Long-lasting insecticide-treated house screens and targeted treatment of productive breeding-sites for dengue vector control in Acapulco, Mexico

Interventions against Aedes/dengue at the household level: a systematic review and meta-analysis

BACKGROUND

Because the evidence for the role of structural housing and combinations of interventions (domestic or peri-domestic) against Aedes mosquitoes or dengue is still lacking, this systematic review and meta-analysis aimed to analyse and synthesize research focusing on the household as the unit of allocation.

METHODS

We searched MEDLINE, LILACS, and Web of Science databases until February 2023 using three general keyword categories: (1) "Aedes" or "dengue"; (2) structural housing interventions including "house", "water", or "drainage"; and (3) vector control interventions of potential relevance and their combinations. We performed a qualitative content analysis and a meta-analysis for 13 entries on dengue seroconversion data.

FINDINGS

14,272 articles were screened by titles, 615 by abstracts, 79 by full-text. 61 were selected. Satisfactory data quality allowed for detailed content analysis. Interventions at the household level against the immature mosquito stages (21 studies, 34%) showed positive or mixed results in entomological and epidemiological outcomes (86% and 75% respectively). Combined interventions against immature and adult stages (11 studies, 18%) performed similarly (91% and 67%) while those against the adult mosquitoes (29 studies, 48%) performed less well (79%, 22%). A meta-analysis on seroconversion outcomes showed a not-statistically significant reduction for interventions (log odds-ratio: -0.18 [-0.51, 0.14 95% CI]).

INTERPRETATION

No basic research on housing structure or modification was eligible for this systematic review but many interventions with clear impact on vector indices and, to a lesser extent, on dengue were described. The small and not-statistically significant effect size of the meta-analysis highlights the difficulty of proving effectiveness against this highly-clustered disease and of overcoming practical implementation obstacles (e.g. efficacy loss, compliance). The long-term success of interventions depends on suitability, community commitment and official support and promotion. The choice of a specific vector control package needs to take all these context-specific aspects into consideration.

FUNDING

This work was funded by a grant from the World Health Organization (2021/1121668-0, PO 202678425, NTD/VVE).

Effectiveness of Aedes-borne infectious disease control in Latin America and the Caribbean region: A scoping review

Background

Aedes aegypti and Aedes albopictus are primary vectors of emerging or re-emerging arboviruses that threaten public health worldwide. Many efforts have been made to develop interventions to control these Aedes species populations. Still, countries in the Latin America and the Caribbean (LAC) region struggle to create/design/develop sustainable and effective control strategies. This scoping review synthesises evidence concerning the effectiveness of Ae. aegypti and Ae. albopictus prevention and control interventions performed in LAC (2000–2021). The findings can be used to evaluate, compare and develop more effective control strategies.

Methodology

The review is based on the methodology by Joanna Briggs Institute for conducting a scoping review. The MEDLINE (via PubMed and Web of Science), Cochrane Library, Scopus, EMBASE and ScienceDirect databases were used to search for articles. Grey literature was searched from governmental and non-governmental organisation websites. Four reviewers independently screened all titles and abstracts and full-text of the articles using the Rayyan web application, based on pre-defined eligibility criteria.

Results

A total of 122 publications were included in the review. Most studies focused on dengue virus infection and data on Ae. aegypti. Entomological data were mainly used to determine the intervention’s effectiveness. An integrated control intervention was the most commonly employed strategy in both regions. Biological control measures, environmental management, and health education campaigns on community participation achieved more sustainable results than an intervention where only a chemical control measure was used. Challenges to implementing interventions were insufficient financial support, resources, workforce, intersectoral collaboration and legislation.

Conclusions

Based on the synthesised data, an integrated vector (Aedes) management focused on community participation seems to be the most effective approach to mitigate Aedes-borne infectious diseases. Maintaining the approach’s effect remains challenging as it requires multisectoral and multi-disciplinary team engagement and active community participation. Future research needs to address the barriers to program implementation and maintenance as data on this topic is lacking.

Prevention and control of mosquito-borne arboviral diseases: lessons learned from a school-based intervention in Brazil (Zikamob)

Background

Since the 1980s, when dengue was reintroduced in Brazil, outbreaks and epidemics caused by different arbovirus strains transmitted by vector mosquitoes such as Aedes aegypti have been an annual occurrence. The aim of this study was to evaluate the behavioural change of high school students and teachers who participated in an educational intervention for the prevention and vector control of arboviral diseases.

Methods

In this school-based intervention, a self-reported questionnaire was used in a pre-post intervention methodology to assess environmental risk factors, sociodemographic variables and to measure attitudes and behaviours. In all, 883 high school students and teachers from the city of Campina Grande, in the state of Paraíba, northeastern Brazil, participated. The e-health intervention consisted of a competition between schools to comply with preventive actions via content production for social networks, and the monitoring was performed over a period of three months through the ZikaMob software developed by the researchers.

Results

Out of the 883 survey participants, 690 were students ranging in age from 14 to 41 years, with an average of 17 ± 2 years; and 193 were teachers from 22 to 64 years old, averaging 38 ± 9 years. The analysis of the data shows that significant differences in most of the target behaviours were apparent after the intervention, with an increase of about 10% in the performance of inspection actions; a 7% greater separation of recyclables and a 40% increase in the screening of windows among students. Students showed lower fear of, and a lower self-perception of the risk of, acquiring arboviruses than teachers on average.

Conclusions

ZikaMob is an innovative strategy with the potential to be replicated in any location that has an internet network and can involve an unlimited number of participants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-12554-w.

Review of the ecology and behaviour of Aedes aegypti and Aedes albopictus in Western Africa and implications for vector control

Western Africa is vulnerable to arboviral disease transmission, having recently experienced major outbreaks of chikungunya, dengue, yellow fever and Zika. However, there have been relatively few studies on the natural history of the two major human arbovirus vectors in this region, Aedes aegypti and Ae. albopictus, potentially limiting the implementation of effective vector control. We systematically searched for and reviewed relevant studies on the behaviour and ecology of Ae. aegypti and Ae. albopictus in Western Africa, published over the last 40 years. We identified 73 relevant studies, over half of which were conducted in Nigeria, Senegal, or Côte d'Ivoire. Most studies investigated the ecology of Ae. aegypti and Ae. albopictus, exploring the impact of seasonality and land cover on mosquito populations and identifying aquatic habitats. This review highlights the adaptation of Ae. albopictus to urban environments and its invasive potential, and the year-round maintenance of Ae. aegypti populations in water storage containers. However, important gaps were identified in the literature on the behaviour of both species, particularly Ae. albopictus. In Western Africa, Ae. aegypti and Ae. albopictus appear to be mainly anthropophilic and to bite predominantly during the day, but further research is needed to confirm this to inform planning of effective vector control strategies. We discuss the public health implications of these findings and comment on the suitability of existing and novel options for control in Western Africa.

