Awareness of body mass index and its associated factors: A cross-sectional study.

This study explores the correlates of sociodemographic factors, smoking, and caloric knowledge to body mass index awareness with a focus on Malaysia. Logistic regressions were estimated to examine sociodemographic factors associated with body mass index awareness. More than half of respondents were unaware of their body mass index (54.8%). Age was negatively associated with body mass index awareness. Adults without formal education were less likely to know their body mass index than those with tertiary-level education. Adults were less likely to be aware of their body mass index if they engaged in smoking. Adults with knowledge of the definition of calories were more aware of their body mass index than others. The findings emphasize the urgent need for a forthcoming sociodemographic factors-specific policy directed toward improving body mass index awareness to lower the prevalence of obesity in Malaysia.

Demographic, lifestyle, social, and psychological factors associated with worry-related sleep problems among school-going adolescents in Timor-Leste.

OBJECTIVE: Adolescent sleep problems are a worldwide public health issue. The present study examines factors associated with worry-related sleep problems among school-going adolescents. The country of interest is Timor-Leste, a low-income country, where studies pertaining to adolescent sleep problems are lacking. DESIGN AND MEASURES: Data were analysed from the Global School-Based Student Health Survey Timor-Leste (n = 3455). An ordered probit model was used to assess the effects of demographic, lifestyle, social, and psychological factors on different levels of worry-related sleep problems (i.e., no, mild and severe sleep problems). RESULTS: School-going adolescents were more likely to face mild or severe worry-related sleep problems if they were older, passive smokers, alcohol drinkers and moderately active. School-going adolescents who sometimes or always went hungry were more likely to experience worry-related sleep problems than those who did not. Involvement in physical fights, being bullied, and loneliness were positively associated with the probability of having modest or severe worry-related sleep problems. CONCLUSION: Age, exposure to second-hand smoke, alcohol consumption, physical activity, going hungry, physical fights, being bullied and loneliness are the important determining factors of adolescent worry-related sleep problems. Policymakers should pay special attention to these factors when formulating intervention measures.

Validity and reliability of the Malay language Perception Towards Smoking Questionnaire (BM-PTSQ) among secondary school adolescents: Further validation using Confirmatory Factor Analysis.

INTRODUCTION: Perception is an essential factor influencing smoking among adolescents. Thus, a valid tool for measuring perception is a requisite in smoking studies. This study further establishes the validity and reliability of a Malay language version of the Perception Towards Smoking Questionnaire (BM-PTSQ) for assessing the perception of smoking among secondary school-going adolescents in Malaysia. METHODS: We administered the BM-PTSQ to 669 secondary school students selected through multistage sampling; 60% of respondents were male (n=398), and 69.9% (n=463) were from rural areas. Respondents were aged 13-16 years, 36.4% (n=241) were 13 years, 40.0% (n=265) were 14 years, and 23.6% (n=156) were 16 years old. We used parallel and exploratory factor analysis (EFA) to determine the domains of the questionnaire. In addition, we also employed EFA, confirmatory factor analyses (CFA), and Cronbach's alpha to evaluate the construct validity and reliability of the BM-PTSQ. RESULTS: EFA and parallel analysis identified two domains in the BM-PTSQ that accounted for 62.9% of the observed variance, and CFA confirmed the two-domain structure. The two domains' internal consistency scores ranged from 0.702 to 0.80, which suggested adequate reliability. CONCLUSIONS: The BM-PTSQ has acceptable psychometric validity and is appropriate for assessing smoking perception and intention among Malaysian secondary school-aged youth. Researchers should further evaluate this tool's applicability in a more sociodemographically diverse population.

Exposure to secondhand smoke among school-going adolescents in Malaysia: Results from the National Health and Morbidity Survey (NHMS) 2022: Adolescent Health Survey (AHS).

