Showing papers in "Journal of The American Mosquito Control Association in 1989"

Carbon dioxide and 1-octen-3-ol as mosquito attractants

Abstract: Interval suction traps were used to study the attractant effect of CO2 and 1-octen-3-ol on trap catches of mosquito populations at 2 different locations in Florida. There was no significant increase in the numbers of mosquitoes caught when the concentration of CO2 was increased from 200 to 1,000 cc/min. One-octen-3-ol used by itself attracted mosquitoes in numbers similar to CO2 released at 200 cc/min. One-octen-3-ol and CO2 acted synergistically in attracting significantly greater numbers of Aedes taeniorhynchus, Anopheles spp. and Wyeomyia mitchellii than either bait used singly, although the response of Culex spp. to this bait combination was less pronounced. Ceratopogonidae (Culicoides furens) and Tabanidae (Diachlorus ferrugatus, Tabanus nigrovittatus and Chrysops spp.) were also attracted to the combined bait.

Repellents and other personal protection strategies against Aedes albopictus.

Abstract: Five chemical repellents, a controlled-release repellent formulation, Avon Skin-So-Soft bath oil and permethrin-impregnated clothing fabric were assayed for personal protection against bites of Aedes albopictus. On skin the chemical repellents provided significant (P = 0.05) protection from biting; however, Ae. albopictus was more sensitive to the repellents than the standard, Ae. aegypti. Two experimental repellents provided 6-7 h protection from bites, 25% deet in ethanol provided greater than 8 h protection, a controlled-release formulation containing 35% deet provided greater than 10 h protection, and the Avon product provided 0.64 h protection from bites. Permethrin-treated fabric provided complete protection from mosquito bites through 0-5 washings. Repellent products containing greater than or equal to 12% deet should provide satisfactory protection against Ae. albopictus; the use of permethrin-impregnated clothing should provide additional protection.

Interspecific mating between Louisiana strains of Aedes albopictus and Aedes aegypti in the field and laboratory.

Abstract: Interspecific mating between Aedes albopictus males and Ae. aegypti females was detected in the field using mark-release-recapture techniques. By 3 days after the release of virgin Ae. aegypti females into a field site containing only Ae. albopictus, 100% of the captured females were inseminated. Laboratory investigations indicated that male Ae. albopictus were very proficient at inseminating Ae. aegypti females and that Ae. aegypti males rarely inseminated Ae. albopictus females, especially if Ae. aegypti females were available. Most of the Ae. aegypti females inseminated by Ae. albopictus males contained only small amounts of dead sperm in their spermathecae, while inseminated females from the converse interspecific mating and from intraspecific matings contained only large amounts of live sperm. The results are discussed in relation to the decline in Ae. aegypti densities observed since the introduction of Ae. albopictus into the southern USA.

Recently introduced Aedes albopictus in the United States: potential vector of La Crosse virus (Bunyaviridae: California serogroup)

Abstract: A population of Aedes albopictus collected in 1986 in Harris County, Texas, was evaluated for its vector competence with 4 California serogroup viruses (Jamestown Canyon, Keystone, La Crosse and trivittatus). Rates of midgut infection, dissemination of virus beyond the midgut and oral transmission to suckling mice were markedly different for the 4 viruses in a pattern representative of the antigenic relationships known for the California serogroup. Only La Crosse virus was shown to be efficiently transmitted by this recently introduced mosquito population. The results suggest that populations of Ae. albopictus originating from the Harris County population might well be as efficient in transmitting La Crosse virus as are populations of the natural mosquito vector. Aedes triseriatus, from the midwestern La Crosse virus enzootic region. The public health implications of these results are discussed in relation to the rapid spread of Ae. albopictus throughout the eastern half of the United States and into regions where La Crosse virus is known to be enzootic.

The runnelling method of habitat modification: an environment-focused tool for salt marsh mosquito management.

