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PubMed1998

Knowledge, attitude and practices related to dengue in rural and slum areas of Delhi after the dengue epidemic of 1996.

To assess the knowledge and attitudes about dengue and practice of prevention followed by the residents of a rural area and an urban resettlement colony of East Delhi, an interview based cross sectional KAP study was undertaken in Jan 97 to Feb 97, a few months after the dengue epidemic in rural area and urban areas of East Delhi. A pre-structured and pre-tested format containing the relevant questions was administered to the subjects. A total of 687 subjects (334 rural and 353 urban) were interviewed. Nearly four fifth (82.3%) of these were aware of Dengue. Audiovisual media was the most common source of information in both the areas. Knowledge about the disease was fair to good. Fever was the commonest symptom of the disease known to 92% urban and 83% rural respondents followed by symptoms of bleeding and headache. Mosquito was known to spread the disease to 71% rural and 89% urban respondents. More than two third respondents in urban and two fifth in rural areas had used some method of mosquito control or personal protection during the epidemic.

Cross-Sectional Studies↗

PubMed1996

Monitoring community response to malaria control using insecticide-impregnated bed nets, curtains and residual spray at Nsukka, Nigeria.

A project testing the efficacy of insecticide (permethrin)-impregnated bed nets, compared with impregnated door and window curtains, residual house spraying, and a control group was implemented in 12 village clusters in the Nsukka Local Government Area of Enugu State, Nigeria, using epidemiologic and entomologic indicators. The appropriate materials and services were given free to all families. During the first year of study, three monitoring exercises were carried out in a random selection of homes where children under 5 years of age resided. Information was collected on perceived effectiveness of the interventions, condition of nets and curtains, reasons for not sleeping under nets, and recall of steps required in caring for nets and curtains. Bed nets were perceived as more effective in reducing mosquito bites compared with the two other interventions. At the last monitoring period, which occurred a few weeks before a re-impregnation exercise, respondents also perceived bed nets to be most effective in preventing malaria. These findings coincided with epidemiologic evidence. Curtains, especially those at doors, were more likely to be torn and dirty than bed nets. Although holes would not reduce the effectiveness of the insecticide, they could reduce the 'beauty' of the curtains, a perceived benefit that initially attracted villagers to both curtains and nets. Bed net owners reported significantly less frequent use of other mosquito control measures in their homes than did members of the other groups. Finally, bed net users demonstrated increased knowledge of use and care steps than did those with curtains. These findings suggested a high level of social acceptability of bed nets, and point to the need to test their acceptability further under conditions where people would pay for nets and communities would manage distribution and re-impregnation systems.

Bedding and Linens↗

PubMed1991

Effect of permethrin treatment of cattle on Psorophora columbiae populations: preliminary field test of a host management concept.

The results of a field test conducted in cooperation with the Jefferson Davis Parish Mosquito Abatement District (JDPMAD) during 1988 in southwestern Louisiana suggested that the biweekly treatment of cattle with permethrin reduced the number of adult Psorophora columbiae in nearby areas. Routine mosquito control operations by JDPMAD were similar from 1987 to 1988 in the cattle-treated area but increased an average of 41% in control areas. In spite of this, during the year of cattle treatment, captures in New Jersey light traps averaged 86 and 26% of the previous 4-year average in control and treated areas, respectively. Similarly, the proportion of trap nights in 1988 when Ps. columbiae captures exceeded 500 averaged 73 and 30% of the previous 4-year average in control and treated areas, respectively. Simulation model projections that took into account differences in JDPMAD operations, weather, cattle density, agricultural practices and the presence of treated cattle were accurate within an average of 9% of observed values for the treated and control areas. The simulation studies indicated that the treatment of cattle with permethrin reduced Ps. columbiae populations by 83%. These results suggest that host management may be a viable method for suppressing populations of Ps. columbiae and that some form of host management be considered for inclusion in integrated control programs in this environment. Further evaluation of this concept is warranted.

