Residual Effectiveness of Permethrin-Treated Clothing for Prevention of Mosquito Bites Under Simulated Conditions.

Biological hazards such as exposure to ticks and mosquitoes can affect health. Permethrin-treated clothing is available to the public. We don't currently understand, however, the effects of environmental factors such as fabric type, washing, sunlight, and temperature on permethrin content in treated clothing with respect to mosquito knockdown and mortality. We evaluated the extent to which fabric type (100% cotton denim jeans, 100% polyester work shirt, 35% cotton/65% polyester work shirt), light exposure (0 or 100%), temperature (18 °C, 32 °C), and number of washes (0, 3, 12, 36) affected mosquito knockdown 2 hours post-exposure, mosquito mortality 24 hours post-exposure, and permethrin content. All fabrics used in this study were treated with permethrin at a concentration of 125 µg/cm2. Denim fabric having no washes and no light exposure showed the highest amount of permethrin. Washing and light exposure significantly reduced the ability of permethrin-treated fabrics to induce mosquito knockdown and/or mortality under the simulated conditions used for this test. Temperatures tested did not affect permethrin content or mosquito knockdown and mortality. Long-lasting impregnation of uniforms protects against mosquito bites under simulated laboratory conditions. Employers and employees should consider the use of permethrin-impregnated clothing and uniforms in addition to daily repellent sprays.

Effects of Blood Coagulate Removal Method on Aedes albopictus (Diptera: Culicidae) Life Table Characteristics and Vector Competence for Dengue Virus.

Commercially available blood can be used as an alternative to live animals to maintain mosquito colonies and deliver infectious bloodmeals during research studies. We analyzed the extent to which two methods for blood coagulate removal (defibrination or addition of sodium citrate) affected life table characteristics (i.e., fecundity, fertility, hatch rate, and adult survival) and vector competence (infection, dissemination, and transmission) of Aedes albopictus (Skuse) for dengue virus (DENV). Two types of bovine blood were tested at two extrinsic incubation temperatures (27 or 30°C) for DENV-infected and uninfected mosquitoes. Fully engorged mosquitoes were transferred to individual cages containing an oviposition cup and a substrate. Eggs (fecundity) and hatched larvae (fertility) were counted. At 14 and 21 d post feeding on a DENV-infected bloodmeal, 15 mosquitoes were sampled from each group, and vector competence was analyzed (bodies [infection], legs [dissemination], and saliva [transmission]). Differences in life table characteristics and vector competence were analyzed for mosquitoes fed blood processed using different methods for removal of coagulates. The method for removal of coagulates significantly impacted fecundity, fertility, and hatch time in the uninfected group, but not DENV-infected group. Infected mosquitoes showed significantly higher fecundity and faster hatch time than uninfected mosquitoes. We show no significant differences in infection or dissemination rates between groups; however, horizontal transmission rate was significantly higher in mosquitoes fed DENV-infected citrated compared with defibrinated blood. We expect the findings of this study to inform research using artificial blood delivery methods to assess vector competence.

Further evidence against a momentum explanation for IOR.

Reaction times to targets presented in the same location as a preceding cue are greater than those to targets presented opposite the cued location. This observation can be explained as a result of inhibition at the attended location (IOR), or as facilitation at the location opposite the cue (opposite facilitation effect or OFE). Past research has demonstrated that IOR is observed reliably, whereas OFE is observed only occasionally. The present series of four experiments allows us to determine whether or not OFE can be explained by eye movements as suggested by previous authors. Participants' eye movements were monitored as they were presented with an array of four placeholders aligned with the four cardinal axes. Exogenous cues and targets were presented successively. Participants (N=37) completed either: i.) cue-manual and cue-saccade experiments, ignoring the cue and then responding with a keypress or saccade, respectively, or ii.) manual-manual and saccade-saccade experiments, responding to both the cue and the target with a keypress or saccade respectively. Results demonstrated a reliable IOR effect in each of the four experiments (reaction time greater for same versus adjacent and opposite cue-target trials). None of the four experiments demonstrated evidence of an OFE (reaction times were not significantly lower for opposite versus adjacent cue-target trials). These results are inconsistent with a momentum-based account of cue-target task performance, and furthermore suggest that the OFE cannot be attributed to occasional eye movements to the cue and/or target in previous studies.

Emergency mosquito control on a selected area in eastern north Carolina after hurricane irene.

Natural disasters such as hurricanes may contribute to mosquito abundance and, consequently, arbovirus transmission risk. In 2011, flooding from Hurricane Irene in eastern North Carolina (NC) resulted in increased mosquito populations that hindered recovery efforts. Budget shortfalls in NC have reduced the functionality of long-term mosquito surveillance and control programs; hence, many counties rely on the Federal Emergency Management Agency for post-disaster mosquito control. This pilot study examines mosquito abundance pre- and post-aerial insecticide spraying at eight study sites in Washington and Tyrrell Counties in rural eastern NC after Hurricane Irene. Percent change was calculated and compared for traps in areas that received aerial pesticide application and those that did not. Traps in spray zones show decreases in mosquito abundance when compared to control traps (treatment: -52.93%; control: 3.55%), although no significant differences (P = 0.286) were found in mosquito abundance between groups. Implications of reactive rather than proactive mosquito control responses are discussed.