Laboratory and field evaluation of Hilmilin against mosquitoes

Hilmilin (diflubenzuron), an insect growth regulator, was tested for efficacy against Anopheles stephensi, Anopheles culicifacies, Aedes aegypti, and Culex quinquefasciatus in the laboratory and in field conditions. Fifty percent and 90% lethal concentrations (LC50 and LC90) of Hilmilin formulations were determined by exposing early 4th-stage larvae to serial dilutions of the formulation, and data were subjected to log probit analysis. Two doses (0.004 and 0.008 g/m2) were applied in different breeding habitats of mosquitoes with the help of stirrup pumps. Percent inhibition of adult emergence was compared according to a previously described procedure. Laboratory results revealed that both 25WP (wettable powder) and 22SL (semiliquid) formulations showed more or less the same degree of efficacy against tested mosquito species (P < 0.05). Of 4 species tested, An. stephensi was more susceptible, followed by An. culicifacies, Ae. aegypti, and Cx. quinquefasciatus. One hundred percent inhibition of adult emergence was observed at a dose of 0.0125 ppm (25WP and 22SL) against all mosquitoes tested in the laboratory. Both formulations showed almost similar effect when applied in the field at doses of 0.004 and 0.008 g/m2 in their respective preferential breeding habitats. However, the effect was more pronounced at a higher concentration (0.008 g/m2) against all species of mosquitoes. Hilmilin at a dose of 0.008 g/m2 can be used to contain mosquito breeding in stone quarries, pools, cement tanks, unused wells, unused coolers, and irrigation channels.     

Relative efficacy of synthetic pyrethroid-impregnated fabrics against mosquitoes under laboratory conditions

The efficacy of synthetic pyrethroid-impregnated fabrics was evaluated against Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus, under laboratory conditions. Results revealed that delta-methrin was significantly superior in comparison to lambdacyhalothrin and cyfluthrin. Results of bioassay tests revealed that deltamethrin was 1.5 and 1.9 times more effective than lambdacyhalothrin and cyfluthrin, respectively, against An. stephensi exposed to cotton fabric treated at 100 g/m2. Deltamethrin was 3.9 and 4.6 times more effective against Ae. aegypti and 3.53 and 4.0 times more effective against Cx. quinquefasciatus. Of cotton, nylon, polyethylene, and jute fabrics, the cotton was the best on the basis of median lethal dose (LD50) and 95% lethal dose (LD90) values and persistence of insecticide.     

Avermectins, MK-933 and MK-936, for mosquito control

Two avermectins were shown to be effective as mosquito larvicides or when fed to adult female mosquitoes in sucrose solution or in blood. Larval LC50 values of compounds MK-933 and MK-936, expressed as parts per billion, were found to be 3.94 and 2.42 for Culex pipiens, 5.85 and 2.90 for Anopheles stephensi and 23.4 and 10.4 for Aedes aegypti. When fed to adult females of An. stephensi, Ae. aegypti or Cx quinquefasciatus, MK-933 at 2.8mg active ingredient per litre in sucrose solution caused complete mortality within 60 hours. When female mosquitos engorged blood from mice injected subcutaneously 12 hours previously with MK-933 at 82 mg a.i./kg, mortality rates after 36 hours were 100% for An. stephensi, over 60% for Ae. aegypti and over 50% for Cx quinquefasciatus. Thus the systemic insecticidal effect was greater against anopheline than against culicine female mosquitoes.     

Host range of Clostridium bifermentans serovar. malaysia, a mosquitocidal anaerobic bacterium.

Clostridium bifermentans serovar. malaysia (C.b.m.) is toxic to mosquito larvae. In this study, we quantified its toxicity to the mosquitoes, Aedes aegypti, Ae. albopictus, Ae. caspius, Ae. detritus, Anopheles stephensi, An. gambiae, Culex pipiens and Cx. quinquefasciatus. Anopheles larvae are the most susceptible, followed by Ae. detritus and Ae. caspius, then Culex and other Aedes larvae. According to mosquito species, the LC50 varies from 7 x 10(3) to 1.3 x 10(6) cells/ml. Three concentrations (10(7), 10(6) and 10(5) cells/ml) of C.b.m., Bacillus thuringiensis var. israelensis (B.t.i.) and Bacillus sphaericus were tested on Ae. aegypti, An. stephensi and Cx. pipiens larvae in order to determine the time necessary for each concentration to kill 50 and 90% of the population. Ninety percent of the 3 mosquito populations are killed within 4-15 h by the C.b.m. concentrations. Whatever the concentrations, C.b.m. kills at least 10 times less rapidly than B.t.i. but always quicker than B. sphaericus. Bioassays of C.b.m. bacterial cells or final whole culture were not toxic to Musca domestica and Drosophila melanogaster (Diptera) as well as to Phaedon cochleariae (Coleoptera) and Spodoptera littoralis (Lepidoptera).     

