KHV: Now it's in Britain's rivers

Fears are growing that the deadly Koi Herpes Virus (KHV) could sweep through the nation’s running water venues after it was discovered in a record-breaking river.

The outbreak, at Brocket Hall in Welwyn Garden City, Hertfordshire, could threaten fish populations in the River Lea ¬ a place that once produced the UK’s biggest ever chub ¬ and a host of other connected waterways, including the Thames network.

Brocket Hall is officially described as a lake, but it is actually a weedy, widened section of the Lea, which flows in at one end and out at the other. Cefas ¬ the Government agency that deals with all aquaculture issues ¬ has placed a Designated Area Order on the site, meaning no fish can be moved from the venue. However, it has stopped short of imposing a similar status on the whole of the Lea because it says it is confident the fish cannot escape.

But Angling Times can reveal that only a small weir separates the carp from the main river ¬ and that means fish could escape in flood conditions. Cefas chief health inspectorate Kevin Denham recognises the risk.

“There is the potential for the spread of KHV if it floods, but you cannot obstruct a river to keep the fish in. Now the fishery owner has a legal requirement to inform us of events that could cause the spread of the disease, ie flood risk. We’ve spoken to owners on the river below the fishery so they can inform us if they have any issues with their fish. There is less risk of KHV in rivers because it has a threshold of 15 - 16°c and there is only a small window for this every year in running water,” he said.

The disease was discovered in carp in the Thames during the summer flooding of 2006, although it was believed at the time that these had been washed out of a stillwater.

But infected carp getting into our river system is a ‘fatal situation’ according to Ruth Lockwood, chairman of the English Carp Heritage Organisation.

“Situations like this are how this virus will eventually spread around the UK. It’s Mother Nature’s wildcard ¬ last year fish originating from ponds in Reading were caught in the Thames.

“We’ve stared in the face of this scenario for a long time, but now suddenly everybody is getting the picture. KHV is not a water-borne virus so if it travelled into the main River Lea it would have to be through fish contact or any shedding of tissue such as scales, mucus or faeces.”