INTRODUCTION: The adverse effects of secondhand smoke (SHS) exposure on health have been well established. Using the NHMS 2002: Adolescent Health Survey (AHS), this study attempts to evaluate the extent and factors associated with SHS exposure among Malaysian school-going adolescents. METHODS: We conducted the NHMS 2022: AHS to gather a representative sample of school-age teenagers. We employed a cross-sectional study design and a multi-stage sampling procedure. We utilized a pre-validated self-administered questionnaire to collect data from the selected respondents. The data analysis included adjusted odds ratios (AORs) with 95% confidence intervals (95% CIs). Additionally, we investigated the possible two-way interactions between the independent variables. RESULTS: The SHS prevalence was 42.0%. Exposure to secondhand smoke (SHS) was associated with male gender (AOR=1.28; 95 CI: 1.20-1.38), older age (AOR=1.46; 95% CI: 1.33-1.60), Malay (AOR=1.88; 95% CI: 1.49-2.37), Bumiputra Sabah (AOR=2.23; 95% CI: 1.67-2.99), Bumiputra Sarawak (AOR=2.43; 95% CI: 1.80-3.28), and Chinese ethnicity (AOR=2.89; 95 CI: % 2.30-3.64), as well as current smoking (AOR=2.78; 95% CI: 2.50-3.09), having separated or divorced parents (AOR=1.12; 95% CI: 1.02-1.23), and parental tobacco product use (AOR=4.75; 95% CI: 4.44-5.08). We found significant interactions between: 1) Age group with gender and ethnicity; 2) Gender and ethnicity; and 3) Parental smoking status with gender, response to tobacco use, parents' marital status, and ethnicity. CONCLUSIONS: Parental characteristics, sociodemographic characteristics, and SHS exposure are strongly correlated. In addition, there is evidence of smoking displacement to the house from other areas by parents/guardians. This study offers a fresh perspective on how these variables influence the likelihood of SHS exposure for Malaysian school-age teenagers. More efforts should focus on parental variables and sociodemographic traits, especially parental smoking cessation support.

Construct validity and reliability of the Malay version of the Fagerström test for nicotine dependence (FTND): A confirmatory factor analysis.

INTRODUCTION: The Fagerström test for nicotine dependence (FTND) was forward-backwards translated into the Malay language (FTND-M) and administered to 152 daily smokers who sought treatment for smoking cessation in government health clinics in Selangor state, Malaysia. METHODS: Using confirmatory factor analysis (CFA), four measurement models with the best relative fit were compared, one uni-dimensional model, and three different two-domain (morning and daytime smoking) models. RESULTS: The findings indicate that the best model of the FTND-M was a two-domain model, wherein domain one represented morning smoking (time to first cigarette of the day, smoking more in the morning, and which cigarette would you hate to give up) and domain two represented daytime smoking (cigarettes per day, difficulty refraining from smoking, and smoking when ill) which showed good model fit [χ2/df=1.932, goodness of fit (GFI) of 0.967, comparative fix index (CFI) of 0.945, incremental fit index (IFI) of 0.98, Tucker-Lewis index (TLI) of 0.95 and a real mean square end of approximation (RMSEA) of 0.079, and substantial reliability >0.70]. CONCLUSIONS: This study indicates that the FTND-M can be used to assess these two dimensions of nicotine addiction among daily smokers in a clinical setting.

Lifestyles and Sexual Behaviour Among School-Going Adolescents: A Mediational Role of Mental Health.

Sexual behaviour and mental health among adolescents are major public health issues. This study examines how lifestyles affect sexual behaviour among school-going adolescents in Malaysia, and the potential mediational role of mental health. It is the first to our knowledge to explore the mediating effect of mental health on sexual behaviour with a focus on a fast-growing developing country. Data were obtained from the National Health and Morbidity Survey 2017 (n = 27,497). Structural equation modelling was utilized to examine depression and anxiety as mediators of the relationships between sexual behaviour and smoking, alcohol drinking and illicit drug use, controlling for sociodemographic factors. Results showed that adolescents who smoked, consumed alcohol, used illicit drugs, and had depression and anxiety were more likely to engage in sexual behaviour than others. Depression and anxiety partially mediated the relationships between sexual behaviour and smoking, and illicit drug use. The association between alcohol drinking and sexual behaviour was fully mediated by depression and anxiety. In conclusion, lifestyles may affect sexual behaviour through mediation of mental health. Therefore, policymakers should take mental health factors into consideration when designing adolescent sexual behaviour preventative interventions.

