Aedes aegypti is a major vector of Dengue fever, whose slight reappearance was
recorded in the Red Sea Governorate in 2017. The present study was carried out
to determine the DNA barcoding of Ae. aegypti and investigate the sensitivity of
its aquatic immature stages to different insecticides, with reference to non-target
organisms, zebrafish, Danio rerio, and Daphnia magna. Genetic identification
of Ae. aegypti was confirmed through PCR amplification and subsequent
sequencing. The obtained DNA sequences were deposited in the National Center
for Biotechnology Information (NCBI) sequence database with the accession
number OR76138. Methomyl, α-cypermethrin, and chlorpyrifos were tested
against immature stages of Ae. aegypti. Additionally, the effect of tested
insecticides on acetylcholinesterase (AChE) and glutathione S-transferase (GST)
activities were assessed. Results showed that the activity of the tested insecticides
varied according to the concentration of the insecticides, exposure time and the
immature stage tested. Complete larval mortality (100%) of the first instar was
attained at 0.007, 0.0009, and 0.005ppm of methomyl, α- cypermethrin, and
chlorpyrifos after 48h of exposure, respectively. Generally, α- cypermethrin was
the most effective insecticide, followed by chlorpyrifos and methomyl. In
addition, methomyl caused the least inhibition of AChE activity (5.53 and 5.90U/
L) in larvae I after 24 and 48h of exposure, compared to 5.74 and 6.13U/ L for the
control group. In addition, the GST activity was significantly increased (P< 0.05)
by all tested insecticides. The highest GST values (1.73 and 1.59U/ g tissue) were
recorded for pupae after 24 and 48h of exposure to α-cypermethrin. On the other
hand, methomyl recorded LC50 of 0.862, 0.011, and 0.575, 0.009 ppm against
zebrafish and Daphnia after 24 and 48h, respectively. Generally, methomyl, α-
cypermethrin, and chlorpyrifos are effective agents against Ae. aegypti, however,
their environmental footprint cannot be overlooked. |
