Herbal insecticides that fight mosquito
BY SADE OGUNTOLA
Apart from using insecticide treated nets,
herbal insecticides are also effective.
The rainy season is gradually coming to an end and with this comes increase in mosquito problems. Mosquitoes are responsible for deaths and illness of millions of people and animals through the transmission of diseases such as malaria, yellow fever, dengue and West Nile virus.
This explains why different communities try different herbs both for preventing the illness and repelling off the insect. For instance, Rev. Tunde Koyejo, an environmental health expert at the University of Ibadan,Ibadan, said in local communities, people cut Ocinum plant (Efinrin) and put this in the corners of the rooms to drive away mosquitoes. This, they keep changing regularly. Other options they try includes smoldering leaves of plants such as pawpaw and lemon grass as well as orange and lemon peels.
Though many may not be aware of nature’s solution to mosquito, Prof. Janet Makinde, an expert on herbs for malaria from the department of Pharmacology, University of Ibadan, Ibadan, said some plants including the anti-mosquito plant that specially grows in the muddy area due to there special smell helps to repel mosquitoes. All that is done is to cut the plant and place it in the room, to repel off mosquitoes.
So many other plants act as repellants against different mosquito species. In Kenya for instance, most commonly known repellant plants include sweet basil (Ocinum americannum) , wild marigold (Tagetes munta), neem (Azaduachta indica), lantana camara and (Heyptis suaveolens).
Some researchers even evaluated their efficacy in the journal, Trans R. Soc Trop. Med. Hygiene. They had the leaves burnt in one case and just placed the branches or the whole plant inside the houses in the other.
Seyoum A., Palsson K. and other members of the group found when thermally expelled, the leaves of Corymbia citriodora leaves and seeds of sweet basil were the most effective. Leaves of corymbia citriodora also exhibited the highest repellency by direct burning.
Also in Guinea Bissau by Palsso K. and Juesson G. from the department of zoology, Uppsala University, Sweden, found smoulder the leaves of Eucalyptus gave 72.2per cent protection; smoke of the leaves of neem gave 76.0 per cent protection; smoke of the infructescence of oil palm gave 69.0 per cent protection and basil gave 63.6 protection.
A similar assessment of local plants in Mpumalanga province, South Africa which was documented in the Central Africa journal of Medicine by Govere J., Durrheim D. N. and others found that the alcohol extract of fever tea (Lippia javanica), lemon grass and rose geranium (Pelargonium reniforme) provided protection from Anopheles mosquitoes for 76.7per cent, 66.7 per cent and 63.3per cent for no less than three hours respectively. The repellent effect of fever tea lasted for five hours.
Several oils extracted from these plants were also helpful in preventing mosquito bites. In a study, 2 per cent neem oil mixed in coconut oil, when applied to exposed body parts of human volunteers, provided complete protection for 12 hours from bites of all anopheles.
Kerosine lamps containing 0.01 to 1 per cent (one measure of neem oil to 100 of kerosine) neem oil, lighted in rooms containing human volunteers, reduced mosquito biting activity as well as the mosquitoes resting on walls in the rooms. Protection with this was even greater against anopheles than against culex mosquito.
Effectiveness of mats with neem oil against mosquitoes has also been demonstrated. As it is being vapourised from the mat, it repels mosquitoes, keeping them off for between five and seven hours.
Another promising repellent is the oil of lemon eucalyptus that in a study by Consumer Reports of August 2005, was said to prevent bites from aggressive mosquitoes for four to eight hours, and more than 12 hours for less aggressive mosquito species.
Researchers including Trongtokit Y in the journal, Phytotherapy Research, found as well that undiluted oils of citronella, clove and cider provide at least two hours of complete repellency from culex and anophelese mosquitoes. Clove oil gave the longest duration of repellency (two to four hours) against the commonest species of mosquito.
There is no need fearing to use these oils as experts even said in the Journal of Ethnopharmacology after evaluating their side effects on the skin that they present low toxicity, pose no cancer risk and does not to irritate the skin.
Some of these plants can also be used to kill larvae of mosquito, hence preventing their bite. Neem oil and other preparation of neem have also been found as potential mosquito larvicide’s. The oil kills the larva and also inhibit growth of larva. A 20 percent concentration of neem oil will both prevent mosquitoes laying eggs and arrest pupal formation and eventually the transformation of pupal to adult mosquito for about 45 days.
http://www.tribune. com.ng/23102006/ hlt1.html