Spatial Distribution and Long-Term Persistence of Wolbachia-Infected Aedes aegypti in the Mentari Court, Malaysia.

Dengue is endemic in Malaysia, and vector control strategies are vital to reduce dengue transmission. The Wolbachia strain wAlbB carried by both sexes of Ae. aegypti was released in Mentari Court, a high-rise residential site, in October 2017 and stopped after 20 weeks. Wolbachia frequencies are still being monitored at multiple traps across this site, providing an opportunity to examine the spatiotemporal distribution of Wolbachia and mosquito density with respect to year, residential block, and floor, using spatial interpolation in ArcGIS, GLMs, and contingency analyses. In just 12 weeks, Wolbachia-infected mosquitoes were established right across the Mentari Court site with an overall infection frequency of >90%. To date, the Wolbachia frequency of Ae. aegypti has remained high in all areas across the site despite releases finishing four years ago. Nevertheless, the Wolbachia invaded more rapidly in some residential blocks than others, and also showed a relatively higher frequency on the eighth floor. The Ae. aegypti index tended to differ somewhat between residential blocks, whilst the Ae. albopictus index was relatively higher at the top and bottom floors of buildings. In Mentari Court, only a short release period was required to infiltrate Wolbachia completely and stably into the natural population. The results inform future releases in comparable sites in a dengue control programme.

Validation of the Malay Version of the Decisional Balance Inventory (MDBI) among secondary school-going adolescents.

INTRODUCTION: The Decisional Balance Inventory is a tool used to measure propensity to maintain or change a habit which takes into consideration the perceived advantages and disadvantages. This study aimed to establish the validity and reliability of a Malay language version of the DBI for assessing inclination for change in smoking behavior among secondary school-going adolescents in Malaysia. METHODS: We administered the MDBI to 669 secondary school students selected through multistage sampling. The sample consisted of 60.1% male (n=398) and 39.9% (n=264) female students, more than two-thirds (69.9%, n=463) of which were from rural areas. The majority of the respondents were aged 13-14 years [13 years, 36.4% (n=241), 14 years, 40.0% (n=265), 16 years, 23.6% (n=156)]. The construct validity of the MDBI was assessed using explanatory (EFA) and confirmatory factor analysis (CFA), and the reliability of the MDBI via Cronbach's alpha. RESULTS: EFA and parallel analysis extracted three factors in the MDBI that accounted for 65.4% of the observed variance, and this was supported by CFA. Internal consistency of the three factors ranged from 0.734 to 0.867, indicating acceptable reliability. CONCLUSIONS: The MDBI has good psychometric properties and is suitable for measuring smoking intention among Malaysian secondary school-going adolescents. However, it should continue to be tested to expand its usefulness and applicability among adolescents in other sociodemographic settings.

Agreement between the Fagerström test for nicotine dependence (FTND) and the heaviness of smoking index (HSI) for assessing the intensity of nicotine dependence among daily smokers.

INTRODUCTION: Measuring the level of nicotine addiction among smokers is an integral part of enhancing smoking cessation as nicotine dependence is one of the barriers to smoking cessation. In this study, we compared the level of agreement between FTND and HSI in detecting high nicotine dependence among daily smokers. METHODS: We collected data from participants of a public smoking cessation clinic in Selangor. A trained pharmacist conducted face-to-face interviews with 152 daily smokers using a structured validated questionnaire. Respondents were classified as having high nicotine dependence using both the HSI (score ≥4) and the FTND (score ≥6), and concordance between the two measures, kappa statistics and sensitivity, specificity of the HSI were then determined with the FTND classification as the reference standard. RESULTS: The HSI had a substantial agreement with the FTND (Cohen's kappa=0.72) in measuring high levels of nicotine addiction, with good sensitivity (83.3%) and specificity (89.4%). CONCLUSIONS: The findings suggest that the HSI can be used instead of the FTND in clinical-based investigations to screen for high nicotine dependence among daily smokers in the clinical setting.

Correlates of dual/poly tobacco use among school-going adolescents in Malaysia: Findings from a nationwide school-based study.

