Prevention Of Mosquito-borne Diseases Research Articles

Mosquito-Disseminated Insecticide for Citywide Vector Control and Its Potential to Block Arbovirus Epidemics: Entomological Observations and Modeling Results from Amazonian Brazil.

BackgroundMosquito-borne viruses threaten public health worldwide. When the ratio of competent vectors to susceptible humans is low enough, the virus’s basic reproductive number (R0) falls below 1.0 (each case generating, on average, <1.0 additional case) and the infection fades out from the population. Conventional mosquito control tactics, however, seldom yield R0 < 1.0. A promising alternative uses mosquitoes to disseminate a potent growth-regulator larvicide, pyriproxyfen (PPF), to aquatic larval habitats; this kills most mosquito juveniles and substantially reduces adult mosquito emergence. We tested mosquito-disseminated PPF in Manacapuru, a 60,000-inhabitant city (~650 ha) in Amazonian Brazil.Methods and FindingsWe sampled juvenile mosquitoes monthly in 100 dwellings over four periods in February 2014–January 2016: 12 baseline months, 5 mo of citywide PPF dissemination, 3 mo of focal PPF dissemination around Aedes-infested dwellings, and 3 mo after dissemination ended. We caught 19,434 juvenile mosquitoes (66% Aedes albopictus, 28% Ae. aegypti) in 8,271 trap-months. Using generalized linear mixed models, we estimated intervention effects on juvenile catch and adult emergence while adjusting for dwelling-level clustering, unequal sampling effort, and weather-related confounders. Following PPF dissemination, Aedes juvenile catch decreased by 79%–92% and juvenile mortality increased from 2%–7% to 80%–90%. Mean adult Aedes emergence fell from 1,077 per month (range 653–1,635) at baseline to 50.4 per month during PPF dissemination (range 2–117). Female Aedes emergence dropped by 96%–98%, such that the number of females emerging per person decreased to 0.06 females per person-month (range 0.002–0.129). Deterministic models predict, under plausible biological-epidemiological scenarios, that the R0 of typical Aedes-borne viruses would fall from 3–45 at baseline to 0.004–0.06 during PPF dissemination. The main limitations of our study were that it was a before–after trial lacking truly independent replicates and that we did not measure mosquito-borne virus transmission empirically.ConclusionsMosquito-disseminated PPF has potential to block mosquito-borne virus transmission citywide, even under adverse scenarios. Our results signal new avenues for mosquito-borne disease prevention, likely including the effective control of Aedes-borne dengue, Zika, and chikungunya epidemics. Cluster-randomized controlled trials will help determine whether mosquito-disseminated PPF can, as our findings suggest, develop into a major tool for improving global public health.

Efficacy of Some Wearable Devices Compared with Spray-On Insect Repellents for the Yellow Fever Mosquito, Aedes aegypti (L.) (Diptera: Culicidae).

The current Zika health crisis in the Americas has created an intense interest in mosquito control methods and products. Mosquito vectors of Zika are of the genus Aedes, mainly the yellow fever mosquito, Aedes aegypti. L. The use of repellents to alter mosquito host seeking behavior is an effective method for the prevention of mosquito-borne diseases. A large number of different spray-on repellents and wearable repellent devices are commercially available. The efficacies of many repellents are unknown. This study focuses on the efficacy of eleven different repellents in reducing the number of Ae. aegypti female mosquitoes attracted to human bait. We performed attraction-inhibition assays using a taxis cage in a wind tunnel setting. One person was placed upwind of the taxis cage and the mosquito movement towards or away from the person was recorded. The person was treated with various spray-on repellents or equipped with different mosquito repellent devices. We found that the spray-on repellents containing N,N-Diethyl-meta-toluamide and p-menthane-3,8-diol had the highest efficacy in repelling mosquitoes compared to repellents with other ingredients. From the five wearable devices that we tested, only the one that releases Metofluthrin significantly reduced the numbers of attracted mosquitoes. The citronella candle had no effect. We conclude that many of the products that we tested that were marketed as repellents do not reduce mosquito attraction to humans.

