Abstract:
With the backdrop of a high incidence of dengue in Jaffna District, Sri Lanka, an
ovitrap based survey was carried out from May 2005 to April 2006 in a residential area to study
the seasonality and insecticide susceptibility of Aedes aegypti and Ae. albopictus. Conventional
ovitraps were placed inside and outside of 10 randomly selected houses to collect indoor
breeding and outdoor breeding Aedes mosquitoes; collections took place fortnightly. A
total of 3,075 Ae. aegypti and 2,665 Ae. albopictus were collected in outdoor ovitraps, whereas
in indoor ovitraps a total of 2,528 Ae. aegypti and 2,002 Ae. albopictus were collected. The
highest values for Aedes density and positive ovitrap percentage were recorded in January
2006. A seasonal shift was observed in the density of Ae. aegypti and Ae. albopictus. Ae
aegypti density was high during and after the Northeast monsoon whilst Ae. albopictus was
the dominant species during the onset of the Northeast monsoon. A significant association
(p<0.05) between Aedes density and rainfall was observed. The association of these two species
to site, either indoors or outdoors, was not statistically significant (p>0.05). Both the
species were found to be highly resistant to 4% DDT and completely susceptible to 5%
malathion. The high prevalence and the ability of both species to breed indoors and outdoors
should be taken into account when formulating a dengue vector control program with community
participation in the Jaffna District, Sri Lanka.