INTRODUCTION: Dual/poly tobacco use is common among youths globally. However, in Malaysia information on dual/poly tobacco use is scarce, thus the present study examines the prevalence and factors associated with dual/poly tobacco users among school-going adolescents in Malaysia. METHODS: We derived data on tobacco and e-cigarette use among Malaysian adolescents from a nationwide school-based study conducted in 2016. A total of 13135 adolescents responded in the cross-sectional survey which used multi-stage sampling to select a representative sample of school-going adolescents aged 11-19 years. A standard validated questionnaire was used to obtain the data and multiple logistic regression was conducted to assess factors associated with dual/ poly tobacco use. RESULTS: The prevalence of dual/poly tobacco use was 6.5%, more than half of which were both conventional and e-cigarette users. Multivariable logistic regression revealed that the likelihood of dual tobacco use was significantly higher among males (AOR=14.73; 95% CI: 9.11-23.81), secondary school students, those aged 16-19 years (AOR=5.99; 95% CI: 4.04-8.87), natives of Sabah (AOR=7.41; 95% CI: 3.48-15.79), and those never been taught on the health hazards of tobacco at school, exposed to secondhand smoke (SHS) at home, school or other public areas, and had a positive perception of e-cigarettes and lower perception of the harms of tobacco smoking. CONCLUSIONS: Although the prevalence of dual/poly users was still low among Malaysian school-going adolescents, proactive measures should be taken to reduce dual tobacco use among youth in Malaysia with focus on the factors identified in this study.

Assessment of association between smoking and all-cause mortality among Malaysian adult population: Findings from a retrospective cohort study.

INTRODUCTION: Smoking is a known risk factor for many chronic diseases. Illness and death due to smoking are a significant public health burden in many countries. This study aims to address the information gap in smoking-related mortality in Malaysia by estimating the risk of cardiovascular disease and all-cause mortalities due to smoking among Malaysian adults. METHODS: We analyzed data on 2525 respondents, aged 24-64 years, of the Malaysian Non-Communicable Disease Surveillance survey conducted September 2005 to February 2006. Mortality records from the Malaysian National Registration Department were linked to the MYNCDS-1 data to determine respondents' mortality status over 12 years from 2006 to 2018. Associations between smoking and all-cause mortalities were assessed using Cox proportional hazards regression with adjustments for non-communicable disease and sociodemographic and lifestyle factors. RESULTS: The prevalence of daily smoking was 21.2% (95% CI: 19.0-23.7). During the 31668 person-years follow-up, 213 deaths from all causes occurred, where 68 deaths were among smokers (13.2%), and 452 were among non-smokers (6.3%). Smoking was associated with a significantly increased risk of all-cause mortality (adjusted hazard ration, AHR=1.79; 95% CI: 1.12- 2.97). These associations remained significant after excluding mortalities in the first two years of follow-up. CONCLUSIONS: Daily smoking is associated with a significantly higher risk of all-cause death. Behavioral and pharmacological smoking cessation interventions should be intensified among smokers to reduce the risk of mortality.

Gender Differences in Factors Associated with the Total Delay in Treatment of Pulmonary Tuberculosis Patients: A Cross-Sectional Study in Selangor, Malaysia.

Background: Gender plays a significant role in health-care-seeking behavior for many diseases. Delays in seeking treatment, diagnosis, and treatment for pulmonary tuberculosis (pTB) may increase the risk of transmission in the community and lead to poorer treatment outcomes and mortality. This study explores the differences in factors associated with the total delay in treatment of male and female pTB patients in Selangor, Malaysia. Methods: A cross-sectional study was conducted from January 2017 to December 2017. Newly diagnosed pTB patients (≥18 years) were recruited from selected government health clinics and hospitals in Selangor during the specified study period. An interviewer-administered questionnaire was used to collect information on sociodemographic characteristics, lifestyle, knowledge about pTB, stigma, distance to the nearest health facility, and chronology of pTB symptom onset, diagnosis, and treatment. The total delay was measured as the length of time between the onset of pTB symptoms to treatment initiation. Factors significantly associated with a longer total delay among men and women were identified using binary logistic regression. Results: A total of 732 patients (61.5% men, 38.5% women) were enrolled in the study. The median total delay was 60 days. Men who have weight loss as a symptom (AOR: 1.63, 95%CI: 1.10-2.41) and are employed (1.89, 1.15-3.11) were more likely to have a longer total delay, while those who know others who have had pTB (0.64, 0.43-0.96) were less likely to have a longer total delay. On the other hand, among women, having a stigma towards TB (0.52, 0.32-0.84) and obtaining a pTB diagnosis at the first medical consultation (0.48, 0.29-0.79) were associated with a shorter total delay. Conclusion: Factors associated with the total delay in pTB treatment were different for male and female pTB patients. Increasing awareness of pTB symptoms and the importance of seeking early medical consultation and a prompt diagnosis among the general public may reduce total delay in pTB treatment.

