Showing papers in "Journal of The American Mosquito Control Association in 1992"

Identification of oviposition attractants for Culex quinquefasciatus from fermented Bermuda grass infusions.

Abstract: Compounds which attract and stimulate oviposition by gravid Culex quinquefasciatus were isolated and identified from a fermented Bermuda grass infusion. The neutral portion of the ether extract of the aqueous infusion contained the stimulatory materials. Fractionation by liquid chromatography yielded an active fraction containing phenol, 4-methylphenol, 4-ethylphenol, indole and 3-methylindole. A blend of the 5 compounds strongly stimulated oviposition, as did blends of any 4 of them. Bioassays with individual compounds showed that only 3-methylindole consistently induced oviposition, in concentrations spanning 5 orders of magnitude.

First record of Aedes albopictus establishment in Italy.

Abstract: In September 1991, the first breeding populations of Aedes albopictus were discovered in Veneto Region, Italy. Larvae were collected in a wide variety of peridomestic containers and in used tires. Attempts were made to eradicate this species from infested areas. No larvae or adults of Ae. albopictus were found from October 1991 onwards. It is not yet assessed if this was because of the control measures taken or due to the low fall temperatures and the short critical photoperiod prevailing in the area (L:D, 12:45). Since tire casings are believed to be the primary mode of introduction and dispersal of Ae. albopictus, an investigation of tire retreading operations was initiated to determine the source and mode of introduction of Ae. albopictus into Italy.

Factors influencing the activity of Bacillus thuringiensis var. israelensis treatments.

Abstract: Environmental factors influence the effectiveness of microbial control agents in mosquito control programs. Four of these factors (water temperature, larval density, sunlight and the effect of associated filter feeders) were studied with Bacillus thuringiensis var. israelensis under laboratory and semifield conditions in Europe using different instars of Aedes vexans, Ae. aegypti and Culex pipiens. Bioassays conducted at a low temperature (5 degrees C) yielded 10-fold higher LC50 and LC90 values compared with those conducted at a high temperature (25 degrees C). The efficacy of B.t.i. decreased in a linear manner with increasing larval density. Sunlight can reduce the effectiveness of B.t.i. by several times. Competition in food intake by filter feeding Daphnia resulted in lower mortality of mosquito larvae after B.t.i. applications.

A review of malaria in Iran, 1975-90.

Abstract: Since 1958, when the malaria eradication program officially started in Iran, great strides has been made in controlling the disease in most of the country. However, because of certain technical, operational and administrative problems, malaria is still highly prevalent in southeastern Iran, affecting 6% of the population. The situation of malaria in Iran from 1975 through 1990 is discussed in detail, with particular emphasis given to the epidemiological characteristics and vector transmission factors in each region of the country.

First record of breeding populations of Aedes albopictus in continental Africa: implications for arboviral transmission.

Abstract: Eggs of Aedes albopictus were collected in oviposition cups from 3 forested areas of Delta State in south-central Nigeria during September 1991 as part of a post-yellow fever outbreak investigation. These eggs were shipped to the Centers for Disease Control in Colorado, where they were reared to the adult stage and identified. This is the first record of breeding populations of Ae. albopictus in continental Africa. Other taxa reared from the same oviposition cups included Ae. aegypti, Ae. apicoargenteus, Ae. africanus, Ae. lilii and Ae. simpsoni subgroup. The introduction and establishment of Ae. albopictus in Africa may have important implications for transmission of indigenous arboviruses.

Cuticular hydrocarbons, isoenzymes and behavior of three populations of Anopheles darlingi from Brazil.

