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Dengue hemorrhagic fever (DHF) remains one of Thailand's main public health problems. Samutsongkhram is one of the areas undergoing an epidemic of this disease. To control this disease, public health officers focus on regulating the population of Aedes aegypti larvae. The aims of this research were to study the susceptibility of Ae. aegypti to Bacillus thuringiensis israelensis (Bti) and juvenile hormone, in order to end the spread of this disease in three epidemic DHF outbreak sub-districts of Ladyai, Suanluang and Jompuak. The results revealed that Ae. aegypti is susceptible to Bti and juvenile hormone in all areas, with a 100% death rate. Exposure to Bti eradicated the larvae in a very short time of less than 18 hours. In addition, juvenile hormone can completely hinder the growth of Ae. aegypti to adult stages. The results demonstrate the effectiveness of these agents for mosquito larvae eradication. Therefore, insecticidal bacterium and juvenile hormone may be an option to reduce the number of DHF patients in Samutsongkhram, Thailand. [ABSTRACT FROM AUTHOR]

Samut Songkhram is one of popular tourist destinations in Thailand; however, it is the very high risk province of the dengue hemorrhagic fever (DHF) outbreak. Therefore, it is essential and urgent to monitor the tourists within the areas from the DHF. This research aimed to study the application of Geographic Information System (GIS) in DHF risk assessment and to study factors influencing of this province. The researcher collected 11 factors data including population density, household number, elevation, temperature, humidity, rainfall, residential areas, drainage areas, agricultural areas and man-made and natural water resources from related organizations to analyze relationship with DHF patients in the province. With the Pearson's Correlations statistic, there were four main factors relating the DHF incidence including population density, household number, residential areas and man-made water resources. According to the created GIS model of DHF risk assessment, it was discovered that 9% of the total areas were the very high risk areas, 23.89% were the high risk areas, 13.14% were the moderate risk areas, and 53.97% were the low risk areas. At a district level including Muang Samut Songkham, Bang Khonthi and Amphawa, it was found that Muang Samut Songkham was the only very high risk area covering 79.78km2. At a subdistrict level, Mae Khlong and Lat Yai were the very high risk areas. The factors influencing showed residential areas. After applying the GIS in DHF risk assessment, it was demonstrated that the GIS was one of an effective tools for DHF surveillance. [ABSTRACT FROM AUTHOR]