Assessing the Spatiotemporal Spread Pattern of the COVID-19 Pandemic in Malaysia.

Introduction: The unprecedented COVID-19 pandemic has greatly affected human health and socioeconomic backgrounds. This study examined the spatiotemporal spread pattern of the COVID-19 pandemic in Malaysia from the index case to 291,774 cases in 13 months, emphasizing on the spatial autocorrelation of the high-risk cluster events and the spatial scan clustering pattern of transmission. Methodology: We obtained the confirmed cases and deaths of COVID-19 in Malaysia from the official GitHub repository of Malaysia's Ministry of Health from January 25, 2020 to February 24, 2021, 1 day before the national vaccination program was initiated. All analyses were based on the daily cumulated cases, which are derived from the sum of retrospective 7 days and the current day for smoothing purposes. We examined the daily global, local spatial autocorrelation and scan statistics of COVID-19 cases at district level using Moran's I and SaTScan™. Results: At the initial stage of the outbreak, Moran's I index > 0.5 (p < 0.05) was observed. Local Moran's I depicted the high-high cluster risk expanded from west to east of Malaysia. The cases surged exponentially after September 2020, with the high-high cluster in Sabah, from Kinabatangan on September 1 (cumulative cases = 9,354; Moran's I = 0.34; p < 0.05), to 11 districts on October 19 (cumulative cases = 21,363, Moran's I = 0.52, p < 0.05). The most likely cluster identified from space-time scanning was centered in Jasin, Melaka (RR = 11.93; p < 0.001) which encompassed 36 districts with a radius of 178.8 km, from November 24, 2020 to February 24, 2021, followed by the Sabah cluster. Discussion and Conclusion: Both analyses complemented each other in depicting underlying spatiotemporal clustering risk, giving detailed space-time spread information at district level. This daily analysis could be valuable insight into real-time reporting of transmission intensity, and alert for the public to avoid visiting the high-risk areas during the pandemic. The spatiotemporal transmission risk pattern could be used to monitor the spread of the pandemic.

COVID-19 in Malaysia: Descriptive Epidemiologic Characteristics of the First Wave.

This study aimed to describe the characteristics of COVID-19 cases and close contacts during the first wave of COVID-19 in Malaysia (23 January 2020 to 26 February 2020), and to analyse the reasons why the outbreak did not continue to spread and lessons that can be learnt from this experience. Characteristics of the cases and close contacts, spatial spread, epidemiological link, and timeline of the cases were examined. An extended SEIR model was developed using several parameters such as the average number of contacts per day per case, the proportion of close contact traced per day and the mean daily rate at which infectious cases are isolated to determine the basic reproduction number (R0) and trajectory of cases. During the first wave, a total of 22 cases with 368 close contacts were traced, identified, tested, quarantine and isolated. Due to the effective and robust outbreak control measures put in place such as early case detection, active screening, extensive contact tracing, testing and prompt isolation/quarantine, the outbreak was successfully contained and controlled. The SEIR model estimated the R0 at 0.9 which further supports the decreasing disease dynamics and early termination of the outbreak. As a result, there was a 11-day gap (free of cases) between the first and second wave which indicates that the first wave was not linked to the second wave.

Prevalence and factors related to secondhand smoke exposure among secondary school-going adolescents in Malaysia: Findings from Malaysia Global Health School Survey 2012 and 2017.