Protective effect of house screening against indoor Aedes aegypti in Mérida, Mexico: A cluster randomised controlled trial

OBJECTIVE

To evaluate the protective effect of house screening (HS) on indoor Aedes aegypti infestation, abundance and arboviral infection in Merida, Mexico.

METHODS

In 2019, we performed a cluster randomised controlled trial (6 control and 6 intervention areas: 100 households/area). Intervention clusters received permanently fixed fiberglass HS on all windows and doors. The study included two cross-sectional entomologic surveys, one baseline (dry season in May 2019) and one post-intervention (PI, rainy season between September and October 2019). The presence and number of indoor Aedes females and blood-fed females (indoor mosquito infestation) as well as arboviral infections with dengue (DENV) and Zika (ZIKV) viruses were evaluated in a subsample of 30 houses within each cluster.

RESULTS

HS houses had significantly lower risk for having Aedes aegypti female mosquitoes (odds ratio [OR] = 0.56, 95% CI 0.33-0.97, p = 0.04) and blood-fed females (OR = 0.53, 95% CI 0.28-0.97, p = 0.04) than unscreened households from the control arm. Compared to control houses, HS houses had significantly lower indoor Ae. aegypti abundance (rate ratio [RR] = 0.50, 95% CI 0.30-0.83, p = 0.01), blood-fed Ae. aegypti females (RR = 0.48, 95% CI 0.27-0.85, p = 0.01) and female Ae. aegypti positive for arboviruses (OR = 0.29, 95% CI 0.10-0.86, p = 0.02). The estimated intervention efficacy in reducing Ae. aegypti arbovirus infection was 71%.

CONCLUSIONS

These results provide evidence supporting the use of HS as an effective pesticide-free method to control house infestations with Aedes aegypti and reduce the transmission of Aedes-transmitted viruses such as DENV, chikungunya (CHIKV) and ZIKV.

Insecticide-treated house screening protects against Zika-infected Aedes aegypti in Merida, Mexico

Background

The integration of house-screening and long-lasting insecticidal nets, known as insecticide-treated screening (ITS), can provide simple, safe, and low-tech Aedes aegypti control. Cluster randomised controlled trials in two endemic localities for Ae. aegypti of south Mexico, showed that ITS conferred both, immediate and sustained (~2 yr) impact on indoor-female Ae. aegypti infestations. Such encouraging results require further validation with studies quantifying more epidemiologically-related endpoints, including arbovirus infection in Ae. aegypti. We evaluated the efficacy of protecting houses with ITS on Ae. aegypti infestation and arbovirus infection during a Zika outbreak in Merida, Yucatan, Mexico.

Methodology/Principal findings

A two-arm cluster-randomised controlled trial evaluated the entomological efficacy of ITS compared to the absence of ITS (with both arms able to receive routine arbovirus vector control) in the neighbourhood Juan Pablo II of Merida. Cross-sectional entomological surveys quantified indoor adult mosquito infestation and arbovirus infection at baseline (pre-ITS installation) and throughout two post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over one year (2016–2017). Household-surveys assessed the social reception of the intervention. Houses with ITS were 79–85% less infested with Aedes females than control houses up to one-year PI. A similar significant trend was observed for blood-fed Ae. aegypti females (76–82%). Houses with ITS had significantly less infected female Ae. aegypti than controls during the peak of the epidemic (OR = 0.15, 95%CI: 0.08–0.29), an effect that was significant up to a year PI (OR = 0.24, 0.15–0.39). Communities strongly accepted the intervention, due to its perceived mode of action, the prevalent risk for Aedes-borne diseases in the area, and the positive feedback from neighbours receiving ITS.

Conclusions/Significance

We show evidence of the protective efficacy of ITS against an arboviral disease of major relevance, and discuss the relevance of our findings for intervention adoption.

We evaluated the efficacy of protecting houses with insecticide-treated nets permanently fixed with aluminium frames on external doors and windows on Ae. aegypti infestation and arbovirus infection during a Zika outbreak in Merida, Yucatan, Mexico. Houses protected with screens were ≈80% less infested with Aedes females and very importantly, had significantly less infected female Ae. aegypti during the peak of the epidemic. Communities strongly accepted the intervention, due to its perceived mode of action, the prevalent risk for Aedes-borne diseases in the area, and the positive feedback from neighbours. House screening provides a simple, affordable sustainable method to reduce human-vector contact inside houses and can protect against dengue, chikungunya and Zika.

Randomized trials of housing interventions to prevent malaria and Aedes-transmitted diseases: A systematic review and meta-analysis

BACKGROUND

Mosquito-borne diseases remain a significant public health problem in tropical regions. Housing improvements such as screening of doors and windows may be effective in reducing disease transmission, but the impact remains unclear.

OBJECTIVES

To examine whether housing interventions were effective in reducing mosquito densities in homes and the impact on the incidence of mosquito-borne diseases.

METHODS

In this systematic review and meta-analysis, we searched 16 online databases, including NIH PubMed, CINAHL Complete, LILACS, Ovid MEDLINE, and Cochrane Central Register of Controlled Trials for randomized trials published from database inception to June 30, 2020. The primary outcome was the incidence of any mosquito-borne diseases. Secondary outcomes encompassed entomological indicators of the disease transmission. I2 values were used to explore heterogeneity between studies. A random-effects meta-analysis was used to assess the primary and secondary outcomes, with sub-group analyses for type of interventions on home environment, study settings (rural, urban, or mixed), and overall house type (traditional or modern housing).

