text: It is the third confirmed diagnosis of the H5N8 strain of avian flu in Lincolnshire in about four weeks.
  Some of the birds at the undisclosed premises in Lincolnshire have died. The rest are due to be culled.
  Defra said an investigation was "under way to determine the source of the infection".
  A 1.8-mile (3km) protection zone and a six-mile (10km) surveillance area have been set up around the turkey rearing farm to reduce the risk of the disease spreading.
  An outbreak of the virus in a flock of about 6,000 turkeys at Low Farm, in Fulstow, near Louth, was "unlikely to be directly linked to the previous case" at the nearby Austen Fen Farm, Defra had said.
  All restrictions were removed around Austen Fen Farm on 18 January but still remain at Low Farm while an inquiry there continues.
  This latest case in Boston comes two days after bird flu was found in pheasants that were being bred at a farm in Wyre, Lancashire.
  The same strain has been discovered in birds in Settle, North Yorkshire, a swannery in Dorset and flocks in Carmarthenshire, south west Wales.
  In December, the government introduced an avian influenza prevention zone, which lasts until 28 February, to help protect poultry and captive birds from avian flu after the strain was found in 14 European countries including Germany and France.
target: Bird flu has been confirmed in a flock of 19,500 turkeys at a farm in Boston, the Department for Environment, Food and Rural Affairs (Defra) said.