Discarded cigarette butts attract females and kill the progeny of Aedes albopictus

Discarded cigarette butts (DCB) waste occurs worldwide, pollutes landscapes, is unsightly, and results in added debris removal costs. There is, therefore, a great deal of current interest in making use of DCBs in beneficial ways. Despite evidence that DCBs are harmful to water fleas (Daphnia magna), which breed in aquatic environments as do mosquito larvae, their impact on dengue vectors is unknown. We examined whether Aedes albopictus alters its ovipositional responses, larval eclosion, and development in response to presence of DCBs in its habitats. We found oviposition activity in DCB-treated water similar to that of control water and that ovipositional activity in DCB solutions steadily increased over time as those solutions aged to 10 days. Larval eclosion was initially suppressed on day 1 in DCB solution, but increased thereafter to levels similar to control larval eclosion rates. The DCB-water solutions produced significantly higher mortality in both 1st and 2nd instars over control larvae for several days after initial exposure. Mortality rates decreased sharply 3 to 5 days postexposure as DCBs continued to decompose. We found increased survival rates during late development, but daily input of fresh DCBs prevented most young larvae from completing development. Taken together, these observations suggest that decomposing did not deter gravid Ae. albopictus females from ovipositing in treated containers and that DCB solutions had larvicidal effects on early instars. Our results are discussed in the context of DCB use to control container-breeding Ae. albopictus, a competent dengue vector in Asia and other parts of the world.     

Laboratory evaluation of Lagenidium giganteum (Oomycetes: Lagenidiales) in water from Contra Costa County, California, mosquito sources

Six bioassays were performed to evaluate the efficacy of the fungus, Lagenidium giganteum, against mosquitoes in water collected from 75 sources. The fungus infected larvae of 4 genera and produced greater than 90% mortality in water from some of the creeks, artificial containers and the wild rice field tested during 4 of the assays. There was no larval mortality due to the fungus in water from irrigated pastures or marshes. Water quality parameters associated with L. giganteum infection varied among the bioassays; low measurements of total dissolved solids (TDS), hardness (CaCO3), conductivity, chemical oxygen demand (COD), ammonium nitrogen (NH3-N), phosphate (PO4) and salinity were significantly (P less than 0.05) correlated with fungal efficacy in one or more of the assays. Regression analyses selected TDS, CaCO3, COD, NH3-N and/or PO4 as the best predictors of larval mortality due to L. giganteum. Turbidity and pH were not correlated with fungal efficacy.     

Population dynamics of Culex quinquefasciatus and the fungal pathogen Lagenidium giganteum (Oomycetes: Lagenidiales) in stagnant water pools

The fungal pathogen Lagenidium giganteum (California isolate), cultured on sunflower seed extract (SFE) and agar, was introduced once (May 15) into outdoor caged replicated stagnant water pools containing all instars of larval Culex quinquefasciatus. Subsequently, first-instar larvae were added daily (May 15-September 30) to simulate natural oviposition. The fungus persisted for the entire 138-day study period, which corresponded with the season of Cx. quinquefasciatus breeding in this region of North Carolina, and recycled in the mosquito larvae producing an 82% reduction of adult mosquitoes produced in comparison to untreated pools. The cycles of fungal activity varied among the pools with 2-4 major epizootics occurring during the study period. Data are presented on the cycling of populations of fungal zoospores, mosquito larvae, pupae and adults during the entire mosquito breeding season.     

Susceptibility of Aedes aegypti larvae to parasitism by Romanomermis culicivorax in laboratory and field conditions in Oaxaca, Mexico]

In June 1996 in the state of Oaxaca, Mexico, larvae of the mosquito species Aedes aegypti were exposed to infective preparasites of the nematode Romanomermis culicivorax, Ross and Smith, in the laboratory and in the field. For the laboratory experiments larvae in instars I-IV were used; they had been collected in natural reservoirs. The laboratory experiments were carried out in triplicate, with 100 larvae of each larval stage per experiment. Three preparasite application dosage ratios were tested: 5, 10, or 15 preparasites per mosquito larva. For the field studies 13 A. aegypti outdoor breeding sites were used, with larvae in instars I-IV and a 15:1 preparasite dosage ratio. With the laboratory experiments, an increase was observed in the average infestation of the larvae as the preparasite application ratio was increased from 5:1 to 15:1. With a 10:1 ratio, the rates of parasitism were 100%, 100%, 85%, and 74% in the larvae in instars I, II, III, and IV, respectively; for the 15:1 preparasite ratio, parasitism rates were 100%, 100%, 90%, and 79%, respectively. The field tests with the 15:1 preparasite dosage ratio in the 13 outdoor reservoirs produced parasitism rates of 80% to 98%, thus demonstrating the susceptibility of this species of mosquito to parasitism by R. culicivorax in Oaxaca, Mexico.     

