M Malau, D James
biodegradability, ethanol extracts, larvae, phytotoxicity, plant extract, s. damnosum
M Malau, D James. Evaluation Of Larvicidal Properties Of Some Plant Extracts On Simulium Damnosum Complex. The Internet Journal of Toxicology. 2007 Volume 4 Number 2.
Objective: The campaign for living in a friendly environment by reducing the rate of pollution through the use of biodegradable substances most especially plant materials for the control of insect vectors of man is major priority. Over the years the vectors of onchocerciasis (Simulium damnosum complex) have been controlled by the use of synthetic chemical compounds and this is known to left behind toxic chemical residues which get accumulated into the food chain. Attempt is therefore carried out to develop alternative control of insect vectors of parasitic disease through the use biodegradable plant materials.
Methodology: Five plants (Parkia biglobosa, Vitelaria paradoxa, Azadrachta indica, Chromolaena odorata and Lippia multiflora) were collected and their leaves extracted using ethanol extract. Serial dilutions of the crude extract was prepared (100mg/ml, 10mg/ml, 1mg/ml, 0.1mg/ml, 0.01mg/ml and 0.001mg/ml) and Simulium larvae exposed in it for a period of 3 hours.
Results: The result of phytotoxicity test of the five plants showed that all the plants extracts are toxic at high concentrations (100mg/ml and 10mg/ml) with 100% larval mortality. Toxicity was however noticed to decrease with decrease in concentration. C. odorata recorded the highest potency with 80.8% larval mortality while V. paradoxa recorded the least (50.4%) at 0.01mg/l. The five plants showed significant difference in their phytotoxicity (F = 25.196; df = 4; P<0.05). The relationship between concentration of plant extract and mortality showed positive correlation (r = 0.538; df = 18; 0.01).
Conclusion: the utilization of some of the plants parts in the control of endemic diseases through vector control and the maintenance of the ecosystem stability is the main objective in this study.
Blackfly (a haematophagous fly) feeds on blood of man and domestic animals for the purpose of the maturation of its eggs. The fly breeds in fast flowing waters of large streams and sluggish rivulets of small streams. The fly has two phases of development; the pre-marginal phase comprising of eggs, larvae and pupae and the post-marginal phase comprising reproductive males and females (1). The fly has a wide distribution in South and Central America, Mexico, Brazil, Venezuela, Ecuador, Colombia and West Africa (1).
The fly transmits the disease onchocerciasis in man. The disease although not a life threatening one, is known to cause severe skin infections ranging from rashes, itching, nodules on bony areas, and de-pigmentation of the skin which usually leads to hanging groins and elephantiasis of the genital organs. The terminal effect of the disease is blindness; a condition that adds more mouths for the community to feed than benefit (2,3, 4, 5, 8, 7).
Over the years, the disease is controlled by using of chemical insecticides on the vector and Ivermictin (Mectizan) drugs on the parasites living inside the tissues of man. The world health organization has over the years sought to reduce the threat of this infection (onchocerciasis) in most of endemic regions of West Africa by attacking the larvae of the fly with chemical insecticides (8, 9, 10). This effort requires that all potential breeding rivers are treated with chemical insecticides. But the major problem faced by this control method is that both targeted and non-targeted organisms are affected and the chemical accumulate within the biotic food change, thereby leaving a negative feedback on the ecosystem. Because of its poor level of biodegradability and its resultant effect on the ecosystem, new approaches to black fly control are currently being carried out. One of such control strategy is the use of biodegradable plant extracts.
Crude extracts of plant materials have been used by farmers in Africa, Asia and Latin America to control insects of medical and Agricultural importance (11, 12, 13). This research aims at evaluating the larvicidal potency of some indigenous plants from Nigeria for the control of black fly (vector of onchocerciasis) as a substitute for non biodegradable compounds that are harmful to the ecosystem.
Materials and Methods
The study area is the federal capital territory (FCT), Abuja, Nigeria (latitude 8o 25'and 9o 20'N and longitude 6o 45' and 7o 39'E) (14). Larvae of
Leaves of five plants (
Result of crude ethanol extract from five plants tested for phytotoxicity on
The mean percentage mortality rate of
The crude ethanol plant extracts from five plants showed different degrees of phytotoxicity.
It was also observed that the toxicity of the extracts varies with increase in concentration. Maximum mortality (100%) was recorded by all the plant extracts at 100mg/ml, while at 0.001mg/ml; all the plant extracts showed decrease in activity. This shows that
Various reports on the use of environmentally friendly substances for the treatment and control of various pest and vectors of disease agents have been documented. Thomas
We wish to thank the University of Abuja, Department of Biological Sciences for providing facilities for this research work to be carried out.