Abstract: Traditional methods of managing salt marsh mosquitoes focus primarily on maximizing the reduction of mosquito populations, with minimizing environmental impact as a secondary consideration. An environment-oriented approach to salt marsh management for mosquito control, runnelling, is described and compared with other forms of habitat modification such as ditching and Open Marsh Water Management (OMWM). Runnelling alters the salt marsh as little as possible while causing significant reductions in mosquito numbers. The effect of runnelling on the environment was monitored via the following variables: water table level, substrate characteristics (moisture, salinity and pH), vegetation (height and density of each Sporobolus virginicus) and the numbers of mosquito larvae. Runnelling had a statistically significant effect on only two of the seven variables. These were the height of Sporobolus, which increased near runnels, and the number of mosquito larvae, which decreased. The main difference between ditching, OMWM and runnelling lies in the magnitude of the habitat modification. Ditching involves the greatest alteration to the marsh, and runnelling the least. Consequently, runnelling has a smaller effect on the estuarine environment as a whole than does either ditching or OMWM.

A broad evaluation of B.t.i. for black fly (Diptera: Simuliidae) control in a Michigan river: efficacy, carry and nontarget effects on invertebrates and fish.

Abstract: Efficacy for black fly control, carry and nontarget effects of B.t.i. (Teknar HP-D), applied in the Betsie River, Michigan, were studied in June 1988. Black fly mortality was high (approximately 100%) for a 2,200 m stretch downstream from the application site, declined to 30% at 3,200 m, and was nil at 4,500 m. Drift of black flies greatly increased after application at a downstream site, but did not change at an upstream site. There were no detectable nontarget effects of B.t.i. application on: 1) invertebrate macro- or micro-drift; 2) numbers of invertebrates in benthic Surber samples; 3) mortality or feeding of drifting and nondrifting insects; 4) growth or mortality of caged Stenomena sp. larvae; 5) invertebrate functional group composition; 6) mortality or weight change of caged rock bass; or 7) fish numbers, species composition, length-weight (rock bass only) relationships or rock bass diet. Sampling of Rheotanytarsus sp. midges on natural substrates indicated low (27%) mortality owing to B.t.i. at only 100 m downstream from the application site, with negligible mortality at all other downstream and upstream sites. This information, combined with no pronounced changes in numbers of midges in macro-drift after application, indicated that midge populations were not adversely affected by B.t.i. in the study.

Biology and distribution of Aedes albopictus and Aedes aegypti in Madagascar

Abstract: The biology and distribution of the 2 Malagasy Stegomyia species, Aedes aegypti and Aedes albopictus, is updated and reported. Aedes aegypti is present in the western and southern regions and Ae. albopictus in the east and on the high plateau. Some unusual locations are noted. The ranges of Ae. albopictus and Ae. aegypti on Madagascar overlap only slightly. Aedes aegypti is present in the west and in the south, while the Ae. albopictus distribution area is in the east and on the central high plateau. Climatic factors (number of dry months, annual rainfall and temperature), rather than competitive interactions, appear to be the major determinants of the distribution of these species. Aedes aegypti is just slightly anthropophilic, contrary to Ae. albopictus. Babanki virus and MMP 158 virus were isolated from Ae. aegypti; no virus has been isolated from Ae. albopictus.

Seasonal abundance and control of Culex spp. in catch basins in Illinois.

Abstract: Street catch basins in western Cook County, IL, were examined regularly June through August of 1987 to determine their seasonal larval production, adult mosquito harborage and the influence of abiotic factors on the associated mosquito population. Only larvae of Culex pipiens (63% of total) and Cx. restuans (37% of total) were recovered. These 2 species and Cx. erraticus were the most frequently collected adults. The abundance of mosquito larvae within catch basins was not correlated with water pH and only showed a weak, positive correlation with water temperature. Only a partial flushing of larvae (22-34% reduction) from catch basins by normal rainfall (less than 25 mm) was generally recorded. Treatments with larvicide oil (mineral seal oil/kerosene 175/tergitol) at a rate of 60-90 ml/catch basin resulted in a mean larval reduction of 97%. Adult females showed a mean reduction of 87%.

Laboratory evaluation of controlled-release repellent formulations on human volunteers under three climatic regimens.

Abstract: Six controlled-release personal-use topical insect/arthropod repellent formulations of diethylmethylbenzamide (deet) were evaluated in an environmental chamber on volunteers for repellency against the mosquitoes Aedes aegypti and Ae. taeniorhynchus under three climatic regimens: basic variable high humidity (tropical environment), basic constant high humidity (forested and wet environment) and basic hot (hot-dry environment). The best protection under all the climatic regimens was provided by the Biotek formulation. In a tropical environment, some formulations induced more biting from mosquitoes than the concurrent untreated control in the late hours of the testing. Repellency was not directly related to the deet concentration in the various controlled-release repellent formulations.