Infection of a field population of Aedes cantator with a polymorphic microsporidium, Amblyospora connecticus via release of the intermediate copepod host, Acanthocyclops vernalis

The microsporidium Amblyospora connecticus was successfully introduced into a larval field population of Aedes cantator via the release of the infected intermediate copepod host, Acanthocyclops vernalis. The tests were conducted in 3 steel drums that were centrally placed within a salt marsh pool that supports breeding populations of both hosts. A total of 2.7 X 10(4) 2nd-instar Ae. cantator larvae were exposed to spore doses ranging from 2.0 X 10(3) to 2.8 X 10(4) spores/larva through the release of more than 2,000 live infected copepods. The majority of infections were acquired by 2nd- and 3rd-instar larvae during the first 3 weeks of exposure, and maximum infection rates ranging from 16 to 24% were obtained by the time of pupation.     

An inexpensive intervention for the control of larval Aedes aegypti assessed by an improved method of surveillance and analysis

A sampling method coupled with statistical calibration factors was developed to accurately assess the numbers of larvae and pupae of Aedes aegypti in large water-storage containers of variable capacities and water levels. Aedes aegypti productivity in different types of breeding sites found in an urban study area in central Colombia was assessed and compared. In this study, water-storage tanks and drums were found to comprise 79% of the containers positive for larval Ae. aegypti, which contributed to 93 and 92% of the total production of populations of 4th-stage larvae and pupae, respectively. These main breeding sites of Ae. aegypti were found at an indoor to outdoor ratio of 2.4:1 and no correlation was found between temporal fluctuation of populations of larval Ae. aegypti and monthly rainfall. Netted lids that used inexpensive local materials were designed to prevent oviposition by Ae. aegypti. During a 6-month trial period, 56% of inspected containers had netted lids correctly in place. Of these, 78% had no mosquito larvae. Because only 37% of uncovered containers were free of mosquito larvae, a significant difference was demonstrated when these inexpensive mechanical barriers were used (chi2 = 138.7; P < 0.001). These netted lids and the improved methods described to assess the productivity of larval and pupal Ae. aegypti in this study are now being used in combination with other strategies to assess and control these populations of dengue virus vectors in the main port city on the Atlantic Coast of Colombia.     

Toxorhynchites amboinensis larvae released in domestic containers fail to control dengue vectors in a rural village in central Java

The efficacy of Toxorhynchites amboinensis larvae for control of dengue vectors in household water storage containers was tested in a rural village in Central Java, Indonesia. Concrete cisterns and clay jars were the most common types of containers used for long-term water storage, although smaller numbers of metal drums were also used. All containers in use in the village received 5-10 second- or third-instar Tx. amboinensis larvae biweekly for 7 months. Vector surveillance (adult and larval) was conducted biweekly between treatments. No differences in man-biting rates or larval population indices were noted between the treatment and control areas. It is hypothesized that the multiplicity of larval habitats in this rural area accounted for the lack of impact of predator releases, which were directed solely toward artificial containers.     

Efficacy of granular formulations of Bacillus thuringiensis (H-14) for the control of Anopheles larvae in rice fields

Three granular formulations of Bacillus thuringiensis (H-14) were applied to dense stands of maturing and mature rice for control of Anopheles crucians and An. quadrimaculatus. Aerial applications of the Vectobac granule (200 ITU/mg) at 5.6, 11.2 and 22.4 kg/ha to 0.4 ha plots resulted in 92, 94 and 96% reduction 48 hr after application, respectively, in populations predominantly consisting of late instars. The Bactimos granule (175 ITU/mg) was applied by aircraft to 0.4 ha plots and by a Cyclone seeder to 100 m2 plots at 2.8, 5.6 and 11.2 kg/ha, resulting in 100% reduction after 48 hr in natural populations of predominantly early instar larvae at all 3 rates with each type of application. Older instars confined to sentinel cages responded with 92, 98 and 100% mortality, respectively. Complete mortality was also observed at the same time in natural populations of predominantly young larvae in similar plots treated with Teknar granules (104 ITU/mg) at 1.7, 3.0 and 7.5 kg/ha. Near complete mortality (98-99%) was also observed in the older larvae used in the sentinel cages.     