Animals↗

PubMed1996

Newsletters as a channel for communication in a community-based Aedes aegypti control program in Marília, Brazil.

In Marília, Brazil, community newsletters were established in a pilot project on community-based Aedes aegypti control. The newsletters were an excellent way of promoting communication between community members and project personnel. While people might not have attended a dengue meeting, they did turn up at meetings to plan the newsletters. During these meetings project staff obtained information about the communities that was crucial for planning a community-based recycling project that targeted many Aedes aegypti larval habitats. The newsletters were not an appropriate channel for transmitting information about dengue prevention and mosquito control.

Aedes↗

PubMed2002

West Nile virus.

West Nile (WN) virus is a mosquito-borne flavivirus and human, equine, and avian neuropathogen. The virus is indigenous to Africa, Asia, Europe, and Australia, and has recently caused large epidemics in Romania, Russia, and Israel. Birds are the natural reservoir (amplifying) hosts, and WN virus is maintained in nature in a mosquito-bird-mosquito transmission cycle primarily involving Culex sp mosquitoes. WN virus was recently introduced to North America, where it was first detected in 1999 during an epidemic of meningoencephalitis in New York City. During 1999-2002, the virus extended its range throughout much of the eastern parts of the USA, and its range within the western hemisphere is expected to continue to expand. During 1999-2001, 142 cases of neuroinvasive WN viral disease of the central nervous system (including 18 fatalities), and seven cases of uncomplicated WN fever were reported in the USA. Most human WN viral infections are subclinical but clinical infections can range in severity from uncomplicated WN fever to fatal meningoencephalitis; the incidence of severe neuroinvasive disease and death increase with age. Serology remains the mainstay of laboratory diagnosis. No WN virus-specific treatment or vaccine is available. Prevention depends on organised, sustained vector mosquito control, and public education.

Adolescent↗

PubMed2005

Potential use of pyriproxyfen for control of Aedes aegypti (Diptera: Culicidae) in Iquitos, Perú.

The effects of pyriproxyfen were tested against a local population of Aedes aegypti (L.) in Iquitos, Perú. Bioassays showed that, when applied to late instars, pyriproxyfen prevented adult emergence at extremely low concentrations (LC50 = 0.012 ppb). There was no adult emergence from water sampled from storage tanks that had been seeded with the equivalent of 50-83 ppb (AI) pyriproxyfen. Five months after treatment, despite constant dilution of these tanks, water sampled from these sources continued to be lethal to larvae and pupae. Additional studies, carried out in the laboratory, showed that groups of five or 20 female blood-fed mosquitoes, exposed to residues of approximately 0.003 g (AI) pyriproxyfen/m2, could transfer enough chemical to new oviposition sites to prevent approximately 80% of adult emergence from larvae developing in that previously uncontaminated water. Moreover, although the fecundity of the adult females used as the transfer vehicles in these tests was unaffected, the subsequent eclosion of the eggs that these mosquitoes laid was decreased by 70-90%. It also was shown that, at very high concentrations (>30,000 ppb), pyriproxyfen-treated water sources were as likely to be used as oviposition sites as untreated sources. These data suggest that treated sites might act as sinks for mosquito reproduction and moreover that such sites might act as dissemination sources for the horizontal transfer of larvicides to new environments by mature females. We review the literature on the environmental and human health effects of this compound and discuss its potential for use as a mosquito control agent in the field.

Aedes↗

PubMed1994

[The mosquitocidal efficacy of microcapsules of alpha-cypermethrin against Anopheles sinensis].

The efficacy of spraying of alpha-cypermethrin microcapsule for the control of Anopheles sinensis was investigated when alpha-cypermethrin microcapsule was sprayed at 0.5 g/m2, the KT50 was 7.9 min and a 100% of 24 hours' mortality of An. sinensis, the efficacy being similar to that of the emulsion. 180 days after spray, the KT50 was 28.2 min, the 24 hours' mortality was 85.7%, the residual efficacy was 3 times over that of the emulsion. In the mimic field experiment, similar results were obtained. In the field trial, the residual efficacy of the alpha-cypermethrin microcapsule was 5.9 times that of the emulsion. Alpha-cypermethrin microcapsules is recommended as a good formulation of mosquitocide for mosquito control, considering its mosquitocidal efficacy and residual efficacy.