Long-lasting permethrin-impregnated clothing: protective efficacy against malaria in hyperendemic foci, and laundering, wearing, and weathering effects on residual bioactivity after worst-case use in the rain forests of French Guiana.

Personal protective measures against hematophagous vectors constitute the first line of defense against arthropod-borne diseases. However, guidelines for the standardized testing and licensing of insecticide-treated clothing are still lacking. The aim of this study was to analyze the preventive effect of long-lasting polymer-coated permethrin-impregnated clothing (PTBDU) against malaria after exposure to high-level disease transmission sites as well as the corresponding loss of permethrin and bioactivity during worst-case field use. Between August 2011 and June 2012, 25 personnel wearing PTBDUs and exposed for 9.5 person-months in hyperendemic malaria foci in the rain forest of French Guiana contracted no cases of malaria, whereas 125 persons wearing untreated uniforms only, exposed for 30.5 person-months, contracted 11 cases of malaria, indicating that PTBDU use significantly (p=0.0139) protected against malaria infection. In the field, PTBDUs were laundered between 1 and 218 times (mean 25.2±44.8). After field use, the mean remaining permethrin concentration in PTBDU fabric was 732.1±321.1min varying between 130 and 1270mg/m2 (mean 743.9±304.2mg/m2) in blouses, and between 95 and 1290mg/m2 (mean 720.2±336.9mg/m2) in trousers. Corresponding bioactivity, measured according to internal licensing conditions as KD99 times against Aedes aegypti mosquitoes, varied between 27.5 and 142.5min (mean 47.7±22.1min) for blouses, and between 25.0 and 360min (mean 60.2±66.1min) for trousers. We strongly recommend the use of long-lasting permethrin-impregnated clothing for the prevention of mosquito-borne diseases, including chikungunya, dengue, and zika fevers, which are currently resurging globally.

Novel integrated systems for controlling and prevention of mosquito-borne diseases caused by poor sanitation and improper water management

Mosquito-borne diseases, as a threat to public health, are primarily caused by the lack of clean water access and poor sanitation. On the way to overcome these problems, the sixth goal of Sustainable Development Goals (SDG–6) is imperative to improve sanitation practices and access to clean water supplies in a safe and sustainable way. By considering weak points of current centralized water and sanitation systems on the way to achieve SDG–6, finding sustainable approaches as alternative to unrealistic, unreliable and uneconomical water supplies (e.g. dams, groundwater and bottled water) and dangerous sanitation practices such as open defecation is essential to protect the public’s health against the recently spreading diseases such as Zika, Ebola, Malaria, etc. In this case, we developed novel integrated systems in which rainwater harvesting systems and waterless toilets, along with self-cleaning ponds. In this paper, suitable key elements and their roles in new water and sanitation management are introduced together with assessments of each key system identified for both public and residential zones. Comparisons with the current treatment plants by using economic analysis are discussed with reasonable parameters.

Bioactivity and laundering resistance of five commercially available, factory-treated permethrin-impregnated fabrics for the prevention of mosquito-borne diseases: the need for a standardized testing and licensing procedure

