Abstract:
There is a growing concern on the effects of insecticides that are used for the control of
mosquito vectors of human diseases. Introducing a self propagating predator into the vector
breeding habitats may present continual biological control of vector population. In order to
control dengue vectors, namely, Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse)
(Diptera: Culicidae), larval control is one of the major strategies. The objective of this study
was to evaluate the larvivorous potential of fish species against dengue vectors. Four fish
species, namely, Poecilia reticulata (guppy), Aplocheilus dayi (Udahandaya), Oreochromis
niloticus (Tilapia) and Puntius bimaculatus were collected from natural breeding habitats.
They were placed in fish stock cement tanks at the Regional Office of the Anti Malaria
Campaign in Kandy till they were used for the study that was conducted from January – June
2015. In order to determine the larvivorous potential of the fish species, five fish of each
species were placed in separate enamel trays containing de-chlorinated water and allowed to
acclimatize for half an hour. Afterwards, a batch of 25 Ae. aegypti larvae was introduced to
each tray and counted the number of larvae remaining after 5, 10, 30 minutes, 1 and 24 hours.
When all 25 larvae are consumed, another batch of 25 larvae was introduced to those trays
and this was continued till the study was completed. At the end of study period (24 hours),
the number of larvae consumed per fish for each fish species was determined. This study was
carried out in the laboratory with 6 replicates. The experiment was repeated for Ae.
albopictus. Overall, Oreochromis niloticus, Poecilia reticulata, Aplocheilus dayi and Puntius
bimaculatus consumed 97.6, 66.9, 49.3 and 47.5 Ae. aegypti and 98.4, 62.3, 51.2 and 45.4 Ae.
albopictus larvae respectively. All four fish species showed larvivorous activity and
Oreochromis niloticus showed the highest larvivorous potential followed by Poecilia
reticulata. Since Ae. aegypti and Ae. albopictus breed in water storage containers such as
cement tanks, barrels and ornamental ponds, the fish species that showed high larvivorous
potential may be considered for dengue vector larval control in such containers. In order to
achieve good community participation for the use of larvivorous fish for dengue vector
control, effective health education is of utmost importance.