RESULTS

The literature search yielded 4,869 articles. After screening, 18 studies were included in the qualitative review, of which nine were included in the meta-analysis. The studies enrolled 7,200 households in Africa and South America, reporting on malaria or dengue only. The type of home environmental interventions included modification to ceilings and ribbons to close eaves, screening doors and windows with nets, insecticide-treated wall linings in homes, nettings over gables and eaves openings, mosquito trapping systems, metal-roofed houses with mosquito screening, gable windows and closed eaves, and prototype houses using southeast Asian designs. Pooled analysis depicted a lower risk of mosquito-borne diseases in the housing intervention group (OR = 0.68; 95% CI = 0.48 to 0.95; P = 0.03). Subgroup analysis depicted housing intervention reduced the risk of malaria in all settings (OR = 0.63; 95% CI = 0.39 to 1.01; P = 0.05). In urban environment, housing intervention was found to decrease the risk of both malaria and dengue infections (OR = 0.52; 95% CI = 0.27 to 0.99; P = 0.05).Meta-analysis of pooled odds ratio showed a significant benefit of improved housing in reducing indoor vector densities of both Aedes and Anopheles (OR = 0.35; 95% CI = 0.23 to 0.54; P<0.001).

CONCLUSIONS

Housing intervention could reduce transmission of malaria and dengue among people living in the homes. Future research should evaluate the protective effect of specific house features and housing improvements associated with urban development.

Recommendations for building out mosquito-transmitted diseases in sub-Saharan Africa: the DELIVER mnemonic

In sub-Saharan Africa, most transmission of mosquito-transmitted diseases, such as malaria or dengue, occurs within or around houses. Preventing mosquito house entry and reducing mosquito production around the home would help reduce the transmission of these diseases. Based on recent research, we make key recommendations for reducing the threat of mosquito-transmitted diseases through changes to the built environment. The mnemonic, DELIVER, recommends the following best practices: (i) Doors should be screened, self-closing and without surrounding gaps; (ii) Eaves, the space between the wall and roof, should be closed or screened; (iii) houses should be Lifted above the ground; (iv) Insecticide-treated nets should be used when sleeping in houses at night; (v) houses should be Ventilated, with at least two large-screened windows to facilitate airflow; (vi) Environmental management should be conducted regularly inside and around the home; and (vii) Roofs should be solid, rather than thatch. DELIVER is a package of interventions to be used in combination for maximum impact. Simple changes to the built environment will reduce exposure to mosquito-transmitted diseases and help keep regions free from these diseases after elimination. This article is part of the theme issue 'Novel control strategies for mosquito-borne diseases'.

Spatial spillover analysis of a cluster-randomized trial against dengue vectors in Trujillo, Venezuela

BACKGROUND

The ability of cluster-randomized trials to capture mass or indirect effects is one reason for their increasing use to test interventions against vector-borne diseases such as malaria and dengue. For the same reason, however, the independence of clusters may be compromised if the distances between clusters is too small to ensure independence. In other words they may be subject to spillover effects.

METHODS

We distinguish two types of spatial spillover effect: between-cluster dependence in outcomes, or spillover dependence; and modification of the intervention effect according to distance to the intervention arm, or spillover indirect effect. We estimate these effects in trial of insecticide-treated materials against the dengue mosquito vector, Aedes aegypti, in Venezuela, the endpoint being the Breteau index. We use a novel random effects Poisson spatial regression model. Spillover dependence is incorporated via an orthogonalized intrinsic conditional autoregression (ICAR) model. Spillover indirect effects are incorporated via the number of locations within a certain radius, set at 200m, that are in the intervention arm.

RESULTS

From the model with ICAR spatial dependence, and the degree of surroundedness, the intervention effect is estimated as 0.74-favouring the intervention-with a 95% credible interval of 0.34 to 1.69. The point estimates are stronger with increasing surroundedness within intervention locations.

CONCLUSION

In this trial there is some evidence of a spillover indirect effect of the intervention, with the Breteau index tending to be lower in locations which are more surrounded by locations in the intervention arm.

Efficacy of Long-lasting Insecticidal Nets With Declining Physical and Chemical Integrity on Aedes aegypti (Diptera: Culicidae)

Fitting long-lasting insecticidal nets (LLIN) as screens on doors/windows has a significant impact on indoor-adult Aedes aegypti (L.), with entomological reductions measured in a previous study being significant for up to 2 yr post-installation, even in the presence of pyrethroid-resistant Aedes populations. To better understand the mode of LLIN protection, bioassays were performed to evaluate the effects of field deployment (0, 6, and 12 mo) and damage type (none, central, lateral, and multiple) on LLIN efficacy. Contact bioassays confirmed that LLIN residual activity (median knockdown time, in minutes, or MKDT) decreased significantly over time: 6.95 (95% confidence interval [CI]: 5.32-8.58) to 9.24 (95% CI: 8.69-9.79) MKDT at 0- and 12-mo age, respectively, using a pyrethroid-susceptible Aedes strain. Tunnel tests (exposing human forearm for 40 min as attractant) showed that deployment time affected negatively Aedes passage inhibition from 54.9% (95% CI: 43.5-66.2) at 0 mo to 35.7% (95% CI: 16.3-55.1) at 12 mo and blood-feeding inhibition from 65.2% (95% CI: 54.2-76.2) to 48.9% (95% CI: 26.4-71.3), respectively; both the passage/blood-feeding inhibition increased by a factor of 1.8-2.9 on LLINs with multiple and central damages compared with nets with lateral damage. Mosquito mortality was 74.6% (95% CI: 65.3-83.9) at 0 mo, 72.3% (95% CI: 64.1-80.5) at 6 mo, and 59% (95% CI: 46.7-71.3) at 12 mo. Despite the LLIN physical integrity could be compromised over time, we demonstrate that the remaining chemical effect after field conditions would still contribute to killing/repelling mosquitoes.

Efficacy of Spinosad Granules and Lambda-Cyhalothrin Contrasts with Reduced Performance of Temephos for Control of Aedes spp. in Vehicle Tires in Veracruz, Mexico

The present study examined the efficacy of λ-cyhalothrin, pyriproxyfen and granular formulations of spinosad and temephos for the control of mosquito larvae present in experimental tires in Veracruz State, Mexico in the period 2015-2016. Both λ-cyhalothrin and spinosad granules provided control of larvae and pupae of Aedes aegypti, Ae. albopictus and Culex spp. in used tires in Veracruz State, Mexico, over a 9-12 week period, although numbers of Culex were low. The numbers of Aedes larvae + pupae in pyriproxyfen and temephos-treated tires were slightly less than half of the untreated control tires, probably a result the pupicidal characteristics of pyriproxyfen and possible resistance in the case of temephos. Spinosad was less harmful to predatory Toxorhynchites spp. than λ-cyhalothrin or temephos. The reduced susceptibility to temephos in Aedes populations was confirmed at five other sites in Veracruz. Public health authorities should consider incorporating spinosad as a larvicide in coastal areas at a high risk of dengue, chikungunya and Zika outbreaks in this region.

