West Bengal has completed culling of chicken after a spate of unnatural bird deaths reported in some poultry farms in Nadia district's Tehatta block. While it has been confirmed that the organism infecting the birds is the H5 strain of influenza, it is still not known if it is the mutant variety. On August 29, the UN Food and Agriculture Organization had raised concerns that the virus circulating in Vietnam and Cambodia are a mutant variety. India was identified as one of the countries at risk of contracting this mutant.
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Confirming if the virus is the mutant form is important to be able to prepare vaccines for the birds, says K K Dutta, former director of the National Institute for Communicable Diseases in Delhi (now called the National Centre for Disease Control). Culling needs to be used along with vaccination to be effective. Meanwhile, we need to keep our fingers crossed that it does not affect people, he adds. When contacted for information on whether the High Security Animal Disease Laboratory in Bhopal is carrying out the full genome analysis of the virus to check if it is the mutant or not, they said they would be in a position to answer this query later.
World Organisation for Animal Health (OIE), in a press release, said that as with the emergence of any new strain, there is a need for sustained monitoring of viruses in animal populations so that changes in viruses circulating in the field are detected at an earliest stage and most appropriate disease control strategies are chosen to best protect animal and public health. OIE is an intergovernmental organisation, responsible for improving animal health worldwide.
The mutant has already been identified in 16 Vietnamese provinces this year. In case the virus does turn out to be harmful, the world would be left without an effective vaccine for the birds. The OIE Reference Laboratory in Harbin in China is in the process of testing a new vaccine seed strain that protects poultry from the mutant clade 2.3.2.1. This year 47 people have been affected; 24 of them died.
In July, the Indian government had declared itself free from bird flu after controlling the disease in Tripura. The disease re-emerged in August in Dhuburi district in Assam. On September 20th, the ministry of agriculture confirmed that bird flu has affected two villages of Tehatta I block. In both cases, rural backyard poultry has been affected.