Efficacy evaluation of a fumigant containing permethrin and deltamethrin against vector mosquitoes

The efficacy of a new smoke-generating formulation (fumigant), containing the active ingredient permethrin (69 g/kg) and deltamethrin (3.9 g/kg) per cartridge, was evaluated against adult female Anopheles albimanus, Aedes aegypti, and Culex quinquefasciatus in a large vehicle storage building (22 x 13 x 4.5 m3), Florida, U.S.A., and against Cx. pipiens complex and Ae. albopictus in a furnished apartment (12 x 7 x 3.5 m3) in Israel. In the storage building, the use of 2 fumigant cartridges resulted in 100% mortality for all 3 species in 15 min. Using 1 cartridge resulted in 100% mortality in An. albimanus, 98% in Ae. aegypti, and 97% in Cx. quinquefasciatus in 15 min; and 100% mortality for both Ae. aegypti and Cx. quinquefasciatus at 30 min. In the apartment in Israel, both Ae. albopictus and Cx. pipiens showed 100% mortality when exposed to the fumigant cartridge for 15 min. Based on these preliminary data, the test formulation (fumigant) could be a valuable tool for controlling mosquitoes.     

Laboratory evaluation of 18 repellent compounds as oviposition deterrents of Aedes albopictus and as larvicides of Aedes aegypti, Anopheles quadrimaculatus, and Culex quinquefasciatus

Among 18 experimental skin repellent compounds tested at five concentrations in the laboratory as oviposition deterrents against Aedes albopictus. 12 compounds showed significant activity, with median effective dose values ranging from 0.005 to 0.052%. The test compounds also were evaluated in the laboratory as larvicides against laboratory-reared 4th instars of Aedes aegypti, Anopheles quadrimaculatus, and Culex quinquefasciatus with the same concentrations employed for the oviposition deterrency tests against Ae. albopictus. Larval mortality data at 24 and 48 h after treatment indicated that 12 test repellents caused larval mortalities in the range of 67 to 100% against An. quadrimaculatus, 10 compounds induced 55-100% larval mortalities of Ae. aegypti, whereas larval mortality caused by 9 compounds ranged from 74 to 100% against Cx. quinquefasciatus. These mortality data did not fit the linear model of the statistical analysis. However, multiway analysis of variance of these data showed that the repellent compounds, concentrations used, species of mosquitoes, and exposure times affect the degree of larval mortalities.     

广东省蚊虫感染沃尔巴克氏体初步调查研究

目的 了解广东省蚊虫种群中沃尔巴克氏体（Wolbachia）的分布及其基因型别.方法 利用Wolbachia的wsp基因序列建立PCR检测方法,对蚊科中库蚊属、伊蚊属、阿蚊属和按蚊属部分蚊虫种类进行检测,同时利用Mega 5.2软件对所获基因序列进行系统分析.结果 分别从致倦库蚊、骚扰阿蚊、白纹伊蚊及未分型蚊种中检测到12条目的基因序列,其中11条成功进行测序,这些序列分别属于A和B2个超级基因组,分布在5个不同的基因族中.结论 广东省白纹伊蚊、骚扰阿蚊和致倦库蚊中均存在A大组（含2个小组）和B大组（含3个小组）基因型的Wolbachia感染,埃及伊蚊和中华按蚊未检测出Wolbachia.     

