Dengue vector mosquitos at a tourist attraction

On Ko Samui, Thailand there were two epidemics of dengue hemorrhagic fever (DHF) in 1966 and 1967, followed by endemics up to 1994. Aedes aegypti and Aedes albopictus were the vectors. From January to July 1995, 51 cases of DHF were reported, out of these were many foreigners who still suffer from dengue fever and return home with negative impression. We carried out an entomological survey around the island and collected the mosquitoes to detect dengue virus by digoxigenin-cDNA probe. The data revealed that Aedes agypti and Aedes albopictus still were abundant and some were infected with dengue virus. Visual larval survey indices (HI, CI and BI) were 90.4, 61.3 and 301.3 respectively. Biting rate (BR) of Aedes mosquitoes was high, the average in-door and outdoor BR were 9.7 and 100.8 mosquitoes/man-hour. From 13 pools of mosquitoes, 8 strains of dengue virus were detected (61.5%). The results may encourage the local authorities to improve vector surveillance and control before the famous island becomes an unplesant island