Animals↗

PubMed2003

California state Mosquito-Borne Virus Surveillance and Response Plan: a retrospective evaluation using conditional simulations.

The California Mosquito-Borne Virus Surveillance and Response Plan recently was developed to provide a semi-quantitative means for assessing risk for western equine encephalomyelitis (WEE) or St. Louis encephalitis (SLE) viruses and to provide intervention guidelines for mosquito control and public health agencies during periods of heightened risk for human infection. West Nile virus recently has arrived in California, and the response plan also will provide a baseline for assessing the risk for human and equine infection with this virus. In the response plan, overall risk is calculated by averaging risk due to 1) environmental conditions, 2) adult mosquito vector abundance, 3) vector infection rates, 4) sentinel chicken seroconversion rates, 5) equine cases (for WEE), 6) human cases, and 7) the proximity of virus activity to populated areas. Overall risk is categorized into three levels: normal season, emergency planning, or epidemic conditions. We evaluated this response plan using historical data from years with no, enzootic, and epidemic activity of WEE and SLE in several areas of California to determine whether calculated risk levels approximated actual conditions. Multiple methods of risk calculation were considered for both viruses. Assessed risk based on cumulative temperature, rainfall, and runoff levels over the entire season provided more or equally accurate assessments than biweekly assessments based solely on the previous half-month. For WEE, during years with enzootic activity or early-season periods of years with WEE epidemic activity, combining horse and human cases as a single risk factor improved the model's ability to forecast pending WEE activity, but separating the two factors allowed a better indication of WEE activity during epidemics and periods with no activity. For SLE, assignment of higher risk to drier conditions as measured by rainfall and runoff yielded the most accurate representation of actual virus activity during all recent study periods.

Animals↗

PubMed1977

St Louis encephalitis. The 1975 epidemic in Mississippi.

In 1975, 229 laboratory-documented cases of St Louis encephalitis, 36 of which resulted in death, occurred in Mississippi. A total of 58% of these persons had encephalitis, 15% had aseptic meningitis, 21% had a febrile illness with no known CNS involvement, and 6% had other syndromes. Attack rates and case-fatality ratios increased with age. Although 60% of the cases occurred in a four-county area of northwest Mississippi, cases occurred in 42 of the 82 counties throughout the state. The epidemic erupted almost simultaneously, with variable intensity, in widely separated areas. Mosquito-control, measures were applied, but the results were not quantified.

Adolescent↗

PubMed1961

Field performance of dieldrin/resin wettable powders on sorptive mud surface.

Recent field experiments on the relative performance of dieldrin and dieldrin/resin wettable powders on sorptive mud surface have not confirmed the promising results obtained with the latter products in earlier laboratory tests. In view of this a renewed investigation into the possible factors governing the performance of such products was considered desirable, and further laboratory and field experiments were carried out in co-operation with the Colonial Pesticides Research Unit at Arusha, Tanganyika.The results of these experiments have given a better understanding of the factors involved, and a coherent interpretation of the differences in performance shown by various products under different conditions. The main factors to be taken into account appear to be: mobility of the insects during exposure, as influenced by insect species and exposure conditions; inherent toxicity of the dieldrin/resin particles; and the average relative humidity inside the experimental huts.The sorption phenomenon can be demonstrated in the field, but in view of the humidity conditions it does not seem likely that it will interfere seriously with practical mosquito control. A potential critical condition might be prevalent only in areas where the presence of sorptive mud is coupled with long periods of low humidity inside the huts, but further experimental data are necessary to confirm this.

Animals↗

PubMed2005

Patterns of insecticide resistance in larval Culex pipiens populations in Israel: dynamics and trends.

