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Learning and memory in the mosquito Aedes aegypti shown by conditioning against oviposition deterrence.

Oviposition site choice by female mosquitoes, Aedes aegypti (L) (Diptera: Culicidae), was affected by rearing them in water treated with 0.016% of the repellent Mozaway trade mark containing citronella and neem. Given a choice between a bowl of repellent-treated and a bowl of untreated water, Ae. aegypti reared in untreated water strongly preferred to oviposit on the clean water (93-98%) instead of repellent-treated water. This demonstrates effective deterrence of oviposition by dilute Mozaway trade mark. Those reared in repellent-treated water were less deterred: 38-46% of their eggs were laid on the repellent-treated water and 54-62% on the clean water. Evidently the female mosquitoes reared in repellent-treated water were conditioned against oviposition site deterrence, as shown when choice tests were conducted 6 days post-emergence from the treated water. This demonstrates learning and memory in the mosquito Ae. aegypti, with implications for dengue vector surveillance and control.

Aedes↗

A novel high-throughput screening system to evaluate the behavioral response of adult mosquitoes to chemicals.

A modular and novel assay system for rapid mass screening of chemical compounds for contact irritant and spatial repellent actions against adult mosquitoes is described. The responses of Aedes aegypti to various concentrations of 3 topical repellents, deet, Bayrepel, and SS220, were evaluated. At treatment concentrations > or = 25 nmol/cm2 of SS220, mosquitoes exhibited significant contact irritant (escape) and spatial repellent (movement away from the chemical source) responses, whereas, a 10-fold increase in the treatment concentration of deet and Bayrepel was required to produce similar responses. The novel bioassay system detected contact irritancy and spatial repellency activity with reproducible results and provided baseline data for determining minimum effective concentrations for other chemicals. The system is compact in size, easy to decontaminate, and requires only a minute quantity of chemical compound.

Aedes↗

Oviposition response of Aedes aegypti mosquitoes to different concentrations of hay infusion in Trinidad, West Indies.

Ovitraps containing various concentrations of hay infusion and tap water were exposed weekly in the field for 15 wk to determine the oviposition patterns of Aedes aegypti. The results showed 10, 20, 60 and 80% hay infusions each attracted similar numbers of Ae. aegypti eggs oviposited and egg occurrences. No repellent effect was observed. In another field study, significantly more eggs and egg occurrences were collected from 25 and 50% hay infusions and tap water. The differences in these results from those of a previous study in Puerto Rico are discussed.

Aedes↗

Repellent activity of Ferronia elephantum Corr. (Rutaceae) leaf extract against Aedes aegypti (L.).

The repellent activity of a methanol extract of Ferronia elephantum leaves against Aedes aegypti was studied in the laboratory. The percentage protection in relation to the dose method was used. The repellent activity at 1.0 and 2.5 mg/cm2 concentrations gave 100% protection up to 2.14 +/- 0.16 h and 4.00 +/- 0.24 h, respectively. The total percentage protection of Ferronia elephantum was 45.8% at 1.0 mg/cm2 and 59.0% at 2.5 mg/cm2 for 10 h.

Aedes↗

Impacts of residual insecticide barriers on perimeter-invading ants, with particular reference to the odorous house ant, Tapinoma sessile.

Three liquid insecticide formulations were evaluated as barrier treatments against perimeter-invading ants at a multifamily housing complex in West Lafayette, IN. Several ant species were present at the study site, including (in order of abundance) pavement ant, Tetramorium caespitum (L.); honey ant, Prenolepis imparis (Say); odorous house ant, Tapinoma sessile (Say); thief ant, Solenopsis molesta (Say); acrobat ant, Crematogaster ashmeadi (Mayr); crazy ant, Paratrechina longicornis (Latrielle), field ants, Formica spp.; and carpenter ant Camponotus pennsylvanicus (DeGeer). Studies began in May 2001 and concluded 8 wk later in July. Individual replicate treatments were placed 0.61 in (2 feet) up and 0.92 m (3 feet) out from the ends of 46.1 by 10.1-m (151 by 33-foot) apartment buildings. Ant sampling was performed with 10 placements of moist cat food for 1 h within treatment zones, followed by capture and removal of recruited ants for later counting. All treatments led to substantial reductions in ant numbers relative to untreated controls. The most effective treatment was fipronil, where 2% of before-treatment ant numbers were present at 8 wk after treatment. Both imidacloprid and cyfluthrin barrier treatments had efficacy comparative with fipronil, but to 4 and 2 wk, respectively. Odorous house ants were not sampled before treatment. Comparisons of ant species composition between treatments and controls revealed an increase in odorous house ant frequencies at 1-8 wk after treatment in treated locations only. These results demonstrate efficacy for both nonrepellent and repellent liquid insecticides as perimeter treatments for pest ants. In addition, our findings with odorous house ant highlight an apparent invasive-like characteristic of this species that may contribute to its dramatic increase in structural infestation rates in many areas of the United States.