Models of effectiveness of interventions against malaria transmitted by Anopheles albimanus

BACKGROUND

Most impact prediction of malaria vector control interventions has been based on African vectors. Anopheles albimanus, the main vector in Central America and the Caribbean, has higher intrinsic mortality, is more zoophilic and less likely to rest indoors. Therefore, relative impact among interventions may be different. Prioritizing interventions, in particular for eliminating Plasmodium falciparum from Haiti, should consider local vector characteristics.

METHODS

Field bionomics data of An. albimanus from Hispaniola and intervention effect data from southern Mexico were used to parameterize mathematical malaria models. Indoor residual spraying (IRS), insecticide-treated nets (ITNs), and house-screening were analysed by inferring their impact on the vectorial capacity in a difference-equation model. Impact of larval source management (LSM) was assumed linear with coverage. Case management, mass drug administration and vaccination were evaluated by estimating their effects on transmission in a susceptible-infected-susceptible model. Analogous analyses were done for Anopheles gambiae parameterized with data from Tanzania, Benin and Nigeria.

RESULTS

While LSM was equally effective against both vectors, impact of ITNs on transmission by An. albimanus was much lower than for An. gambiae. Assuming that people are outside until bedtime, this was similar for the impact of IRS with dichlorodiphenyltrichloroethane (DDT) or bendiocarb, and impact of IRS was less than that of ITNs. However, assuming people go inside when biting starts, IRS had more impact on An. albimanus than ITNs. While house-screening had less impact than ITNs or IRS on An. gambiae, it had more impact on An. albimanus than ITNs or IRS. The impacts of chemoprevention and chemotherapy were comparable in magnitude to those of strategies against An. albimanus. Chemo-prevention impact increased steeply as coverage approached 100%, whilst clinical-case management impact saturated because of remaining asymptomatic infections.

CONCLUSIONS

House-screening and repellent IRS are potentially highly effective against An. albimanus if people are indoors during the evening. This is consistent with historical impacts of IRS with DDT, which can be largely attributed to excito-repellency. It also supports the idea that housing improvements have played a critical role in malaria control in North America. For elimination planning, impact estimates need to be combined with feasibility and cost-analysis.

Interventions for the control of Aedes aegypti in Latin America and the Caribbean: systematic review and meta-analysis

OBJECTIVE

To determine the effectiveness and degree of implementation of interventions for the control of Aedes aegypti in Latin America and the Caribbean (LAC) as reported in scientific literature.

METHODS

We searched MEDLINE, EMBASE, CENTRAL, SOCINDEX, and LILACS, for experimental and observational studies, economic assessments and qualitative experiences carried out in LAC from 2000 to 2016. We assessed incidence and morbimortality of Aedes aegypti-related diseases and entomological indices: Breteau (containers), House, and Pupae per Person. We used GRADE methodology for assessing quality of evidence.

RESULTS

Of 1826 records retrieved, 75 were included and 9 cluster randomised clinical trials could be meta-analysed. We did not identify any intervention supported by a high certainty of evidence. In consistency with qualitative evidence, health education and community engagement probably reduces the entomological indices, as do the use of insecticide-treated materials, indoor residual spraying and the management of containers. There is low certainty of evidence supporting the use of ovitraps or larvitraps, and the integrated epidemiological surveillance strategy to improve indices and reduce the incidence of dengue. The reported degree of implementation of these vector control interventions was variable and most did not extend to whole cities and were not sustained beyond 2 years.

CONCLUSIONS

We found a general lack of evidence on effectiveness of vector control in the region, despite a few interventions that showed moderate to low certainty of evidence. It is important to engage and educate the community, apart from achieving the implementation of integrated actions between the health and other sectors at national and regional level.

Supporting and strengthening research on urban health interventions for the prevention and control of vector-borne and other infectious diseases of poverty: scoping reviews and research gap analysis

BACKGROUND

More than half of the world's population currently lives in urban settlements that grow both in size and number. By 2050, approximately 70% of the global population will be living in urban conglomerations, mainly in low- and middle-income countries. Mobility, poverty, different layers of inequalities as well as climate variability and change are some of the social and environmental factors that influence the exposure of human populations in urban settings to vector-borne diseases, which pose eminent public health threats. Accurate, consistent, and evidence-based interventions for prevention and control of vector-borne and other infectious diseases of poverty in urban settings are needed to implement innovative and cost-effective public policy and to promote inclusive and equitable urban health services.

MAIN BODY

While there is growing awareness of vector-borne diseases epidemiology at the urban level, there is still a paucity of research and action being undertaken in this area, hindering evidence-based public health policy decisions and practice and strategies for active community engagement. This paper describes the collaboration and partnership of the Special Programme for Research and Training in Tropical Diseases (TDR) hosted by the World Health Organization (WHO) and the "VEctor boRne DiseAses Scoping reviews" (VERDAS) Research Consortium as they joined efforts in response to filling this gap in knowledge and evidence by supporting the development of a series of scoping reviews that highlight priority research gaps and policy implications to address vector-borne and other infectious diseases at the urban level.

CONCLUSIONS

The set of scoping reviews proposed in this special issue presents a critical analysis of the state-of-the-art of research on urban health interventions for the prevention and control of vector-borne and other infectious diseases of poverty. The authors of the 6 reviews highlighted severe gaps in knowledge and identified organizational and theoretical limitations that need to be urgently tackled to improve cities preparedness and vector control response. The more pressing need at present is to ensure that more implementation research on vector-borne diseases in urban settings is conducted, addressing policy and practice implications and calling for more political commitment and social mobilization through adequate citizen engagement strategies.

Interventions for vector-borne diseases focused on housing and hygiene in urban areas: a scoping review

BACKGROUND

Over half the world's human populations are currently at risk from vector-borne diseases (VBDs), and the heaviest burden is borne by the world's poorest people, communities, and countries. The aim of this study was to conduct a review on VBD interventions relevant to housing and hygiene (including sanitation and waste management) in urban areas.

