Prevalence of antibodies to Japanese encephalitis and West Nile viruses among wild birds in the Krishna-Godavari Delta, Andhra Pradesh, India.

In the Krishna-Godavari Delta region of the State of Andhra Pradesh, India, 866 sera obtained from trapped birds of 13 species were tested for neutralizing antibody to Japanese encephalitis (JE) virus; two species of birds belonging to the family Ardeidae, Ardeola grayii (pond heron) and Bubulcus ibis (cattle egret), contributed 514 of these sera. Neutralizing antibody to JE virus--i.e. sera giving positive reactions--was detected in 179 sera (34.8%) from these two species; in addition, two sera (0.4%) gave equivocal reactions, presumably indicating partial protection. There were only nine positive reactors (2.6%) among the remaining 352 sera from all other bird species. Of the 181 sera from ardeid birds in which neutralizing activity was detected, 174 were tested for neutralizing antibody to West Nile (WN) virus. The results indicated that 35.6% of these 179 sera had antibody specific to JE virus only and 63.8% possessed neutralizing antibodies to JE virus or to WN virus or to both; these figures represent 12.5% and 22.5% , respectively, of the total of 514 birds of these two species which were tested for neutralizing antibody to JE virus. The findings suggest that ardeid birds may be involved in the natural cycle of JE virus and, possibly, also of WN virus in India.