Dengue surveillance using gravid oviposition sticky (GOS) trap and dengue non-structural 1 (NS1) antigen test in Malaysia: randomized controlled trial

Dengue remains a major public threat and existing dengue control/surveillance programs lack sensitivity and proactivity. More efficient methods are needed. A cluster randomized controlled trial was conducted for 18 months to determine the efficacy of using a combination of gravid oviposition sticky (GOS) traps and dengue non-structural 1 (NS1) antigen for early surveillance of dengue among Aedes mosquito. Eight residential apartments were randomly assigned into intervention and control groups. GOS traps were placed at the intervention apartments weekly to trap Aedes mosquitoes and these tested for dengue NS1 antigen. When dengue-positive pool was detected, the community were notified and advised to execute protective measures. Fewer dengue cases were recorded in the intervention group than the control. Detection of NS1-positive mosquitoes was significantly associated with GOS Aedes index (rs = 0.68, P < 0.01) and occurrence of dengue cases (rs = 0.31, P < 0.01). Participants’ knowledge, attitude, and practice (KAP) toward dengue control indicated significant improvement for knowledge (P < 0.01), practice (P < 0.01) and total scores (P < 0.01). Most respondents thought this surveillance method is good (81.2%) and supported its use nationwide. Thus, GOS trap and dengue NS1 antigen test can supplement the current dengue surveillance/control, in alignment with the advocated integrated vector management for reducing Aedes-borne diseases.

Sex-specific distribution and classification of Wolbachia infections and mitochondrial DNA haplogroups in Aedes albopictus from the Indo-Pacific

The arbovirus vector Aedes albopictus (Asian tiger mosquito) is common throughout the Indo-Pacific region, where most global dengue transmission occurs. We analysed population genomic data and tested for cryptic species in 160 Ae. albopictus sampled from 16 locations across this region. We found no evidence of cryptic Ae. albopictus but found multiple intraspecific COI haplotypes partitioned into groups representing three Asian lineages: East Asia, Southeast Asia and Indonesia. Papua New Guinea (PNG), Vanuatu and Christmas Island shared recent coancestry, and Indonesia and Timor-Leste were likely invaded from East Asia. We used a machine learning trained on morphologically sexed samples to classify sexes using multiple genetic features and then characterized the w AlbA and w AlbB Wolbachia infections in 664 other samples. The w AlbA and w AlbB infections as detected by qPCR showed markedly different patterns in the sexes. For females, most populations had a very high double infection incidence, with 67% being the lowest value (from Timor-Leste). For males, the incidence of double infections ranged from 100% (PNG) to 0% (Vanuatu). Only 6 females were infected solely by the w AlbA infection, while rare uninfected mosquitoes were found in both sexes. The w AlbA and w AlbB densities varied significantly among populations. For mosquitoes from Torres Strait and Vietnam, the w AlbB density was similar in single-infected and superinfected ( w AlbA and w AlbB) mosquitoes. There was a positive association between w AlbA and w AlbB infection densities in superinfected Ae. albopictus . Our findings provide no evidence of cryptic species of Ae. albopictus in the region and suggest site-specific factors influencing the incidence of Wolbachia infections and their densities. We also demonstrate the usefulness of SNPs as sex-specific mosquito markers. The results provide baseline data for the exploitation of Wolbachia -induced cytoplasmic incompatibility (CI) in dengue control.

Dengue virus seroprevalence study in Bangphae district, Ratchaburi, Thailand: A cohort study in 2012-2015

Background To determine the seroprevalence and transmission dynamics of dengue virus (DENV), age-stratified longitudinal serological surveys were conducted in Bangphae district, Ratchaburi province, Thailand, for 3 years between April 2012 and April 2015. Methodology The surveys enrolled 2012 healthy children and adults between 1 and 55 years-of-age, and a longitudinal serosurvey of six repeated bleeds of the same cohort of individuals was conducted every 8 months for the first 2 years (M0, M8, M16) and every half a year (M24, M30, M36) for the rest of the study period. All samples were tested using in-house indirect sandwich dengue IgG ELISA to determine DENV antibody titer, and 640 paired samples which showed rising of DENV IgG titers in paired serum were further tested using in-house neutralization assay, Plaque Reduction Neutralization Test (PRNT50). Principal findings When compared against the gold standard based on the results of PRNT50, sensitivity and specificity of indirect ELISA were found to be both about 85%. The overall DENV IgG positivity determined by ELISA was 74.3% in 2012 and increased to 79.4% by the final sample collection in 2015. In our study sample, more than 98% of subjects older than 25 years were found to be seropositive. Among 518 IgG negative subjects at enrollment, the seroconversion rates were measured in paired bleeds; the rates (between successive visits, approximately 6 months) ranged between 4.8% (between M16 and M24) and 14.7% (between M0 and M8). The dominant serotype of primary DENV infection cases based on seroconversion was identified from the PRNT results and it was DENV-2. Conclusions Our study documented high levels of seroprevalence and rate of transmission. Given the importance of the serostatus and disease burden in consideration for dengue vaccine introduction, our data could be used in decision-making on implementation of various dengue control and preventive measures.

