Entomological Indices Research Articles

Assessing Entomological and Epidemiological Efficacy of Pyriproxyfen-Treated Ovitraps in the Reduction of Aedes Species: A Quasi-Experiment on Dengue Infection Using Saliva Samples.

Our study assessed the impact of using ovitraps with pyriproxyfen on mosquito populations and the feasibility of using human saliva samples to test for seroconversion to dengue virus (DENV). We used a quasi-experimental research design by forming the intervention (n = 220) and the control (n = 223) groups in neighboring Taguig City, Philippines, over 4 months. Socio-demographic data, entomological indices, and IgG antibodies against DENV were measured. Associations between the implementation of ovitraps dosed with pyriproxyfen and mosquito densities (percentage positive ovitraps and container indices) and DENV seroconversion were calculated post-intervention in Months 2, 3, and 4. Among the participants recruited at baseline, 17 and 13 were seropositive for dengue (DENV) in the intervention and control groups, respectively. Both entomological indices were lower in the treated area than the control site at post-intervention Months 2, 3, and 4, but not earlier. Dengue seroconversions rates decreased in the treated population, but not significantly so. In conclusion, the use of PPF-treated ovitraps may have impacted the mosquito population, but not seroconversion rates. Compliance in providing saliva samples and the ability to detect IgG antibodies within these samples was encouraging and suggests that further studies on larger populations for longer durations are warranted.

Evaluation of insecticide treated window curtains and water container covers for dengue vector control in a large-scale cluster-randomized trial in Venezuela.

Following earlier trials indicating that their potential in dengue vector control was constrained by housing structure, a large-scale cluster-randomized trial of insecticide treated curtains (ITCs) and water jar covers (ITJCs) was undertaken in Venezuela. In Trujillo, Venezuela, 60 clusters (6223 houses total) were randomized so that 15 clusters each received either PermaNet insecticide-treated window curtains (ITCs), permanent insecticide-treated water storage jar covers (ITJCs), a combination of both ITCs and ITJCs, or no insecticide treated materials (ITMs). A further 15 clusters located at least 5km from the edge of the study site were selected to act as an external control. Entomological surveys were carried out immediately before and after intervention, and then at 6-month intervals over the following 27 months. The Breteau and House indices were used as primary outcome measures and ovitrap indices as secondary. Negative binomial regression models were used to compare cluster-level values of these indices between the trial arms. Reductions in entomological indices followed deployment of all ITMs and throughout the trial, indices in the external control arm remained substantially higher than in the ITM study arms including the internal control. Comparing the ratios of between-arm means to summarise the entomological indices throughout the study, the combined ITC+ITJC intervention had the greatest impact on the indices, with a 63% difference in the pupae per person indices between the ITC+ITJC arm and the internal control. However, coverage had fallen below 60% by 14-months post-intervention and remained below 40% for most of the remaining study period. ITMs can impact dengue vector populations in the long term, particularly when ITCs and ITJCs are deployed in combination. ClinicalTrials.gov ISRCTN08474420; www.isrctn.com.

Entomological outcomes of cluster-randomised, community-driven dengue vector-suppression interventions in Kampong Cham province, Cambodia.

Cambodia has one of the highest dengue infection rates in Southeast Asia. Here we report quantitative entomological results of a large-scale cluster-randomised trial assessing the impact on vector populations of a package of vector control interventions including larvivorous guppy fish in household water containers, mosquito trapping with gravid-ovitraps, solid waste management, breeding-container coverage through community education and engagement for behavioural change, particularly through the participation of school children. These activities resulted in major reductions in Container Index, House Index, Breteau Index, Pupal Index and Adult Index (all p-values 0.002 or lower) in the Intervention Arm compared with the Control Arm in a series of household surveys conducted over a follow-up period of more than one year, although the project was not able to measure the longer-term sustainability of the interventions. Despite comparative reductions in Adult Index between the study arms, the Adult Index was higher in the Intervention Arm in the final household survey than in the first household survey. This package of biophysical and community engagement interventions was highly effective in reducing entomological indices for dengue compared with the control group, but caution is required in extrapolating the reduction in household Adult Index to a reduction in the overall population of adult Aedes mosquitoes, and in interpreting the relationship between a reduction in entomological indices and a reduction in the number of dengue cases. The package of interventions should be trialled in other locations.