Experimental test of the influence of aquatic macrophyte cover on the survival of Anopheles larvae.

Abstract: Emergent or submergent macrophytes can enhance the survival of Anopheles larvae by providing favorable microhabitat and refuge from predation. The relationships among the amount of aquatic macrophyte cover, the density of Gambusia affinis, and survivorship of Anopheles freeborni larvae were tested experimentally. Larval survivorship was positively related to amount of plant cover and negatively related to Gambusia density. Larval survivorship was lowest in treatments with low plant cover and high fish density (0-15% survivorship) and highest in treatments with high plant cover and no fish (41-76% survivorship). Similar patterns of larval survivorship were found in enclosure experiments conducted at 3 sites, using 3 species of aquatic macrophytes (Potamogeton pectinatus, Myriophyllum aquaticum and M. spicatum).

Effects of sublethal dosages of insecticides on Culex quinquefasciatus.

Abstract: Groups of Culex quinquefasciatus were exposed as fourth instar larvae to sublethal concentrations (0.1 LC50 and LC50) of malathion, methoprene, propoxur or resmethrin. Females exposed as larvae to an LC50 level of methoprene had reduced wing length and longevity. Egg production was reduced by 50% and 39% in those mosquitoes exposed to LC50 levels of malathion or methoprene, respectively. In contrast, egg production and egg raft size increased following treatment with 0.1 LC50 levels of malathion or methoprene. Females exposed as larvae to methoprene laid 30% fewer eggs per raft, and egg hatching decreased 36% compared with controls. Females exposed as larvae to LC50 levels of malathion or methoprene laid shorter eggs than controls. The proportion of females in the adult population was reduced following exposure to either propoxur or resmethrin, and increased following exposure to malathion. Time to pupation and time of emergence of the adult populations were increased following exposure to most of the insecticidal treatments. These results indicated that a single, sublethal exposure to certain insecticides had a significant effect on mosquito reproduction.

Impact of new insect growth regulators and their formulations on mosquito larval development in impoundment and floodwater habitats.

Abstract: Four insect growth regulators were evaluated in the laboratory and field. In the laboratory, AC-291898 showed excellent activity, inducing 90% mortality in Culex quinquefasciatus and Aedes aegypti at 0.5-0.7 ppb. The EC formulation of XRD-473 was slightly more active than the technical material with an LC90 of 0.84 ppb and 0.92 ppb against Ae. aegypti and Cx. quinquefasciatus, respectively. In the field, AC-291898 at the rates of 0.005 and 0.01 lb AI/acre caused 85 and 100% inhibition of adult emergence of Cx. tarsalis 2 days after treatment. Activity, however, declined at the low rate, while the high rate remained active for more than 7 days. In the same species, XRD-473 induced complete inhibition of adult emergence 2 days after treatment at the rates of 0.01, 0.025 and 0.05 lb AI/acre. At the low rate (0.01 lb AI/acre), activity declined markedly, while the 2 higher rates remained active for one week. In Cx. peus larvae, AC-291898 at the rates of 0.005, 0.01 and 0.025 lb AI/acre produced complete inhibition of adult emergence 2 days after treatment, but activity declined at the 2 lower rates 7 days after treatment, while the high rate (0.025 lb AI/acre) remained active for more than one week. Methoprene (4%) pellets were effective against Cx. tarsalis for 7 days at the rates of 0.25 lb AI/acre whereas 0.5 lb AI/acre was required to obtain similar results against Cx. peus larvae.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between wing length and protein content of mosquitoes.

Abstract: Wing length and protein content were compared in individual specimens of male and nonbloodfed, nongravid female mosquitoes. The following groups were tested: field-collected and colonized Aedes aegypti, field-collected Culex nigripalpus and Aedes vexans, and colonized Culex quinquefasciatus and Psorophora columbiae. The correlation coefficient varied from 0.91 in Ae. aegypti males to 0.98 in Ae. vexans females, and in each group the P value was less than 0.001. This close correlation suggests that both wing length and protein measurement are reliable expressions of size in adult mosquitoes.

Personal protection afforded by controlled-release topical repellents and permethrin-treated clothing against natural populations of Aedes taeniorhynchus.

