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What is Pigs are important source of: and explain in detail?
Japanese encephalitis virus: 

JE virus is a flavivirus, which causes JE, the most common cause of epidemic encephalitis. Birds and pigs are two main reservoir hosts. 
JE is transmitted to humans by certain species of Culex mosquitoes widely prevalent in rice fields in Asia.

Parija SC. Textbook of Microbiology & Immunology. Elsevier Health Sciences; 2014. Page:539