Indoor thermal fogging application of pesguard FG 161, a mixture of d-tetramethrin and cyphenothrin, using portable sprayer against vector mosquitoes in the tropical environment

Indoor bioefficacy of the thermal fogging application of Pesguard FG 161, a formulation containing both knockdown and killing agents (active ingredient [AI]: d-tetramethrin 4% [w/w] and cyphenothrin 12% [w/w]) was compared with Resigen5 (AI: s-bioallethrin 0.8% [w/w], permethrin 125/75] 18.7% [w/w], and piperonyl butoxide 16.8% [w/w]), another pyrethroid formulation, as larvicides and adulticides against Aedes aegypti, Aedes albopictus, Anopheles sinensis, and Culex quinquefasciatus using a portable Agrofog AF35 sprayer indoors in houses on Penang Island, Malaysia. Pesguard FG 161 at the concentrations tested was effective against all 4 mosquito species tested. The water-based Pesguard FG 161 performed far better as a larvicide than the diesel-based formulation. Resigen was also effective as a larvicide and adulticide against all 4 mosquito species tested. Larvae of Ae. aegypti were most susceptible to water-based Pesguard FG 161, followed by Cx. quinquefasciatus, An. sinensis, and Ae. albopictus. Even at the lowest concentrations tested, Pesguard FG 161 showed adequate adulticidal properties. At higher dosages, water-based Pesguard FG 161 proved effective as a larvicide against all 4 mosquito species.     

Larvicidal activity of Hibiscus abelmoschus Linn. (Malvaceae) against mosquitoes

The larvicidal activity of roots of Hibiscus abelmoschus was evaluated against the larvae of mosquitoes in the genera Anopheles and Culex. Mean median lethal concentration values of the aqueous extract from the roots of H. abelmoschus against the larvae of Anopheles culicifacies, An. stephensi, and Culex quinquefasciatus were 52.3, 52.6, and 43.8 ppm, respectively. Efficacy of fraction code HAM-4 decreased with an increase in water depth when sprayed at a dose calculated by surface area. Fraction code HAM-4 at the rate of 82 ppm showed 91.1% reduction of larval An. stephensi in a tank, whereas 87.4% reduction of larval Cx. quinquefaisciatus occurred in a blocked drain 24 h after application of HAM-4 under field conditions.     

Effectiveness and residual activity comparison of granular formulations of insect growth regulators pyriproxyfen and s-methoprene against Florida mosquitoes in laboratory and outdoor conditions

Effectiveness and residual activity tests of granular formulations of 2 insect growth regulators (IGRs), s-methoprene and pyriproxyfen, against laboratory-reared larvae of 5 colonized mosquitoes, Aedes aegypti, Aedes albopictus, Aedes taeniorhynchus, Anopheles quadrimaculatus, and Culex nigripalpus, were conducted in the laboratory and outdoors in plastic tubs. Culex quinquefasciatus was exposed to these two IGRs in the laboratory only. Each IGR formulation was applied at 0.02 and 0.05 ppm active ingredient (Al) against 5 of the 6 mosquito species both in the laboratory and the outdoor evaluations, whereas Cx. quinquefasciatus was exposed to 0.2 and 0.4 ppm AI of s-methoprene, and 0.1 and 0.2 ppm AI of pyriproxyfen in the laboratory. s-Methoprene at 0.02 and 0.05 ppm AI resulted in variable levels (<39-100%) of inhibition of adult emergence in the 5 species monitored for 6 weeks after treatment under both test conditions. Aedes taeniorhynchus was the most susceptible to s-methoprene in terms of initial and residual activity. Culex quinquefasciatus and Ae. albopictus were the most tolerant to s-methopene, with maximum emergence inhibitions amounting to 84% in Cx. quinquefasciatus at 0.4 ppm and 44.3% in Ae. albopictus at 0.05 ppm during the 1st week in the laboratory. Pyriproxyfen at comparable treatment rates to s-methoprene caused very high levels (>80-100% in most cases) of initial and residual emergence inhibitions of the tested species in the laboratory as well as outdoors. In several species, pyriproxyfen induced complete inhibition of adult emergence for several weeks after treatment, even at the lower rate of 0.02 ppm. The World Health Organization has recently recommended the use of pyriproxyfen for the control of some mosquito species at specified rates in certain habitats.     