MAIN BODY

We conducted a scoping review, which involved systematically searching peer-reviewed and grey literature published between 2000 and 2016 using five scientific databases and one database for grey literature. Different data extraction tools were used for data coding and extraction. We assessed the quality of each study using the Mixed Methods Appraisal Tool and extracted descriptive characteristics and data about implementation process and transferability from all studies using the Template for Intervention Description and Replication and ASTAIRE (a tool for analyzing the transferability of health promotion interventions) tools. We reviewed 44 studies. Overall, the studies were judged to be of high risk for bias. Our results suggest multifaceted interventions, particularly community-based interventions, have the potential to achieve wider and more sustained effects than do standard vertical single-component programs. The evaluations of multifaceted interventions tend to include integrated evaluations, using not only entomological indicators but also acceptability and sustainability indicators.

CONCLUSIONS

This review highlighted the important need for higher quality research in VBDs and improved and standardized reporting of interventions. Significant research gaps were found regarding qualitative research and implementation research, and results highlighted the need for more interventions focus on sanitation and hygiene practices.

The Use of Insecticide-Treated Curtains for Control of Aedes aegypti and Dengue Virus Transmission in "Fraccionamiento" Style Houses in México

Dengue, chikungunya, yellow fever, and Zika viruses transmitted by Aedes aegypti mosquitoes are major public health threats in the tropical and subtropical world. In México, construction of large tracts of “fraccionamientos” high density housing to accommodate population growth and urbanization has provided fertile ground for Ae. aegypti-transmitted viruses. We investigated the utility of pyrethroid-treated window curtains to reduce both the abundance of Ae. aegypti and to prevent dengue virus (DENV) transmission in fraccionamiento housing. Windows and doors of fraccionamiento homes in urban/suburban areas, where Ae. aegypti pyrethroid resistance associated with the Ile1016 knock down resistance (kdr) mutation in the voltage gated sodium channel gene was high, and in rural areas, where kdr resistance was low, were fitted with either insecticide-treated curtains (ITCs) or non-treated curtains (NTCs). The homes were monitored for mosquito abundance and DENV infection. ITCs reduced the indoor abundance of Ae. aegypti and the number of DENV-infected mosquitoes in homes in rural but not in urban/suburban study sites. The presence of non-treated screens also was associated with reduced numbers of mosquitoes in homes. “Super-infested” homes, yielding more than 50 mosquitoes, including DENV-infected mosquitoes, provide a significant public health risk to occupants, visitors, and people in neighboring homes.

House screening with insecticide-treated netting provides sustained reductions in domestic populations of Aedes aegypti in Merida, Mexico

BACKGROUND

There is a need for effective methods to control Aedes aegypti and prevent the transmission of dengue, chikungunya, yellow fever and Zika viruses. Insecticide treated screening (ITS) is a promising approach, particularly as it targets adult mosquitoes to reduce human-mosquito contact.

METHODOLOGY/PRINCIPAL FINDINGS

A cluster-randomised controlled trial evaluated the entomological efficacy of ITS based intervention, which consisted of the installation of pyrethroid-impregnated long-lasting insecticide-treated netting material fixed as framed screens on external doors and windows. A total of 10 treatment and 10 control clusters (100 houses/cluster) were distributed throughout the city of Merida, Mexico. Cross-sectional entomological surveys quantified indoor adult mosquito infestation at baseline (pre-intervention) and throughout four post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over two years (2012-2014). A total of 844 households from intervention clusters (86% coverage) were protected with ITS at the start of the trial. Significant reductions in the indoor presence and abundance of Ae. aegypti adults (OR = 0.48 and IRR = 0.45, P<0.05 respectively) and the indoor presence and abundance of Ae. aegypti female mosquitoes (OR = 0.47 and IRR = 0.44, P<0.05 respectively) were detected in intervention clusters compared to controls. This high level of protective effect was sustained for up to 24 months PI. Insecticidal activity of the ITS material declined with time, with ~70% mortality being demonstrated in susceptible mosquito cohorts up to 24 months after installation.

CONCLUSIONS/SIGNIFICANCE

The strong and sustained entomological impact observed in this study demonstrates the potential of house screening as a feasible, alternative approach to a sustained long-term impact on household infestations of Ae. aegypti. Larger trials quantifying the effectiveness of ITS on epidemiological endpoints are warranted and therefore recommended.

Improved tools and strategies for the prevention and control of arboviral diseases: A research-to-policy forum

BACKGROUND

Research has been conducted on interventions to control dengue transmission and respond to outbreaks. A summary of the available evidence will help inform disease control policy decisions and research directions, both for dengue and, more broadly, for all Aedes-borne arboviral diseases.

METHOD

A research-to-policy forum was convened by TDR, the Special Programme for Research and Training in Tropical Diseases, with researchers and representatives from ministries of health, in order to review research findings and discuss their implications for policy and research.

RESULTS

The participants reviewed findings of research supported by TDR and others. Surveillance and early outbreak warning. Systematic reviews and country studies identify the critical characteristics that an alert system should have to document trends reliably and trigger timely responses (i.e., early enough to prevent the epidemic spread of the virus) to dengue outbreaks. A range of variables that, according to the literature, either indicate risk of forthcoming dengue transmission or predict dengue outbreaks were tested and some of them could be successfully applied in an Early Warning and Response System (EWARS). Entomological surveillance and vector management. A summary of the published literature shows that controlling Aedes vectors requires complex interventions and points to the need for more rigorous, standardised study designs, with disease reduction as the primary outcome to be measured. House screening and targeted vector interventions are promising vector management approaches. Sampling vector populations, both for surveillance purposes and evaluation of control activities, is usually conducted in an unsystematic way, limiting the potentials of entomological surveillance for outbreak prediction. Combining outbreak alert and improved approaches of vector management will help to overcome the present uncertainties about major risk groups or areas where outbreak response should be initiated and where resources for vector management should be allocated during the interepidemic period.

CONCLUSIONS

The Forum concluded that the evidence collected can inform policy decisions, but also that important research gaps have yet to be filled.

Insecticide treated curtains and residual insecticide treatment to control Aedes aegypti: An acceptability study in Santiago de Cuba

Background

Within the context of a field trial conducted by the Cuban vector control program (AaCP), we assessed acceptability of insecticide-treated curtains (ITCs) and residual insecticide treatment (RIT) with deltamethrin by the community. We also assessed the potential influence of interviewees’ risk perceptions for getting dengue and disease severity.

