Detection and isolation of chikungunya virus from field collected Aedes albopictus skuse in selected sites, Peninsular Malaysia

Chikungunya fever, an Aedes borne viral disease, is becoming a serious public health concern today since the first reported outbreak in Port Klang in 1998/99. Recently, more outbreaks were reported in Malaysia. Entomological investigations were conducted in Chikungunya virus cases localities in Peninsular Malaysia which cover Johor, Negeri Sembilan, Melaka, Perak, Pahang and Selangor state in order to identify the vector responsible for transmitting the Chikungunya virus. The adult mosquitoes were collected using modified aspirator and sweep net methods, whereas water holding containers were inspected for larvae. Reverse transcriptase polymerase chain reaction (RT-PCR) were used as the detection of the virus. Positive samples were inoculated on the cell to isolate the virus. The most common species collected at the localities was Aedes albopictus followed by Culex quinquefasciatus, Aedes aegypti and Armigeres sp. Five pools (n=78) of female, adult Aedes albopictus collected from Tangkak, Johor were positive for the Chikungunya virus as detected by reverse transcription-polymerase chain reaction. Three isolates were obtained and grouped with Central/East African genotype. The presence of Chikungunya virus in wild Aedes albopictus indicated that this mosquito is the most likely vector responsible for the transmission of virus to humans in Johor during the outbreak

Surveillance of Aedes albopictus Skuse breeding preference in selected dengue outbreak localities, peninsular Malaysia

Abstract. Entomological surveillance was conducted in order to determine the abundance and to evaluate any changes of biological vectors or ecology, especially in the dengue outbreak areas. The abundance and breeding preference of Aedes albopictus and Aedes aegypti were conducted in selected dengue outbreak localities in three states of peninsular Malaysia namely Selangor, Federal Territory of Kuala Lumpur, and Penang Island using ovitraps and larval survey method. It was determined that Ae. albopictus was predominant in most of the localities and found to breed more outdoor than indoor. A wide range of breeding foci were recorded in this study. It was also determined that ovitrap method was more effective to detect the presence of Aedes mosquitoes when the larval survey was at low rate of infestation. The abundance of Ae. albopictus in dengue outbreak localities emphasis that the vector control programme should also target this species together with the primary dengue vector, Ae. aegypti

Life table characteristics of Malaysian strain Aedes albopictus (Skuse)

The survival of a mosquito is the most important aspect that affects its ability as a pathogen transmitting vector, such as Aedes albopictus, which is a vector of chikungunya and dengue. Knowledge on mosquito life demographics is important in providing a foundation for a successful vector control programme. In this study, two strains of Ae. albopictus [Selangor (SEL) and Kuala Lumpur (KL)] were employed in order to determine the life demographics, including the development period, survival rate, mortality rate, and reproductive capability undercontrolled laboratory conditions. A cohort life table was developed based on the data collected. The complete life cycle period was inconsistent and ranged between 6 to 14 days. The males have a shorter survival period compared to the females. The percentage of females surviving and producing eggs has decreased across the gonotrophic cycle for both strains. A fluctuating pattern of oviposition among most of the females was observed throughout the gonotrophic cycle. The apparent mortality was highest at the embryogenesis stage than the other life stages across the gonotrophic cycle, with the pupae stage being recorded as the lowest mortality rate for both strains. Based on the demographic growth parameters calculated in this study, both strains showed favourable capability to be established in the laboratory. The data provided in this study can be used as a basic guideline on the population growth of the mosquito species and their capability as a pathogen vector

