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Published Date: 2019-08-22 06:14:52
Subject: PRO/AH/EDR> Infectious hypodermal & hematopoietic necrosis - UK: shrimp, OIE
Archive Number: 20190822.6634372
INFECTIOUS HYPODERMAL & HEMATOPOIETIC NECROSIS - UK: (SCOTLAND, ENGLAND) SHRIMP, OIE
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Date: Tue 20 Aug 2019
Source: OIE, WAHID [edited]
https://www.oie.int/wahis_2/public/wahid.php/Reviewreport/Review?page_refer=MapFullEventReport&reportid=31455


Infectious hypodermal and haematopoietic necrosis, United Kingdom
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Information received on 20 Aug 2019 from Dr Christine Middlemiss, chief veterinary officer, DEFRA (Department for Environment, Food and Rural Affairs) London, United Kingdom

Summary
Report type: immediate notification
Date of start of the event: 15 Jul 2019
Date of confirmation of the event: 13 Aug 2019
Report date: 19 Aug 2019
Reason for notification: 1st occurrence of a listed disease in the country
Causal agent: infectious hypodermal and hematopoietic necrosis virus [IHHNV]
Nature of diagnosis: laboratory (advanced)
This event pertains to a defined zone within the country.

New outbreaks (2)
Outbreak 1 (IHHNV-1): Stirlingshire, Scotland
Date of start of the outbreak: 15 Jul 2019
Outbreak status: resolved 16 Aug 2019
Epidemiological unit: farm
Water type: saltwater
Population type: farmed
Production system: closed
Total animals affected
Species / Morbidity / Mortality / Susceptible / Cases / Deaths / Killed and disposed of / Slaughtered
White leg shrimp (_Litopenaeus vannamei_) / 4 (scale 0 to 5) / 4 (scale 0 to 5) / 350 300 / - / - / - / 0

Affected population: The affected population consisted of 350 000 post-hatch larval whiteleg shrimps, imported from suppliers from the United States of America (USA) on [18 Apr 2019]. The animals were imported by a small, inland aquaculture site in Scotland and placed in closed containment units, with artificial heated seawater and recirculation units to recreate the environment necessary for the production of warm water shrimp. Any effluent was treated, and final discharge was collected and also treated. This is an experimental facility looking to prove a concept using an artificial environment, well away from coastal waters. The animals were culled on [16 Jul 2019], immediately after suspicion of IHHNV and the site has been disinfected. A population of 300 animals for broodstock was moved from the same facility in the USA, separate to the movement of the infected and in a different tank, showed no clinical signs of disease, but were also culled.

Outbreak 2 (IHHNV-2): Lincoln, Lincolnshire, England
Date of start of the outbreak: 8 Aug 2019
Outbreak status: continuing (or date resolved not provided)
Epidemiological unit: farm
Water type: saltwater
Population type: farmed
Production system: closed
Total animals affected
Species / Morbidity / Mortality / Susceptible / Cases / Deaths / Killed and disposed of / Slaughtered
White leg shrimp (_Litopenaeus vannamei_) / 0 per cent / 0 per cent / - / - / - / - / -

Affected population: The affected population consists of shrimp imported from suppliers in the USA in a total of 5 consignments from January to August 2019. The animals are imported as specific pathogen-free (SPF) post larval shrimp and grown for human consumption for the United Kingdom market only. Live animals are not exported from the facility, and with the exception of 2 movements to bio-secure research facilities which occurred earlier in the year [2019], live animals do not leave the site. The shrimp are grown on in a fully enclosed recirculation facility, using artificial seawater made up on site and which is heated to 28 C. The site is located inland about 55 km [about 34 miles] from coastal waters, and except for a contained irrigation reservoir, there are no other water courses within 1000 m of the facility. All effluent discharges into a soak away, and waste is disposed of in a bio-secure manner. The animals showed no clinical signs of disease or increased mortality associated with infectious hypodermal and haematopoietic necrosis virus (IHHNV), the reason for the investigation is because the Competent Authority received a report that one of the exporting suppliers had become positive for IHHNV, prompting an investigation on suspicion.