Comparative studies of Metarhizium anisopliae and Tolypocladium cylindrosporum as pathogens of mosquito larvae

Mosquito fungal pathogens, Metarhizium anisopliae and Tolypocladium cylindrosporum, were compared with regard to virulence against the larvae of Aedes aegypti, Anopheles stephensi and Culex pipiens. Culex pipiens larvae were much more susceptible to M. anisopliae conidia than An. stephensi or Ae. aegypti. But Ae. aegypti and Cx. pipiens larvae were equally susceptible to T. cylindrosporum propagules which weakly attack An. stephensi. Using a high concentration conidial suspension (10(7) sp/ml) of M. anisopliae no. 139, Ae. aegypti larvae were killed immediately within 1.1 days, before intrahemocoelian invasion; but at lower concentrations (10(6) and 10(5) sp/ml), typical mycosis occurred. However, T. cylindrosporum no. 3 blastospores were much more pathogenic to Ae. aegypti larvae than conidia. Conidial suspension of 10(7) spores/ml killed 68% fourth-instar larvae, relative to the 96% invaded by blastospores under the same conditions. Presoaked conidia virulence appeared still intermediate between conidia and blastospores. At low temperatures, 15 degrees C, virulence of M. anisopliae highly decreased, while at the same temperature, T. cylindrosporum blastospores were still virulent.     

Bioefficacy of Olyset nets against mosquitoes in India

Olyset nets are highly effective in killing anopheline mosquitoes within 3 min of exposure, as evidenced in cone bioassay tests. These nets also showed their efficacy on other vector mosquitoes (Aedes aegypti and Cx. quinquefasciatus) at higher exposure periods. The efficacy remained at approximately 90% even after 20 washings at an interval of 24 h against Anopheles culicifacies and Cx. quinquefasciatus. Use of the nets inside the house also resulted in drastic reduction of daytime resting density of mosquitoes because of high repellency, excitorepellency, and killing action of the nets. Pilot studies are indicated to evaluate the impact of use of Olyset nets on vector-borne diseases, particularly malaria, and its cost-effectiveness in comparison to conventional indoor residual spraying.     

Associations between two mosquito populations and West Nile virus in Harris County, Texas, 2003-06

Associations between Culex quinquefasciatus, Aedes albopictus and West Nile virus (WNV) activity, temperature, and rainfall in Harris County, Texas 2003-06 are discussed. Human cases were highly correlated to Cx. quinquefasciatus (r = 0.87) and Ae. albopictus (r = 0.78) pools, blue jays (r = 0.83), and Ae. albopictus collected (r = 0.71), but not Cx. quinquefasciatus collected (r = 0.45). Human cases were associated with temperature (r = 0.71), not rainfall (r = 0.29), whereas temperature correlated with Ae. albopictus and Cx. quinquefasciatus collections (r = 0.88 and 0.70, respectively) and Cx. quinqueftsciatus pools (r = 0.75), but not Ae. albopictus pools (r = 0.55). Both species (collections and pools) and blue jays were weakly correlated (r 5 0.41) with rainfall, but blue jays were better correlated with Cx. quinquefasciatus pools (r = 0.87), compared with Ae. albopictus pools (r = 0.67), Ae. albopictus collections (r = 0.69), and Cx. quinquefasciatus collections (r = 0.46). Peak minimum infection rate for Cx. quinquefasciatus (4.55), and Ae. albopictus (4.41) was in August with highest human cases (17.87), blue jays (55.58), and temperature (29.01 degrees C). Between both species, blood meal analysis indicated 68.18% of Cx. quinquefasciatus mammalian hosts were dog, while 22.72% were human, whereas Ae. albopictus had higher human (44.44%) but fewer dog hosts (22.22%). Ten bird species were identified as hosts for Cx. quinquefasciatus, with northern cardinal and blue jay representing 26.66% and 20.00%, respectively. No bird feeding activity was observed in Ae. albopictus. The earliest and latest human blood meal occurred in May (Ae. albopictus) and November (Cx. quinquefasciatus); 66.66% of human host identifications between both species occurred in October-November, after the seasonal human case peak. Based upon our data, WNV activity in both mosquito species warrants further investigation of their individual roles in WNV ecology within this region.     