Abstract: Three populations of Anopheles darlingi were studied for cuticular hydrocarbons, isoenzymes and patterns of peak biting activity. Differences were found in specimens from Costa Marques, a malaria endemic area; Dourado, a site with a very exophilic population and Juturnaiba, located near the type locality. Twelve hour collections from sunset to sunrise showed that An. darlingi from Costa Marques had a bimodal biting activity profile with a major peak at sunset and a minor peak at sunrise. At Dourado, the pattern was trimodal, with peaks at both morning and evening periods of twilight and near midnight. The Juturnaiba population showed a slight increase in activity near 2000 and 0100 h. Nei's genetic distances, determined by isoenzyme electrophoresis between pairs of populations, were low (D < or = 0.049). Using discriminant analysis for the cuticular hydrocarbons, 92.4% of the specimens from Costa Marques, 91.2% of the specimens from Dourado and 61.3% from Juturnaiba were correctly identified. Cuticular hydrocarbon and isoenzyme results matched very well: the smaller the Nei's distance, the more misidentifications occurred in the jackknife estimator used in the cuticular hydrocarbon analysis. This is the first report of cuticular hydrocarbon analysis in combination with isoenzymes to investigate neotropical anopheline species.

Influence of temperature and larval nutrition on the diapause inducing photoperiod of Aedes albopictus.

Abstract: Photoperiod induced dormancy for 14 North American strains of Aedes albopictus were determined at 21, 26 and 29 degrees C. Strains tested at 21 degrees C and intermediate temperatures of 25-27 degrees C demonstrated clear photoperiodic responses whereas temperatures of 29 degrees C and above, greatly reduced or negated diapause incidence. A suboptimal larval diet increased the percentage diapause in eggs laid by resulting adults. This larval diet was also associated with a slight increase in critical photoperiod.

Invasion of cemeteries in Florida by Aedes albopictus.

Abstract: Aedes albopictus has been found in 53 of the 67 Florida counties. The initial discoveries in 11 of these counties were made in cemeteries. At several locations, Ae. albopictus became well-established in cemeteries before appearing in nearby accumulations of waste tires. The recycling of plastic floral baskets may be aiding the spread of Ae. albopictus. Mosquitoes were commonly found in all types of flower-holding containers in cemeteries, except bronze vases. In the laboratory, most Aedes aegypti eggs laid in bronze vases hatched, but larvae subsequently died. The spread of Ae. albopictus in cemeteries seems to occur at the expense of Ae. aegypti populations. At one cemetery immature Ae. albopictus and Ae. aegypti were found in about 70% of the Aedes-positive containers at the start of a monitoring program. In subsequent collections from this site, Ae. albopictus was found in nearly all Aedes-positive containers, whereas there was a progressive decrease in containers with Ae. aegypti. This trend did not appear to be the result of any seasonal pattern because in a nearby cemetery where Ae. albopictus was absent, Ae. aegypti did not show a similar decline. Limiting flower-holding containers to those with drain holes or to bronze vases would greatly limit mosquito production.

Efficacy of Bacillus sphaericus against the malaria vector Anopheles gambiae and other mosquitoes in swamps and rice fields in Zaire.

Abstract: The microbial control of Anopheles gambiae and other mosquitoes with a granular formulation of Bacillus sphaericus (Vectolex) was evaluated in rice fields and swamps, located around the suburban region of Kingabwa-village in Kinshasa, Zaire. Ten treatment cycles with 15-day intervals were carried out with the same application rate, 10 kg/ha, during the dry season (May to September 1991). The treatments reduced larval populations of An. gambiae by 98% after 48 h, but repetitive applications were required every 15 days to maintain control. The persistence of B. sphaericus spores was more apparent in rice fields than in swamps. A significant reduction in nuisance biting by Culex quinquefasciatus and Mansonia uniformis was observed. For An. gambiae, a decrease of 13.6% in human biting was noted during the post-treatment period. The entomological inoculation rate was reduced from 0.238 to 0.143. The efficacy of B. sphaericus does not appear to offer outstanding potential for control of An. gambiae in rice fields and swamps and seems to be limited due to different factors tied to ecology and natural conditions in the fields.