Personal protective measures against hematophagous vectors constitute the first line of defense against arthropod-borne diseases. In this regard, a major advance has been the development of residual insecticides that can be impregnated into clothing. Currently, however, information on specific treatment procedures, initial insecticide concentrations, arthropod toxicity, residual activity, and laundering resistance is either fragmentary or non-existent, and no World Health Organization Pesticides Evaluation Scheme or other guidelines exist for the standardized testing and licensing of insecticide-treated clothing. The aim of this study was to analyze the insecticide content, contact toxicity, laundering resistance, and residual activity of five commercially available and commonly used permethrin-treated fabrics-Insect Shield, ExOfficio, Sol's Monarch T-shirts, battle dress uniforms (BDUs), and Labonal socks-against vector-competent Aedes aegypti, Anopheles stephensi, and Culex pipiens mosquitoes under laboratory conditions. Prior to laundering, permethrin concentrations ranged from 4300 to 870 mg/m(2) whereas, after 100 defined machine launderings, the remaining permethrin content fell to between 1800 and 20 mg/m(2), a percentage permethrin loss of 58.1 to 98.5 %. The highest 99 % knockdown (KD99) efficacy of permethrin was detected in Ae. aegypti, followed by An. stephensi and Cx. pipiens demonstrating that Ae. aegypti is the most sensitive species and Cx. pipiens the least sensitive. After 100 launderings, the remaining biocidal efficacy differed markedly among the five brands, with KD99 times varying from 38.8 ± 2.9 to >360 min for Ae. aegypti, from 44 ± 3.5 to >360 min for An. stephensi, and from 98 ± 10.6 to >360 min for Cx. pipiens. Overall, the ranking of the residual biocidal efficacies within the five brands tested was as follows: BDU ≈ Labonal > Sol's Monarch > ExOfficio > Insect Shield. When applying German Armed Forces licensing conditions, none of the four products available in the civilian market would completely meet all the necessary efficacy and safety requirements fulfilled by BDUs. Therefore, we strongly recommend standardized testing and licensing procedures for insecticide-treated clothing, with defined cutoff values for initial maximum and post-laundering minimum concentrations of permethrin as well as figures for permethrin migration rates, arthropod toxicity, homogeneity on fabrics, residual activity, and laundering resistance.

Knowledge Attitude and Practices Related on Prevention of Mosquito Borne Diseases and Sanitation Conditions in a Salvadoran Urban Community

Introduction: In El Salvador Mosquito Borne Diseases (MBDs) is a serious public health problem due to produce morbidity and mortality. They produce a high economic loss, which contributes to the collapse of the public health system. Over the years, the Salvadoran public health system has invested large amounts of resources to minimize the problem through campaigns against MBDs. Despite this, the population is still affected by diseases such as dengue, and more recently chikungunya and zika outbreaks. The aim of this study is to evaluate sanitation conditions variables and identify knowledge, attitudes, practices related to the prevention of MBDs. Methods: A cross-sectional survey about sanitation conditions and knowledge, attitudes and practices on prevention of MBDs of inhabitant’s ≥ 15 years from an urban community of a municipality with the highest number of cases reported in 2015. Results: Majority of respondents (98.2%) had direct supply of drinking water; however 96.4% of respondents were agreed that they had an inconsistent water supply. Regarding MBDs prevention respondents showed high acceptable knowledge (76.8%), high favorable attitude (92.1%) and an acceptable implementation of practices toward prevention reproduction of mosquitoes (58.5%) and a poor implementation of practices to prevent mosquito bites (38.3%). Conclusions: The findings revealed high acceptable knowledge about MBDs and a high favorable attitude regarding to prevent them, but also revealed a scarce implementation of prevention practices. The generalized storage of water on non-covered barrels because the inconsistent water supplies, can be source of proliferation of mosquitoes and therefore increases the risk of transmission of MBDs. High population density of the community can magnify this risk. It is necessary to enhance education to promote better implementation of practices using the most common media together with the local health workers.

Applicability of citronella oil (Cymbopogon winteratus) for the prevention of mosquito-borne diseases in the rural area of Tikapur, far-western Nepal