Laboratory and field evaluations of the insect repellent 3535 (ethyl butylacetylaminopropionate) and deet against mosquito vectors in Thailand

The insect repellents 3535 (ethyl butylacetylaminopropionate or IR3535) and deet (N,N-diethyl-3-methylbenzamide) were prepared as 20% solutions in absolute ethanol and evaluated for repellency against many mosquito species in Thailand under laboratory and field conditions using human subjects. In the laboratory, 0.1 ml was applied per 30-cm2 of exposed area on a volunteer's forearm (0.66-0.67 mg active ingredient [AI]/ cm2), whereas in the field, volunteers' legs (from knee to ankle, with a surface area of about 712-782 cm2) were treated with 3 ml per exposed area (0.76-0.84 mg AI/cm2). In the laboratory, both IR3535 and deet showed equal repellency (P > 0.05) for 9.8 and 9.7 h against Aedes aegypti, for 13.7 and 12.7 h against Culex quinquefasciatus, and for 14.8 and 14.5 h against Cx. tritaeniorhynchus, respectively. Anopheles dirus was significantly less sensitive to IR3535 than to deet (P < 0.05), with a mean protection time of 3.8 and 5.8 h, respectively. Under field conditions, both IR3535 and deet provided a high degree of protection against various mosquito vectors ranging from 94 to 100% during the test periods. Both repellents provided a high level of protection for at least 8 h against Ae. albopictus and for at least 5 h against Cx. gelidus, Cx. tritaeniorhynchus, Cx. quinquefasciatus, Mansonia dives, Ma. uniformis, Ma. annulata, Ma. annulifera, Anopheles minimus, and An. maculatus. This study clearly documents the potential of IR3535 for use as a topical treatment against a wide range of mosquito species belonging to several genera.     

Larval survey of tire-breeding mosquitoes in Alabama

A state-wide survey of tire-breeding mosquitoes in Alabama was conducted in 2004 and 2005. Tire sites in all 67 counties in the state of Alabama were sampled for mosquito larvae. A total of 13,022 mosquito larvae, representing 12 species in 7 genera, was collected. The most frequently collected species were Aedes albopictus (70.4%), Culex territans (8.0%), and Ochlerotatus triseriatus (7.1%). The following species were also collected: Cx. restuans (6.0%), Cx. salinarius (2.7%), Orthopodomyia signifera (2.4%), and Cx. quinquefasciatus (1.4%). Ochlerotatus atropalpus, Toxorhynchites rutilus, Anopheles punctipennis, An. quadrimaculatus, and Psorophora columbiae each represented <1.0% of the total larval collections. No Ae. aegypti or Oc. japonicus were collected from tires during this survey. The first known collection of Ps. columbiae breeding in water-filled tires is reported.     

Adult repellency and larvicidal activity of five plant essential oils against mosquitoes

The larvicidal activity and repellency of 5 plant essential oils--thyme oil, catnip oil, amyris oil, eucalyptus oil, and cinnamon oil--were tested against 3 mosquito species: Aedes albopictus, Ae. aegypti, and Culex pipiens pallens. Larvicidal activity of these essentials oils was evaluated in the laboratory against 4th instars of each of the 3 mosquito species, and amyris oil demonstrated the greatest inhibitory effect with LC50 values in 24 h of 58 microg/ml (LC90 = 72 microg/ml) for Ae. aegypti, 78 microg/ml (LC90 = 130 microg/ml) for Ae. albopictus, and 77 microg/ml (LC90 = 123 microg/ml) for Cx. p. pallens. The topical repellency of these selected essential oils and deet against laboratory-reared female blood-starved Ae. albopictus was examined. Catnip oil seemed to be the most effective and provided 6-h protection at both concentrations tested (23 and 468 microg/ cm2). Thyme oil had the highest effectiveness in repelling this species, but the repellency duration was only 2 h. The applications using these natural product essential oils in mosquito control are discussed.     

