Abstract
(T)his study was designed to gain more advanced insights about the efficacy of some marine organisms that thrive along the Saudi Arabian red sea coast against the larvae of Aedes aegypti mosquito, the main transmitter of the dengue fever virus in Jeddah Governorate. Ethanolic extracts were prepared from marine organisms of seagrass Thalassia hemprichii and sea cucumber Holothuria atra in addition to the use of a commercial insecticide from a botanical origin Bug Slug as a kind of a positive control comparison. The preparation of the aqueous measuring solutions of the alcoholic crude extracts was conducted in addition to a series of concentrations for testing their efficacy against the 4th larval stage of Ae. aegypti according to the assessment and recommended protocols of the World Health Oiganization (WHO, 2005). Five replicates for each concentration was prepared with the positive control comparison and the recording of data on the mortality rate was all conducted 24 hours post larval treatment for all the aforementioned series of the concentrations. Our results showed that the percentage mortality of the 4th larval stage of Ae. Aegypti mosquito vector post-treatment with the extracts under investigation was positively correlated with the applied concentrations, however the commercial insecticide Bug Slug have produced the highest efficacy of the larval mortality of the mosquito vector with the LC50 values (the concentration that kills 50% of the larval population) as 0.0287 ppm and the Lower Confident Limit was (LCL = 0.02) and the Upper Confident Limit (UCL = 0.04 ppm) and this was followed by the efficacy of H. atra extract that gave LC50 = 188.6 ppm (LCL = 181.9 and UCL = 194.9 ppm) then followed by the efficacy of T hemprichii extract with LC50 = 201.7 (LCL = 181.9 and UCL = 194.9 ppm). Based on the outcome of this investigation it is fair enough to say that the ethanolic extract of the sea cucumber H. atra contains promising constituents as insecticides against the larvae of the mosquito vector of dengue fever followed by the seagrass T hemprichii.