Defra is reviewing plans to relax controls on the movement of poultry after two new cases of avian flu were detected during the past four days.

Government avian flu controls were due to be lifted on 15 May in England after Defra changed its risk assessment over the spread of the virus from medium to low.

However, it has now confirmed these controls could potentially be extended after a new case of H5N8 avian flu was detected in a small backyard flock of chickens at a farm near Thornton in Lancashire on 4 May, with 30 birds affected.

A 12th case of the outbreak - which began in December - was announced by Defra yesterday (7 May) in a flock of nine birds at a nearby farm.

A number had died while the remaining live birds were humanely culled, Defra said. A full investigation is under way to determine the source of the infection, while 3km protection zones and 10km surveillance zones have been put in place around the two recently infected premises.

As a result of the new outbreaks, a Defra spokesman refused to rule out scrapping the relaxation of its nationwide prevention zone on 15 May. “We always keep things under review based on scientific evidence and veterinary advice,” he said.

The Northern Ireland executive had already extended its restrictions on bird movement until 31 May, while the Welsh and Scottish governments relaxed their own prevention zone rules on 30 April.

Poultry farmers and backyard flock keepers should “continue to practice enhanced biosecurity at all times and be vigilant for signs of disease”, said NFU chief poultry adviser Gary Ford.

The poultrymeat industry had shown an “exemplary level of patience” since the first case of bird flu was declared in December, said British Poultry Council CEO Richard Griffiths, who also urged BPC members to remain vigilant.

“We have been working tremendously hard towards implementing effective solutions to deal with the outbreak,” he added. “The health of our birds remains the top priority for BPC members up and down the country and we will continue practising the highest levels of biosecurity.”