Arbovirus infections in reptiles: Immunological evidence for a high incidence of japanese encephalitis virus in the cobra Naja naja

The plasma of 80 cobra snakes (Naja naja) was investigated in the haemagglutination inhibition (HAI) and virus neutralization (NT) tests for evidence of Japanese encephalitis (JE) virus infection. 71% were antibody positive by both tests, 20% by the one or the other and the remaining 9% negative by both. The mean HAI and NT titres of plasma samples collected in spring/summer were considerably higher than those of the autumn/winter seasons. Macroglobulin and 7S antibodies were detected in autumn/winter and only 7S in spring/summer seasons. It is suggested that the cobra could be a host for JE virus throughout the Oriental Region depending on suitable vector distribution. Circumstantial evidence that the cobra may be an overwintering host for JE virus is considered.