Insecticide resistance of Aedes mosquito larvae to temephos / Muhammad Zubair Jamaludin

In areas of South East Asia, Aedes aegypti (Linnaeus) and Aedes a/bopictus Skuse have been implicated in the transmission of dengue fever and dengue haemorrhagic fever (Smith, 1956). As in other South East Asia countries, Ae. aegypti and Ae. albopictus are widely distributed throughout Malaysia and have been incriminated as vectors of dengue (Lo, 1984). Insecticide resistance originates in the genetic variability of an insect population. Mutations give rise to some individuals with an enhanced ability to survive exposure to chemicals that would kill fully susceptible individuals. In Malaysia, temephos (Abate®) is recommended as a larvicide by Ministry of Health and widely used since 1973 (Chen, 2005). World Health Organization (WHO) standard procedures were used namely, larval bioassay to determine the susceptibility of lethal concentration (LC) and Resistance Ratio (RR). Aedes larvae collected from both the stated localities had mortality indicating resistance. When the early third instar larvae were selected for bioassay test, the LC50 of Bangsar strain was the highest, with value of 0.015mg/L while Kolej jati strain showed 0.012mg/L. These values were divided by the LC50 of the lab Strain which is 0.003mg/L. In this study, the calculated value for the resistance ratio for Kolej Jati and Bangsar were 4 and 5 respectively. This showed that Aedes Mosquito larvae from both localities have developed resistance to temephos. Emphasis need to be given more to the variability of control measures rather than depending on one method.