Animals↗

Mosquito repellents and superwarfarin rodenticides--are they really toxic in children?

PURPOSE OF REVIEW: In many United States households, there are many substances used to control the exposure of our children to mosquitoes, mice and rats. This review provides information on common mosquito repellents and rodenticides used in households and discusses their toxicity, in order to help pediatricians better advise their patients of their proper use. RECENT FINDINGS: A recent study has demonstrated that many continue to have practices of applying DEET (N,N-diethyl-3-methylbenzamide) based repellents that may lead to undesirable effects. Picaridin and oil of lemon eucalyptus are two products that have recently been shown to have an efficacy similar to that of DEET-based repellents. Studies within the last five years show that most unintentional superwarfarin ingestions can be managed at home with close outpatient follow-up. There does not appear to be a benefit of prophylactic vitamin K or gastrointestinal decontamination in patients with relatively small ingestions of superwarfarins. SUMMARY: With education and correct usage, mosquito repellents and the superwarfarin rodenticides can help protect children from significant vector-borne diseases. Not all exposures lead to significant morbidity or mortality. With recognition of the current literature, most of these exposures can be managed safely at home or as an outpatient, ultimately saving healthcare costs.

4-Hydroxycoumarins↗

Thanaka (Limonia acidissima) and deet (di-methyl benzamide) mixture as a mosquito repellent for use by Karen women.

The prevention and treatment of drug-resistant malaria is becoming increasingly difficult. On the Thai-Myanmar border multi-drug resistant strains of falciparum malaria are increasing and, because the malaria vector Anopheles bite outdoors during early evening, insecticide house-spraying or impregnated bednets provide only limited protection. Therefore, the protective efficacy of repellent formulations containing di-methyl benzamide (deet) and permethrin against local vectors was estimated, when applied to the skin, and their acceptability amongst pregnant Karen women who are at relatively high risk from malaria was assessed. Human landing catches of mosquitoes showed that almost complete protection was achieved using different formulations of 20% deet and 0.5% permethrin for up to 6 h. All-night collections from human subjects indicated that this repellent combination reduced exposure to malaria parasites by at least 65 and 85% for those transmitted by Anopheles minimus and An. maculatus, respectively, the two principal vectors in this area. Pregnant women in the camps preferred repellents which were mixed with 'thanaka', a root paste made from pulp of the wood apple tree, Limonia acidissima, used locally as a cosmetic. Apart from a temporary warming sensation where repellent thanaka was applied to the skin, the repellents were well tolerated. An intervention trial is currently in progress to determine whether deet mixed with thanaka can protect pregnant women against malaria in this part of the world. Bioassays using a laboratory strain of Aedes aegypti demonstrated that thanaka is itself slightly repellent at high dosages and the mixture with deet provides protection for over 10 h. This treatment would therefore also provide some personal protection against dengue, which is increasing locally, transmitted by Ae. aegypti and Ae. albopictus biting during the daytime.

Biological Assay↗

Comparative activity of deet and AI3-37220 repellents against the ticks Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) in laboratory bioassays.

