Studies on the identification and control of larval stages of culex vishnui the potent vector of Japanese encephalitis using medicinal plant bio molecules

Abstract

Japanese Encephalitis (JE), a mosquito borne flaviviral encephalitis is one of the major forms of viral encephalitis which affects a large portion of the population mainly in the tropical regions of Asia (Ghosh and Basu, 2009). Although, JE mainly occurs in Southeast Asian countries, the geographic regions facing the threat of JE have increased in the last five decades. There are three distinct epidemiological regions; (i) The endemic region consisting of Southern India, Southern Vietnam, Southern Thailand, Philippines, Malaysia, and Indonesia. (ii) The sub-tropical region, covering Northern India, Nepal, Northern and Central Myanmar, Northern Thailand, Northern Vietnam, Southern China, and Bangladesh. (iii) The temperate epidemic region spanning Northern China, Korea, Japan, Taiwan to the southern extremities of Russia (Vaughn and Hoke, 1992, Igarshi et al., 1994, Zimmerman et al., 1997 and Hanna et al., 1999). newlineJE is caused by JEV, a Flavivirus bearing a single stranded, positive-sense RNA of eleven kilobases, packed in a nucleocapsid surrounded by a lipid envelope (Solomon et al., 2000). Mosquitoes serve as vectors of JEV, breeding in paddy fields, irrigation canals, puddles with stagnant water, drains, ponds etc. Members of the Vishnui complex serve as the primary vectors of JE in the Asian countries with Culex tritaeniorhynchus being the chief vector. However, in the Indian subcontinent, there is an interplay of other secondary vectors like Mansonia indiana, Cx. pseudovishnui, Cx. whitmorei, Cx. gelidus, Cx. epidesmus, Anopheles subpictus, An. peditaeniatus, and Ma. uniformis (Kanojia et al., 2003). In nature, JEV is maintained by a complex cycle that involves pigs as amplifying hosts, birds as reservoirs and mosquitoes as vectors while man and horse are the incidental dead end hosts as the virus cannot be transmitted from one infected person to another (Dutta et al., 2010).JE mainly affects children and young adults. The onset of disease is usually marked with a fever above 100.4ºF.