广州地区白纹伊蚊自然种群幼虫的分布特征

目的掌握自然种群白纹伊蚊幼虫在广州地区的孳生分布特点,为白纹伊蚊自然种群变动的监测与控制提供依据。方法对广州市2004、2005年不同场所孳生白纹伊蚊的积水容器进行全年监测及调查,对获取的与分布特征有关的数据进行统计分析。结果在广州地区,孳生白纹伊蚊幼虫的各种积水容器在不同场所的分布比例有很大差异,其中居民区的水生植物容器所占比例最大,为44.68%;各种环境场所均具有其不同的孳生白纹伊蚊积水容器种类分布特征。结论广州地区白纹伊蚊自然种群幼虫的分布特征因不同环境而异。摸清白纹伊蚊幼虫在不同场所的分布特征及各类孳生白纹伊蚊积水容器在不同场所的重要性,对有效监测与控制白纹伊蚊种群具有指导性意义。     

Efficacy of encapsulated Lagenidium giganteum (Oomycetes: Lagenidiales) against Culex quinquefasciatus and Aedes aegypti larvae in artificial containers

Presporangial mycelia of Lagenidium giganteum cultured on sunflower seed extract were encapsulated in calcium alginate and added once (July 18) to outdoor (Raleigh, NC) caged tires, wood and concrete containers populated with first instars of Culex quinquefasciatus or Aedes aegypti. First instars were added twice weekly (for 10 wk) to simulate natural oviposition. The fungus persisted for 10 wk and recycled in the mosquito larvae of both species. The overall reductions of Cx. quinquefasciatus and Ae. aegypti immatures were higher in tires (55 and 45%, respectively) and wood (67 and 38%) than in concrete containers (17 and 14%). There were low correlations of the numbers of mosquito immatures with measurements of water quality (chemical oxygen demand, ammonia nitrogen and conductivity) in the containers.     

Possible utilization of metallic copper to inhibit Aedes Albopictus (Skuse) larval development

The effect of metallic copper on development of Aedes albopictus was studied in the laboratory. Multiwire electric cable was used as a source of metallic copper in flower saucers colonized by Ae. albopictus. A linear regression coefficient of 0.68 was obtained between copper concentration in the water during larval development and the relative production of adults. Larval mortality was higher in earlier instars with less evident effect on 4th-instar larvae and pupae. The effect of copper on larval development time and adult weight in both sexes was also observed. The strong algicidal action is presumed to only partially explain the effect of metallic copper on Ae. albopictus larvae. A direct toxic effect also may be involved. The use of metallic copper is suggested as a practical alternative method for preventing development of Ae. albopictus in small containers such as flower saucers found in urban areas.     

水体中8-羟基喹啉对大鳞副泥鳅胚胎毒性作用

目的 探讨水体中8-羟基喹啉对鱼类胚胎及仔鱼的毒性作用。方法 在大鳞副泥鳅胚胎发育的胚盘隆起期、原肠胚中期、神经胚期、尾芽期和仔鱼孵出期,分别用不同浓度(1.00×10^-4,5.00×10^-5,2.50×10^-5,1.25×10^-5,6.25×10^-6mol/L)的8-羟基喹啉进行处理,检测胚胎孵化率与畸形率、仔鱼死亡率及体长。结果 随着8-羟基喹啉浓度增加,在胚盘隆起期、原肠胚中期、神经胚期、尾芽期开始处理时,大鳞副泥鳅胚胎的孵化率分别由95%减少至87%,78%,74.5%,73%,畸形率由2%增加至63%,75%,72%,64%。在仔鱼孵出期开始处理时,大鳞副泥鳅仔鱼死亡率由4%增加至100%;处理组仔鱼体长短于对照组,并有剂量-效应关系。结论 8-羟基喹啉对大鳞副泥鳅胚胎及仔鱼的发育,有明显的抑制、致畸、致死作用。     

Evaluation of the residual effect of temephos on Aedes aegypti (Diptera,Culicidae) larvae in artificial containers in Manaus,Amazonas State,Brazil

Trial tests and container observations were conducted in households to verify the residual effect of temephos in Manaus, Amazonas State, Brazil. Three plastic buckets, three tin cans, and three tires filled with water from an artesian well and larvicide were used in the experiment, with twenty-five third-instar larvae, which remained exposed for 24h, followed by mortality readings. The same types of containers were selected from common households. Collection and counts followed by chemical treatment were carried out on the larvae that were found. Follow-up was performed weekly to verify recolonization by Aedes aegypti.The experiment showed 100% mortality in the plastic buckets until day 90, and 80% in the tin cans until day 30, decreasing from day 45 onwards. Mortality in the tires decreased to 35% in the first month. Household results showed 100% mortality for all containers after 24h and differentiated values in the subsequent readings. Larvae were observed on day 35 in a tin can and on day 21 in a gallon can. There was a large diversity of results in the tires, with recolonization observed from day 7 onwards.     