The repellents N,N-diethyl-3-methylbenzamide (deet) and racemic 2-methylpiperidinyl-3-cyclohexene-1-carboxamide (AI3-37220) were evaluated using two different laboratory bioassays to determine their relative effectiveness against host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say, and the lone star tick, Amblyomma americanum (L.). In a petri dish bioassay, ticks were released within a ring of repellent on a horizontal filter paper disk. In the second bioassay, ticks were allowed to climb a vertical strip of filter paper whose central portion was treated with a repellent. Deet and AI3-37220 were more effective against I. scapularis than A. americanum nymphs. In the petri dish bioassay, none of the concentrations of deet or AI3-37220 tested confined A. americanum within the treated ring. However, in the vertical bioassay, both species exhibited avoidance of the repellents, and I. scapularis was repelled by much lower concentrations than A. americanum. I. scapularis were repelled by lower concentrations in the vertical bioassay than in the petri dish bioassay. Deet was slightly more effective against I. scapularis than AI3-37220 in both bioassays, but AI3-37220 was significantly more effective than deet against A. americanum in the vertical bioassay.

Animals↗

Protein-enriched pea flour extract protects stored milled rice against the rice weevil, Sitophilus oryzae.

Studies were conducted to evaluate the effect of a protein-enriched pea (Pisum sativum var. Bonneville) flour extract against the rice weevil, Sitophilus oryzae in its repellency, toxicity, effect on fecundity, stability and sensory properties. Milled rice admixed with pea flour extract at 1% concentration significantly repelled S. oryzae. Mortality of S. oryzae was found to increase and fecundity was markedly suppressed, in rice treated with 1% pea flour extract. The toxicity and reproductive effects of the pea protein-enriched rice were found to be stable for a period of 5 months. The sensory characteristics of stored rice when eaten were not affected by the treatment with pea flour extract. This study indicates that the protein-enriched flour extract obtained from the Bonneville pea may be feasible to protect stored milled rice from insect attack.

Animals↗

Endogenous free fatty acids repel and attract Collembola.

We used video recording of the movement pattern of Protaphorura armata (Collembola) to test whether its avoidance of the odor of dead conspecifics extends to related species. P. armata was repelled by the odor of dead individuals of Onychiurus scotarius and Onychiurus circulans, but not by live individuals. Free palmitic, oleic, and linoleic acids were present in extracts of the three repellent species, but only free palmitic acid was detected in extracts of a fourth nonrepellent species, Folsomia candida. Synthetic palmitic acid was attractive to P. armata, linoleic acid was repellent, and oleic acid gave no response. o. scotarius and O. circulans also contained 2,3-dimethoxy-pyrido[2,3-b]pyrazine, known as a defense substance. We discuss the role of free fatty acids in predator avoidance, conspecifics attraction, and food recognition in P. armata.

Animals↗

[Testing of industrial repellents against gnats and horseflies].

According to the Austrian Cosmetic Recommendation a minimum period of protection of 2 hours is to be provided. This applies to the preparation on the market with the substance "Merck 3535" in aqueous concentration in the tested area. However, this protection period was not achieved for horseflies. In test trials the characteristic of the individual nuisance should be taken into account.

Alanine↗

Public perception of mosquito annoyance measured by a survey and simultaneous mosquito sampling.

For randomly chosen residents of the Minneapolis-St. Paul, Minnesota, metropolitan area, survey responses, reported bites, and observed defensive behaviors (e.g., brushing, swatting) for a 5-min period in their yard were compared with simultaneous mosquito counts from a human-baited drop-net trap 6 m from the resident. When mosquitoes trapped, reported bites, or observed behaviors per 5 min were 3 or more, the majority of respondents described the mosquito levels as greater than "moderate" and anticipated reduced outdoor time and/or possible repellent use. At 25 or more mosquitoes trapped, 11 or more reported bites, or 16 or more observed behaviors per 5 min, response was "bad", with most people anticipating a major reduction in outdoor time (without repellent), "probably" or "definitely" planning to use repellent, and anticipating some outdoor time loss even if using repellent. Levels of less than 3 mosquitoes trapped per 5 min were related to moderate annoyance in 20-45% of the population. Individual response was highly variable, and the personal and environmental covariates measured did not account for more than half the variability.

Adult↗

Response of Anopheles dirus and Aedes albopictus to repellents in the laboratory.