Mosquito-borne diseases are a serious global problem, particularly in tropical and sub-tropical countries such as Nepal. Citronella oil is a natural mosquito repellent as well as a local fragrance in Nepal, which is accessible at very low cost because citronella plants are widely cultivated in rural areas of the Terai belt in Nepal. This study was conducted using a real-life randomized controlled pilot trial to confirm the effectiveness and applicability of locally-produced citronella oil as a mosquito repellent for the prevention of mosquito-borne diseases in Nepal. A repellency activity test was performed with 100% citronella oil (Cymbopogon winteratus) from April to May 2013 in the Tikapur Municipality of the Kailali district, Nepal. The test was divided into two trials: an indoor exposure (IE) test (N=101) and an outdoor exposure (OE) test (N=140) from 5.00 pm to 7.00 pm. Each trial contained an experimental citronella oil-applied group and a non-applied (control) group. The outcome measures were the protective effect of citronella oil against mosquitoes, the number of mosquito bites, the repellency percentage, the smell satisfaction and the irritation level. Experimental group had a significant protective effect against mosquito bites in IE (96.5%, n=57) and OE (95.7%, n=70) tests compared to the control group in IE (29.5%, n=44) and OE (28.6%, n=70) tests (experimental vs control groups, p<0.001). The repellency percentage for the OE test was 96.7%. In the smell satisfaction test (n=127), most of the participants responded with high satisfaction: 'good' (67.7%), 'very good' (16.5%), 'bad' (13.4%) and 'very bad' (2.4%). IE and OE tests showed similar satisfaction levels in each category. In the irritation level test (n=127), 87.4% and 12.6% responded with no irritation and slight irritation, respectively. There were no reports of moderate or severe irritation. The topical application of citronella oil can be employed as an easily-available, affordable and effective alternative mosquito repellent to prevent mosquito-borne diseases in rural areas such as Tikapur, Nepal.

Adulticidal and repellent properties of indigenous plant extracts against Larvae of mosquito: A Review

One method of prevention of mosquito borne diseases is the reduction of the mosquito population in the various stages of development, such as the use of ovicidal, larvicidal, pupicidal, adulticidal, and mosquitocidal substances. The application of chemical insecticides in mosquito control has resulted in the persistence and accumulation of non-biodegradable chemicals in the ecosystem, biological magnification through the food chain, insecticide resistance, and a toxic effect in human health and non-target organisms. Many studies on plant extracts against the mosquito population have been conducted around the world. The plant-mediated repellents are advantageous over chemical and physical methods, since it is cheap, single-step, and does not require high pressure, energy, temperature, or the use of highly toxic chemicals. In the latest years, a growing number of plant-borne compounds have been proposed for efficient and rapid extracellular synthesis of metal nanoparticles effective against mosquitoes at very low doses. The present study reveals that the aqueous extract of this leaf has a suitable property for a larvicidal natural product and may replace harmful chemical pesticides.

A Study on Knowledge and Preventive Practices about Mosquito Borne Diseases in Delhi

Background: Mosquito-borne diseases constitute an important cause of morbidity and mortality, especially in India. Assessment of knowledge and practices of community about prevention of mosquito borne diseases is important for designing community-based interventions. Therefore, the study was carried out to assess such information. Materials and Methods: A community-based cross-sectional study was conducted among 350 adults selected by systematic sampling method in a rural and urban area in Delhi. Data was collected using pretested semi-structured questionnaire after taking written informed consent. Data was analyzed using SPSS version 17. Chi-square and Fisher's Exact test was used for qualitative variables to find association and P < 0.05 was considered significant. Results: One hundred and forty-two (67.6%) subjects in rural and 89 (63.6%) in the urban area were able to name at least one mosquito borne disease. Only small number of participants (from rural 28.1% and urban 18.6% areas) was aware of fever with chills and rigor as a symptom of malaria. Television was most common source of information in both rural and urban areas. Desert coolers were reported to be cleaned regularly in a week in 86.4% houses in a rural area, and 88.4% houses in the urban area. Potential breeding sites were significantly more in urban (n = 34, 24.3%) than rural (n = 13, 6.2%) houses (P = 0.01). Similarly actual breeding of mosquitoes was found significantly more in urban houses (n = 29, 20.7%) than rural houses (n = 14, 6.7%), which was statistically significant (P = 0.01). Knowledge about mosquito borne diseases was significantly associated with education status of the participants. Conclusion and Recommendation: Level of awareness was good; however mosquito breeding was occurring more in urban areas, which demands innovative mass media techniques to convey health messages to the public for prevention and control of mosquito borne diseases.