Ecological and social determinants of Aedes aegypti and Aedes albopictus larval habitat in northeastern India

Dengue, the arboviral threat to public health affecting millions of people globally, is transmitted by the bite of female Aedes aegypti and Aedes albopictus. The factors contributing to Ae. spp. abundance is variable, region-specific, and needs to be identified region-wise for effective vector control programs. In this study, based on dengue fever case statistics from the previous years, we selected two representatives of natural (forest and riverine) and two urbanized (Oil industrial and tea-estates) areas of upper Brahmaputra valley and dengue prone Kamrup district in the lower Brahmaputra valley of Assam for mosquito surveillance through container search. The count of both species was the highest in the urbanized regions having higher container habitats. All the entomological indices, House index, Container index, and Breteau index were higher than the WHO criteria of dengue sensitive areas from pre-monsoon to post-monsoon seasons. The temperature was the most prominent driver having a significant correlation with entomological indices with R2 values ranging from 0.825 to 0.965 in urbanized areas and 0.723 to 0.801in natural areas, followed by rainfall and humidity. Response survey of inhabitants of the study sites revealed the status of awareness and practice regarding the vector habitats. The results indicated that the combined action of urbanization, social factors, and changes in meteorological factors have primarily contributed to the large population size of dengue vectors throughout the year. Adaptive expansion of the Aedes vectors warrants the adoption of necessary precautionary measures to prevent colonization by Ae. aegypti and Ae. albopictus in urbanized areas to prevent Aedes-borne diseases, dengue, chikungunya, and zika.

Studies on the breeding potential and entomological indices of dengue vector Aedes aegypti and Aedes albopictus in the district Ghaziabad of Uttar Pradesh, India.

The female Aedes mosquito is a vector of many arboviruses-borne diseases. The evidence and information regarding their breeding habitats are vital for implementing appropriate control policies. An entomological survey was done at three sites in Ghaziabad district of Uttar Pradesh, India viz. Indirapuram, Vasundhara, and Vaishali to generate the first boundary line information of breeding sites of Aedes aegypti larvae for the early prevention and control interventions for dengue management. A total of 2994 containers were checked in 1169 households at the time of the survey for breeding sites of Aedes mosquito during the pre-monsoon, monsoon, and post-monsoon period, out of which 667 containers were found positive in 518 positive households. The total HI, CI, and BI were 44.31, 22.27, and 57.05 respectively. The maximum and minimum breeding indices were found during monsoon and pre-monsoon respectively. The most preferred containers for Aedes breeding were cement tanks for lotus plants in nurseries, drums, and small and large size pots for storage of water and ornamental plants mostly in 8 plant nurseries. Breeding of Aedes was found in nurseries and desert coolers which were the primary breeding containers found during the survey. The containers found positive during surveys were emptied or destroyed with the help of the local community and the breeding status of nurseries was informed to the health authorities of Ghaziabad to take necessary action against the breeding sites of the Aedes mosquitoes.

KEPADATAN JENTIK Aedes aegypti SEBAGAI VEKTOR DEMAM BERDARAH DENGUE (DBD) DI DESA KALIANCAR WONOGIRI

Dengue Hemorrhagic Fever (DHF) is a disease caused by the dengue virus which is transmitted through the bite of the Aedes sp. These mosquitoes are found throughout the world and their breeding is quite fast. Density of larvae found in breeding sites in an area. This density can be measured by entomological indicators. This larval density measurement can indicate the potential for larvae in Kaliancar Village, Selogiri District, Wonogiri Regency. This research is an observational study (survey) with cross sectional. The sampling technique used is simple random sampling with single larvae method. The samples of this study were 100 houses of residents of Kaliancar Village RW 01, RW 03, RW 04 and RW 05. The results showed that the HI value was 20%, CI 7,22%, BI 20%, ABJ 80% and DF 3,66. The conclusion of this study is that the larval density in Kaliancar Village, Selogiri District, Wonogiri Regency is classified as moderate because the DF value is on a scale of 3 to 4 with an average of 3,66.

