สถาบันวิจัยวิทยาศาสตร์สาธารณสุข

NATIONAL INSTITUTE OF HEALTH OF THAILAND

Larval occurraence, oviposition behavier and biting activity of adult mosquitoes potential vectors of dengue on Samui island, Thailand

Authors : Usavadee Thavara*, Apiwat Tawatsin*, Chitti Changsang*, Wichai Kong-ngamsuk*, Supol Paosriwong*, Jotika Boon-Long*, Yupa Rongsriyam**, Narumon Komalamisra**

Affiliations:        *National Institute of Health, Department of Medical Sciences,

Ministry of Public Health, 88/7 Tiwanon Road, Nonthaburi 11000,

Thailand

**Faculty of Tropical Medicine, Mahidol University, Rajavithi Road,

Bangkok 10400, Thailand

           

Source:            Journal of Vector Ecology 2001; 26(2)

 

Language:       English

 

Abstract:

 

Samui Island is an important tourist attraction in Thailand, visited by many foreign and local tourists each year. A recent outbreak of dengue haemorrhagic fever (DHF) occurred on this island in 1995 with an incidence of almost 500 cases/100,000 population. Because of the endemic nature of DHF, there is a critical need to find and develop effective strategies to control this disease through cost-effective vector control program. To obtain needed information on vectors for developing future vector control programs, entomological studies were carried out on the island from 1996 to 1998. It was found that there are two species of DHF vectors, Aedes aegypti and Ae. albopictus prevailing on the island, and the population of Ae. aegypti  remained relatively constant throughout the year while the abundance of Ae. albopictus  increased substantially during the rainy season (May-December)  and then declined drastically in the dry season (January-April). The ranges of the three Aedes  larval indices, Breteau index (BI), house index (HI) and container index (CI) were 93-310, 43-89 and 16-50 respectively. On this island, the ceramic or earthen jars both inside and outside the dwellings and concrete water storage tanks (mostly in toilets and bathrooms) served as the main breeding places of Ae. aegypti whereas coconut husks and coconut floral spathes found outdoors were the major breeding sites of Ae. albopictus. The number of washing water jars, concrete tanks and natural sites infested with Aedes  larvae increased significantly in rainy season (P>0.05). As to the oviposition of outdoor mosquitoes, 60% of ovitraps become positive for Ae. albopictus  eggs with an average number of 26 eggs/trap in 3 days of setting. There was a complete lack of oviposition by Ae. aegypti  in outdoor ovitraps (15 m away from the houses). The indoor biting rate ranged from 1.5 to 8.1 mosquitoes/man-hour, while that of outdoor was between 5 and 78 mosquitoes/man-hour. The indoor biting mosquitoes were identified to be 75.4% Ae. aegypti and the outdoor ones were 99% Ae. albopictus. The diel biting activity of Aedes  during the period from 0800 h to 1700 h in the houses was higher in the morning than in the afternoon period, with a low prevalence between 1300 h and 1400 h.