Amplifier host for Japanese encephalitis is: September 2011
Ans. B: Pig In Japanese encephalitis, pigs are the amplifier host (they themselves didn't manifest ove symptoms but circulate the virus) Japanese encephalitis/ Japanese B encephalitis The Japanese encephalitis virus is a virus from the family Flaviviridae. Domestic pigs and wild birds (herons) are reservoirs of the virus; transmission to humans may cause severe symptoms. One of the most impoant vectors of this disease is the mosquito Culex tritaeniorhynchus. This disease is most prevalent in Southeast Asia and the Far East. Japanese encephalitis has an incubation period of 5 to 15 days and the vast majority of infections are asymptomatic Only 1 in 250 infections develop into encephalitis. Severe rigors mark the onset of this disease in humans. Fever, headache and malaise are other non-specific symptoms of this disease which may last for a period of between 1 and 6 days. Signs which develop during the acute encephalitic stage include neck rigidity, cachexia, hemiparesis, convulsions and a raised body temperature between 38 and 41 degrees Celsius. Moality of this disease varies but is generally much higher in children. Increased microglial activation following JEV infection has been found to influence the outcome of viral pathogenesis. Activated microglia secrete cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-a), which can cause toxic effects in the brain. Additionally, other soluble factors such as neurotoxins, excitatory neurotransmitters, prostaglandin, reactive oxygen, and nitrogen species are secreted by activated microglia. The causative agent Japanese encephalitis virus is an enveloped virus of the genus flavivirus and is closely related to the West Nile virus and St. Louis encephalitis virus. The positive sense single stranded RNA genome is packaged in the capsid which is formed by the capsid protein. The outer envelope is formed by envelope (E) protein and is the protective antigen. It aids in entry of the virus to the inside of the cell. Japanese Encephalitis is diagnosed by detection of antibodies in serum and CSF (cerebrospinal fluid) by IgM capture ELISA. Viral antigen can also be shown in tissues by indirect fluorescent antibody staining.
Man
Pig
Donkey
Culex mosquito