EFFECTIVENESS OF COMPREHENSIVE CAMPAIGN FOR DENGUE CONTROL IN SOUTHERN PUNJAB, PAKISTAN - AN EXPERIENCE OF 2 YEARS

Objective: To determine the effect of comprehensive campaign for dengue control in Southern Punjab, Pakistan. Study Design: Cross sectional study. Place and Duration of the Study: Station Health Organization Multan and Departments of Pathology, Combined Military Hospital Multan, from Mar 2019 to Dec 2020. Methodology: This study was conducted by implementing a comprehensive campaign by involvement of public health workers in high risk dengue area of Multan. There were five phases of this campaign; awareness, situation analysis, vector surveillance, indoor residual sprays where vector was found and contact tracing of dengue fever cases. The system was developed in 46 Mohallas/localities of Multan. Hot spot for mosquitoes breeding were identified at 15 places. Total of 23 health workers were recruited including 3 female workers. Insecticide spraying was carried out by indoor residual spray pumps & thermal foggers in a cyclic pattern. Results: During 2019, 42 larvae were identified followed by insecticide sprays & follow up visits; 26 cases of dengue fever were diagnosed and treated at CMH Multan in a dedicated dengue ward. Contact tracing was carried out and indoor residual sprays were carried out in 20 houses around residence of these cases. In 2020, 5 larvae were identified followed by sprays & follow up visits; 2 cases of dengue fever were diagnosed and treated. Conclusion: Comprehensive campaign against dengue fever was quite successful to control spread of dengue fever.

Potential Development of Digital Environmental Surveillance System in Dengue Control: A Qualitative Study

Background: The development of digital environmental technology can be conducted to implement reports, surveillance, and manage dengue control. Therefore, this study aims to determine the barriers to the use of paper-based and the potential development of digital environmental technology in dengue control. Methods In-depth qualitative interviews were conducted using 14 key informants and four focus group discussions (FGD) from May-August 2021 in Denpasar City, Bali. The interviews were consistent with the flow of the epidemiological and entomological surveillance system, the obstacles to the dengue control program, the potential for the application of digital technology, and the challenges in the application of digital surveillance technology. Furthermore, open-ended questions and content analysis by qualitative study procedures were adopted. The results were transcribed verbatim and triangulation of sources was conducted for data validation. Results The reporting system that used paper-based was not optimally implemented due to repetition of reporting, speed of information, data bias, performance measurement as well as case surveillance and reporting system constraints. An integrated digital environmental surveillance system (SILIRA) was also developed for dengue control. In the current Covid-19 pandemic, the need for digital applications is high due to the policy of not accepting guests and keeping a distance. Epidemiological surveillance for case data collection, entomological surveillance for larva density, case reporting, and educational videos are the required data in the application. Conclusion The development of an integrated application for an environmental monitoring system can be created for the continuous reporting of case information and larval density for dengue hemorrhagic fever control. Keywords: digital, surveillance, environment, dengue

High Temperature Cycles Result in Maternal Transmission and Dengue Infection Differences Between Wolbachia Strains in Aedes aegypti

In the past decades, dengue incidence has dramatically increased all over the world. An emerging dengue control strategy utilizes Aedes aegypti mosquitoes artificially transinfected with the bacterial symbiont Wolbachia , with the ultimate aim of replacing wild mosquito populations.

Wolbachia strain wAu differs in cellular perturbation and virus inhibition profiles from previously characterised Wolbachia strains

Some strains of the inherited bacterium Wolbachia have been shown to be effective at reducing the transmission of dengue and other positive-sense RNA viruses by Aedes aegypti in both laboratory and field settings and are being deployed for dengue control. The degree of virus inhibition varies between Wolbachia strains density and tissue tropism can contribute to these differences but there are also indications that this is not the only factor involved: for example, strains wAu and wAlbA are maintained at similar densities but only wAu produces strong dengue inhibition. We previously reported perturbations in lipid transport dynamics, including sequestration of cholesterol in lipid droplets, with strains wMel/wMelPop in Ae.aegypti. Here we show that strain wAu does not produce the same cholesterol sequestration phenotype despite displaying strong virus inhibition and moreover, in contrast to wMel, wAu antiviral activity was not rescued by cyclodextrin treatment. To further investigate the cellular basis underlying these differences, proteomic analysis of midguts was carried out on Ae. aegypti lines and revealed that wAu-carrying midguts showed a distinct proteome when compared to Wolbachia-free, wMel- or wAlbA-carrying midguts, in particular with respect to lipid transport and metabolism. The data suggest a possible role for perturbed RNA processing pathways in wAu virus inhibition. Together these results indicate that wAu shows unique features in its inhibition of arboviruses compared to previously characterized Wolbachia strains.