Validation of the Early Warning and Response System (EWARS) for dengue outbreaks: Evidence from the national vector control program in Mexico.

BackgroundDuring 2017, twenty health districts (locations) implemented a dengue outbreak Early Warning and Response System (EWARS) in Mexico, which processes epidemiological, meteorological and entomological alarm indicators to predict dengue outbreaks and triggers early response activities.Out of the 20 priority districts where more than one fifth of all national disease transmission in Mexico occur, eleven districts were purposely selected and analyzed. Nine districts presented outbreak alarms by EWARS but without subsequent outbreaks (“non-outbreak districts”) and two presented alarms with subsequent dengue outbreaks (“outbreak districts”). This evaluation study assesses and compares the impact of alarm-informed response activities and the consequences of failing a timely and adequate response across the outbreak groups.MethodsFive indicators of dengue outbreak response (larval control, entomological studies with water container interventions, focal spraying and indoor residual spraying) were quantitatively analyzed across two groups (”outbreak districts” and “non-outbreak districts”). However, for quality control purposes, only qualitative concluding remarks were derived from the fifth response indicator (fogging).ResultsThe average coverage of vector control responses was significantly higher in non-outbreak districts and across all four indicators. In the “outbreak districts” the response activities started late and were of much lower intensity compared to “non-outbreak districts”. Vector control teams at districts-level demonstrated diverse levels of compliance with local guidelines for ‘initial’, ‘early’ and ‘late’ responses to outbreak alarms, which could potentially explain the different outcomes observed following the outbreak alarms.ConclusionFailing timely and adequate response of alarm signals generated by EWARS showed to negatively impact the disease outbreak control process. On the other hand, districts with adequate and timely response guided by alarm signals demonstrated successful records of outbreak prevention. This study presents important operational scenarios when failing or successding EWARS but warrants investigating the effectiveness and cost-effectiveness of EWARS using a more robust designs.

Endemicity of Dengue with Density Figure and Maya Index in Bengkulu City, Indonesia

BACKGROUND: One of the factors contributing to dengue’s endemicity is the density of the dengue vector, namely, Aedes aegypti as the primary vector and Aedes albopictus as the secondary vector. Bentiring and Kandang Limun villages are high endemic areas of dengue. AIM: This study aimed to determine the relationship between dengue endemicity and density figure (DF) and Maya index (MI) in Bentiring and Kandang Limun villages, Bengkulu city. METHODS: This study used a cross-sectional design. The sampling technique used proportionate stratified sampling. The sampling refers to the guidelines for dengue entomology surveys according to the WHO 1999 criteria. A total of 400 ovitraps were installed, 200 ovitraps inside the house and 200 ovitraps outside the house. RESULTS: The results showed that Bentiring and Kandang Limun villages had a high risk of dengue transmission based on entomological parameters, namely, ovitrap index (OI) 56% and 55% (DF 6), house index (HI) 45% and 44% (DF 6), container index (CI) 23% and 23% (DF 6), and BI 96% and 120% (DF 7 and 8). The areas have a high risk of dengue transmission based on the MI 71% and 76%, respectively. There is a relationship between dengue endemicity and entomological index in Bentiring and Kandang Limun villages, Bengkulu city, with a significance value (p = 0.000) and a powerful correlation (r = 1.000). CONCLUSION: There is a relationship between dengue endemicity and the MI in Bentiring village and Kandang Limun village, Bengkulu city, with a significance value (p = 0.014 and 0.058) and a powerful correlation (r = 0.920 and r = 1.000), respectively. The entomological index and DF are predictors for dengue prevention and control environment to minimize mosquito breeding sites and reduce disease transmission.

First evaluation of antibody responses to Culex quinquefasciatus salivary antigens as a serological biomarker of human exposure to Culex bites: A pilot study in Côte d'Ivoire.

