Following an outbreak of avian influenza (bird flu) in domestic laying hens in Friesland, the Netherlands, poultry farmers in the UK are being urged to remain vigilant by DEFRA.

The Department for Environment, Food and Rural Affairs (DEFRA) in the UK has said that the risk level remains the same, low but heightened, as there are several strains of avian influenza viruses which have been reported in recent months across Europe.

Over 48,000 birds were present on the premises in two production systems in the Netherlands with outside access of 16,000 free range birds and 32,000 organic birds, according to DEFRA.

The virus was reported as H7N9 low pathogenicity, with only very mild clinical signs observed of slight egg drop and dullness. Disease control measures have been put in place, and the birds are being culled.

There are no other premises in the 1km zone and initial information from the World Animal Health Organisation (OIE) suggests this is a European strain.

DEFRA is now reminding all poultry keepers to maintain high standards of biosecurity, remain vigilant and report any suspect clinical signs promptly and in addition using the testing to exclude scheme for avian notifiable disease where appropriate for early safeguard.

The last time this virus was detected in the EU was in 2009 in the Czech Republic and a case also occurred in domestic ducks in France also in 2009.

It is highly possible it has been circulating in wild birds in the intervening years, according to DEFRA.

This latest outbreak in the Netherlands was in laying hens, it is important that mild clinical signs, such as egg drop, are reported quickly, so testing can take place, it advises.

This type of production system provides a suitable environment for viral circulation to take place, it said, and possible mutations to occur which lead to highly pathogenic viruses. DEFRA advises that rapid, reactive control measures reduce the risk of these viruses spreading widely.