Abstract: This study investigated the seasonal prevalence of
Aedes aegypti and Ae. albopictus larvae in three topographical areas
(i.e. mangrove, rice paddy and mountainous areas). Samples were
collected from 300 households in both wet and dry seasons in nine
districts in Nakhon Si Thammarat province. Ae. aegypti and Ae.
albopictus were found in 21 out of 29 types of water containers in
mangrove, rice paddy and mountainous areas. Ae. aegypti and Ae.
albopictus laid eggs in different container types depending on season
and topographical areas. Ae. aegypti larvae were found most in metal
box in mangrove and mountainous areas in wet season. Ae.
albopictus larvae were also found most in metal box in mangrove and
mountainous areas in both wet and dry seasons. All Ae. albopictus
larval indices were higher than Ae. aegypti larval indices in all three
topographical areas and both seasons. HI and BI did not differ in
three topographical areas but differed between Aedes sp. HI for both
Ae. aegypti and Ae. albopictus in all three topographical areas in both
seasons were greater than 10 %, except Aedes aegypti in rice paddy
area in wet season. This indicated high risks of DHF transmission in
these areas.
Abstract: This study investigated the number of Aedes larvae,
the key breeding sites of Aedes sp., and the relationship between
climatic factors and the incidence of DHF in Samui Islands. We
conducted our questionnaire and larval surveys from randomly
selected 105 households in Samui Islands in July-September 2006.
Pearson-s correlation coefficient was used to explore the primary
association between the DHF incidence and all climatic factors.
Multiple stepwise regression technique was then used to fit the
statistical model. The results showed that the positive indoor
containers were small jars, cement tanks, and plastic tanks. The
positive outdoor containers were small jars, cement tanks, plastic
tanks, used cans, tires, plastic bottles, discarded objects, pot saucers,
plant pots, and areca husks. All Ae. albopictus larval indices (i.e., CI,
HI, and BI) were higher than Ae. aegypti larval indices in this area.
These larval indices were higher than WHO standard. This indicated
a high risk of DHF transmission at Samui Islands. The multiple
stepwise regression model was y = –288.80 + 11.024xmean temp. The
mean temperature was positively associated with the DHF incidence
in this area.