Abstract: Field tests evaluated repellent formulations containing deet in combination with permethrin-impregnated or untreated military uniforms against Aedes taeniorhynchus. No significant difference was determined between repellents in duration of protection whether or not permethrin-treated clothing was worn, but there were differences in efficacy relative to site of application. The head was the site of shorter duration of protection regardless of repellent tested. On repellent-treated skin, 12-30% of the bites were on arms, whereas 70-88% were on the head. When military repellent was used, the head was bitten 35% more often than with experimental repellents. On untreated clothing 80% of bites were through pants and 20% through shirts. Mean bites through untreated clothing were 0.7 bites/min/person (42/hr), whereas mean bites through permethrin-impregnated clothing were 0.0004/min/person (0.02/hr). Protection by permethrin-treated clothing relative to untreated clothing was 99.9%.

Comparison of several different trapping methods for Culicoides variipennis (Diptera: Ceratopogonidae).

Abstract: When battery operated CDC miniature incandescent and black light traps (with and without light bulbs) were operated with and without CO2, the rank of trap effectiveness for total numbers of female Culicoides variipennis caught was: black light plus CO2; CO2-baited trap without light bulb; black light without CO2; incandescent light plus CO2 and incandescent light without CO2. In 1983, the black light trap plus CO2 caught significantly more males and females than any other traps, and the incandescent light trap without CO2 caught significantly fewer females than any other traps. There were significant differences also in times gnats were collected, as well as in the gonotrophic condition of females caught in traps and that different traps caught different physiological/reproductive segments of the population. All catches revealed that gravid females began flying only a few min before sunset and peaked in the 1st h after sunset. Because it caught significantly larger numbers of females than other traps and because it was selectively attractive to gravid and parous females, the black light trap would be the trap of choice when large numbers of parous females are desired in arbovirus isolation studies.

Recent research on impregnated mosquito nets.

Abstract: The present status of impregnated mosquito nets and other impregnated materials is discussed. Research projects which have produced most of the publications on this subject were conducted in areas in Africa with relatively high endemicity of malaria. In these areas, usage of impregnated mosquito nets caused substantial reductions in the sporozoite inoculation rates and some reduction in incidence of malaria attacks. However, there was little or no reduction in parasite rates in the human population. In several countries in Asia and the Pacific, vector control with impregnated mosquito nets has been introduced on a large scale, thus proving its affordability and compatibility with local customs in these countries. Substantial reductions in malaria parasite rates have been obtained in areas with low levels of malaria transmission. In order to develop the vector control method which is most appropriate for each area, much more research is needed on the technical and organizational aspects of vector control with impregnated mosquito nets. Examples are given of data already available as well as an indication of gaps in knowledge which still exist and will need more attention.

Effects of weathering on fabrics treated with permethrin for protection against mosquitoes.

Abstract: Permethrin-impregnated and untreated fabrics were evaluated for their toxic and repellent effects against Anopheles stephensi and Aedes aegypti after both types of fabrics were subjected to accelerated weathering for 9 weeks, under a simulated wet/tropical environment. The toxic (knockdown) effect of permethrin-impregnated fabrics against both species of mosquitoes diminished rapidly after 1 week compared to the repellent effect. After 6 weeks of weathering, the remaining low amounts of permethrin provided fair protection from mosquito bites; however, no knockdown was observed at those levels. Permethrin-treated fabric was effective in providing protection from mosquito bites and appears to be a means of attenuating both the nuisance effects and, possibly, disease transmission by mosquitoes.

Biting and resting behavior of Anopheles darlingi in the Suriname rainforest.

Abstract: An experimental hut study was conducted on the biting and house resting behavior of Anopheles darlingi in the rainforest of Suriname. Of all anophelines collected on human bait at indoor and peridomestic sites, An. darlingi comprised 100% and 98%, respectively. A single peak in biting activity occurred around 2300 h. With hourly exit trap collections, a peak of exit from the hut was observed at sunrise. Of these mosquitoes, 91% were freshly fed. The indoor resting period was calculated to be about 4 h. When the human bait in the hut was protected by a mosquito net, only 18% of the exiting mosquitoes were fed and the resting period was about 3 h.

Community based bioenvironmental control of malaria in Kheda District, Gujarat, India.