Blood-feeding of Culex mosquitoes in an urban environment

Abstract: The modified capillary tube precipitin test was used to identify blood meal sources of Culex quinquefasciatus emerging from sewage ditches in East Baton Rouge Parish, Louisiana. Canines were the primary hosts, but Passeriformes and humans were also suitable blood meal sources. The percentage of Cx. quinquefasciatus feeding on these 3 hosts fluctuated with the habitat and the season.

Evaluation of different methods of catching anopheline mosquitoes in western Venezuela.

Abstract: During a longitudinal study of vector biology and malaria transmission in western Venezuela, adult mosquitoes were collected by different methods and their efficiency was compared with human landing catches. CDC light traps, a double-net, a calf-baited trap and collection of resting mosquitoes on vegetation were tested. These methods did not prove to be effective substitutes for human landing catches.

Wetland management strategies that enhance waterfowl habitats can also control mosquitoes.

Abstract: Two studies in California wetlands and a third in Minnesota wetlands indicate that management practices designed to enhance habitat quality for waterfowl can concurrently reduce mosquito problems In a seasonally flooded pickleweed wetland in Suisun Marsh, Solano Co, CA, we demonstrated that reducing plant-cover by 50% increased benthic densities of chironomid midge and dytiscid beetle larvae; these insects can be important in waterfowl diets This manipulation also concentrated Aedes melanimon and Culiseta inornata mosquito larvae along wetland perimeters; thus, the need for control measures was greatly restricted spatially A study in 9 experimental ponds in Suisun Marsh demonstrated that higher water levels could enhance populations of the macroinvertebrates important in waterfowl diets; general macroinvertebrate densities were higher at 60 cm depths than 20 cm or 40 cm depths In contrast, Cs inornata densities were lowest at 60 cm depths and highest at 20 cm depths A study conducted in a perennial-water cattail wetland in Minneapolis-St Paul, MN, demonstrated that a temporary water-level drawdown, designed to enhance waterfowl habitat quality of perennial-water wetlands, also reduced densities of Coquillettidia perturbans mosquito larvae These mosquitoes disappeared immediately after the drawdown, but even after water depths were restored to pre-drawdown levels, significant numbers did not reappear until 4 years post-drawdown Studies in 202 other Minnesota wetlands also demonstrated the susceptibility of Cq perturbans populations to drawdown, but the impact of drawdown was greater in stands of emergent cattail than in floating cattail

A simple method for cultivating freshwater copepods used in biological control of Aedes aegypti.

Abstract: A simple method for indoor and outdoor cultivation of Mesocyclops aspericornis, Macrocyclops albidus and Mesocyclops n. sp. copepods is presented. This method utilizes Chilomonas sp., Paramecium caudatum and fresh lettuce as food sources for copepod cultures. Steps for initiating and maintaining copepod cultures are provided.

Dispersal of adult female Culex annulirostris in Griffith, New South Wales, Australia: a further study.

Abstract: The dispersal of Culex annulirostris was studied during February 1986 in Griffith, N.S.W. using a mark-release-recapture technique. Parity was determined of recaptured females and a sample of the population at release. Parity rates of the 2 populations were comparable, and no significant differences were detected between the dispersal characteristics of the nulliparous and parous recaptured females. The maximum flight distance observed was 12 km, the limit of the trapping network. It was estimated that the mean distance traveled was 4.4 km and 36.6% (n = 377) of the population dispersed further than 5 km. The majority (81.2%, n = 377) of recaptures were taken within 2 days of release and the rate of dispersal of the population was estimated at 2.2 km/day.

Sublethal effects of larval methoprene exposure on adult mosquito longevity.