Methodology/principal findings

We embedded a qualitative study using in-depth interviews in a cluster randomized trial (CRT) testing the effectiveness of ITCs and RIT in Santiago de Cuba. In-depth interviews (N = 38) were conducted four and twelve months after deployment of the tools with people who accepted the tools, who stopped using them and who did not accept the tools. Data analysis was deductive. Main reasons for accepting ITCs at the start of the trial were perceived efficacy and not being harmful to health. Constraints linked to manufacturer instructions were the main reason for not using ITCs. People stopped using the ITCs due to perceived allergy, toxicity and low efficacy. Few heads of households refused RIT despite the noting reasons for rejection, such as allergy, health hazard and toxicity. Positive opinions of the vector control program influenced acceptability of both tools. However, frequent insecticide fogging as part of routine AaCP vector control actions diminished perceived efficacy of both tools and, therefore, acceptability. Fifty percent of interviewees did feel at risk for getting dengue and considered dengue a severe disease. However, this did not appear to influence acceptability of ITCs or RIT.

Conclusion/significance

Acceptability of ITCs and RIT was linked to acceptability of AaCP routine vector control activities. However, uptake and use were not always an indication of acceptability. Factors leading to acceptability may be best identified using qualitative methods, but more research is needed on the concept of acceptability and its measurement.

We aimed to understand what makes insecticide-treated curtains (ITCs) and residual insecticide treatment (RIT) with deltamethrin acceptable or not to users of these tools. In-depth interviews were conducted as part of a field trial conducted by the Cuban vector control program (AaCP) to test the effectiveness of these tools in Santiago de Cuba. Perceived efficacy was the main reason for interviewees who accepted the tools. Constraints linked to manufacturer instructions were the main reason for not using the ITCs when offered at the start of the trial. People stopped using the ITCs due to perceived allergy, toxicity and low efficacy. Few heads of households refused RIT despite identifying various reasons for rejection, such as allergy, health hazard and toxicity. Positive opinions of the Cuban vector control program influenced acceptability of both tools. On the contrary, perceptions of dengue risk did not appear to influence acceptability of ITCs or RIT. Our findings add on the importance of the growing body of qualitative research assessing acceptability of health interventions.

Protection of the house against Chagas disease, dengue, leishmaniasis, and lymphatic filariasis: a systematic review

In light of the recent Zika virus outbreak, vector control has received renewed interest. However, which interventions are efficacious and community effective and how to best deliver them remains unclear. Following PRISMA guidelines, we did a systematic review to assess evidence for applied vector control interventions providing protection against Chagas disease, dengue, leishmaniasis, and lymphatic filariasis at the household level. We searched for published literature and grey literature between Jan 1, 1980, and Nov 30, 2015, and updated our search on April 2, 2017, using databases including the Cochrane, Embase, LILACS, PubMed, Web of Science, and WHOLIS. The Cochrane Collaboration's tool for assessing risk of bias was used. Inclusion criteria included studies reporting vector control interventions in and around a house or dwelling; and use of insecticides as sprays on netting or screens, and any method to control larval breeding in water containers in and around the home. 1416 articles were assessed and 32 articles included. The most effective interventions affecting vector indices for multiple diseases were found to be intradomiciliary residual spraying, insecticide-treated materials (especially insecticide-treated nets or curtains), and treatment of larval habitats with biological and chemical methods. Waste management and clean-up campaigns reduce vector populations, although to a lesser extent than other interventions and not consistently. Modifications to the structure of homes (eg, wall plastering) had no impact on the control of vectors. Protection of the house and its surroundings might affect the transmission of several diseases. The most effective interventions should be prioritised when vector control programmes are designed; however, the quality of delivery (ie, coverage and reapplication) of interventions is a crucial factor to ensure their effectiveness. Additional randomised trials that assess the measures of human disease and eventually target several diseases with a combination of interventions that protect the household and its inhabitants against multiple vectors, are needed to inform global policy in this area.

Taking innovative vector control interventions in urban Latin America to scale: lessons learnt from multi-country implementation research

Prior to the current public health emergency following the emergence of chikungunya and Zika Virus Disease in the Americas during 2014 and 2015, multi-country research investigated between 2011 and 2013 the efficacy of novel Aedes aegypti intervention packages through cluster randomised controlled trials in four Latin-American cities: Fortaleza (Brazil); Girardot (Colombia), Acapulco (Mexico) and Salto (Uruguay). Results from the trials led to a scaling up effort of the interventions at city levels. Scaling up refers to deliberate efforts to increase the impact of successfully tested health interventions to benefit more people and foster policy and program development in a sustainable way. The different scenarios represent examples for  a 'vertical approach' and a 'horizontal approach'. This paper presents the analysis of a preliminary process evaluation of the scaling up efforts in the mentioned cites, with a focus on challenges and enabling factors encountered by the research teams, analysing the main social, political, administrative, financial and acceptance factors.

International workshop on insecticide resistance in vectors of arboviruses, December 2016, Rio de Janeiro, Brazil

Vector-borne diseases transmitted by insect vectors such as mosquitoes occur in over 100 countries and affect almost half of the world’s population. Dengue is currently the most prevalent arboviral disease but chikungunya, Zika and yellow fever show increasing prevalence and severity. Vector control, mainly by the use of insecticides, play a key role in disease prevention but the use of the same chemicals for more than 40 years, together with the dissemination of mosquitoes by trade and environmental changes, resulted in the global spread of insecticide resistance. In this context, innovative tools and strategies for vector control, including the management of resistance, are urgently needed. This report summarizes the main outputs of the first international workshop on Insecticide resistance in vectors of arboviruses held in Rio de Janeiro, Brazil, 5–8 December 2016. The primary aims of this workshop were to identify strategies for the development and implementation of standardized insecticide resistance management, also to allow comparisons across nations and across time, and to define research priorities for control of vectors of arboviruses. The workshop brought together 163 participants from 28 nationalities and was accessible, live, through the web (> 70,000 web-accesses over 3 days).