1475Effects of climate factors on the dengue fever in Paraguay: generalized additive model in 2014-2020

Background Dengue fever is disease transmitted by mostly Aedes spp. This study aims investigate the association between climate factors and dengue incidence in Paraguay, considered as an endemic disease since 2009. Methods We extracted incidence of dengue by week from 2014-2020 national health surveillance, Paraguay. The climate factors, including rainfall, sunshine, minimum temperate, air pressure, relative humidity and wind were extracted from Directorate of Meteorology and Hydrology and aggregated as a weekly data. Generalized additive modeling was performed, adjusted by seasonality and population. Lags between 0-10 weeks were chosen for according to rho statistics of Spearman’s test. Results A total of dengue fever was 40,593 in study period. The mean cumulative incidence per 10,000 populations was 22.37 (standard deviation: 93.27). All six climate factors and seasonality were significant in the final model with the adjusted R-square 18.6%. Rainfall (relative risk [RR]: 0.51), relative humidity (RR: 0.25) and wind (RR: 0.19) showed negative trends with the increase of dengue while atmospheric pressure (RR: 9.32) and sunshine (RR: 0.12) showed positive associations. Minimum temperature showed increasing trend until 15ºC (1ºC increase in 4-fold incidence). The lag of each factor was selected between 2 to 10 weeks. Conclusion Climate factors showed associations with dengue fever in Paraguay. Such climate factors should be considered along with the dengue surveillance in endemic areas for effective dengue control. Key messages Climate factors showed significant dynamic associations with dengue incidence in Paraguay.

Pengendalian Demam Berdarah Dengue (DBD) Berbasis Masyarakat di Indonesia: Systematic Review

Demam berdarah dengue (DBD) masih menjadi maslah kesehatan di Indonesia. Berbagai program telah dilaksanakan oleh pemerintah untuk menanggulangi DBD. Pelibatan masyarakat dalam pengendalian menjadi penting dalam upaya pengendalian DBD. Kajian sistematis ini bertujuan untuk mengetahui pelibatan komunitas dalam intervensi pengendalain DBD di Indonesia. Metode dalam penelitian ini adalah systematic review dengan menggunakan metode PRISMA. Kami melakukan pencarian literatur empat data base elektronik : Google Scholar, PubMed, Web of Science, Scopus dengan data open access dari tahun 2015 hingga 2020. Artikel dipilih berdasarkan kriteria inklusi community dengue control, engangment dengue control, sosial capital dengue control dan didapatkan 5 artikel yang sesuai untuk dikaji. Penelitian ini menggunakan metode studi pustaka dengan menggunakan data penelitian dengan topik yang sama sebagai data sekunder. Pelibatan komunitas menjadi bagian keberhasilan dalam pengendalian DBD di Indonesia.hasil intervensi meliputi pengetahuan, sikap dan praktik di komunitas; partisipasi masyarakat; modal social dan pemberdayaan masyrakat mampu menurunkan parameter terhadap kejadian maupun kasus DBD. Keberhasilan pelibatan komunitas dalam pengendalian DBD di Indonesia perlu adanya program keberlanjutan dan kesinambungan.

MATHEMATICAL MODEL OF DENGUE CONTROL WITH CONTROL OF MOSQUITO LARVAE AND MOSQUITO AFFECTED BY CLIMATE CHANGE

Consider a SIR model for the spread of dengue hemorrhagic fever involving three populations, mosquito eggs, mosquitoes, and humans. The parameters of the SIR model were estimated using rainfall data and air temperature for the cities of Pekanbaru and Solok. The main aim of this paper is to determine the effect of mosquito larvae and adult mosquito control on the spread of the dengue virus. Numerical solutions were also presented by using the Runge-Kutta method of order 4. Based on the results, the SIR model was obtained by involving the control parameters of mosquito larvae and adult mosquitoes. Besides, the mosquito population is affected by changes in temperature, rainfall, and fog. Numerical simulations illustrate that the number of infected mosquitoes and infected humans is influenced by the parameters of the percentage of mortality of mosquito larvae and adult mosquitoes.