kline and Strickman 67 2015). By contacting target vectors in a gaseous state, as opposed to the liquid droplets employed 68 by the vast array of mosquito control operations, several different and beneficial properties are 69 achieved in their use. The marketing drive for their use revolves around repellency. Some 70 compounds exhibit repellency, such as metofluthrin repelling Ae. albopictus (Argueta et al. 71 2004), and prallethrin repelling Cx. quinquefasciatus and Culex tritaeniorhynchus Giles (Liu et 72 al. 2009). More consistently, these and similar compounds instigate a confusion or disorientation 73 in vectors including Ae. aegypti (Achee et al. 2009, Ritchie and Devine 2013). Some research 74 studies have reported mosquito mortality following use of these compounds, such as in Ae. 75 aegypti exposure to metofluthrin (Bibbs and Xue 2015, Ritchie and Devine 2013), Ae. albopictus 76 exposure to transfluthrin (Lee 2007), and Anopheles albimanus, Cx. quinquefasciatus, and Ae. 77 albopictus exposure to metofluthrin (Xue et al. 2012). 78 There is a need to measure the toxicity of volatile pyrethroids strictly in the vapor phase 79 to maximize the possibility of these chemicals preventing vector-borne pathogen transmission. 80 Being that volatile pyrethroids already have a pre-existing market in public-use products, a 81 systematic approach comparing the toxicity of candidate vapor active chemicals in a single study 82 may guide future use of these compounds and will provide valuable information to the end user. 83 This project will provide efficacy data on several available volatile pyrethroid compounds 84 against a variety of common domestic vector threats. This would provide an assessment on 4 FDACS Project P0010729 Final Report: September 2017 85 whether these compounds are detrimental or supplemental to the efforts of Florida mosquito 86 control programs, information that will be quite valuable as Florida continues to face the pending 87 arrival of vector-borne threats. 88 MATERIALS AND METHODS 89 Mosquitoes. Mosquito species used in this study were pyrethroid susceptible strains 90 acquired from the United States Department of Agriculture, Agricultural Research Service, 91 Center for Medical, Agricultural, and Veterinary Entomology (USDA-ARS-CMAVE) in 92 Gainesville, Florida. The strains used were the 1952 Orlando, FL, strain Ae. aegypti; 1998 93 Gainesville, FL, strain Ae. albopictus; 1952 Orlando, FL, strain Cx. quinquefasciatus; and 1952 94 Orlando, FL, strain An. quadrimaculatus. Mosquito strains were not exposed to insecticides prior 95 to evaluation and were not supplemented with wild-type introductions to the colonies. Rearing 96 conditions consisted of 26.6 °C, 85 ± 5% relative humidity (RH), with a photoperiod of 14:10 97 (L:D). Batches of 2,000 eggs were placed in larval pans containing 2,500 ml of reverse osmosis 98 (RO) water. Larvae were fed 1-3 g of liver and yeast mixture at a 3:2 ratio ad libitum in a 50-ml 99 suspension. Adult mosquitoes were kept in flight cages containing separate supplies of 10% 100 sucrose solution and reverse osmosis (RO) water. Subjects used in experiments were non-blood- 101 fed, 5-7 day-old female mosquitoes. 102 Chemicals. Technical grade prallethrin (32917 Pestanal, Sigma-Aldrich Co. LLC, St. 103 Louis, MO), flumethrin (N-13139, Chem Service, Inc., West Chester, PA), transfluthrin (N- 104 13626, Chem Service, Inc., West Chester, PA), meperfluthrin (32065 Pestanal, Sigma-Aldrich 105 Co. LLC, St. Louis, MO), and metofluthrin were selected for this test. Metofluthrin was 106 extracted from OFF! Clip-on over-the-counter refill packs (31.2% metofluthrin, S. C. Johnson & 107 Son, Racine, WI) using pentane. Extracts were fractionated using automated flash 5 FDACS Project P0010729 Final Report: September 2017 108 chromatography (CombiFlash Rd 200i, Teledyne ISCO, Lincoln, NE) (Fig. 1) with simultaneous 109 electrospray ionization mass spectrometry (ESI-MS/MS) (Expressions CMS, Advion, Inc., 110 Ithaca, NY) (Fig. 2). Fractions were delivered using pentane as the non-polar solvent and ethyl 111 ether as the polar solvent at a 10 ml/min flow rate and a 5 ml peak runtime. Solvent was reduced 112 in a rotary evaporator and the resultant technical grade product