Resistance to insecticides of larval Culex pipiens populations in Israel has been monitored for ten years and the results were used for control planning. The insecticides tested were the organophosphates chlorpyrifos, fenthion, and temephos and the pyrethroids permethrin and cypermethrin. Over the years the relative resistance (R/R) values to chlorpyrifos in most populations tested were between 200-400, with records of up to 700 R/R. Practically no susceptible populations were found and the compound has been withdrawn from use, resulting in a decrease in the relative resistance values. In 1996 when fenthion was reintroduced, no resistant populations were found, but in the following years significant resistance appeared in an increasing number of populations with values lower than recorded for chlorpyrifos but still high (up to 100 R/R). All populations tested were found to be susceptible to temephos and accordingly the compound was reintroduced in 2002. Over the ten years, no significant resistance to cypermethrin was found in the majority of the populations tested, while a trend of increased resistance to permethrin was noted with a few records of >1000 R/R. The results demonstrate the importance of continuous monitoring of insecticide resistance for efficient mosquito control. Alternative insecticides and methods of control are discussed.

Animals↗

PubMed1978

Eastern equine encephalitis in Massachusetts, 1957-1976. A prospective study centered upon analyses of mosquitoes.

Reappearance of eastern equine encephalitis (EEE) in Massachusetts residents in the 1970's provided an opportunity to assess the predictive value of data on rainfall, EEE in horses, and carriage of EEE virus (EEEV) by mosquitoes, factors which had been studied annually since the last EEE outbreak in 1955-1956. The cycle of multiple cases during 1973-1975 started in a second consecutive year of rainfall that exceeded the annual mean by more than 20 cm, conditions recapitulating the 1955-1956 experience. In 1973, widespread EEE fatalities in horses presaged human cases, another recapitulation of the 1955-1956 experience. However, in 1974, when horses were immunized extensively, no equine cases were seen even though three human fatalities occurred. An unseasonably early appearance of EEEV in mosquitoes was the only basis upon which the threat to humans could have been recognized. These changes in the recognition and distribution of EEEV activity from season to season illustrate the difficulty in making rational decisions regarding widespread aerial insecticide applications for mosquito control.

Animals↗

PubMed1995

Risk factors for dengue infection during an outbreak in Yanes, Puerto Rico in 1991.

In November 1991, during a five-month dengue outbreak, we performed epidemiologic and serologic surveys linked to an earlier entomologic study in a community of 425 houses in Yanes (Florida), Puerto Rico. We obtained a household response rate of 95% (98 of 103) and blood samples from 84% (345 of 410) of the participants. Dengue incidence, as volunteered by the respondents, was 5% (21 of 410), but serologic diagnosis (immunoglobulin M and IgG-enzyme-linked immunosorbent assays [ELISA]) indicated a recent infection rate of 18% (59 of 331). The presence of anti-dengue antibodies was detected in 277 (84%) of 331 persons tested. In our final sample of 65 households and 112 persons, we analyzed (by univariate and multivariate logistic regression methods) the association of 12 entomologic, environmental, and behavioral variables with the proportion of household members with laboratory-confirmed recent dengue. The number of female Aedes aegypti per person was the only significant (P = 0.02) household risk factor. The results of our study underscore the importance of intradomiciliary mosquito populations in dengue transmission, and may serve as a guide for mosquito control efforts.

Adolescent↗

PubMed2005

Carlos Finlay and yellow fever: triumph over adversity.

The eradication of yellow fever in Havana, Cuba, was achieved by a fruitful collaboration between American and Cuban physicians. Carlos Finlay, a Cuban physician who proposed the mosquito-vector theory in 1881, shared his ideas, his publications, and a sample of mosquito eggs with the U.S. Army Yellow Fever Commission. The commission, headed by MAJ Walter Reed, used human volunteers to confirm Finlay's theory. MAJ William Gorgas adopted mosquito-control measures in his sanitation program and, within 6 months, yellow fever was controlled in Havana for the first time. Finlay held fast to his ideas despite incredulity and ridicule. His tenacity and scientific honesty vindicated his ideas about yellow fever.