BackgroundCulex mosquitoes are vectors for a variety of pathogens of public health concern. New indicators of exposure to Culex bites are needed to evaluate the risk of transmission of associated pathogens and to assess the efficacy of vector control strategies. An alternative to entomological indices is the serological measure of antibodies specific to mosquito salivary antigens. This study investigated whether the human IgG response to both the salivary gland extract and the 30 kDa salivary protein of Culex quinquefasciatus may represent a proxy of human exposure to Culex bites.Methodology/Principal findingsA multidisciplinary survey was conducted with children aged 1 to 14 years living in neighborhoods with varying exposure to Culex quinquefasciatus in the city of Bouaké, Côte d’Ivoire. Children living in sites with high exposure to Cx quinquefasciatus had a significantly higher IgG response to both salivary antigens compared with children living in the control site where only very few Culex were recorded. Moreover, children from any Culex-high exposed sites had significantly higher IgG responses only to the salivary gland extract compared with children from the control village, whereas no difference was noted in the anti-30 kDa IgG response. No significant differences were noted in the specific IgG responses between age and gender. Sites and the use of a bed net were associated with the level of IgG response to the salivary gland extract and to the 30 kDa antigen, respectively.Conclusions/SignificanceThese findings suggest that the IgG response to Culex salivary gland extracts is suitable as proxy of exposure; however, the specificity to the Culex genus needs further investigation. The lower antigenicity of the 30 kDa recombinant protein represents a limitation to its use. The high specificity of this protein to the Culex genus makes it an attractive candidate and other specific antibody responses might be more relevant as a biomarker of exposure. These epidemiological observations may form a starting point for additional work on developing serological biomarkers of Culex exposure.

DengueChat: A Social and Software Platform for Community-based Arbovirus Vector Control.

The mosquito Aedes aegypti transmits arboviral diseases at extraordinary rates. Dengue alone afflicts 50 to 100 million people each year, with more than 3 billion at risk globally. This indicates that current approaches to prevention and control are inadequate, and that a paradigm shift from one that largely promotes vertical chemical-based control and vaccine development to one that also concentrates on eliminating the mosquito through actions by the communities it plagues is necessary. We have developed a new social and software platform, DengueChat (denguechat.org), to advance community interventions in arbovirus vector control. It is an interactive platform combining open-source digital communication technologies with face-to-face assemblies. It promotes resident participation in evidence collection, reporting, and analysis, and it incorporates pedagogic information, key messaging, and game concepts to motivate communities to implement vector reduction strategies. Using DengueChat, we conducted a 19-month pilot study in five neighborhoods of Managua, Nicaragua. The results strongly suggest that using the software produced value-added features that enhance community engagement. We measured the entomological and behavioral impacts at different time points and relative risk reduction of entomological indices at the end of the study. The entomological results showed significant risk reductions in disease transmission: Ae. aegypti larvae and pupae indices were reduced by approximately 44% in neighborhoods using DengueChat during one epidemic year, whereas control neighborhoods experienced an increase of more than 500%. A cluster permutation test determined that the probability of household positivity was significantly reduced in neighborhoods that participated in DengueChat compared with the reference neighborhoods (P = 0.0265). Therefore, DengueChat is a promising resource for vector control.

Density and habitat characterization of Aedes sp. breeding places in dengue Endemic Area in Bandar Lampung

Aedes sp. are vectors of the dengue virus that causes Dengue Haemorrhagic Fever (DHF). The purposed of this study to analyze habitat characteristics of Aedes sp. based on the entomological index and measure the density and species of larvae Aedes sp. The research was analytic observational with a cross-sectional study was conducted 3 subdistricts of endemic in Bandar Lampung. The results showed that from 3 locations, namely Sukarame, Kemiling and Tanjung Seneng, the House Index (HI) values were 41, 38, 31, respectively. The Container Index (CI) values were 14, 12, 10 respectively and the Breteau index (BI) values were 105, 77, 60 respectively. The result of density figure (DF) were 5-6 which means the density of Aedes sp. were moderate to high. The result of identification of larvae were 3 species of mosquito were Aedes aegypti, Aedes albopictus and Culex quinquefasciatus. The dominant spesies of larvae were found are Ae. aegypti. The characteristics of larvae habitat as a risk factor for increasing the density of mosquito in Bandar Lampung are buckets or container made of plastic or cement and dispenser, light colour, direct light exposure, 1-20 liters water volume, no cover container, no drainage, and no fish rearing.