Mesocyclops brevisetosus (Cyclopoida: Cyclopoidae) as a potential biological control agent against mosquito larvae in Indonesia

Mesocyclops brevisetosus Dussart and Sarnita, an indigenous copepod in Indonesia, was evaluated as a potentially useful biological control agent against larval Aedes (Stegomyia). In the laboratory, female M. brevisetosus were found to readily consume mosquito larvae of species from 3 genera (Aedes aegypti, Culex quinquefaciatus, and Anopheles farauti). Mesocyclops brevisetosus preferentially fed on larvae of Ae. aegypti (mean 95% consumed), followed by Cx. quinquefasciatus (71%) and An. farauti (54%) during a 24-h period. An individual copepod consumed up to 43 1st and 2nd instars of Ae. aegypti within a 24-h period. In the field, a density of 25 adult copepods/400 ml of water in an artificial container prevented the establishment of Aedes mosquitoes by 98% compared to the control container (without copepods). A density of 50 copepods/400 ml of water completely prevented infestation with Aedes. Over a 12-wk period, evaluation of M. brevisetosus-treated ovitraps reduced Ae. aegypti by 38-100% compared to ovitraps without copepods. The introduced gravid copepods increased 2.5-6.7 times over the original cohort. Mesocyclops brevisetosus showed high fecundity in culture, with a mean of 58 nauplii produced per individual gestation cycle.     

Efficacy assessment of Quwenling, a mosquito repellent from China.

Quwenling, an insect repellent product of China derived from extracts of the lemon eucalyptus plant (Eucalyptus maculata citriodon), was evaluated. Laboratory tests compared Quwenling with deet against Anopheles albimanus, An. quadrimaculatus, Aedes aegypti, Ae. albopictus and field tests with Ae. taeniorhynchus. Cloth treated with Quwenling at greater than 2x the dosage of deet was effective against 2 of 4 species tested (Ae. albopictus 29 days, An. quadrimaculatus 28 days). On the skin of volunteers at 2x the dosage of deet, the duration of protection for Quwenling was significantly less than deet with Ae. aegypti and Ae. taeniorhynchus, and was not significantly different with Ae. albopictus. Both repellents were ineffective against the anopheline species. As a topically applied mosquito repellent, Quwenling has a shorter duration of effectiveness than deet.     

The association of Aedes aegypti and Ae. albopictus in Allende, Nuevo León, Mexico

The recent appearance of Aedes Stegomyia albopictus (Skuse) in Nuevo León (NL) worries health officials. It is a vector of dengue fever in Asia and is more resistant to lower temperatures than Ae. aegypti. The objective of this study was to learn about some ecological parameters of Ae. albopictus and their association with Ae. aegypti, and other culicids in Allende, NL, Mexico, during 1999. Allende is a small town close to metropolitan Monterrey, which has 4 million inhabitants. The design was random with monthly sampling of 175 ovitraps. Chi-square analyses were performed with data of presence, absence, frequency, and relative abundances. During the study, the species Culex tarsalis (Coquillet), Cx. thriambus (Dyar), Cx. pipiens (Linnaeus), Cx. coronator (Dyar and Knab), Ae. albopictus, Ae. aegypti, Toxorhynchites rutilus (Coquillet), and Ae. triseriatus (Say) were found. April is the month for large numbers of mosquito species. September had the highest populations in positive ovitraps (66.67%), followed by July (63.27% of traps). Aedes aegypti was the most abundant (65.13%), followed by Ae. albopictus (19.71%). Both Ae. albopictus and Ae. aegypti were found from April until December. Aedes aegypti was more abundant than Ae. albopictus, except in August, when they were similar (chi2 = 0.197, P < 0.05). We found significant association between the presence of both species for every study month (chi2 = 9.837, P < 0.05), with a contingency coefficient of 0.247. September and November were the months having the most mosquitoes in this association. Only considering Ae. albopictus, more were found in ovitraps in July (34.6%), followed by September (33.3%). However, its presence was not significant throughout the year. Of 2 zones, in town and at the river, prevalence indicated that Ae. albopictus preferred the river. This mosquito is in its establishment phase in this area and requires further studies.     

Controlled release repellent formulations on human volunteers under three climatic regimens.

Two controlled-release repellent formulations containing 33% (3M) and 42% (Biotek) deet and an Army repellent containing 75% deet were evaluated in 3 different climatic regimens (tropical forested, tropical open and basic hot environments). The 3 repellents provided similar protection for different time periods after application under all 3 climates against Aedes aegypti, Ae. taeniorhynchus and Anopheles stephensi whereas there was no difference in protection period against An. albimanus.