Dual infection in human by Japanese encephalitis virus & chikungunya virus in Alappuzha district, Kerala, India

Sir,

Japanese encephalitis virus (JEV) is a major mosquito-borne encephalitic flavivirus of rural eastern, south eastern and southern Asia. Outbreaks of Japanese encephalitis (JE) have occurred in many States in India1. An explosive insular outbreak of meningoencephalitis occurred during early 1996 in the Kuttanad area of Allepey district, Kerala2.

Numerous cases of chikungunya virus (CHIKV) infection have been reported from a major outbreak around the Indian Ocean which included southern India3. In India, during 2006, 14 States and Lakshadweep Island were affected by chikungunya fever45. In Kerala, outbreak of chikungunya began for the first time in 2006 affecting nearly 70,000 persons from 14 districts5. In May 2007, another outbreak occurred affecting almost all the districts6. Increased death toll was due to chikungunya in Kerala7.

Alappuzha district lies at the western part of Kerala and was worst affected. During the outbreak in May 2011, 23 cases were recorded in Alappuzha district. An epidemic survey was done by a team of Centre for Research in Medical Entomology (CRME), Madurai and Kerala State Institute of Virology and Infectious Diseases.

After obtaining informed written consent from the suspected JE patients blood samples (2 ml) were obtained with the help of Government Tirumala Devaswom (TD) Medical college hospital staff and Kerala State Institute of Virology staff. The serum samples were analyzed for JEV-specific immunoglobulin M (IgM) antibodies, dengue virus (DENV) - specific IgM antibodies and CHIKV specific IgM antibodies separately by using separate and specific MAC ELISA kits supplied by National Institute of Virology, Pune, India. The serum samples were simultaneously tested for JE, DEN and CHIK IgM antibodies using separate negative and positive controls supplied in the respective kits.

Serum samples were collected from 23 suspected fever cases reported to the hospital. Of the 23 samples tested, four were found positive for JE IgM/CHIK IGM. Of these four positive patients, two male adult patients (37 & 47 yr old) were from Muhamma and Pollathai area of Kerala, respectively, had dual infection showing the presence of both JE IgM and CHIK IgM antibodies. A 40 yr old male patient was positive for CHIK IgM antibodies alone and a 76 yr old female patient had JE IgM antibodies alone. The age group found positive ranged between 37-76 yr. No serum sample was found positive for dengue IgM.

Two cases are described in the present study with dual infection with JEV and CHIKV. This report highlights the multifaceted mosquito-borne arboviral infections. Dual infection by dengue virus and Plasmodium vivax has been earlier reported from Alappuzha district, Kerala8. So far, for patients with CHIKV infection, simultaneous co-infection has been reported for dengue virus910. A French man travelled and returned from India was documented with dual infection by CHIKV and systemic amoebiasis11. Most of the JE cases reported from Kerala were adults as pointed out earlier also12.

In conclusion, the two patients with dual infection with JEV and CHIKV indicate the multifaceted infection that can be encountered in Kerala with water saturated places which are the ideal breeding sources for different species of mosquitoes.