ISOLATION AND CHARACTERIZATION OF BACILLUS THURINGIENSIS AND ITS LARVICIDAL ACTIVITY AGAINST MOSQUITO
CHAPTER ONE
1.0Â Â Â INTRODUCTION
Bacillus thuringiensis belongs to the family Bacillaceae; which taxonomists consider as sub-species of Bacillus cereus because they are closely related (Leonard et al., 1997; Helgason et al., 2000; Chen and Tsen, 2002). According to Priest (2000), the genotypic and phenotypic characteristics of Bacillus thuringiensis are very similar to Bacillus cereus; the only difference between these two species being the formation of large proteinaceous parasporal inclusions observed in Bacillus thuringiensis.
All over the world, the medical and economic burden caused by vector-borne diseases continues to increase as current control measures are not adequate to cope with the trend of the diseases. In view of this development, there is an urgent need to identify new control strategies that will remain effective, even in the face of growing insecticide and drug resistance (Achs and Malaney, 2002). One such strategy is vector control. Vector control strategies include chemical based control measures, non – chemical based control measures and biological control agents (Poopathi and Tyagi, 2006). Repetitive use of man-made insecticides for mosquito control disrupts natural biological control systems and leads to reappearance of mosquito populations. It also results in the development of resistance, detrimental effects on non-target organisms and human health problems and subsequently these necessitate a search for alternative control measures (Das et al., 2007; Zhang et al., 2011).
The use of biological control agents such as predatory fish (Legner, 1995), bacteria (Becker and Ascher, 1998), protozoa (Chapman, 1974), fungus (Murugesan et al., 2009) and nematodes (Kaya and Gaugler, 1993) have shown promising results for the control mosquito populations.
The development of new strategies, including naturally occurring larvicides to control mosquitoes, is important in order to counter the evolution of resistance in target populations and the possible effects on non target organisms (Cetin and Yanikoglu, 2006).
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ISOLATION AND CHARACTERIZATION OF BACILLUS THURINGIENSIS AND ITS LARVICIDAL ACTIVITY AGAINST MOSQUITO
