Virus alerts Bengal ignored - Japanese encephalitis strains flagged in four districts in 2011-12

Junior health minister Chandrima Bhattacharya at NBMCH on Saturday. Picture by Kundan Yolmo

SANJAY MANDAL AND PRANESH SARKAR, TT, Calcutta, July 26: The state government allegedly ignored alerts from the Centre for Research in Medical Entomology, Madurai, in 2012 on Japanese encephalitis, the revelation coming on a day the administration announced a slew of measures to tackle the outbreak in north Bengal.

A team of scientists from the CRME, Madurai, had detected mosquito strains carrying the Japanese encephalitis virus in four north Bengal districts in 2011 and 2012 and informed Bengal, sources in the state health department said.

The team had visited Jalpaiguri, Cooch Behar, South Dinajpur and Darjeeling thrice in September 2011, January 2012 and May 2012 to investigate Japanese encephalitis cases.

A National Institute of Virology, Pune, report today said that six of the 10 blood samples sent to it from north Bengal had tested positive for the Japanese encephalitis virus. A 50 per cent positive result qualifies as an “outbreak”.

Earlier this week, the School of Tropical Medicine, Calcutta, had tested eight samples and found five to be positive.

“This shows the high density of Japanese encephalitis cases in the area (north Bengal),” an expert said.

In 2011-12, the CRME team had collected 279 mosquito pools in north Bengal, of which one pool of Culex pseudovishnui and three pools of Culex quinquefasciatus were found to be carrying the Japanese encephalitis virus.

The study was published in the International Journal of Mosquito Research this year. The number of mosquitoes in a pool vary, entomologists said.

“The present study calls for further investigations on the ecology and vector potential ofCx quinquefasciatus,” the study said.

“As research progresses, the role of the various proven and suspected mosquito vectors will become clearer and no doubt many new agents and cycles involving hitherto unsuspected mosquito species will be revealed.”

Allegations have been made that the state government did not act on warnings from the Indian Council of Medical Research (ICMR) in Calcutta two years ago.

According to senior Swastha Bhavan officials, nearly 75 blood samples from north Bengal had been sent to the ICMR between July 2011 and June 2012 after several people died of an unknown fever.

“The central agency, which tries to identify the virus whenever an unknown disease is reported, said that 50 of the 75 samples carried the Japanese encephalitis virus,” a health department official said.

“The report was sent to health officials in Darjeeling and the Integrated Disease Surveillance Programme unit at Swastha Bhavan. The ICMR had warned the health department that proper monitoring was required to keep the spread of the virus in check in north Bengal.”

Sources in the virus unit of the ICMR said they had expected the state government to send samples regularly from north Bengal to keep a check on the virus.

“But surprisingly, no sample has been sent to us since June 2012. Had blood samples taken from suspected patients been sent to us on a regular basis, we could have informed the state whether the virus had spread to new areas,” a scientist in the unit said.

State health department officials said that hardly any steps had been taken to reduce the mosquito population and remove piggeries from human habitats.

Pigs are hosts of the Japanese encephalitis virus. The virus reproduces in pigs and infects mosquitoes that pass the infection on to humans.

“The number of fever cases has been rising in the north Bengal districts since March, and senior officials at Swastha Bhavan were aware of it. But they did not seek any help from experts in conducting studies,” a health department official said.

He said a study could have revealed the rising population of Japanese encephalitis virus-carrying mosquitoes.

The government said there were no entomologists in the districts to conduct studies on a regular basis.

“One vector disease-control officer is posted in Siliguri, but he has no assistants,” an official said.

There appears to be little coordination between the health and animal husbandry departments, which experts said was necessary to prevent the spread of Japanese encephalitis.

“During the outbreak of bird flu in Bengal in 2008, a disaster management team had been set up with officials from the health and animal husbandry departments,” an official said.

“But in the case of Japanese encephalitis, no such team was formed despite several outbreaks.”

The official said the animal husbandry department’s help could have been taken to spot piggeries and remove the animals from human habitats.

“We’ll hire entomologists in all north Bengal districts after taking the CRME’s permission,” Chandrima Bhattacharya, the minister of state for health, said today.

“Today, the first coordination meeting of officials from the health, public health and engineering, and animal husbandry departments was held in Siliguri. They’ll work together.”