Determination of appropriate positioning of the ovitraps for dengue mosquito surveillance

Abstract

Three months ovitrap survey was conducted to assess the suitable position in placing the
ovitraps for dengue vector mosquito surveillance and this study was initiated due to loss of
valuable data from our previous studies as a result of physical damage of the ground kept
ovitarps. Thirty four households in the Ragama Medical Officer of Health area in Gampaha
District were selected to conduct the ovitrap survey during the period of May to July, 2015 to
select the most appropriate positioning of the ovitrap. The conventional black plastic ovitraps
(3.2x 2.7 cm) were used in this purpose to collect aquatic stages of Aedes mosquitoes while
placing plywood paddle (4 x 0.5 cm) over the upper rim of each coded ovitrap. A total of 136
ovitraps were used in the study site providing four ovitraps (2 each indoor & outdoor) for
each house while one of the ovitraps of indoor and outdoor being hung and other being kept
on the ground. In positioning ovitraps, the outdoor ones were kept 3m away from the house
while leaving indoor ovitraps in the living room in close proximity to racks/hanging clothes
or partially shaded places. Following collection of samples at each week, ovitraps were
washed thoroughly, refilled with new water and a new paddle, and corresponding data were
recorded and analyzed. These analyses revealed that number of larvae and the number of
Aedes mosquito eggs present in the two different ovitrap positions (Ground kept vs Hung)
were not significantly different; in spite of significant difference (P=0.001) between the
outside and inside placements. Further, significantly higher values were observed for both
number of mosquito eggs and larvae present in each ovitrap kept outside (60 and 13
respectively) than those placed inside (32 and 3 respectively). Furthermore, slightly higher
values were observed for hung ovitraps (49 and 9 respectively) than ones kept on the ground
(43 and 7 respectively). Finally, ovitrap placed above the ground level was selected in
continuing the routine ovitrap survey, as there was considerable reduction of mechanical
damage to the latter thus facilitating continuous data collection.

Full text

1
International Postgraduate Research Conference
2015
University of Kelaniya, Sri Lanka
Conference Programme
10th – 11th December
Faculty of Graduate Studies
University of Kelaniya
Sri Lanka
www.kln.ac.lk/fgs

137
Determination of appropriate positioning of the ovitraps for dengue mosquito
surveillance
N.D.A.D.Wijegunawardana.1, Y.I.N.Silva Gunawardene 1, T.G.A.N.Chandrasena2,
R.S.Dassanayake 3, P.A.D.H.N.Gunathilaka 4, W Abeyewickreme, 1&2
Three months ovitrap survey was conducted to assess the suitable position in placing the
ovitraps for dengue vector mosquito surveillance and this study was initiated due to loss of
valuable data from our previous studies as a result of physical damage of the ground kept
ovitarps. Thirty four households in the Ragama Medical Officer of Health area in Gampaha
District were selected to conduct the ovitrap survey during the period of May to July, 2015 to
select the most appropriate positioning of the ovitrap. The conventional black plastic ovitraps
(3.2x 2.7 cm) were used in this purpose to collect aquatic stages of Aedes mosquitoes while
placing plywood paddle (4 x 0.5 cm) over the upper rim of each coded ovitrap. A total of 136
ovitraps were used in the study site providing four ovitraps (2 each indoor & outdoor) for
each house while one of the ovitraps of indoor and outdoor being hung and other being kept
on the ground. In positioning ovitraps, the outdoor ones were kept 3m away from the house
while leaving indoor ovitraps in the living room in close proximity to racks/hanging clothes
or partially shaded places. Following collection of samples at each week, ovitraps were
washed thoroughly, refilled with new water and a new paddle, and corresponding data were
recorded and analyzed. These analyses revealed that number of larvae and the number of
Aedes mosquito eggs present in the two different ovitrap positions (Ground kept vs Hung)
were not significantly different; in spite of significant difference (P=0.001) between the
outside and inside placements. Further, significantly higher values were observed for both
number of mosquito eggs and larvae present in each ovitrap kept outside (60 and 13
respectively) than those placed inside (32 and 3 respectively). Furthermore, slightly higher
values were observed for hung ovitraps (49 and 9 respectively) than ones kept on the ground
(43 and 7 respectively). Finally, ovitrap placed above the ground level was selected in
continuing the routine ovitrap survey, as there was considerable reduction of mechanical
damage to the latter thus facilitating continuous data collection.
Key words: Aedes mosquito, ovitrap
1Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka
2Department of Parasitology, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka
3Department of Chemistry, Faculty of Science, University of Colombo, Sri Lanka
4Biotechnology Unit, Industrial Technology Institute, Colombo07, Sri Lanka.