Epidemiology
Source of the outbreak(s) or origin of infection: introduction of new live animals, legal movement of animals

Epidemiological comments:
1. Scottish site - At the time of import to this isolated and contained artificial facility, IHHNV was not confirmed at the exporting site, but it has been notified to the OIE since. As the animals showed poor growth and mortality, a husbandry investigation was undertaken which led to the batch being suspected of IHHNV on 15 Jul 2019. The batch was culled before official confirmatory tests were finalized. This site is some distance from coastal waters, and the United Kingdom has no IHHNV susceptible species. No shrimp are on the site and disinfection occurred. The sealed boxes used for the initial shipment were incinerated on arrival. The site was constructed well away from coastal waters and used artificially made warm seawater made from freshwater. The 350 000 plus stock was placed into a closed recirculation unit, with the effluent treated. There was never any risk of contact with native aquatic species. Immediately after culling, the part of the site where infected stock had been kept was fully disinfected. The compound HTH was applied to achieve 500ppm free chlorine in the storage reservoir and pipework. A different, small batch of shrimp from the same exporting site, kept within a separate contained artificial environment, were also culled. There has not been any movement off this site. There are no remaining susceptible animals on site, and disinfection took place. The UK has written to the USA authorities to inform them of this incident and the connection to the now known infected unit.

2. Lincoln site - As a precautionary measure, statutory movement restrictions have been applied on suspicion of new and emerging disease, to ensure there are no movements of live animals off site. With the exception of 2 movements of live animals to fully enclosed, bio-secure research facilities, which took place prior to the start of the investigation there have been no movements of live animals from this facility. The site produces animals for human consumption only, the animals leave the site as raw product, on ice. As the animals were imported as SPF for IHHNV, the Competent Authority in the exporting country has been formally notified. We were alerted to suspicion of IHHNV after receiving reports that the supply site in the USA had become positive for this disease.

3. General comments - There is a nil/negligible risk from this disease to the UK as there are no native susceptible species, and the susceptible species infected in this incident cannot survive in northern European waters, which regardless, the coast of which was a long distance away.

Control measures
Measures applied: movement control inside the country, surveillance within infected and/or protection zone, traceability, quarantine, official disposal of carcasses, by-products and waste, selective killing and disposal, vaccination permitted (if a vaccine exists), no treatment of affected animals.

Measures to be applied: emergency harvest

Diagnostic test results:
Laboratory name and type / Species / Test / Test date / Result
Stirling University (Local laboratory) / white leg shrimp (_L. vannamei_) / polymerase chain reaction (PCR) / 15 Jul 2019 / positive
Marine Scotland Science Marine Laboratory, Aberdeen (National laboratory) / white leg shrimp (_L. vannamei_) / polymerase chain reaction (PCR) / 13 Aug 2019 / positive
CEFAS Laboratory, Weymouth (Regional Reference Laboratory) / white leg shrimp (_L. vannamei_) / gene sequencing / 15 Aug 2019 / positive
CEFAS Laboratory, Weymouth (Regional Reference Laboratory) / white leg shrimp (_L. vannamei_) / polymerase chain reaction (PCR) / 15 Aug 2019 / positive

Future reporting
The event is continuing. Weekly follow-up reports will be submitted.

[The location of the outbreaks can be seen on the interactive map included in the OIE report at the source URL above.]

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["IHHNV appears to have a world-wide distribution in both wild and cultured penaeid shrimp. Although infection with IHHNV has been reported from cultured _Penaeus vannamei_ and _P. stylirostris_ [Litopenaeus vannamei and Litopenaeus stylirostris] in most of the shrimp-culturing regions of the Western Hemisphere and in wild penaeids throughout their range along the Pacific coast of the Americas (Peru to northern Mexico), the virus has not been reported in wild penaeid shrimp on the Atlantic coast of the Americas. Infection with IHHNV has also been reported in cultured penaeid shrimp from Pacific islands including the Hawaiian Islands, French Polynesia, Guam, and New Caledonia. In the Indo-Pacific region, the virus has been reported from cultured and wild penaeid shrimp in East Asia, South-East Asia, and the Middle East." Source: https://www.oie.int/index.php?id=2439&L=0&htmfile=chapitre_ihhn.htm. - Mod.CRD

HealthMap/ProMED maps available at:
Scotland, United Kingdom: http://healthmap.org/promed/p/280
England, United Kingdom: http://healthmap.org/promed/p/279]

See Also

Infectious hypodermal & hematopoietic necrosis - Canada: (AB) shrimp, OIE 20190820.6630515
Infectious hypodermal & hematopoietic necrosis - USA: (TX, FL) shrimp, OIE 20190615.6522441
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