Abstract: Larvae of Aedes aegypti were exposed to sublethal concentrations of the insect growth regulator, methoprene, and the glycogen content of pupae and surviving adults was compared and effects on adult longevity determined. The glycogen reserves in both male and female Ae. aegypti pupae were significantly reduced as a result of methoprene exposure. The longevity of adult females was also significantly reduced, but exposure affected neither the longevity nor the glycogen content of adult males. Adult sugar feeding increased the amount of glycogen in both treated and control females. The reduced longevity of adult females from larval methoprene treatment appeared not to be directly related to reduced glycogen, but rather reflected neuroendocrine abnormalities induced by this juvenile hormone analogue.

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

Abstract: 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).

Susceptibility of Phlebotomus papatasi (Diptera: Psychodidae) to DDT in some foci of cutaneous leishmaniasis in Iran.

Abstract: The susceptibility of Phlebotomus papatasi to DDT was studied in field surveys at localities in different areas of Iran during 1985-88. In many parts of Iran houses had been treated with DDT for malaria control (1950-68). Tests were carried out in localities where the application of DDT had been discontinued since 1969. This investigation showed that P. papatasi from Isfahan is more tolerant to DDT than flies from other areas, probably a manifestation of DDT resistance.

Impact of the black fly (Diptera: Simuliidae) control agent Bacillus thuringiensis var. israelensis on chironomids (Diptera: Chironomidae) and other nontarget insects: results of ten field trials.

Abstract: Except for moderate mortality among filter-feeding chironomids, Rheotanytarsus spp., the results of 10 field trials with Bacillus thuringiensis var. israelensis (B.t.i.) indicated a wide margin of safety to the chironomid community and other stream nontarget insects. Mayflies, caddisflies and 2 other types of chironomids, i.e., tube-dwelling (Chironominae) and surface-dwelling, caseless larvae (mix of Chironominae, Diamesinae, Orthocladiinae, Tanypodinae), did not appear to be affected. The susceptibility of filter-feeding chironomids was considerably less than black flies; for example, 4 months of data collected during an operational black fly control program indicated a mean (+/- 95% CI) mortality among Rheotanytarsus larvae of 23 (15-32)% vs. 98 (97-99)% among black flies. Although clearly demonstrating the potential of adverse impact on filter-feeding chironomids in operational black fly programs, these trials also confirmed the narrow impact of B.t.i. on the overall stream insect community.

Use of an indigenous fish species, Fundulus zebrinus, in a mosquito abatement program: a field comparison with the mosquitofish, Gambusia affinis.

Abstract: Studies were conducted relating mosquito production in small ponds to presence or absence of larvivorous fishes. Data collected showed that native killifish and introduced mosquitofish controlled mosquito larvae at the same level and support the use of indigenous fish species in mosquito abatement programs.

Evaluation of methoprene (Altosid XR) sustained-release briquets for control of culex mosquitoes in urban catch basins.

Abstract: A sustained-release, briquet formulation of methoprene (Altosid XR), applied at a rate of one briquet per catch basin in Saginaw, Michigan, provided ca. 70% reduction in emergence of Culex pipiens and Cx. restuans adults, compared with nontreated catch basins, during a period of 15 wk in the summer of 1990. In a parallel study using one briquet per 10.5 liter bucket, there was 99% reduction in adult emergence of these species for a period of 12 weeks. The difference between catch basins and buckets may be attributable to water movement through the catch basins with each rainfall, causing a dilution of methoprene through time. However, both studies indicated that the briquets released methoprene for 12-15 wk, suggesting that this formulation may offer season-long control of Culex mosquitoes from urban catch basins in Michigan, with a single treatment of insecticide.

Fate of Bacillus sphaericus and Bacillus thuringiensis serovar israelensis in the aquatic environment.