Epidemiologia de Triatominos en la Provincia de Río Negro

Chagas is an endemic epidemic disease of vector transmission in the Province of Rio Negro caused by Trypanosoma cruzi, transmitted by triatomines. The Chagas control program in the province of Rio Negro certified, through serological and entomological indicators, the interruption of vector transmission throughout the province. However, in recent years, conditions have been generated that may allow the re-emergence of the disease, such as the eventual domiciliation of wild vinchucas such as T patagonico. The objective was to evaluate the epidemiological situation of the vector through studies of home and peri-home infestation by triatomines and to carry out resistance analyzes to insecticides that were applied for many years in control. As a result, 143 homes were evaluated and 66 light traps were placed. In the intra-domicile all the dwellings were negative, with 3 being positive in the peri-domicile (2.1%) with captures of T-infestans and T. patagonica. No triatomines were captured with the light traps. The captured triatomines were T. infestans and T. patagonica, which were all negative for T. cruzi. Insecticide resistance studies showed that the colonies are still susceptible to deltamethrin.colonies are still susceptible to deltamethrin.

Assessment of the Receptivity of Dengue Vector Breeding through Pre- and Post-Monsoon Vector Surveillance at Some International Airports in India

As per the International Health Regulations (2005), all the International airports and seaports are to be kept free from the risk of infection through any pathogen transmitted by vectors, thereby resulting in public health hazard. Therefore, all the international airports and seaports premises are to be kept free from any vector breeding along with the 400 perimeter areas surrounding the airports and seaports. To assess the receptivity of Vector breeding i.e. Aedesaegypti (Vector for Dengue, Yellow fever, Zika and Chikunguniya), the entomological teams from the Centre for Medical Entomology and Vector Control, NCDC have been undertaking vector surveillance activities (Pre & Post Monsoon) at POE’s of some International Airports & Seaports. The vector surveillance is being done on regular basis and the findings are being shared with the respective authorities for undertaking immediate control measures. From the years 2015 to 2020, Dengue vector surveillance activities were carried out at 10 international airports including 400 meters peripheral areas during pre- and post-monsoon periods. An attempt has been made to describe the receptivity of the airports with the key findings with entomological indices with regard to the prevention and control of dengue vector and for proper planning to undertaking timely control measures to regulate the International Health Regulations in the respective international airports. Such studies on the assessment of receptivity would help the local airport health authorities in understanding the breeding potential habitats of Aedes vector and planning the appropriate vector control strategy in the respective areas.

A Report on Vector Surveillance for Zika/Dengue at CCS International Airport, Lucknow, India

In view of reports of Zika outbreak from Gujarat & Rajasthan states, an entomological surveillance of Aedes aegypti vector was carried out at Adani Chaudhary Charan Singh (CCS) International Airport, Lucknow and its adjoining areas between 2016 to 2019. The regular monitoring of the vector and effective intervention measures prevented the invasion of new pathogen of Zika and Yellow fever pathogen (virus) by bringing down the Aedes aegypti vector density at lowest level. The entomological indices worked out in 2016 as the premise index in the month of February, June and August, were remained positive for Aedes aegypti and container index (CI) was found 14.14. The House Index (HI), Container Index (CI) & Breteau Index (BI) were 24.50, 17.51 & 25.27, respectively in residential colony of Air Port Staff located at a distance of 0.50 km, whereas, indices were found very high i.e. 37.50, 25.50 & 57.62, respectively in Farrukhabad/Chillawan civil inhabitation located at a distance of 2.0 Kilometre. With the dedicated efforts of Airport Authority of India and State Health Department, Aedes aegypti indices gradually declined to very low level as the premise were positive for Aedes aegypti larvae but container index inside & outside airport premise became 2.70 & 4.37 respectively in early half of 2019. The HI, CI & BI were found 2.57, 2.69 & 3.09 in the airport residential colony and 3.15, 2.57 & 2.77, respectively in civil inhabitation i.e. Farrukhabad/Chillawan area in early half of 2019. The collateral impact of low vector density resulted drastic decline in dengue morbidity by 83.73% & 74.74% and in mortality by 88.89% & 94.44%, during 2017 & 2018 respectively in comparison to 2016 and the case fatality rate (CFR) declined from 0.65% in 2016 to 0.14% in 2018. However no death was documented due to Chikungunya in Lucknow and the morbidity though was doubled in 2017 & declined again to the level of 2016, but remained very less in comparison to dengue, as only 44, 80 & 47 cases of Chikungunya were reported during 2016, 2017 & 2018, respectively. The Airport also achieved the dividend in the form of conferring the title of Best Airport of the year 2018 in size & region managing the cleanliness in increased thrust of passengers’ load to more than double in limited resources.