Laboratory tests were conducted to study the response of Anopheles dirus and Aedes albopictus to repellent formulations containing diethyl methylbenzamide (deet) and dimethyl phthalate. Anopheles dirus was tolerant of low concentrations of deet (5-20%), and formulations containing < or = 35% deet provided protection for < or = 90 min. In contrast, Ae. albopictus was sensitive to these formulations, which provided > or = 180 min protection from bites.

Aedes↗

[Scalp pediculosis and its treatment: bioclinical trials of different pediculicides and repellents in Antananarivo].

After a recall of different existing kinds of louse, pediculicides and their mode of action, the authors report the bio-clinical trials they carried out in Antananarivo using different associations and galenic forms of medicines. The objectives of these studies on the treatment of scalp pediculosis is either the development of efficient insecticides or the application for the official permit of sale.

Animals↗

Plant products used as mosquito repellents in Guinea Bissau, West Africa.

By standardized interviews of people in 23 rural villages, in the Oio region of Guinea Bissau, we collected data on which plant species and plant derived products or methods people use to reduce mosquito biting activity. The following plants were used to reduce numbers of mosquitoes indoors at night: fresh or smouldering Hyptis suaveolens Poit. (Lamiaceae), smoke of the bark of Daniellia oliveri Rolfe (Caesalpiniaceae), smoke of the infructescence of Elaeis guineensis Jacq. (Arecaceae), smoke of the seed capsules of Parkia biglobosa (Jacq.) Benth. (Mimosaceae), smoke of the leaves of Azadirachta indica A.Juss. (Meliaceae) and Eucalyptus sp. (Myrtaceae), fresh Ocimum canum Sims (Lamiaceae), and fresh Senna occidentalis (L.) Link (Caesalpiniaceae). In two field experiments we estimated the 'repellent activity' of certain of these plants and compared their efficacies with those of two commercially available mosquito repellents, i.e. 'positive' controls. In the first experiment we tested: smouldering H. suaveolens (85.4% repellency); fresh H. suaveolens (73.2%); burning of the bark of D. oliveri (74.7%); and smoke of the leaves of Eucalyptus (72.2%). In the second experiment we tested: smouldering H. suaveolens (83.6% repellency); fresh H. suaveolens (66.5%); burning of the bark of D. oliveri (77.9%); smoke of the leaves of A. indica (76.0%); smoke of the infructescence of E. guineensis (69.0%); fresh O. canum (63.6%); and fresh S. occidentalis; (29.4%). All the products tested, except S. occidentalis were significantly more effective than the negative control.

Animals↗

Effect of delayed toxicity of chemical barriers to control Argentine ants (Hymenoptera: Formicidae).

Brief exposures of Argentine ants to four different insecticide treatments, bifenthrin, beta-cyfluthrin, bifenthrin + beta-cyfluthrin, and fipronil, were conducted to determine Kaplan-Meier product limit survivorship percentiles (SPs) at 21-23 and 27-29 degrees C. Bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin provided rapid kill at 21-23 degrees C with SP10 values ranging from 11.2 to 33.7 min. Fipronil provided delayed toxicity at 21-23 degrees C with SP10 values ranging from 270 to 960 min. At 27-29 degrees C, all of the SP10 values significantly decreased. Field tests in which Argentine ants were induced to forage across insecticide-treated surfaces were used to determine the effect that speed of action has on foraging and recruitment ability, and whether these insecticides are repellent. The slower-acting fipronil allowed a greater amount of foraging and consequently a greater fraction of the colony to be exposed, whereas fast-acting bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin inhibited recruitment, resulting in fewer ants being exposed and killed. Implications for controlling ants by using perimeter barrier treatments are discussed.

Animals↗

Development of an in vitro method for the evaluation of candidate repellents against Leptotrombidium (Acari: Trombiculidae) chiggers.

We developed a rapid and economical in vitro procedure with which to evaluate the efficacy of candidate repellents against chiggers. The procedure requires only 5 min and a small number of chiggers to obtain a valid estimate of the median effective dose. We used this procedure to evaluate the repellent activity of 11 compounds against the chigger, Leptotrombidium imphalum Vercammen-Grandjean and Langston. Median effective doses were determined for 10 of the 11 compounds. DM-165-2 (N,N-diethyl-3-flurobenzamide) was the only compound that was significantly more effective than deet.

Animals↗