Animals↗

PubMed1988

Method for determining settling rates of Bacillus thuringiensis serotype H-14 formulations.

A water-column apparatus is described in which settling rates of Bacillus thuringiensis serotype H-14 [B.t. (H-14)] formulations can be indirectly quantified using mortality of mosquito larvae at restricted depths as an index of B.t. (H-14) activity. To illustrate the type of data provided by this method, commercial B.t. (H-14) products (Bactimos, Teknar, Vectobac) and experimental formulations were compared at the manufacturers' recommended rates for mosquito control. All evaluations utilized laboratory-reared, 4th-instar Aedes aegypti larvae. The procedure can be used to provide an index of suspension properties of different B.t. (H-14) formulations and to measure dispersion rates of granular formulations resting at the bottom of a water column. Standardization of the method provides a convenient and practical means of generating comparative data on the effectiveness of B.t. (H-14) and other mosquito larvicides against specific target species.

Aedes↗

PubMed1987

The residual effect of temephos (Abate 4-E) on nontarget communities.

The impact of mosquito control on nontarget organisms using Abate-4-E was investigated in terms of immediate mortality and residual activity. Three 10 year old, man-made ponds having similar community structures and population densities were studied. The residual activity, determined by bioassays with 4th instar Aedes communis, was significantly longer in a relatively cooler pond. Populations of copepods and Cladocera took longer to return to control densities in that same pond. The role played by the physicochemical characteristics of the pond water as well as the intrinsic susceptibility and recovery capacity of the populations considered are discussed.

Aedes↗

PubMed2000

Murray Valley encephalitis in Western Australia in 2000, with evidence of southerly spread.

We describe the epidemiological and clinical features of human Murray Valley encephalitis (MVE) and Kunjin (KUN) virus infections in Western Australia (WA) during March to July 2000. A case series was performed. For laboratory-confirmed cases, travel histories and clinical details were collected from patients, family members, friends or treating physicians. Surveillance data from the sentinel chicken program and climatic conditions were reviewed. Nine encephalitic cases of MVE were recorded. Eight were non-Aboriginal adults (age range, 25 to 79 years; 5 male, 3 female) and 1 was an Aboriginal boy. Four cases acquired infection in the Murchison and Midwest regions of WA from which no human cases of MVE have been reported previously. One of the 9 cases was fatal and 3 had severe neurological sequelae. Five non-encephalitic infections were also recorded, 3 MVE and 2 KUN. Encephalitis caused by MVE virus remains a serious problem with no improvement in clinical outcomes in the last 25 years. Excessive rainfall with widespread flooding in the northern two-thirds of WA provided ideal conditions for mosquito breeding and favoured southerly spread of the virus into new and more heavily populated areas. Surveillance in WA with sentinel chickens and mosquito trapping needs expansion to define the boundaries of MVE virus activity. To enable timely warnings to the public, and to institute mosquito control where feasible, continued surveillance in all Australian areas at risk is indicated.

Adult↗

PubMed1993

Application of radar rainfall estimates for surveillance of Aedes taeniorhynchus larvae.

A preliminary investigation of land-based radar rainfall estimates for surveillance of Aedes taeniorhynchus larvae was conducted from January 1 to May 21, 1991 in Collier County, FL. Rainfall estimates from the National Weather Service RADAP II radar system, supplemented with tide gauge data, served as criteria for larval inspection. Rain, rain+tide and tide, respectively, triggered 48, 26 and 26% of the 14 proposed inspection trips. This system detected 7/8 larval broods found by Collier Mosquito Control District surveillance; the only brood not detected consisted of stragglers from an earlier brood exposed to cool weather and methoprene. A QUICKBASIC program that extracts Cartesian coordinates and rainfall estimates from RADAP II B-SCAN data was developed.

Aedes↗