Mosquito Population Regulation and Larval Source Management in Heterogeneous Environments

An important question for mosquito population dynamics, mosquito-borne pathogen transmission and vector control is how mosquito populations are regulated. Here we develop simple models with heterogeneity in egg laying patterns and in the responses of larval populations to crowding in aquatic habitats. We use the models to evaluate how such heterogeneity affects mosquito population regulation and the effects of larval source management (LSM). We revisit the notion of a carrying capacity and show how heterogeneity changes our understanding of density dependence and the outcome of LSM. Crowding in and productivity of aquatic habitats is highly uneven unless egg-laying distributions are fine-tuned to match the distribution of habitats’ carrying capacities. LSM reduces mosquito population density linearly with coverage if adult mosquitoes avoid laying eggs in treated habitats, but quadratically if eggs are laid in treated habitats and the effort is therefore wasted (i.e., treating 50% of habitat reduces mosquito density by approximately 75%). Unsurprisingly, targeting (i.e. treating a subset of the most productive pools) gives much larger reductions for similar coverage, but with poor targeting, increasing coverage could increase adult mosquito population densities if eggs are laid in higher capacity habitats. Our analysis suggests that, in some contexts, LSM models that accounts for heterogeneity in production of adult mosquitoes provide theoretical support for pursuing mosquito-borne disease prevention through strategic and repeated application of modern larvicides.

Ross, Macdonald, and a Theory for the Dynamics and Control of Mosquito-Transmitted Pathogens

Ronald Ross and George Macdonald are credited with developing a mathematical model of mosquito-borne pathogen transmission. A systematic historical review suggests that several mathematicians and scientists contributed to development of the Ross-Macdonald model over a period of 70 years. Ross developed two different mathematical models, Macdonald a third, and various “Ross-Macdonald” mathematical models exist. Ross-Macdonald models are best defined by a consensus set of assumptions. The mathematical model is just one part of a theory for the dynamics and control of mosquito-transmitted pathogens that also includes epidemiological and entomological concepts and metrics for measuring transmission. All the basic elements of the theory had fallen into place by the end of the Global Malaria Eradication Programme (GMEP, 1955–1969) with the concept of vectorial capacity, methods for measuring key components of transmission by mosquitoes, and a quantitative theory of vector control. The Ross-Macdonald theory has since played a central role in development of research on mosquito-borne pathogen transmission and the development of strategies for mosquito-borne disease prevention.

Chikungunya Virus: A Novel and Potentially Serious Threat to New Zealand and the South Pacific Islands

There has never been a locally transmitted outbreak of mosquito-borne disease in New Zealand, but the risk of an outbreak occurring is increasing with on-going interceptions of exotic mosquito vectors across its border, increasing traffic of goods and passengers, higher numbers of viremic travelers arriving, and local, regional, and global environmental change. The risk posed to New Zealand by chikungunya virus is potentially high because of the transmissibility of this virus in subtropical climates, compounded by a population that is predominantly immunologically naive to exotic arboviruses. However, risk reduction in New Zealand should not be considered in isolation but must be viewed within a wider South Pacific context. In this report, we discuss the potential threat posed by chikungunya to the region, focusing in particular on New Zealand, and re-emphasizing the need for a South Pacific-wide approach towards mosquito-borne disease prevention.

School-Based Health Promotion for Mosquito-Borne Disease Prevention in Children

We enrolled 345 fourth-grade students in a classroom-randomized, controlled trial to evaluate a school-based West Nile virus health education program's impact on knowledge, attitudes, and personal protective behavior use. Immediate and sustained improvements in West Nile virus knowledge and greater frequencies of reported personal protective behaviors resulted from the educational intervention.

