PRODUCTION OF MOSQUITO REPELLENT INSECTICIDES USING PLANT EXTRACTS
1.1 INTRODUCTION
Malaria is one of the commonest and major parasitic infections of public health interest in the globe especially in the tropics and sub-tropics. It still remains the principal cause of morbidity and mortality in all sub-saharan countries up to this day. Malaria accounts for 10% – 30% of all hospital admissions, and is responsible for 15% – 25% of all deaths in children under the age of 5 years. Pregnant women are not be exonerated from the risk of malaria infections as the disease is also said to be responsible for a substantial number of miscarriages and underweight births (WHO, 1996; RMB, 2007). Globally, only mosquitoes of the genus Anopheles have been incriminated as the vectors of this life-threatening disease. Therefore the control of malaria invariably implies sustainable control of its vectors.
One of the best control measures is the application of intervention methods. Such intervention methods involve the use of insecticides, larvicides, topical repellents among others, to intercept the vector-host interactions or contact. Cutting off or breaking the link between mosquito vectors and human hosts consequently disrupts the life cycle of malaria parasite. The overall result is the reduction in morbidity and mortality rates following reduced transmission of the disease (Toure, 2002). Beside from the use of insecticide treated nets (ITNS), many other different types of substances, natural and synthetic, have been discovered and adopted to protect human hosts against mosquito bites. These substances keep mosquitoes from biting humans and make human hosts undetectable, or are anti-mosquito cloak that conceal or hide the host from recognition by mosquitoes, as a meal source (Jacobson, 1990; Foster and Duke, 1990; ICMR, 2003). Today citrus essential oils as well as extracts from other plants such as Cedar wood, Citronella, Eucalyptus, Pennyxoyai, Turpentine, Winter green (Sadik, 1973), have been identified as very important natural resource of either pesticides or insecticides (Raguraman and Singh, 1997; Gbolade, 2001), or repellent (Sadik, 1973; Thorsell et al., 1998; Oyedele et al., 2000; Govere et al., 2000; Girgenti and Suss, 2003). They have been used as both topical preparations and combustible products like incense sticks to repel insects such as mosquitoes.
In some places, dried citrus fruit peels are burnt on charcoal fire to repel and/or destroy mosquitoes in homes.The global preference of phytochemicals in malaria vector control may be based on their unique properties which include environmental sustainability, easily biodegradable, readily available and cheap andnon-toxicity to man and his domestic animals (Herrera and Vieto, 1980; Duke, 1992). Repellent and attractant properties of phytochemicals from plants other than citrus plant species have been investigated by various scholars (Tyagi et al., 1994; Ansari and Razdam, 1995; Trigg, 1996; Pathak et al., 2000; Moore et al., 2002).
Mosquitoe insecticides are quick and powerful way to get rid of mosquitoes but unfortunately they are only temporary. The effect usually lasts only as long as the insecticide is present, as soon as it drift away or dries out, the mosquitoes are back. Mosquitoes control officials use insecticides only in combination with other form of mosquito control. The same method should apply to use around the house. Insecticides are not long-term solution. Insecticides are commonly dispersed through a fog or ultralow volume mist. Insecticides are available at most home and garden stores, and it come in hand- held applicator or devices that can be attached to a lawn mower. Example of two popular insecticides are Malathion and Permethrin.
Malathion is an organophosphate often used to treat crops against a wide array of insects. It can be sprayed directly onto vegetation such as bushes where mosquitoes like to rest, or used in a 5% solution to fog in the yard. In small amount used for mosquito control , it poses no threat to humans or wide life. In fact, Malathion is also used to kill headlice.