Aedes larval population dynamics and risk for dengue epidemics in Malaysia

Early detection of a dengue outbreak is an important first step towards implementing effective dengue interventions resulting in reduced mortality and morbidity.A dengue mathematical model would be useful for the prediction of an outbreak and evaluation of control measures.However, such a model must be carefully parameterized and validated with epidemiological, ecological and entomological data.A field study was conducted to collect and analyse various parameters to model dengue transmission and outbreak.Dengue-prone areas in Kuala Lumpur, Pahang, Kedah and Johor were chosen for this study.Ovitraps were placed outdoor and used to determine the effects of meteorological parameters on vector breeding.Vector population in each area was monitored weekly for 87 weeks.Weather stations, consisting of a temperature and relative humidity data logger and an automated rain gauge, were installed at key locations in each study site.Correlation and Autoregressive Distributed Lag (ADL) model were used to study the relationship among the variables. Previous week rainfall plays a significant role in increasing the mosquito population, followed by maximum humidity and temperature. The secondary data of rainfall, temperature and humidity provided by the meteorological department showed an insignificant relationship with the mosquito population compared to the primary data recorded by the researchers.A well fit model was obtained for each locality to be used as a predictive model to foretell possible outbreak

Eco-virological survey of aedes mosquito larvae in selected dengue outbreak areas in Malaysia

Background & objectivesi: Transovarial transmission of dengue virus in the Aedes vectors is now a well-documented phenomenon reported from many parts of the endemic areas in the world, which played an important role in initiating and maintaining the outbreak in human populations. This study investigated the factors affecting breeding habitats and the relationship with transovarial dengue virus in larvae of Aedes aegypti and Ae. albopictus. Methods: Larval surveillance was conducted in dengue outbreak areas in Malaysia from 2008 until 2009. Sampling was carried out based on habitat type, water condition (substrate type), canopy coverage, temperature and pH at breeding habitats. RT-PCR was performed to detect presence of transovarial dengue virus in larvae collected in the study areas. Results: A total of 789 breeding habitats were identified during this study and the majority of these breeding sites were plastic containers (57.46%). Aedes albopictus dominated most of the water condition surveyed, while Ac. aegypti indicated preference toward habitats with clear water. Aedes aegypti was selective in selecting ovipositional sites compared to Ac. albopictus where shaded areas were shown to be the most preferred. From a total of 363 mosquito larvae pools, 23 (6.3%) pools were positive for dengue virus where 18 of them were from Ae. albopictus and five were from Ac. aegypti mosquito larvae pools. nterpretation & conclusion: This study indicated the presence of transovarial transmission of dengue virus in immature Ac. aegypti and Ac. albopictus in the field. This study also showed that combination of water conditions, canopy coverage, temperature and pH of breeding habitats were the factors affecting the larval population. The study suggested that larval survey programme could serve as a tool not only to monitor the local dengue vector distribution but also to provide objective information for taking appropriate action by the community against dengue vectors

Eco-virological survey of Aedes mosquito larvae in selected dengue outbreak areas in Malaysia

Background & objectivesi: Transovarial transmission of dengue virus in the Aedes vectors is now a well-documented phenomenon reported from many parts of the endemic areas in the world, which played an important role in initiating and maintaining the outbreak in human populations. This study investigated the factors affecting breeding habitats and the relationship with transovarial dengue virus in larvae of Aedes aegypti and Ae. albopictus. Methods: Larval surveillance was conducted in dengue outbreak areas in Malaysia from 2008 until 2009. Sampling was carried out based on habitat type, water condition (substrate type), canopy coverage, temperature and pH at breeding habitats. RT-PCR was performed to detect presence of transovarial dengue virus in larvae collected in the study areas. Results: A total of 789 breeding habitats were identified during this study and the majority of these breeding sites were plastic containers (57.46%). Aedes albopictus dominated most of the water condition surveyed, while Ae. aegypti indicated preference toward habitats with clear water. Aedes aegypti was selective in selecting ovipositional sites compared to Ae. albopictus where shaded areas were shown to be the most preferred. From a total of 363 mosquito larvae pools, 23 (6.3%) pools were positive for dengue virus where 18 of them were from Ae. albopictus and five were from Ae. aegypti mosquito larvae pools. Interpretation & conclusion: This study indicated the presence of transovarial transmission of dengue virus in immature Ae. aegypti and Ae. albopictus in the field. This study also showed that combination of water conditions, canopy coverage, temperature and pH of breeding habitats were the factors affecting the larval population. The study suggested that larval survey programme could serve as a tool not only to monitor the local dengue vector distribution but also to provide objective information for taking appropriate action by the community against dengue vectors