Commentary
Migration of H5N1 Into Bangladesh
Recombinomics Commentary 12:57
July 7, 2008
Migratory birds are mainly responsible for the outbreak of avian influenza (AI) or bird flu in the country, according to a study report.
The report said that migratory birds might be responsible for initial introduction of highly pathogenic avian influenza (HPAI) in Bangladesh.
Bangladesh Livestock Research Institute (BLRI), Bangladesh Agriculture University, Chittagong Veterinary University, Department of Livestock Service and Food and Agricultural Organisation (FAO) jointly conducted the study from February to June this year.
The study involved phylogenetic, epidemiological and socio-economic analysis.
The above comments on H5N1 in Bangladesh are not a surprise. Although no H5N1 sequences from Bangladesh have been made public, media reports indicated the H5N1 in Bangladesh was similar to H5N1 in West Bengal. Sequences from West Bengal have also not been made published, but earlier outbreaks in India, Pakistan, Afghanistan, and Iran were the Qinghai sub-clade 2.2.3.
The Qinghai strain was first reported at Qinghai Lake in the spring of 2005. Qinghai Lake is due north of Bangladesh, and migratory birds that winter in south Asia migrate to the Qinghai Lake in the spring, and summer in areas to the north in Siberia and Mongolia. The Ganges Delta in Bangladesh and West Bengal attract a variety of waterfowl, which would facilitate movement of H5N1 into both countries.
The involvement of waterfowl in the recent outbreaks provoked the standard disclaimers by conservation groups, which rely on negative data linked to minimal testing of waterfowl, or surveillance programs which target fecal samples or cloacal swabs, which have low or undetectable levels of clade 2.2.
In the recent outbreak in Bangladesh, dead crows tested positive for H5N1 as did one child. Crows also died in West Bengal in association with poultry outbreaks, but there are no reports of wild bird H5N1 in India. Testing in India is minimal, and only poultry has tested positive, even though resident and migratory wild birds have died in association with H5N1 positive poultry deaths. The reporting failures in India are common.
The migratory bird linkage to outbreaks in Bangladesh and India were expected. Release of sequence data by both countries would be useful.
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