Abstract: A study on the bioenvironmental control of malaria was launched in 1983 in Nadiad taluka, Gujarat, with help of village communities. The implementation of strategy resulted in the successful control of larval mosquitoes and reduction in the adult vector populations, and the impact was visible in the curtailment of malaria transmission in large rural areas. When compared with the residual spraying of insecticides under the National Malaria Eradication Programme, the alternate strategy was found feasible, socially acceptable, cost effective and brought about environmental improvement and awareness in the rural areas.

Behavioral responses of Anopheles darlingi in Suriname to DDT residues on house walls.

Abstract: A study was conducted in Suriname on the effects of DDT residual house spray on the main vector of malaria, Anopheles darlingi. Results obtained with an experimental hut sprayed with DDT wettable powder (2 g/m2 AI) were compared with results obtained with an unsprayed control hut. In the sprayed hut, entry rates were reduced by 32% and feeding success by 43.6%. The 24-h mortality of mosquitoes which entered the sprayed hut was 95% (range 85-100%) over the 10-month study period. After furnishing the sprayed hut according to local custom, no reduction in mortality was observed despite an abundance of unsprayed resting surfaces. Bioassays showed that the DDT deposits remained effective for at least 14 months. With excito-repellency test boxes an irritant effect caused by DDT on recently fed An. darlingi females was shown. With a choice-box experiment no preference for unsprayed over sprayed resting places could be demonstrated.

Cemetery vase breeding of dengue vectors in Manila, Republic of the Philippines.

Abstract: Aedes albopictus and Ae. aegypti were found breeding abundantly in cement vases within cemeteries in Manila. Aedes albopictus dominated in cemeteries containing vegetation which provided both shade and plant debris for the vase water. The highest larval densities for both species were found from August to December, which is from mid-to-late rainy season. Aedes albopictus is unable to compete successfully with Ae. aegypti in residential areas with sparce vegetation and thus is very limited in its distribution within the city. Biting activity of both species is similar, with peaks occurring between 0530-0600 h and 1730-1800 h.

Environmental factors affecting mortality of adult Culicoides variipennis (Diptera: Ceratopogonidae) in the laboratory.

Abstract: The effects of several environmental factors on mortality of adult Culicoides variipennis in the laboratory were evaluated. Daily mortality rates significantly increased when adult midges were maintained at an elevated constant temperature (26 degrees C). Adult C. variipennis handled the least during routine maintenance procedures had the lowest daily mortality rate. Survival was not significantly affected by varying density levels of adult midges in the size of container routinely used in our laboratory. Implications of these observations using adult C. variipennis for future studies are discussed.

Evaporation and skin penetration characteristics of mosquito repellent formulations.

Abstract: Formulations of the mosquito repellent N,N-diethyl-3-methylbenzamide (deet) in combination with a variety of additives were developed to control repellent evaporation and percutaneous penetration. Deet was also formulated with the repellent dimethyl phthalate to study the interaction of the two compounds on the skin. The evaporation and penetration processes were evaluated on whole and split-thickness pig skin using radiolabeled repellents with an in vitro apparatus. Under essentially still air and air flow conditions, one of the deet formulations resulted in significantly reduced total evaporation and percutaneous penetration of deet as compared to unformulated repellent. When deet and dimethyl phthalate were combined, neither repellent affected the total amount of evaporation and penetration of the other compound. However, initial percutaneous penetration and evaporation rates were slightly less and decayed less rapidly than when both chemicals were tested separately at the same dose. These results indicated a degree of competition of the two compounds for the same avenues of loss.

Detection of organophosphate detoxifying esterases by dot-blot immunoassay in Culex mosquitoes.

Abstract: A dot-blot immunoassay, using antiserum raised against esterase B1 responsible for organophosphate (OP) resistance in Culex quinquefasciatus, was used to study different laboratory strains and field collections of this species, as well as of Cx. pipiens, Cx. tarsalis, Anopheles albimanus and An. stephensi. The frequency of esterase B1 positive individuals revealed by this test was in agreement with the data obtained by other methods, indicating the potential of this method for the detection and monitoring of resistance due to increased detoxification by esterases.

Identification of species D, a new member of the Anopheles quadrimaculatus species complex: a biochemical key.