Assessing the effects of interventions for Aedes aegypti control: systematic review and meta-analysis of cluster randomised controlled trials

Background

The Aedes aegypti mosquito is the vector for dengue fever, yellow fever, chikungunya, and zika viruses. Inadequate vector control has contributed to persistence and increase of these diseases. This review assesses the evidence of effectiveness of different control measures in reducing Aedes aegypti proliferation, using standard entomological indices.

Methods

A systematic search of Medline, Ovid, BVS, LILACS, ARTEMISA, IMBIOMED and MEDIGRAPHIC databases identified cluster randomised controlled trials (CRCTs) of interventions to control Aedes aegypti published between January 2003 and October 2016. Eligible studies were CRCTs of chemical or biological control measures, or community mobilization, with entomological indices as an endpoint. A meta-analysis of eligible studies, using a random effects model, assessed the impact on household index (HI), container index (CI), and Breteau index (BI).

Results

From 848 papers identified by the search, eighteen met the inclusion criteria: eight for chemical control, one for biological control and nine for community mobilisation. Seven of the nine CRCTs of community mobilisation reported significantly lower entomological indices in intervention than control clusters; findings from the eight CRCTs of chemical control were more mixed. The CRCT of biological control reported a significant impact on the pupae per person index only. Ten papers provided enough detail for meta-analysis. Community mobilisation (four studies) was consistently effective, with an overall intervention effectiveness estimate of −0.10 (95%CI -0.20 – 0.00) for HI, −0.03 (95%CI -0.05 – -0.01) for CI, and −0.13 (95%CI -0.22 – -0.05) for BI. The single CRCT of biological control had effectiveness of −0.02 (95%CI -0.07– 0.03) for HI, −0.02 (95%CI -0.04– -0.01) for CI and −0.08 (95%CI -0.15– -0.01) for BI. The five studies of chemical control did not show a significant impact on indices: the overall effectiveness was −0.01 (95%CI -0.05– 0.03) for HI, 0.01 (95% CI -0.01– 0.02) for CI, and 0.01 (95%CI -0.03 – 0.05) for BI.

Conclusion

Governments that rely on chemical control of Aedes aegypti should consider adding community mobilization to their prevention efforts. More well-conducted CRCTs of complex interventions, including those with biological control, are needed to provide evidence of real life impact. Trials of all interventions should measure impact on dengue risk.

Indoor Resting Behavior of Aedes aegypti (Diptera: Culicidae) in Acapulco, Mexico

The markedly anthropophilic and endophilic behaviors of Aedes aegypti (L.) make it a very efficient vector of dengue, chikungunya, and Zika viruses. Although a large body of research has investigated the immature habitats and conditions for adult emergence, relatively few studies have focused on the indoor resting behavior and distribution of vectors within houses. We investigated the resting behavior of Ae. aegypti indoors in 979 houses of the city of Acapulco, Mexico, by performing exhaustive indoor mosquito collections to describe the rooms and height at which mosquitoes were found resting. In total, 1,403 adult and 747 female Ae. aegypti were collected, primarily indoors (98% adults and 99% females). Primary resting locations included bedrooms (44%), living rooms (25%), and bathrooms (20%), followed by kitchens (9%). Aedes aegypti significantly rested below 1.5 m of height (82% adults, 83% females, and 87% bloodfed females); the odds of finding adult Ae. aegypti mosquitoes below 1.5 m was 17 times higher than above 1.5 m. Our findings provide relevant information for the design of insecticide-based interventions selectively targeting the adult resting population, such as indoor residual spraying.

Innovative dengue vector control interventions in Latin America: what do they cost?

Background

Five studies were conducted in Fortaleza (Brazil), Girardot (Colombia), Machala (Ecuador), Acapulco (Mexico), and Salto (Uruguay) to assess dengue vector control interventions tailored to the context. The studies involved the community explicitly in the implementation, and focused on the most productive breeding places for Aedes aegypti. This article reports the cost analysis of these interventions.

Methods

We conducted the costing from the perspective of the vector control program. We collected data on quantities and unit costs of the resources used to deliver the interventions. Comparable information was requested for the routine activities. Cost items were classified, analyzed descriptively, and aggregated to calculate total costs, costs per house reached, and incremental costs.

Results

Cost per house of the interventions were $18.89 (Fortaleza), $21.86 (Girardot), $30.61 (Machala), $39.47 (Acapulco), and $6.98 (Salto). Intervention components that focused mainly on changes to the established vector control programs seem affordable; cost savings were identified in Salto (−21%) and the clean patio component in Machala (−12%). An incremental cost of 10% was estimated in Fortaleza. On the other hand, there were also completely new components that would require sizeable financial efforts (installing insecticide-treated nets in Girardot and Acapulco costs $16.97 and $24.96 per house, respectively).

Conclusions

The interventions are promising, seem affordable and may improve the cost profile of the established vector control programs. The costs of the new components could be considerable, and should be assessed in relation to the benefits in reduced dengue burden.

Draft Genome of the Scarab Beetle Oryctes borbonicus on La Réunion Island

Beetles represent the largest insect order and they display extreme morphological, ecological and behavioral diversity, which makes them ideal models for evolutionary studies. Here, we present the draft genome of the scarab beetle Oryctes borbonicus, which has a more basal phylogenetic position than the two previously sequenced pest species Tribolium castaneum and Dendroctonus ponderosae providing the potential for sequence polarization. Oryctes borbonicus is endemic to La Réunion, an island located in the Indian Ocean, and is the host of the nematode Pristionchus pacificus, a well-established model organism for integrative evolutionary biology. At 518 Mb, the O. borbonicus genome is substantially larger and encodes more genes than T. castaneum and D. ponderosae. We found that only 25% of the predicted genes of O. borbonicus are conserved as single copy genes across the nine investigated insect genomes, suggesting substantial gene turnover within insects. Even within beetles, up to 21% of genes are restricted to only one species, whereas most other genes have undergone lineage-specific duplications and losses. We illustrate lineage-specific duplications using detailed phylogenetic analysis of two gene families. This study serves as a reference point for insect/coleopteran genomics, although its original motivation was to find evidence for potential horizontal gene transfer (HGT) between O. borbonicus and P. pacificus. The latter was previously shown to be the recipient of multiple horizontally transferred genes including some genes from insect donors. However, our study failed to provide any clear evidence for additional HGTs between the two species.