Aedes Mosquito Distribution along a Transect from Rural to Urban Settings in Yaoundé, Cameroon.

Simple SummaryVector surveillance is key for the prevention of arbovirus disease outbreaks. In the present study, the distribution of the Aedes vector population between the city centre and a close rural setting was assessed. Larval mosquito collections were undertaken from November 2019 to November 2020 along a transect from the rural area to the city centre. All containers with water were inspected. Some entomological indices evaluating transmission risk were estimated. A total of 6332 mosquito larvae were collected. Different Aedes species were recorded, including Ae. albopictus, Ae. aegytpi, Ae. simpsoni and Aedes spp. The density of mosquitoes collected during the rainy season (4706) was high compared to the dry season (1626). Ae. albopictus was the most abundant Aedes species in the urban (96.89%) and peri-urban (95.09%) sites while Ae. aegypti was the most abundant species in rural settings (68.56%). Ae. Albopictus preferred breeding habitats were discarded tires (42.51%), whereas Ae. aegypti was more prevalent in plastic containers used for storing water (65.87%). High stegomyia indexes traducing a high arbovirus transmission risk were recorded. The study suggests a high frequency of Aedes species in Yaoundé and its neighbourhood and stresses the need for urgent action to control Aedes populations in the city of Yaoundé.Introduction: The surveillance of mosquito vectors is important for the control of arboviruses diseases worldwide. Detailed information on the bionomics and distribution of their main vectors, Aedes aegypti and Aedes albopictus, is essential for assessing disease transmission risk and for better planning of control interventions. Methods: Entomological surveys were carried out from November 2019 to November 2020 in six localities of Yaoundé city following a transect from urban to rural settings: two urban (Obili, Mvan), two peri-urban (Simbock, Ahala) and two rural areas (Lendom, Elig-essomballa)—during rainy and dry seasons. All water containers were inspected. Aedes mosquito abundance, species distribution and seasonal distribution patterns were compared using generalized linear models. Stegomyia indexes were estimated to determine the risk of arbovirus transmission. Results: A total of 6332 mosquitoes larvae were collected (2342 in urban areas, 1694 in peri-urban areas and 2296 in rural sites). Aedes species recorded included Ae. albopictus, Ae. aegytpi, Ae. simpsoni and Aedes spp. High mosquito abundance was registered in the rainy season (4706) compared to the dry season (1626) (p < 0.0001). Ae. albopictus was the most abundant Aedes species in urban (96.89%) and peri-urban (95.09%) sites whereas Ae. aegypti was more prevalent in rural sites (68.56%) (p < 0.0001). Both species were found together in 71 larval habitats. Ae. albopictus was mostly found in discarded tires (42.51%), whereas Ae. aegypti was more prevalent in plastic containers used for storing water (65.87%). The majority of Aedes mosquitoes’ breeding places were situated close to human dwellings (0–10 m). Conclusion: Uncontrolled urbanization seems to greatly favour the presence of Aedes mosquito species around human dwellings in Yaoundé. Controlling Aedes mosquito distribution is becoming urgent to reduce the risk of arbovirus outbreaks in the city of Yaoundé.