Suppression of larval Aedes aegypti populations in household water storage containers in Jakarta, Indonesia, through releases of first-instar Toxorhynchites splendens larvae

Weekly releases of first-instar Toxorhynchites splendens larvae were made in household water storage containers in a neighborhood in Jakarta, Indonesia, between April 1987 and April 1988. A single larva was placed in each container surveyed. Forty-one percent of all containers in the treatment area were treated each week and the average container was treated once every 2.4 weeks. Aedes aegypti populations were suppressed but not controlled by treatment. It is hypothesized that first-instar Toxorhynchites larvae were poor control agents due to their inability to withstand periods of starvation and to their accidental removal from containers during the act of water consumption.     

Effect of per os Edhazardia aedis (Microsporida: Amblyosporidae) infection on Aedes aegypti mortality and body size.

Infection with Edhazardia aedis uninucleate spores had less effect on Aedes aegypti larval mortality and adult body size than did larval diet. Larval mortality averaged 60-81% in starved larvae and 2-16% in well-fed larvae. No significant amounts of larval mortality could consistently be attributed to exposure to the parasite at dosages of 1.5 x 10(3) or 1.5 x 10(5) spores/ml. Infection rates in adults surviving exposure to the parasites as larvae ranged from 30 to 59%. Infected adults had significantly smaller body sizes than uninfected adults or controls. Storage of spores in water reduced infectivity gradually over the course of 36 h. By 48 h, the spores were not able to infect mosquito larvae. Spore infectivity was eliminated by drying.     

Floating bait formulations increase effectiveness of Bacillus thuringiensis var. israelensis against Anopheles larvae

The development and screening of floating-type bait formulations designed to improve the activity of bacterial toxins against larval Anopheles is described. Floating and spreading abilities of carrier particles (wheat flour) were compared using corn oil, lecithin, and two products yielding surface films on water (Arosurf and Liparol). Mixtures containing 1 or 5% Arosurf showed the best spreading abilities on a water surface, but strongly inhibited the ingestion of wheat flour by Anopheles albimanus larvae. Corn oil and lecithin improved spreading satisfactorily at a concentration of 5% and inhibited larval feeding by only 6-25%. To select a suitable concentration of active ingredient in formulations, Bacillus thuringiensis var. israelensis (B.t.i.) primary powder in concentrations ranging from 0.01 to 0.5% was mixed with wheat flour/corn oil mixtures and tested in quantities exceeding the gut volumes of treated larvae. Complete mortality was obtained with concentrations of 0.1% (Anopheles stephensi), 0.2% (An. albimanus), or 0.3% (An. quadrimaculatus) B.t.i. When in 175-liter containers the activity of formulations (5% corn oil, 0.2% B.t.i.) and of toxin suspensions was compared by conventional dosage-mortality regression, formulations were more active by a factor of 68 against An. stephensi, 39 against An. albimanus and 67 against An. quadrimaculatus.     

南宁市广州管圆线虫中间宿主感染情况的调查研究

本文报道了南宁市６个调查点广州管圆线虫中间宿主自然感染情况的调查结果。发现褐云玛瑙螺、大型蛞蝓和小型蜗牛等３类陆生软体动物携带幼虫，其感染率分别为５５．９８％（１９２／３４３）、４４．１９％（１９／４３）和９.１７％（１１／１２０），平均每只阳性宿主含幼虫分别为８１３．１、６１５．４和４．４条。６个点均查到阳性褐云玛瑙螺，感染率最低为２９．５８％（２０／７１），最高达８８．５７％（６２／７０）。实验感染大鼠均能在其右心和肺获得成虫。成虫和各期幼虫、虫卵的形态结构与广州管圆线虫相符。说明本虫在南宁市广泛存在，中间宿主尤以褐云玛琐螺自然感染非常严重，有引起人体感染的可能，值得重视．     

