Abstract

Japanese encephalitis (JE) is a major public health problem in India. To study the influence of climatic factors on JE, cases and the transmitting mosquito species were analysed during 2001 to 2006. To know the status of Japanese encephalitis virus activity in human population, sero-epidemiological studies were undertaken in villages of Kurnool district, Andhra Pradesh, India. Similarly, mosquitoes were sampled from study areas at bimonthly intervals during 2001 to 2006 and identified to species level. The collected mosquitoes were screened for JE virus by using an antigen-capture enzyme linked immunosorbent assay. Out of 2051 samples collected from the study areas, 156 (8%) sera samples were found to be positive for JE virus. The highest number of JE positive cases was observed in 2005 (14%), followed by 2003­­­ (10.6%) and 2001 ­(9.1%). The seasonal pattern on occurrence of JE cases clustered among different seasons (that is, monsoon, winter and summer) showed that JE cases occurred in all seasons of the year. The vector, Culex tritaeniorhynchus per man hour density was correlated with (minimum and maximum temperature, p < 0.035 and p < 0.013), whereas Culex gelidus was positively correlated with rainfall (p < 0.05). JE transmission in temperate areas is dependent on climatic factors; however this study suggests that effects of weather variables such as rainfall, temperature and relative humidity might be responsible for increase of vector populations and also the JEV infection. Apart from these, the other factors like agricultural practices, virus amplifying hosts such as pigs and its density and virus reservoirs might also play a major role in the disease transmission in the study areas.

Key words: Epidemiological survey, vector surveillance, Japanese encephalitis virus, climatic variables.