Partial indoor residual spraying with pirimiphos-methyl as an effective and cost-saving measure for the control of Anopheles gambiae s.l. in northern Ghana

The scale up of indoor residual spraying (IRS) and insecticide treated nets have contributed significantly to global reductions in malaria prevalence over the last two decades. However, widespread pyrethroid resistance has necessitated the use of new and more expensive insecticides for IRS. Partial IRS with pirimiphos-methyl in experimental huts and houses in a village-wide trial was evaluated against Anopheles gambiae s.l. in northern Ghana. Four different scenarios in which either only the top or bottom half of the walls of experimental huts were sprayed, with or without also spraying the ceiling were compared. Mortality of An. gambiae s.l. on partially sprayed walls was compared with the standard procedures in which all walls and ceiling surfaces are sprayed. A small-scale trial was then conducted to assess the effectiveness, feasibility, and cost of spraying only the upper walls and ceiling as compared to full IRS and no spraying in northern Ghana. Human landing catches were conducted to estimate entomological indices and determine the effectiveness of partial IRS. An established transmission dynamics model was parameterized by an analysis of the experimental hut data and used to predict the epidemiological impact and cost effectiveness of partial IRS for malaria control in northern Ghana. In the experimental huts, partial IRS of the top (IRR 0.89, p = 0.13) or bottom (IRR 0.90, p = 0.15) half of walls and the ceiling was not significantly less effective than full IRS in terms of mosquito mortality. In the village trial, the annual entomological inoculation rate was higher for the unsprayed control (217 infective bites/person/year (ib/p/yr)) compared with the fully and partially sprayed sites, with 28 and 38 ib/p/yr, respectively. The transmission model predicts that the efficacy of partial IRS against all-age prevalence of malaria after six months would be broadly equivalent to a full IRS campaign in which 40% reduction is expected relative to no spray campaign. At scale, partial IRS in northern Ghana would have resulted in a 33% cost savings ($496,426) that would enable spraying of 36,000 additional rooms. These findings suggest that partial IRS is an effective, feasible, and cost saving approach to IRS that could be adopted to sustain and expand implementation of this key malaria control intervention.

Field Efficacy of Larvivorous Fish and Pyriproxyfen Combined with Community Engagement on Dengue Vectors in Cambodia: A Randomized Controlled Trial.

ABSTRACT.Evidence on the effectiveness of low-cost, sustainable biological vector control tools for Aedes mosquitoes is limited. Therefore, the purpose of this trial was to estimate the impact of guppy fish in combination with the larvicide pyriproxyfen (PPF) (Sumilarv® 2MR) and communication for behavioral impact (COMBI) activities to reduce entomological indices in Cambodia. In this cluster randomized, controlled superiority trial, 30 clusters comprised of one or more villages each was allocated in a 1:1:1 ratio to receive either 1) all three interventions (guppies, PPF, and COMBI), 2) two interventions (guppies and COMBI), or 3) control (standard vector control). Entomological surveys among 40 randomly selected households per cluster were carried out quarterly. The primary outcome was the population abundance of adult female Aedes mosquitoes trapped using adult resting collections. In the primary analysis, adult female Aedes abundance and mosquito infection rates was aggregated over follow-up time points to give a single rate per cluster. These data were analyzed by negative binomial regression, yielding abundance ratios (ARs). The number of Aedes females was reduced roughly by half compared with the control in both the guppy, PPF, and COMBI arm (AR = 0.54; 95% CI, 0.34–0.85; P = 0.0073); and the guppy and COMBI arm (AR = 0.49; 95% CI, 0.31–0.77; P = 0.0021). The effectiveness demonstrated and extremely low cost of including fish rearing in community-based health structures suggest they should be considered as a vector control tool as long as the benefits outweigh any potential environmental concerns. Sumilarv® 2MR was also highly accepted and preferred over current vector control tools used in Cambodia.

