Abstract:
Dengue is the most important vector borne disease in Sri Lanka and globally due to its increasing
incidence over the years. Climate changes coupled with rapid urban development result in increasing
the breeding and survival of Aedes mosquitoes, the vector for dengue, hence the success of dengue
virus transmission.
This study aims to identify the relationship between Aedeslaval indices (House Index [HI], Container
Index [CI] and Breteau Index [BI]) and dengue risk, and study the insecticide susceptibility to
strengthen future mosquito control strategies in the Batticaloa district. The two locations selected for
collection of Aedes larvae were Batticaloa and Oddamavadi, in Batticaloa District.
Larval collections were made fortnightly using conventional ovitraps for nine months covering the dry
and wet seasons. 15 Ovitraps were placed in randomly selected houses on each locality based on the
data obtained from Anti Malaria Campaign where dengue cases were available. WHO kit with
insecticide impregnated papers with the following concentration recommended by WHO were used
for the susceptibility test (Malathion – 0.8%, DDT – 4% and Permathrin – 0.25%).
This study demonstrates that all larval indices HI, CI and BI were higher than WHO standard. This
indicated a high risk of DF/DHF transmission in both localities. Present investigations revealed that,
Ae.aegypti and Ae.albopictus from all study sites were completely resistant to 4% DDT, moderate to
high level resistance to 0.8% Malathion but were susceptible to 0.25% Permathrin. This study
suggests that regular and continuous monitoring of resistance should be conducted in all dengueendemic
sites, to confirm the continued efficacy of insecticides, and to help choose the most effective
insecticides for dengue control.
