Kenneth H. Posey

Synergistic Attraction of Aedes aegypti (L.) to Binary Blends of L-Lactic Acid and Acetone, Dichloromethane, or Dimethyl Disulfide

Abstract Kairomones produced by humans provide female anthropophilic mosquitoes with vital cues used in host-seeking for a blood meal. These chemicals are emanated primarily by the skin and provide the mosquitoes a means to orient themselves to humans at a relatively close range. Chemical studies of these emanations have provided new ideas for the formulation of attractant blends. We report mosquito attraction responses for three binary blends and their separate components. The blends are comprised of L-lactic acid plus either acetone, dichloromethane, or dimethyl disulfide. At the emission rates used in our bioassays, these blends synergistically attract laboratory-reared female Aedes aegypti. Carbon dioxide is not a necessary component to yield high levels of attraction with these blends. It is postulated that at least one of these synergistic blends (L-lactic acid and acetone) produces mosquito attraction behavior similar to L-lactic acid and CO2.

Mosquito density, biting rate and cage size effects on repellent tests.

Mosquito biting rates and the mean duration of protection (in hours) from bites (MDPB) of Aedes aegypti and Anopheles quadrimaculatus, using the repellent ‘deet’ (N,N‐diethyl‐3‐methylbenzamide) on a 50 cm2 area of healthy human skin, were observed in small (27 l), medium (≈65 l) and large (125 l) cages containing low, medium or high densities of mosquitoes: respectively, 640, 128 or 49 cm3 of cage volume per female. At the initial treatment rate of ≈ 0.4 μl/cm2 (1 ml of 25% deet in ethanol on 650 cm2 of skin), the MDPB for deet against Ae.aegypti ranged from 4.5 to 6.5 h and was significantly less (5.0 ± 0.8 h) in large cages compared with medium (6.2 ± 0.9 h) and small (6.2 ± 0.8 h) cages, regardless of the density. Against An.quadrimaculatus the MDPB for deet 0.4 μl/cm2 was 1.5–8.0 h, less in small (3.7 ± 2.3 h) and large (2.2 ± 1.1 h) cages at medium (3.7 ± 2.3 h) and high (2.5 ± 1.7 h) mosquito densities, and was longest in medium cages (6.2 ± 2.6 h) at low mosquito densities (5.8 ± 2.8 h). With equinoxial photoperiodicity (light on 06.00–18.00 hours) the biting rate was influenced by the time of observation (08.00, 12.00, 16.00 hours) for Ae.aegypti but not for An.quadrimaculatus. For both species, the biting rate was inversely proportional to mosquito density and the MDPB. The shortest MDPBs were obtained in large cages with high densities of mosquitoes and longest protection times occurred in medium sized cages with low mosquito densities.

Olfactometer and Large Cage Evaluation of a Solid Phase Technology for the Controlled Production of CO2

ABSTRACT New technology by ICA for chemical generation of carbon dioxide (CO2) was evaluated in olfactometer and large outdoor cage tests against laboratory-reared Aedes aegypti for potential use in mosquito surveillance programs. The proprietary CO2 generation system consists of a poly-Tyvek® sachet containing 2 solid ingredients. Activated sachets immediately react to generate and release predictable levels of CO2 over time. In noncompetitive olfactometer studies, a freshly activated sachet attracted an average ± SE of 96.6 ± 0.9% of the available mosquitoes compared with 20.2 ± 6.5% for 5 ml/min CO2 released from a compressed gas cylinder. In competitive tests, the sachet attracted 92.4 ± 1.2% compared with 0.9 ± 0.5% for the compressed gas. In the olfactometer, aged sachets attracted >90% of the available mosquitoes up to 8 h and ca. 27% 1 wk after activation. In the large outdoor cages, traps baited with activated sachets captured 2.2–5.4 times as many mosquitoes as unbaited traps, depending on time of testing after activation.