Detection of VHS in Ouse catchment

Background Nidderdale Trout reported mortalities to Cefas on 17 th May Virus isolated from samples taken by Cefas FHI confirmed to be VHS on 26 th May Mortalities at the farm are reported to date back to 23 rd March 2006.

Movement Controls Notices were served on 26 th May prohibiting the movement of live fish or eggs from 33 farms within the River Ouse catchment. Designated Area Order made on 1st June. –Movements of live fish to and from the Ouse catchment area restricted, except for retail movements of ornamental fish. Controls extended to cover additional parts of the catchment area and movements of dead fish on 7 th June.

Nidderdale Trout Infected farm de-stocked by 28 th Ma 19 tonnes of fish were humanely killed with the full co-operation of the site management Dead fish were rendered locally prior to incineration Farm dewatered pending disinfection Farm owner has suggested that the farm may remain fallow pending investigations into the VHS status of wild fish in the vicinity of the farm, or identification of the source of the infection.

Contact Chasing and Epidemiology Nidderdale trout was supplied with live fish from a single trout farm, also on the Ouse catchment Upstream of Nidderdale Trout is a single trout farm with a processing unit. All three units and their records were inspected and the two trout farms sampled (225 fish) on the 27 th and 28 th of May. No trout farms downstream of Nidderdale on the River Nidd. FRS were advised of possible contacts in Scotland through live fish and dead fish for processing.

Contact Chasing and Epidemiology Results from the first round of sampling on all other salmonid farms in the River Ouse catchment are negative. Inspections have as yet shown no clinical evidence of VHS on any of the other sites inspected.

Contact Chasing and Epidemiology Inspection of the trout processing unit on the river Nidd showed that it had adequate bio-security, and that it had only processed fish from other farms within the catchment. Investigations at a smokery upstream from Nidderdale trout are underway to eliminate it as a source of infection.

Contact Chasing and Epidemiology Wild fish were sampled on 31 st May to: –Determine whether VHSV was established in the River Nidd –Look for evidence that VHSV may be detected above or below postulated points of introduction to the catchment. VHSV was isolated from a grayling.

Contact Chasing and Epidemiology Investigations are underway to look at: Potential routes of introduction of the disease. Likelihood of disease transfer within the catchment by wild fish movements. Susceptibility of wild fish to the VHS strain. Risk of introduction with dead imported fish. Risk of disease transfer by people or equipment from sites subject to fish movement controls. Other avenues as identified.

Suspension of Approved Zone status Following the confirmation of VHS at Nidderdale the EU fish health regime requires GB to suspend its Approved Zone status for VHS. The minimum area to which controls must be applied is the river catchment area in which the disease outbreak has occurred, down to its estuarial limit. Controls have been placed on the Ouse and Don catchments due to water exchange between these catchments.

Re-establishment of trade Movements from the area will be permitted where such trade is allowed under Council Directive 91/67/EEC. –Dead eviscerated fish for consumption. –Non-susceptible live fish from enclosed waters with no susceptibles. –To a non-approved zone. Live fish movements will otherwise be confined to re-stocking of waters within the designated areas, subject to appropriate constraints.

Re-establishment of Approved Zone status Approved Zone status for VHS is currently suspended for the whole of GB. Approved Zone status will be re-instated for the rest of GB as soon as possible. Detailed rules exist for surveillance and testing to re- establish Approved Zone status following the eradication of disease from an infected zone – minimum 4 years (Council Directive 91/67/EEC).

3 trout farms in Scotland received fish from the farm that supplied Nidderdale Trout Movement of live and dead fish to and from these farms prohibited 300 fish sampled from each farm Results negative Movement restrictions revoked.

Fish from Nidderdale gutted at processing plant in Bellshill near Glasgow Biosecurity at processing plant satisfactory Viscera transpored to Aberdeen for processing into fish meal 600 wild fish from River Clyde tested downstream from effluent discharge from sewerage works Results pending.