INTRODUCTION: Secondhand (SHS) smoke exposure has caused various health problems. Therefore, continuous monitoring of SHS exposure is important to determine the efficacy of various anti-tobacco measure implemented. The study aims to compare the prevalence and factor(s) associated with SHS exposure among secondary school-going adolescents in Malaysia during 2012 and 2017. METHODS: We derived data from the Global School Health Survey (GSHS) 2012 and GSHS 2017, which was carried out in Malaysia using multistage sampling to select representative samples of secondary school-going adolescents. Both surveys used similar questionnaires to measure SHS exposure. Descriptive and multivariate logistic regression was used to determine the prevalence and factors associated with SHS exposure. RESULTS: Approximately four in ten respondents were exposed to SHS in the past week in both surveys (41.5% in GSHS 2012 and 42.0% in GSHS 2017, respectively). Both surveys revealed a significantly higher SHS exposure among respondents who smoked than among non-smokers and higher among males compared to females. The likelihood of SHS exposure in both surveys was also similar, with a higher likelihood of SHS exposure among smoking adolescents and non-smoking adolescents who had at least one smoking parent/guardian, regardless of their own smoking status. Male adolescents had a higher risk of SHS exposure compared to their female counterparts. Meanwhile, SHS risk also increased with age, regardless of smoking status. CONCLUSIONS: Our findings suggested that there were no changes in the prevalence of SHS exposure and recorded only a slight change in the factors associated with exposure to SHS among school-going adolescents in Malaysia between the years 2012 and 2017. A more pro-active, extensive and comprehensive programme should be implemented to address the problem of SHS exposure. Parents should be advised to stop smoking or abstain from smoking in the presence of their children, and smoking cessation interventions are necessary for smoking adolescents and their parents.

Insecticide resistance in dengue vectors from hotspots in Selangor, Malaysia.

BACKGROUND: In Malaysia, dengue remains a top priority disease and usage of insecticides is the main method for dengue vector control. Limited baseline insecticide resistance data in dengue hotspots has prompted us to conduct this study. The present study reports the use of a map on the insecticide susceptibility status of Aedes aegypti and Aedes albopictus to provide a quick visualization and overview of the distribution of insecticide resistance. METHOD AND RESULTS: The insecticide resistance status of Aedes populations collected from 24 dengue hotspot areas from the period of December 2018 until June 2019 was proactively monitored using the World Health Organization standard protocol for adult and larval susceptibility testing was conducted, together with elucidation of the mechanisms involved in observed resistance. For resistance monitoring, susceptibility to three adulticides (permethrin, deltamethrin, and malathion) was tested, as well as susceptibility to the larvicide, temephos. Data showed significant resistance to both deltamethrin and permethrin (pyrethroid insecticides), and to malathion (organophosphate insecticide) in all sampled Aedes aegypti populations, while variable resistance patterns were found in the sampled Aedes albopictus populations. Temephos resistance was observed when larvae were tested using the diagnostic dosage of 0.012mg/L but not at the operational dosage of 1mg/L for both species. CONCLUSION: The present study highlights evidence of a potential threat to the effectiveness of insecticides currently used in dengue vector control, and the urgent requirement for insecticide resistance management to be integrated into the National Dengue Control Program.

Modelling the Effectiveness of Epidemic Control Measures in Preventing the Transmission of COVID-19 in Malaysia.

Malaysia is currently facing an outbreak of COVID-19. We aim to present the first study in Malaysia to report the reproduction numbers and develop a mathematical model forecasting COVID-19 transmission by including isolation, quarantine, and movement control measures. We utilized a susceptible, exposed, infectious, and recovered (SEIR) model by incorporating isolation, quarantine, and movement control order (MCO) taken in Malaysia. The simulations were fitted into the Malaysian COVID-19 active case numbers, allowing approximation of parameters consisting of probability of transmission per contact (ß), average number of contacts per day per case (ζ), and proportion of close-contact traced per day (q). The effective reproduction number (Rt) was also determined through this model. Our model calibration estimated that (ß), (ζ), and (q) were 0.052, 25 persons, and 0.23, respectively. The (Rt) was estimated to be 1.68. MCO measures reduce the peak number of active COVID-19 cases by 99.1% and reduce (ζ) from 25 (pre-MCO) to 7 (during MCO). The flattening of the epidemic curve was also observed with the implementation of these control measures. We conclude that isolation, quarantine, and MCO measures are essential to break the transmission of COVID-19 in Malaysia.