First record of Ascogregarina taiwanensis (Apicomplexa: Lecudinidae) in North American Aedes albopictus

Aedes albopictus collected in the East St. Louis, Illinois, area were found infected with the gregarine protozoan, Ascogregarina taiwanensis. Infection rates varied from 67 to 95% at 4 sites and 0 to 10% at 2 others. Lower infection levels were found in Ae. epactius (42%) and Culex restuans (one larva). Four mosquito species were cross-infected in the laboratory with gregarines isolated from field-collected hosts. Aedes atropalpus was 90% susceptible to A. taiwanensis (100% in Ae. albopictus), with abnormal development and some melanization of trophozoites and gametocysts. In Ae. aegypti and Cx. restuans, the experimental infection was much lower (12-56%) and exhibited abnormalities similar to the Ae. atropalpus infections. Ascogregarina oocysts recovered from both Ae. aegypti and Ae. atropalpus hosts were subsequently infective to Ae. albopictus. In Ae. triseriatus, A. taiwanensis infection was very low (25%, 1-2 trophozoites per larva); gametocysts were not observed nor were infectious oocysts obtained. We conclude that A. taiwanensis, newly introduced to the USA with Ae. albopictus, can develop in 4 indigenous mosquito species and can produce deleterious effects in at least 2, Ae. aegypti and Ae. atropalpus.     

Efficacy and longevity of a new formulation of temephos larvicide tested in village-scale trials against larval Aedes aegypti in water-storage containers

Field trials on the initial and long-term efficacy of a new formulation of temephos granules (1% on zeolite) applied at 1 ppm active ingredient (AI) were conducted in water-storage containers against Aedes aegypti in 3 villages in the Kanchanaburi Province in Thailand. A total of 316 water-storage containers of various types and sizes were included in the study. In the initial survey, we found that some containers were positive for larval Ae. aegypti, whereas others were devoid of larvae before the initiation of treatments. The containers all were numbered with paint and divided into 4 groups: with larvae and treated, without larvae and treated, with larvae untreated, and without larvae and untreated. Assessment of larval abundance was made 48 h after treatment and monthly thereafter for 5 months. Containers with larvae and that were treated exhibited almost complete absence of larval Ae. aegypti for 2 months, but a small proportion became positive after 3 months. Most of these positive containers were devoid of zeolite granules, which are visible in the containers. The number of positive containers increased in months 4 and 5, despite the fact that residues of temephos granules were present in some of the larvae-positive containers. The containers initially without larvae and treated with temephos essentially were devoid of larvae for 2 months. After 3, 4, and 5 months, about 6-23% of the containers became positive despite the fact that some had visible amounts of temephos granules. In the 2 control groups initially with and without larvae, sustained and consistent production of larvae occurred. Even in the group initially without a larval population, the containers became positive for larvae 1 month after the start of the experiment and the positivity rate increased as the trial progressed. From these studies, the conclusion can be made that a single application of temephos zeolite granules at 1 ppm AI can provide highly satisfactory control of larval Ae. aegypti in water-storage containers for at least 3 months in the field under normal water-use practices.     

Use of the continuity principle to evaluate water processing rate of suspension-feeding mosquito larvae.

Water processing rates of active suspension-feeding larvae of Culiseta morsitans and Culex quinquefasciatus 2nd and 4th instars were estimated through video image analysis of the conical jet flow driving the large recirculation patterns surrounding the organisms. In accordance with the principle of continuity, individual processing rates (PRs) were assessed by averaging a series of consecutive flow rates (Qx) defined as the product of the water velocity (Ux) and the associated cross-sectional area (Ax) along a transect passing through the center of the delineated jet flow. Results clearly show very tight adherence to the principle of continuity. They also demonstrate that, although extreme care must be taken when streamtube delineation is performed, the methodology used can generate reliable assessment of individual processing rates regardless of the instars or species studied. The small coefficient of variation observed in assessing PR at the larval level further underlines the consistency of the method. Significant differences in water processing rates were observed for different species and instars. These could partially be related to body size, head width, and the length of the lateral palatal brushes (LPBs), which are the structures involved in the production of the water jet. Assessment of the jet velocity at the feeding groove level suggests the key role of LPB beating frequency in the jet intensity, and consequently the magnitude of the processing rate. Analysis of data further indicates that obligate suspension feeders such as Cs. morsitans must sustain a larger flow pattern around the larvae to ensure sufficient particle entrapment than facultative suspension feeders (or even brushers) such as Cx. quinquefasciatus.