Abstract: Sibling species D, a new member of the Anopheles quadrimaculatus species complex was identified in collections from Pickwick Lake, Tishomingo County, Mississippi and Choctawhatchee, Bay County, in West Florida. This species occurred sympatrically with the previously described species, A, B and C. Evidence for identification of species D includes diagnostic allozymes, a lack of polytene chromosomes in the ovarian nurse cells, and inviability of F1 progeny and lack of sperm transfer in hybridization crosses. An electrophoretic taxonomic key for distinguishing species D from A, B and C is presented.

Irritability to DDT of natural populations of the primary malaria vectors in Colombia.

Abstract: Natural populations of Anopheles albimanus, An. darlingi and An. nuneztovari were tested for their irritability to DDT in different regions of Colombia. Individual anophelines were exposed to filter papers impregnated with 2% DDT and irritability was determined based on the number of flights a mosquito made in 15 min. All three species showed variability in their irritability to DDT. Anopheles albimanus showed irritability only in Bolivar, but not in three other regions. Anopheles darlingi showed no irritability in neither the Atlantico nor Llanos regions, while An. nuneztovari showed irritability in the Oriente but not in Uraba. The irritability to DDT shown in some populations of An. albimanus and An. nuneztovari may reduce the effectiveness of residual applications of this insecticide by causing the mosquitoes to seek untreated surfaces and/or leave the house to rest outdoors and thus avoid a lethal dose.

Fate and toxicity of temephos applied to an intertidal mangrove community.

Abstract: The distribution, persistence, and toxicity of the mosquito larvicide temephos was monitored following aerial applications to an intertidal mangrove community in Lee County, Florida. The amount of temephos penetrating to the mangrove floor ranged from 15 to 70% of the amount entering the upper leaf canopy, with 50-60% of that applied remaining on the mangrove leaves. Rainfall caused an additional influx of temephos from the leaves to the mangrove floor. Residues were detected in intertidal water at 2 h, but not 4 h after application. However, temephos was observed to persist in simulated tidal pools and on mangrove leaves for up to 72 h and in oysters for up to 48 h after application. Marine organisms placed in cages at 3 test sites and a control site were monitored for toxic effects. Mortality among natural mosquito larvae was simultaneously monitored. Mysids (Mysidopsis bahia) exhibited a significant mortality at one site during 1 of 3 applications monitored; however, no correlation was observed between mortality and temephos concentration in water. No significant mortality was observed for the other organisms, which included: brown shrimp (Panaeus aztecus), grass shrimp (Palaemonetes pugio), juvenile snook (Centropomis undecimalis) and sheepshead minnow (Cyprinodon variegatus).

Surveillance of St. Louis encephalitis virus vectors in Grand Junction, Colorado, in 1987.

Abstract: Grand Junction, Colorado, was the site of a St. Louis encephalitis (SLE) outbreak in 1985. Epidemiologic and ecologic investigations in 1985 and 1986 suggested that Culex tarsalis may not have been the exclusive vector in the outbreak and that Cx. pipiens may have contributed to transmission as an accessory vector. A limited field study in 1987 generally confirmed observations from 1986 that Cx. pipiens was more abundant than Cx. tarsalis in late summer when SLE virus transmission normally occurs. In both years, infection rates in Cx. tarsalis were higher than in Cx. pipiens, but in 1987 the only SLE virus isolate from Cx. pipiens was obtained early in the season. Truck trap collections showed that Cx. pipiens was the principal vector species collected, comprising 86% of the total. Light trap collections underestimated the population of Cx. pipiens; gravid trap collections gave a closer approximation of the relative proportions of Cx. pipiens and Cx. tarsalis in the vector mosquito population after midsummer.

Aedes bahamensis: its invasion of south Florida and association with Aedes aegypti.

Abstract: The exotic mosquito, Aedes bahamensis, is now well-established in south Florida, where it is widely distributed throughout Dade and southern Broward Counties in both urban and rural areas east of the Everglades. When discarded automobile tires were sampled in areas near human habitation, larvae and pupae of Ae. bahamensis were frequently found in association with immature Ae. aegypti. Elsewhere, however, Ae. bahamensis generally occurred in the absence of Ae. aegypti. The persistence of Ae. bahamensis populations at specific sites was documented in egg collections from ovitraps and in larval samples from the water retained in discarded tires.