MOSQUITO-LARVICIDAL EFFICACY OF CRUDE AND FRACTIONS OF PILOSTIGMA RETICULATUM AND COCUMA LONGA AGAINST CULEX QUINQUEFASCIATUS, AN INTERMEDIATE HOST OF FILARIASIS

Abstract

The challenges posed by the management of mosquito vector by using synthetic insecticide have resulted into the development of resistance and have diverted the attention of mosquito control experts to the exploitation of plant products for mosquito vector control. This study was therefore designed to elucidate the mosquito larvicidal efficacy of the crude and solvent fractions of Pilostigma reticulatum and Cocuma longa against the filarial vector, Culex quinquefasciatus. The crude methanol extracts of the plants were assessed for the presence of bioactive photochemicals following standard procedure. Early 4th instar larve of the mosquito species were exposed to graded concentration (ranging from 0.2 to 1.00 mg/L) of the crude and solvent fractions of the two plant extract following the World Health Organization protocol for testing the efficacy of natural products. Mortality was measured after 24 hrs exposure period and lethal concentrations were evaluated using probit regression analysis. Phytochemical screening revealed the presence of flavonoids, tannis, saponin, alkaloids and terpenoid in both plant crude methanol extract. Saponin content (321.10±1.34 mg/100g) was significantly higher (p<0.05) than other phytochemical observed. The result also indicated that mosquito larvae mortality increases with increase in time of exposure and significantly (p<0.05) increase with increase in extract concentration. The n-hexane fraction recorded the highest larvae concentration compared to crude and ethyl-acetate fractions. Similarly, only the n-hexane recorded 100% larvae mortality compared to crude and fractions tested. The result showed that the C. longa n-hexane fraction was more potent against the tested mosquito species, with LC50 of 0.047 mg/L compared to the P. reticulatum n-hexane fraction (0.54 mg/L). Findings from the current study thus suggest the two tested plant as a promising candidate in the development of novel and effective larvicidal agents.