Rodziah Ismail

Generating temporal model using climate variables for the prediction of dengue cases in Subang Jaya, Malaysia

Objective To develop a forecasting model for the incidence of dengue cases in Subang Jaya using time series analysis.

Coupling of remote sensing data and environmental-related parameters for dengue transmission risk assessment in Subang Jaya, Malaysia

In Malaysia, the endemic level of dengue fever (DF) has already changed morbidity indicators, and the magnitude of these incidences in the last few years has surpassed the incidences of all other diseases of compulsory notification. The reasons for the dramatic emergence of DF are complex and not well understood. There are many factors that contribute to the epidemiological conditions that favour viral transmission by the main mosquito vector. This study, therefore, is filling this gap by analysing the impact of dengue incidence at a local (Subang Jaya) scale using environmental factors. Meteorological data and land-use pattern were consolidated using geographic information system (GIS) and its components as an analytical tool. We have shown that weather variables (relative humidity, temperature and precipitation) have significant correlation with DF incidence with seasonal variation. Besides land-use pattern, DF incidence shows the higher distribution in the residential area, followed by commercial and industrial area. This is due to the higher population density in residential area as well as favourable places for the breeding of dengue-carrying Aedes mosquitos created by humans in the residential area, especially one-storey houses. The analysis on the trends of DF incidence towards various housing types indicate that most of the victims’ houses fall into interconnection houses and mixed houses types compared to the independent houses area. The outcome driven from this analysis suggested that each character of the environmental factors has their own risk towards dengue incidence. In line with that, it is possible to develop a dynamic model of DF transmission using the knowledge produced by this comprehensive time series data and the results provided by the different analyses.

Mitochondrial Cytochrome Oxidase I Gene Sequence Analysis of Aedes Albopictus in Malaysia

Abstract A study was conducted to establish polymorphic variation of the mitochondrial DNA encoding the cytochrome oxidase subunit 1 (CO1) gene in Aedes albopictus isolated from 2 hot spot dengue-infested areas in the Subang Jaya District, Malaysia. A phylogenetic analysis was performed with the use of sequences obtained from USJ6 and Taman Subang Mas (TSM). Comparison of the local CO1 sequences with a laboratory strain (USM), alongside reference strains derived from the GenBank database revealed low genetic variation in terms of nucleotide differences and haplotype diversity. Four methods were used to construct a phylogenetic tree and illustrate the genetic relationship of the 37 Ae. albopictus populations based on the CO1 sequences, namely neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML), and Bayesian method, which revealed a distinct relationship between isolates from USJ6 and TSM. Our findings provide new information regarding the genetic diversity among morphologically similar Ae. albopictus, which has not been reported to date.

Spatial mapping of temporal risk characteristic of dengue cases in Subang Jaya

Dengue has become the most widespread vector borne viral diseases of human with the rough estimate of between 60 and 100 million cases of dengue fever worldwide annually. This study proposed a new set of parameters which defined dengue occurrence at an area according to its time characteristics. The objectives of this study were to measure the temporally defined risk indices, to map the measured temporal risk indices and to statistically prove the relationship between each temporal risk indices. Measurement of the three temporal risk indices found that there were areas with significant high value for each of the temporal indices. This suggested that areas within Subang Jaya Municipality had different temporal characteristics for dengue occurrence. The value of frequency index was quite low which was below the minimum of 1. 1 indicates that dengue will occur every week throughout the year. The mean value of duration index was 1.66 which pointed out that the mean duration of an epidemic wave was about 2 weeks. 5.41 was the mean value for intensity index and it signified that during an epidemic wave, about 5 to 6 people in a population of 1000 would be infected by dengue fever. Mapping, which is a spatial analysis method, is utilized for the visual analysis of the three temporal indices. It was found that most areas had high frequency indices. Visual analysis of the duration index showed that there was a distribution pattern where areas with a history of high duration per wave would experience it in the future. There is no significant distribution pattern for intensity index as the high value tended to stay at the same locality throughout the years. Three types of relationship, frequency-duration relation, frequency-intensity relation and duration-intensity relation were identified. The correlation coefficient for all the three types of relationship was above 0.7. The value indicated that there was a strong correlation between each temporal risk indices. As a recommendation, the temporal risk indices can be utilized by public health officials to characterize dengue rather than relying on the traditional case incidence data.

