Aerial ULV control of Aedes aegypti with naled (Dibrom) inside simulated rural village and urban cryptic habitats

Abstract

We conducted aerial fixed wing ultra low volume (ULV) spray trials with naled to investigate penetration of exposed and simulated cryptic habitat within opened buildings, partially sealed buildings, and outdoor locations targeting sentinel adult Aedes aegypti mosquitoes in north central Florida. Mortality was observed in open and closed buildings and outdoors, even in mosquitoes placed in cryptic habitats. Observations on the impact of building type, mosquito exposure method such as placement in cryptic habitat, and spray nozzle size on mosquito mortality are described and analyzed.

Fig 1. Overview image of the study area.

Image shows the position of Controls near the intersection of State Road 21 and County Road 315 (upper right) and the MOUT South, Village, and two road Transect spray areas with positioning of weather recorders. Each Transect spray area consists of 10 sentinel/spinner positions, with 5 positions placed on each side of either MOUT South (R11–R20) or Village (R31–R40) spray areas. Inset Florida state maps at upper left show location of the Camp Blanding Joint Training Center (yellow boundary) and indicate position of study area. The overview also shows the approximate locations of the two sets of 6 upwind swaths and the prevailing wind direction for 29–30 October 2013. Inset images on the mid- and lower right side show detailed views of MOUT South and Village with building names and indications to show which ones were closed up or had courtyard walls present. Inset photo at mid-left shows spray trails from C-130H fuselage booms during one of the applications. Additional detailed maps are in Figure Sets A–J in S1 Fig. Maps were created using ArcGIS software by Esri under license as described in S2 File.

Fig 2. Representative views of MOUT South and Village structures, building interiors, and surrounding habitat.

(A) Meat Market, Bazaar, and Holiday Hotel buildings at MOUT South. Inset shows typical interior, with shutters opened and closed. (B) Buildings 2 and 3 at the Village. Note lack of doors or windows, and inset shows typical interior with window openings lacking shutters.

Fig 3

Example of indoor (A), outdoor (B), and road Transect (C) arrangements of adult Aedes aegypti sentinel cages with adjacent FLB spinners. Indoor and outdoor examples were photographed at MOUT South structures. “Protected” sentinel mosquito locations consist of 1 ft³ cardboard boxes with ⅜-in holes drilled in all exposed sides, with the boxes left partially opened and placed on their sides. “Unprotected” locations consist of placement of sentinel mosquito cages indoors directly on the floor of buildings, or outdoors at the base of a tread-in post.

Fig 4. Mean 12 hr sentinel Ae. aegypti percent mortality in MOUT South and Village outdoor and indoor protected (“in box”) and unprotected (“on pole” or “on floor”) locations across both days.

Non-zero mortality values in all locations across both days confirmed that the aerially applied material reached throughout the MOUT South and the Village sites and penetrated buildings and experimental refugia. Each histogram for each of the four cage location types at each site for each trial was based on percent mortality data from 20 sentinel cages.

Fig 5. Efficacy maps of 12 hr interpolated mortality data.

These maps represent spray efficacy for (A) indoor unprotected (“outside boxes”) and (B) outdoor protected (“inside boxes”) sentinel cage locations at Village on (left) 29 October (8001 nozzles) and (right) 30 October (8003 nozzles). These interpolated “heat maps” show a range of mortality from very low (blues and light greens) to very high (oranges and reds). The aircraft silhouette symbol shows the actual size, position, and flightpath of the first upwind swath of the C-130H relative to the map scale. Additional efficacy maps of interpolated mortality data for all sentinel cage locations in all trials are shown in Figure Sets A–D in S1 Fig. Maps were created using ArcGIS software by Esri under license as described in S2 File.