Amplifier host in Japanese encephalitis-
Ans. is 'b' i.e., Pigs Japanese encephalitis* JE is caused by flavivirus, a group B arbovirus. It is a zoonotic disease infecting mainly animals and incidentally man.* In south, epidemics have occured in Karnataka, Andhra pradesh, Tamil-Nadu and Kerala. Now Gorakhpur district of U.P. contributes largest number of cases.* Main vector of JE transmission is culex mosquito (culex tritaeniorhynchus), a zoophilic rural mosquito that breeds in rice paddy fields, shallow ditches and pools. Other important vector species are culex vishnuii and culex gelidus.* Pigs are amplifier host i.e., infected pigs do not manifest overt symptoms but circulate the virus so that mosquito get infected and can transmit virus to man. Horses are the only domestic animals showing symptoms of JE. Man is an 'incidental dead-end host\ there is no man-to-man transmission. 'Cattle and buffaloes' act as mosquito attractants, i.e. infected but are not the natural hosts. Herons (birds) are the reservoir hosts.* There are two natural cycles of JE virus :* i) Pig - mosquito - pig* ii) Ardeid bird - mosquito - Ardeid bird.* Most of the cases are subclinical, ratio of overt disease to inappearent infection varies 1:1000, i.e., cases show tip of iceberg. For clinical cases incubation period is 5-15 days. The disease passes through sequential stages of prodrome, acute encephalitis, and late stage with sequelae. There is no rash at the site of mosquito bite.* Case fatality rate is 20-40%. The endemicity of cases is 1-2 case per village.* The vast majoirty of cases (about 85%) occur among children < 15 years of age. But JE is infrequent in infancy.
Horse
Pigs
Dogs
Monkey
Communicable Diseases