Abstract: Bacillus sphaericus spores were suspended in bottles of filtered (0.45 microns) freshwater and seawater under various conditions of temperature, pH and salinity. Heat resistant culturable counts (spores) slowly decreased with time. Spores suspended in dialysis bags submerged in a freshwater pond or in flowing seawater underwent a more rapid drop in heat resistant spore counts than did spores held in bottles. Thus, laboratory studies may overestimate spore longevity in the environment. Spore settling rate was related to the nature of particulate material in the water column. Paraspores (or perhaps spores and toxin) of B. thuringiensis serovar israelensis (B.t.i.) had a greater tendency to adhere to and settle with suspended sediment and fine particulates than did paraspores of B. sphaericus. These observations may at least partially explain the greater persistence of B. sphaericus larvicidal activity in field tests than that of B.t.i..

Lethal effects of ivermectin on Anopheles quadrimaculatus.

Abstract: Female Anopheles quadrimaculatus adults were blood fed on 15 mixed breed dogs 4 h after the dogs were given oral dosages of ivermectin Dogs were divided into 5 treatment groups of 3 dogs each, at 10, 500, 1,000, 2,500 micrograms/kg, and untreated Additionally, An quadrimaculatus were fed on lambskin-membranes containing blood drawn from one dog in each treatment group Mosquitoes were allowed to feed on the dogs or the lambskin-membranes and were observed for death at 24 and 48 h post-feeding Greater than 90% mortality was recorded in all ivermectin treatment groups except at the 24 h post-feeding period with the 10 micrograms/kg dog dose blood fed through the lambskin-membrane (654% mortality) The highest 2 dosages produced 100% mosquito mortality at 48 h post-feeding from either a dog or the in vitro system using a lambskin-membrane

Influence of moonlight on light trap catches of the malaria vector Anopheles nuneztovari in Venezuela.

Abstract: A significant effect (P = 0.002) of moonlight on light trap catches of Anopheles nuneztovari females was observed during a longitudinal study in western Venezuela. The catch with no moon was 1.86 times larger than with full moon. Nevertheless, moonlight does not seem to have any effect on the composition of adult mosquito population since the difference in the parous rate of females collected during full moon and during no moon was not significant (P greater than 0.05).

Evaluation of a funnel trap for collecting copepods and immature mosquitoes from wells.

Abstract: A simple funnel trap which inverts on entry to and exit from the water, was evaluated with respect to sampling the aquatic fauna of wells in and around Fortaleza, Brazil. Mosquito larvae, copepods, ostracods, fish and tadpoles were collected. When known numbers of Culex quinquefasciatus larvae and Mesocyclops aspericornis copepods were introduced into negative wells, overnight sampling resulted in 50% positivity of traps when 10 larvae (1/1,000 cm2) and 25 copepods (1/176 liters) were introduced. All traps were positive when 100 and 400 larve and copepods, respectively, were present. Over a range of 10-2,000 and 25-800 released larvae and copepods, respectively, average recovery rates were 6.1 and 3.6%, but on the basis of one sample, the variability was such that a precise estimate of absolute abundance could not be made.

Variation in Aedes aegypti larval indices over a one year period in a neighborhood of Mérida, Yucatán, México

Abstract: Surveys for Aedes aegypti larvae were conducted to provide an estimate of the magnitude and timing of seasonal variations in larval indices in one colonia in Merida, Yucatan, Mexico, and to assess how the proportion of disposable and non-disposable containers as larval production sites varies. Breteau indices exceeded 200 during the months of July and August, and disposable containers were important year-round larval production sites.

Transmission of La Crosse virus by four strains of Aedes albopictus to and from the eastern chipmunk (Tamias striatus).

Abstract: Eastern chipmunks were successfully infected with La Crosse virus by bites of 3 New World strains of Aedes albopictus infected orally or transovarially. The virus was subsequently passed from the chipmunks to Ae. albopictus, POTOSI strain, and Ae. triseriatus. The chipmunks developed viremias of 1-4 days duration and antibody titers were similar in intensity and duration to those reported in chipmunks infected by Ae. triseriatus. After feeding on viremic chipmunks, Ae. albopictus became infected and transmitted La Crosse virus at rates similar to the native vector, Ae. triseriatus. Aedes albopictus transmitted La Crosse virus transovarially to first gonotrophic cycle offspring.