Impact of climate and landuse variability based on dengue epidemic outbreak in Subang Jaya

Dengue disease has continually been a major public health problem in Malaysia. The numbers of cases have risen yearly and it had become more serious in the early of 21st century. Therefore, effort to reduce the number incidences must be taken seriously and should be supported from various agencies. Concerted effort from various agencies is vital effectively manage the dengue problem. Despite all of the effort taken by the Ministry of Health in fighting dengue in Malaysia, the numbers of cases have risen yearly and it had become more serious in the early 21st century. Subang Jaya was chosen due to its highly reported dengue cases year by year. Meteorological data and landuse pattern being consolidated using GIS software and its components as an analytical tool. As a results, weather variables including relative humidity, temperature and precipitation have significant correlation with confirmed dengue cases distribution; Rainfall (t = 0.750**), (t−1=0.649**), (t−2=0.430**). For temperature (t = −0.405**), (t−1= −0.414**), (t−2= − 0.485**). As for relative humidity, the correlation is not continuously significant throughout the year 2006 until 2010 but still have good correlation weightage in 2006 for (t−1 = 0.662**). In line with that, hotspot identification of dengue cases map was fabricated by clustering pattern analysis. So, it will benefit the decision makers as well as the planning actors in just not to concentrating on the current conventional method in controlling dengue occurrence but also to better understand other contributing factors which statistically proved to have correlation with the dengue cases distribution number in Subang Jaya.

Measurement of dengue epidemic spreading pattern using density analysis method: retrospective spatial statistical study of dengue in Subang Jaya, Malaysia, 2006-2010

BACKGROUND Dengue has emerged as one of the major public health problems in Malaysia. The Ministry of Health, Malaysia, is committed in monitoring and controlling this disease for many years. The objective of this study is to analyze the dengue outbreak pattern on a monthly basis in Subang Jaya in terms of their spatial dissemination and hotspot identification. METHODS Collated dengue cases data covering a 5-year period (2006-2010) retrieved from a municipal surveillance system of Subang Jaya were georeferenced and then converted into Geographical Information System format. Average nearest neighbor (ANN) analysis and kernel density (KD) estimation were used to assess the spatial dissemination of dengue cases and detect dengue hotspots, respectively. RESULTS The spatial patterns of dengue fever cases during the 5-year period were spatially clustered (with R values < 1) based on the monthly frequency data. The hotspot map produced by the KD techniques showed a spatially diffused pattern. CONCLUSION The methodology used in the study and the result obtained could be useful not only for documentation by epidemiologists but also for active surveillance of dengue outbreak in a locality.

Profile distribution of juvenile Aedes species in an urban area of Malaysia

BACKGROUND Dengue fever (DF) is an urban vector-borne disease transmitted by Aedes aegypti and Aedes albopictus. Both species deposit their eggs in favorable breeding sites either in natural or artificial containers. An understanding of their habitat characteristics is crucial in curbing DF outbreaks METHODS A search and destroy survey was carried out at 10 dengue hotspot localities in Shah Alam, Malaysia. A quantitative in-situ measurement of selected physical parameters was conducted focusing on the environmental characteristics and the presence of vegetation. Larvae and pupae found in different types of container were morphologically identified. RESULTS Evidence of breeding was discovered in 62 containers. Rubber materials (container efficiency: 2.10), with clear water in the presence of dead vegetation (71 and 33% respectively) were found to be most efficient for pupae development. Furthermore, low water volume (60%) was preferred for breeding purposes. Kruskal-Wallis test demonstrated that water volume, wind velocity and distance from habitation were statistically significant towards dengue vectors. CONCLUSIONS Our findings have provided the profile of Aedes species based on environmental and water conditions in hotspot areas in Malaysia. These outcomes provide useful information regarding container characteristics that can enable selective elimination of vector habitat thus minimizing the risk of dengue outbreak.