Malaria in Children Following International Travel

Source: Stager K, Legros F, Krause G, et al. Imported malaria in children in industrialized countries, 1992–2002. Emerg Infect Dis. 2009;15(2):185–190; doi:10.3201/eid1502.080712A multinational group of investigators evaluated the epidemiology of imported malaria in children ≤18 years of age in 11 industrialized countries, identified trends and risk groups, and ranked destinations according to malaria risk for children. Data from 1992 to 2002 were collected directly from the 11 countries’ health authorities. Imported malaria was defined as parasitologically confirmed malaria that had been acquired in a disease-endemic area, diagnosed after clinical disease had developed and when the person was in an industrialized country where the disease was not endemic. Data from the United Nations World Tourism Organization was used to estimate the total numbers of travelers to malaria-endemic countries; the investigators assumed that 1 of 10 travelers was <18 years of age.A total of 17,009 cases of imported malaria were reported. The frequency of reported malaria in different age groups ranged from 13.5% (for children 0–2 years old) to 18.1% (15–17 years old). Greater than 75% of cases were reported from France (6,618), the UK (3,816), and the US (2,614). More than 50% of all imported malaria world-wide was imported from Africa, principally West Africa. Plasmodium falciparum accounted for 70% of all cases. The case-fatality ratio for all countries was <0.4%. Less than 20% of infected children had taken malaria chemoprophylaxis. In the US, cases were most often imported from Central America and South America, followed by West and East Africa and Asia. In the US, P falciparum accounted for 47% of cases, P vivax 38%, P ovale 2.5%, and P malaria 4.8%. Among US children, there were four deaths among the 1,225 cases.The authors recognize limitations of the study included underreporting, missing data, inadequate surveillance systems, and differing malaria case definitions (clinical vs laboratory-confirmed cases). They caution that many immigrants think the partial immunity acquired while living in the endemic county will protect them during a return trip and are not aware that the immunity wanes within six months. Practitioners need to ensure that their patients take malaria chemoprophylaxis when traveling to malaria-endemic areas.Dr Dinerman has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.This study is a reminder of the importance of providing pre-travel advice on malaria prevention and remaining aware of the possibility of malaria in children returning to the US from endemic areas. Malaria continues to be one of the most important and devastating infectious diseases in developing areas of the world, responsible for one million deaths each year, mostly from sub-Saharan Africa.1 Malaria is the 3rd leading cause of global mortality in children younger than 5 years of age (see AAP Grand Rounds, August 2005;14:22–232). Malaria is the most common cause of fever (59%) in patients with a systemic febrile illness after travel to endemic countries.3 (See also AAP Grand Rounds, October 2007;18:43–44.4)The diagnosis should be considered in the febrile child returning from an area with known transmission. Symptoms of malaria are generally non-specific, including fever, chills, weakness, nausea, vomiting, diarrhea, headache, dizziness, myalgia, and cough. Pediatricians needing assistance with the diagnosis or management of suspected cases can call the CDC Malaria Hotline at (770) 488–7788 to consult with a specialist. Additionally, concise treatment guidelines are available online at http://www.cdc.gov/Malaria/pdf/treatmenttable.pdf.To enhance malaria surveillance in the US, be aware that malaria is a nationally notifiable disease. Cases should be reported to the state and local health department which forwards the information to the National Malaria Surveillance System (NMSS) managed by the CDC’s Division of Parasitic Diseases.International travel offers children a potentially culturally enriching and life-enhancing experience. As this study demonstrates, however, it is not without risk. While the authors emphasize malaria chemoprophylaxis for travelers to endemic malaria regions, we believe clinicians should also stress the importance of primary prevention of mosquito-borne diseases by using long-sleeved shirts and long pants, insect repellents, and mosquito netting.Although malaria is not currently a vaccine-preventable disease, increased funding and research have led to the development of several promising candidate vaccines which are currently undergoing large-scale clinical trials.5,6

蚊媒介病防除に関与する基礎的な問題

蚊媒介病防除に関与する基礎的な問題

The Prevention of Mosquito-Borne Diseases in Tropical and Sub-Tropical Towns

The Prevention of Mosquito-Borne Diseases in Tropical and Sub-Tropical Towns