Sporozoite transmission by Anopheles freeborni and Anopheles gambiae experimentally infected with Plasmodium falciparum

Abstract: A micro-membrane feeding technique was used to evaluate sporozoite transmission for Anopheles freeborni and An. gambiae experimentally infected with Plasmodium falciparum. From cohorts of infected mosquitoes with equivalent sporozoite loads, 75.9% of 29 An. freeborni transmitted a geometric mean (GM) of 4.9 sporozoites and 80% of 30 An. gambiae transmitted a GM of 11.3 sporozoites. Ingested sporozoites, in the blood meal immediately after feeding, were detected in 86.2% of 29 An. freeborni (GM = 9.0) and in 70% of 30 An. gambiae (GM = 44.1). Overall, sporozoites were transmitted and/or ingested by 90% of both species. Most infective mosquitoes transmitted < 1% of the total sporozoites in the salivary glands, and only up to 30% of the variation in transmission, ingestion, or total sporozoite output was related to sporozoite loads. The demonstration that An. gambiae transmitted more than twice as many sporozoites as An. freeborni is the first indication that vector species of anopheline mosquitoes differ in their innate potential for sporozoite transmission.

Seasonal incidence and horizontal distribution patterns of oviposition by Aedes aegypti in an urban environment in Trinidad, west Indies.

Abstract: The oviposition patterns of Aedes aegypti in ovitraps placed along 5 horizontal transects were monitored weekly for 52 wk (January to December 1988) in St. Joseph, Trinidad. Of the 2,550 ovitraps exposed, 270 were lost and 1,177 (52%) out of 2,280 were used by gravid females, containing 38,118 eggs. During the dry season 43% (16,265 eggs) of the eggs were collected whereas during the wet season 57% (21,853 eggs) were collected. Ovitraps exposed under eaves, under houses and in the open yard attracted similar oviposition occurrences and proportions of eggs. Inspections of the 52 properties within St. Joseph revealed that 17 (House Index = 32.7%) harbored Ae. aegypti pre-adult stages. The container index was 5.5%. This study revealed no evidence of behavioral changes in the container preferences of Ae. aegypti in St. Joseph, Trinidad, after 12 years of treating with fenthion and temephos.

Reduced mosquito production in cemetery vases with copper liners.

Abstract: Water-holding stone vases were sampled in 4 central Florida cemeteries to compare the prevalence of mosquitoes in containers with and without metallic liners. Overall, immature mosquitoes were found in more than 60% of the vases lacking liners and in more than 50% of the vases with aluminum liners. Significantly fewer vases with copper liners were positive for mosquitoes. High mortality and a lack of development were observed in a field test involving the introduction of Aedes aegypti larvae into stone vases with copper liners.

Effects of ultra-low volume and thermal fog malathion, Scourge and naled applied against caged adult Culicoides furens and Culex quinquefasciatus in open and vegetated terrain.

Abstract: The adulticidal effect of ULV and thermal fog malathion, Scourge and naled was tested at 2x label dosage (1.42, 0.22, 0.39 oz/acre, respectively) against caged Culicoides furens and Culex quinquefasciatus in open and vegetated (orange grove) terrain. Cages were at 122 cm elevation and positioned at 15.2, 45.7, 76.2, 106.7, 137.2 and 167.6 m from the line of insecticide release. Ultra-low volume applications of all 3 insecticides were markedly more effective than thermal fog under all conditions, especially in vegetated terrain. Of the 3 insecticides, malathion performed the poorest, especially against Cx. quinquefasciatus (in which there was some resistance) and particularly when applied as thermal fog. Scourge and naled were about equally effective. The best adulticide against C. furens was naled, which was clearly superior applied as ULV. It yielded 75% mortality out to 283 m in the open, and to 38 m in the presence of dense vegetation.