Epidemiological features for japanese encephalitis include all of the following except -

<p> Infected pigs do not manifest any ove symptoms of illness but circulate the virus so that mosquitoes get infected and can transmit the virus to man. The pigs are thus considered as &;amplifiers &;of the virus. Reference:Park&;s textbook of preventive and social medicine,K.Park,23rd edition,page no:285. <\p>