Characterization of Sodium Channel Mutations in the Dengue Vector Mosquitoes Aedes aegypti and Aedes albopictus within the Context of Ongoing Wolbachia Releases in Kuala Lumpur, Malaysia.

Specific sodium channel gene mutations confer target site resistance to pyrethroid insecticides in mosquitoes and other insects. In Aedes mosquito species, multiple mutations that contribute to resistance vary in their importance around the world. Here, we characterize voltage sensitive sodium channel (Vssc) mutations in populations of Aedesaegypti from Kuala Lumpur, Malaysia, and look at their persistence in populations affected by ongoing Wolbachia releases (a dengue control measure). We also describe a Vssc mutation in Aedesalbopictus (F1534L) found for the first time in Malaysia. We show that there are three predominant Vssc haplotypes in Aedesaegypti in this region, which all persist with regular backcrossing, thereby maintaining the original genetic composition of the populations. We identify changes in genotype frequency in closed populations of Ae. aegypti maintained for multiple generations in laboratory culture, suggesting different fitness costs associated with the genotypes, some of which may be associated with the sex of the mosquito. Following population replacement of Ae. aegypti by Wolbachia in the target area, however, we find that the Vssc mutations have persisted at pre-release levels. Mosquitoes in two genotype classes demonstrate a type I pyrethroid resistance advantage over wildtype mosquitoes when exposed to 0.25% permethrin. This resistance advantage is even more pronounced with a type II pyrethroid, deltamethrin (0.03%). The results point to the importance of these mutations in pyrethroid resistance in mosquito populations and the need for regular backcrossing with male mosquitoes from the field to maintain similarity of genetic background and population integrity during Wolbachia releases.

Establishment of Wolbachia Strain wAlbB in Malaysian Populations of Aedes aegypti for Dengue Control.

Dengue has enormous health impacts globally. A novel approach to decrease dengue incidence involves the introduction of Wolbachia endosymbionts that block dengue virus transmission into populations of the primary vector mosquito, Aedes aegypti. The wMel Wolbachia strain has previously been trialed in open releases of Ae. aegypti; however, the wAlbB strain has been shown to maintain higher density than wMel at high larval rearing temperatures. Releases of Ae. aegypti mosquitoes carrying wAlbB were carried out in 6 diverse sites in greater Kuala Lumpur, Malaysia, with high endemic dengue transmission. The strain was successfully established and maintained at very high population frequency at some sites or persisted with additional releases following fluctuations at other sites. Based on passive case monitoring, reduced human dengue incidence was observed in the release sites when compared to control sites. The wAlbB strain of Wolbachia provides a promising option as a tool for dengue control, particularly in very hot climates.

Assessment of land use factors associated with dengue cases in Malaysia using Boosted Regression Trees.

The transmission of dengue disease is influenced by complex interactions among vector, host and virus. Land use such as water bodies or certain agricultural practices have been identified as likely risk factors for dengue because of the provision of suitable habitats for the vector. Many studies have focused on the land use factors of dengue vector abundance in small areas but have not yet studied the relationship between land use factors and dengue cases for large regions. This study aims to clarify if land use factors other than human settlements, e.g. different types of agricultural land use, water bodies and forest are associated with reported dengue cases from 2008 to 2010 in the state of Selangor, Malaysia. From the correlative relationship, we aim to generate a prediction risk map. We used Boosted Regression Trees (BRT) to account for nonlinearities and interactions between the factors with high predictive accuracies. Our model with a cross-validated performance score (Area Under the Receiver Operator Characteristic Curve, ROC AUC) of 0.81 showed that the most important land use factors are human settlements (model importance of 39.2%), followed by water bodies (16.1%), mixed horticulture (8.7%), open land (7.5%) and neglected grassland (6.7%). A risk map after 100 model runs with a cross-validated ROC AUC mean of 0.81 (±0.001 s.d.) is presented. Our findings may be an important asset for improving surveillance and control interventions for dengue.