Bird flu raging uncontrolled in neighbouring Bangladesh was proving to be a continuing threat to Tripura, where culling was under way after the outbreak of the H5N1 virus in the State. "Even if we cull all our birds within a five km radius of the disease-hit areas, bird-flu affected areas in Bangladesh are very close to our border villages and there are places which fall within 100 yards of affected areas in the neighbouring country,' Animal Resource Department Director Asish Roy Burman said today. "The affected villages in Dhalai and Sadar subdivisions are within hundred yard radius of the affected Bangladeshi villages. So it is not possible to control bird-flu unless affected neighbouring villages in Bangladesh are controlled,' he said. Under the Indira-Mujib pact signed in 1971, barbed wire fencing was constructed 150 yard away from the international border with Bangladesh as a result of which a sizeable Indian population lived on the other side of the fencing, he said. Burman said these people often bought poultry from Bangladesh when prices went down there because of bird-flu and sold them in Indian markets, which was leading to the spread of bird flu in Tripura. Burman also pointed put that ducks shared common water bodies, while migratory birds and crows posed risk. Principal Secretary in-charge of Animal Resource Department U Venkateswarlu said all the bird-flu hit areas were near the border and as Bangladesh was badly hit by avian influenza there was every reason to believe that the infection in the State came from there. It was also difficult to check movement of poultry because of the porous border, he said. Culling operations were on in eight gram panchayat areas in Bishalgrah sub-division and eight gram panchayat areas of Sadar subdivision of West Tripura district. Import of poultry from outside the State, including Bangladesh with which the state shares 856 km porous border, has been banned. Of the 64 districts in Bangladesh, 47 were reported to be affected by the disease.