What is Which of the following mosquitos transmits Japanese encephalitis? and explain in detail?
Ans. a (Culex) (Ref: PSM by Park 22nd / P., 259 636).JAPANESE ENCEPHALITIS# JE cases mostly (85%) occur among children less than 15 years of age.# It was observed in northern India, the number of cases recorded per village (population 500 to 5000) were no more than 1 to 2.# The ratio of overt disease to inapparent infection varies from 1:300 to 1:1000.# It is a mosquito-borne zoonotic encephalitis caused by group B arbovirus (flavi virus) and transmitted by Culicine mosquito: Culex Tritaeniorhynchus, C. vishnuvi and C. gelidus. Most important in south India is - culex tritaeniorhynchus.# Basic cycles of transmission are:- Pig -Mosquito -Pig- Ardeid bird -Mosquito -Ardeid bird# Pig- amplifiers of the virus# Man is incidental dead end host.# No man to man transmission yet recorded.# The "rice fields/paddy fields" are probably the most important breeding places.- JE vaccine is an integral part of National Immunization Schedule in India in 11 endemic districts in UP, Assam, West Bengal and Karnataka. Live attenuated vaccine (SA-14-14-2) single dose followed by a booster after 1 year.- The virus is maintained in a bird-vertebrate cycle involving Culex tritaeniorhynchus mosquitoes that breed in rice fields, domestic pigs, young buffalo, herons and other wading birds.- The virus may infect brain stem nuclei, leading to acute respiratory failure and death.- Infection of the basal ganglia and thalamus presents as tremors during the acute disease and result in parkinsonian mask-like facies, rigidity, tremor, and dystonia in survivors.- Decorticate and decerebrate posturing are notorious clinical features in Japanese encephalitis.- Infection may be prevented with an inactivated Japanese encephalitis virus vaccine prepared by infected mouse brains successfully.- For travellers aged more than one yr, visiting endemic areas for at least 2 wks, the established current practice is to administer 3 primary doses at days 0, 7 and 28.Q Types of mosquitoDiseases1.AnophelesMalaria, filariasis (not in India).2.CulexBancroftian filariasisJapanese encephalitisWest Nile feverViral arthritis (epidemic polyarthritis)3.AedesYellow fever (not in India)Dengue, Dengue hemorrhagic feverChikungunya fever, Chikungunya hemorrhagic feverRift valley fever4.MansonoidesMalayan (Brugia) filariasisChikungunya fever "NUISANCE MOSQUITOES"# It breeds profusely in dirty water collections, viz., stagnant drains, cesspools, septic tanks, burrow pits, and in fact, in all types of water collection.# Culex fatigans is a strong winged mosquito; its dispersal has been found to be 11 km in the rural areas of Delhi.# The peak biting time is about midnight.# Distinguished by white stripes on a black body, the first proved vector of a virus disease yellow fever.# It breeds in artificial accumulations of water in and around human dwellings, water found in discarded tins, broken bottles, fire buckets, flowerpots, coconut shells, earthen pots, tree holes.# Eggs singly, cigar-shaped. Females are fearless biters, chiefly during the day usually less than 100 m (110 yards).# Other diseases transmitted by Culex are:- Bancroftian filariasis,- Japanese encephalitis,- West Nile fever and- Viral arthritis (epidemic/polyarthritis).Educational points:# Airports and seaports are kept free from all types of mosquitoes for a distance of 4 meters around the perimeter of the ports.# Vector of Malaria: An. culicifacies in rural areas and An. stephensi in urban areas.# Anopheles is "tiger mosquito".- Bite of female anopheles is the most common mode of transmission.- Urban malaria -Anopheles stephensi- Rural malaria -Anopheles culicifacies- Anthrophilic (Human blood) and transmits at low density - Anopheles fluvitalis- Zoophilic (animal blood) and transmits at high density -Anopheles culicifacies.VECTORFAMILYDDT RESISTANCE statusPhlebotomousA Sandfly# Resistance to DDT has not been demonstrated.# A single application of 1 to 2g/m2 of DDT or 0.25g/m2 of lindane has been found to be effective for a period of 1 to 2 years.Culex & anophelesA Mosquito# The organochlorine compounds like DDT, HCH are not recommended for larviciding operations because of their long residual effect.# But for adults DDT is insecticide of choice.# At few places resistance to DDT is there where malathion, propoxur are recommended.MuscaA Housefly# It showed resistance to DDT long back in 1948.