SYSTEMATIC REVIEW ON IMPACT OF MASS DRUG ADMINISTRATION ON LYMPHATIC FILARIASIS PREVENTION

introduction: Lymphatic filariasis (LF) is a disease caused by filarial parasites transmitted to human by mosquitoes and infecting 120 million people worldwide. Mass drug administration (MDA) involves delivering treatment to every person living in a defined geographical area, is the current practice in place and has shown to be very useful in reducing the global transmission of LF. This review aims to explore into the effectiveness of MDA in interrupting the transmission of LF in terms of the types of MDA, number of cycles, coverage, and percentage of transmission reduction. Methods: A systematic search via Scopus, PubMed, and Cochrane was done for articles published from 2015 to 2019 by using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. The articles identified from the databases searched and any that appeared to relate to the research questions were included. A total number of 14 articles fulfilled the criteria for review. Results: Overall, the review showed a reduction in LF indices of more than 50% and up to 100% post-MDA in endemic communities with high prevalence. The entomological assessment revealed a reduction in LF transmission post-MDA, which strongly supported the reduction of LF indices. Biannual MDA conducted further showed a marked reduction in LF indices compared to annual MDA. Double therapy of MDA significantly reduced the transmission indices to almost nil compared to single therapy. Conclusion: Review of MDA showed promising effects in which it reduced the prevalence microfilaraemia (mf) and Circulating Filarial Antigen (CFA) from baseline, as well as the clinical prevalence and entomological indices. Combination therapy showed better outcome compared to single therapy. Therefore, complementary vector control is suggested in addition to MDA, as well as education delivery to the endemic communities.

Evaluation of the « Time/Risk » Probability of being Infected and its Evolution Before/After a Long Term Village Scale Malaria Vector Control Programme in Angola

Three main entomological indicators are classically used in the epidemiology of malaria: the inoculation rate (“h”) of Ross, the vectorial capacity (“C”) of Garrett-Jones and the reproduction rate (“z”) of Macdonald. In spite of their undoubtfully usefulness it appeared that their formulae did not integrate the key parameter of “t” i.e. the time of exposure and therefore the probabilities of being infected according to the entomological condition (density, infectivity, longevity of the vectors) but also the time/risk and the reduction of this risk when some village-scale vector control measures are implemented.&#x0D; To deal with this approach we used the Briley’s formula, elaborated some years ago, to analyze the time/risk of being infected in the framework of a long term village scale vector control programme implemented around Balombo (Benguela Province, Angola) with classical method (inside residual spraying) and newly developed tool s (insecticide treated plastic sheeting) used alone or in association with the classical long lasting insecticide treated nets.&#x0D; Before vector control the risk was almost 20% in one week, 60% in one month and 100% in 3 months and this explain why plasmodic index are so high in this area without any organized vector control programme.&#x0D; The 3 methods actually reduced the risks which become of the order of 2% in one week, 10% in one month, 26% in one trimester but 70% in one year; the three methods had the same efficacy in reducing these risks. The fact that the risk reach 70% in one year even with right vector control shows the needs of renewing regularly the operations, the needs of other than entomological methods of prevention but also that immunity could be maintained and feared “rebound” was not observed even during the long term of the programme.

ENTOMOLOGICAL INDEX AND INSECTICIDE SUSCEPTIBILITY STATUS IN DENGUE-ENDEMIC AREAS YOGYAKARTA

Backgrounds: Dengue Hemorrhagic Fever (DHF) is a disease that receives special attention because of causing outbreaks in some countries, including Indonesia. The problems that often emerge on the DHF Control Program are the high vector density (Aedes aegypti) and the vector resistance resulting from continuous insecticide use. This study describes the entomological index and susceptibility status of Aedes aegypti against malathion and permethrin insecticides in Sorosutan, Umbulharjo, Yogyakarta.Methods: This study used a descriptive observational method with a cross-sectional design. An entomological survey is done at 354 houses in Sorosutan, which is randomly selected. The sample of Aedes aegypti was obtained through the larval collection and ovitrap installation in 100 places. Susceptibility tests performed using the bioassay method with impregnated paper were based on the WHO standard. This study was conducted from December 2018 – February 2019. The data were analyzed using univariate analysisResults: The entomological survey in Sorosutan showed the House Index value was 35.03%; Container Index was 16.68%; Breteau Index was 46.33; Density Figure was 5.00, and Larva Free Rate was 64.97%; meaning that Sorosutan had a high level of vector density. So, the risk of DHF transmission was high. The population of Aedes aegypti in Sorosutan has been tolerant against Malathion, with 87.83% mosquito mortality.Conclusion: Sorosutan was an area with high DHF transmission risk. Aedes aegypti population in Sorosutan has been tolerant against Malathion.