[NEW DELHI] Researchers in West Bengal have reported a second strain of the Japanese Encephalitis Virus (JEV) circulating in the eastern Indian state.
According to a study published online in Virology Journal, last month (15 November), the researchers confirmed genotype I (GI) of JEV coexisting with the predominant genotype III (GIII) strain in over a quarter of 135 patients hospitalised for acute encephalitis syndrome.
The GI strain was first detected in India three years ago in the Gorakhpur area of the northern state of Uttar Pradesh.
Led by Shyamalendu Chatterjee at the virus unit of the Indian Council of Medical Research (ICMR) in Kolkata, the researchers have now confirmed the GI strain in the samples of blood, and fluid from brain and spinal column, of patients admitted to government hospitals in eight West Bengal districts between July and December 2010.
The ICMR scientists, who were joined by Subhra Kanti Mukhopadhyay from the microbiology department of the University of Burdwan, were unable to ascertain how the GI strain, earlier reported circulating in South Korea, Thailand and China, had reached India.
But, the researchers said the possibilities were that the GI strains were brought in by travellers, migratory birds (such as herons) or mosquitoes blown in by cyclonic winds. Domestic pigs are known reservoirs of JEV.
Transmitted to humans by the culex mosquito, the symptoms of JE include severe rigors, convulsions and high temperature. Patients may go into coma and the fatality rate is high among child victims.
First isolated in Japan in 1935, JEV has become a major public health menace with a worldwide case-fatality rate of 30 per cent and 3050 per cent of survivors develop permanent brain damage.
The isolation of the GI strain in West Bengal has cast doubts about the efficacy of vaccines currently used against JE derived from the GIII strain. In future, JE outbreak is quite likely in the state if this vaccine fails to protect sufficiently against GI of JEV, the researchers noted in their study.
Other experts said there was no cause for panic. GIII-derived vaccine is used in countries where the GI strain is prevalent and has been found to be effective. I do not think there is any risk, Komal Kushwaha, a physician at the Baba Raghav Das Medical College in Gorakhpur, told SciDev.Net.
Kushwaha suggested carrying out a study by completely immunising one district and keeping another as control over a period of two years.