Application of geographical information system-based analytical hierarchy process as a tool for dengue risk assessment

Abstract Objective To highlight the use of analytical hierarchy process (AHP) in geographical information system that incorporates environmental indices to generate dengue risk zonation area. Methods The medical database considered for the study was referenced to the environmental data layers. Factors related to the risk of dengue fever (DF) were selected throughout previous research and were arranged in a hierarchical structure. The relative weights of factors were calculated, which were within acceptable range with the consistency ratio being less than 0.1. The outcomes from AHP based DF risk zonation area produced useful information on different levels of risks. Results As a result, factor weights used in AHP were evaluated and found to be acceptable as the consistency ratio of 0.05, which was Conclusions This attempt, if successful, will have significant implications that could strengthen public health interventions and offers priorities in designing the most optimum and sustainable control program to combat dengue in Malaysia.

Heavy Metals Concentration in Water Convolvulus (Ipomoea aquatica and Ipomoea reptans) and Potential Health Risk

Water convolvulus (Ipomoea aquatica and Ipomoea reptans) or their Malay name “kangkung” is tropical, semiaquatic, and fast-growing vegetables belonging to the morning glory family. They are among the green leafy vegetables widely consumed by Malaysian population. However, excessive use of fertilizer and pesticides in “kangkung” cultivation and contaminated source of irrigation may cause harm to the human health. Samples of Ipomea were collected from local wet market and supermarket, and digested and analyzed by Atomic Absorption Spectrophotometer (AAS). There were significant differences of heavy metal concentration for zinc, copper, manganese, and nickel in both species. The average concentration of Fe, Mn, Zn, Cu, and Ni in I. aquatica was found to be 270.20, 91.14, 32.95, 3.99, and 1.79 mg/kg, respectively, while Fe, Mn, Zn, Cu, and Ni in I. reptans was 275.97, 212.63, 87.33, 18.56, and 3.14 mg/kg, respectively. The daily intake of aforementioned heavy metals was within the safe limit values under Malaysia Food Regulations 1985 and World Health Organization’s provisional tolerable daily intake. Subsequently, the Health Risk Index (HRI) for daily intake of Fe, Zn, Cu, and Ni was less than 1 except for Mn (HRI > 1) indicating possible health effect upon consumption. The use of fertilizers and pesticides should be monitored, and regular sampling of the vegetables is recommended to minimize the heavy metal uptake by water convolvulus, thus reducing human exposure.

The Genetic Diversity, Haplotype Analysis, and Phylogenetic Relationship of Aedes albopictus (Diptera: Culicidae) Based on the Cytochrome Oxidase 1 Marker: A Malaysian Scenario

Abstract The global expansion of Ae. albopictus from its native range in Southeast Asia has been implicated in the recent emergence of dengue endemicity in Malaysia. Genetic variability studies of Ae. albopictus are currently lacking in the Malaysian setting, yet are crucial to enhancing the existing vector control strategies. The study was conducted to establish the genetic variability of maternally inherited mitochondrial DNA encoding for cytochrome oxidase subunit 1 (CO1) gene in Ae. albopictus. Twelve localities were selected in the Subang Jaya district based on temporal indices utilizing 120 mosquito samples. Genetic polymorphism and phylogenetic analysis were conducted to unveil the genetic variability and geographic origins of Ae. albopictus. The haplotype network was mapped to determine the genealogical relationship of sequences among groups of population in the Asian region. Comparison of Malaysian CO1 sequences with sequences derived from five Asian countries revealed genetically distinct Ae. albopictus populations. Phylogenetic analysis revealed that all sequences from other Asian countries descended from the same genetic lineage as the Malaysian sequences. Noteworthy, our study highlights the discovery of 20 novel haplotypes within the Malaysian population which to date had not been reported. These findings could help determine the genetic variation of this invasive species, which in turn could possibly improve the current dengue vector surveillance strategies, locally and regionally.