Projected Impact of Dengue Vaccination in Yucatán, Mexico

Dengue vaccines will soon provide a new tool for reducing dengue disease, but the effectiveness of widespread vaccination campaigns has not yet been determined. We developed an agent-based dengue model representing movement of and transmission dynamics among people and mosquitoes in Yucatán, Mexico, and simulated various vaccine scenarios to evaluate effectiveness under those conditions. This model includes detailed spatial representation of the Yucatán population, including the location and movement of 1.8 million people between 375,000 households and 100,000 workplaces and schools. Where possible, we designed the model to use data sources with international coverage, to simplify re-parameterization for other regions. The simulation and analysis integrate 35 years of mild and severe case data (including dengue serotype when available), results of a seroprevalence survey, satellite imagery, and climatological, census, and economic data. To fit model parameters that are not directly informed by available data, such as disease reporting rates and dengue transmission parameters, we developed a parameter estimation toolkit called AbcSmc, which we have made publicly available. After fitting the simulation model to dengue case data, we forecasted transmission and assessed the relative effectiveness of several vaccination strategies over a 20 year period. Vaccine efficacy is based on phase III trial results for the Sanofi-Pasteur vaccine, Dengvaxia. We consider routine vaccination of 2, 9, or 16 year-olds, with and without a one-time catch-up campaign to age 30. Because the durability of Dengvaxia is not yet established, we consider hypothetical vaccines that confer either durable or waning immunity, and we evaluate the use of booster doses to counter waning. We find that plausible vaccination scenarios with a durable vaccine reduce annual dengue incidence by as much as 80% within five years. However, if vaccine efficacy wanes after administration, we find that there can be years with larger epidemics than would occur without any vaccination, and that vaccine booster doses are necessary to prevent this outcome.

Dengue is a mosquito-transmitted viral disease that is common throughout the tropics. Despite a long history in humans and extensive efforts to control dengue transmission in many countries, the number, severity, and geographic range of reported cases is increasing. Most control efforts have focused on controlling mosquito populations, but the main vector, Aedes aegypti, flourishes in human-disturbed and indoor environments. Because the mosquitoes prefer to bite during the day when people are active and potentially moving around high-risk locations, fixed barriers like bed nets are not effective. Several dengue vaccines are being actively developed and may become valuable tools in dengue control. Using historical dengue data from Yucatán, Mexico, we fit a detailed simulation of human and mosquito populations to project future transmission, then used efficacy data from vaccine trials to evaluate the benefit of potential vaccination deployment strategies in the region. For a durable vaccine, we find that population-level, annual vaccine effectiveness approaches 65% by the end of the 20-year forecast period. For waning vaccines, however, effectiveness is greatly reduced–and sometimes negative–unless booster vaccinations are used.

Spatial variation of insecticide resistance in the dengue vector Aedes aegypti presents unique vector control challenges

BACKGROUND

Dengue is a major public health problem in Mexico, where the use of chemical insecticides to control the principal dengue vector, Aedes aegypti, is widespread. Resistance to insecticides has been reported in multiple sites, and the frequency of kdr mutations associated with pyrethroid resistance has increased rapidly in recent years. In the present study, we characterized patterns of insecticide resistance in Ae. aegypti populations in five small towns surrounding the city of Merida, Mexico.

METHODS

A cross-sectional, entomological survey was performed between June and August 2013 in 250 houses in each of the five towns. Indoor resting adult mosquitoes were collected in all houses and four ovitraps were placed in each study block. CDC bottle bioassays were conducted using F0-F2 individuals reared from the ovitraps and kdr allele (Ile1016 and Cys1534) frequencies were determined.

RESULTS

High, but varying, levels of resistance to chorpyrifos-ethyl was detected in all study towns, complete susceptibility to bendiocarb in all except one town, and variations in resistance to deltamethrin between towns, ranging from 63-88% mortality. Significant associations were detected between deltamethrin resistance and the presence of both kdr alleles. Phenotypic resistance was highly predictive of the presence of both alleles, however, not all mosquitoes containing a mutant allele were phenotypically resistant. An analysis of genotypic differentiation (exact G test) between the five towns based on the adult female Ae. aegypti collected from inside houses showed highly significant differences (p < 0.0001) between genotypes for both loci. When this was further analyzed to look for fine scale differences at the block level within towns, genotypic differentiation was significant for both loci in San Lorenzo (Ile1016, p = 0.018 and Cys1534, p = 0.007) and for Ile1016 in Acanceh (p = 0.013) and Conkal (p = 0.031).

CONCLUSIONS

The results from this study suggest that 3 years after switching chemical groups, deltamethrin resistance and a high frequency of kdr alleles persisted in Ae. aegypti populations. The spatial variation that was detected in both resistance phenotypes and genotypes has practical implications, both for vector control operations as well as insecticide resistance management strategies.

Integrating vector control across diseases

BACKGROUND

Vector-borne diseases cause a significant proportion of the overall burden of disease across the globe, accounting for over 10 % of the burden of infectious diseases. Despite the availability of effective interventions for many of these diseases, a lack of resources prevents their effective control. Many existing vector control interventions are known to be effective against multiple diseases, so combining vector control programmes to simultaneously tackle several diseases could offer more cost-effective and therefore sustainable disease reductions.

DISCUSSION

The highly successful cross-disease integration of vaccine and mass drug administration programmes in low-resource settings acts a precedent for cross-disease vector control. Whilst deliberate implementation of vector control programmes across multiple diseases has yet to be trialled on a large scale, a number of examples of 'accidental' cross-disease vector control suggest the potential of such an approach. Combining contemporary high-resolution global maps of the major vector-borne pathogens enables us to quantify overlap in their distributions and to estimate the populations jointly at risk of multiple diseases. Such an analysis shows that over 80 % of the global population live in regions of the world at risk from one vector-borne disease, and more than half the world's population live in areas where at least two different vector-borne diseases pose a threat to health. Combining information on co-endemicity with an assessment of the overlap of vector control methods effective against these diseases allows us to highlight opportunities for such integration. Malaria, leishmaniasis, lymphatic filariasis, and dengue are prime candidates for combined vector control. All four of these diseases overlap considerably in their distributions and there is a growing body of evidence for the effectiveness of insecticide-treated nets, screens, and curtains for controlling all of their vectors. The real-world effectiveness of cross-disease vector control programmes can only be evaluated by large-scale trials, but there is clear evidence of the potential of such an approach to enable greater overall health benefit using the limited funds available.