Deadly Wasting Disease
Epidemic Hits 70%
UK Salmon Farms

From Patricia Doyle, PhD
A ProMED-mail post ProMED-mail is a program of the International Society for Infectious Diseases
Warning Of Epidemic On Salmon Farms
By Paul Kelbie
The Independent - UK
Anti salmon-farm campaigners fear that Scotland could be facing a foot-and-mouth-style epidemic after the discovery of a deadly wasting disease among stocks at more than 70 percent of fish farms.
Infectious pancreatic necrosis (IPN) has been found in 7 out of 10 sea cage salmon farms. Although harmless to humans, IPN can kill up to 80 percent of susceptible fish.
A report, published by the Fisheries Research Service for the Scottish Executive, in December 2003, revealed that positive tests for the virus had increased from less than 50 percent in 2000 to 82 percent in 2002.
"Infectious diseases are spreading like wildfire throughout the Scottish salmon farming sector," Don Staniford, managing director of the Salmon Farm Protest Group, said. But John Webster, of Scottish Quality Salmon, said yesterday [1 Jun 2004] that the fears had been exaggerated.
[2] Date: Sun 6 Jun 2004 From: ProMED-mail Source: Fisheries Research Services (FRS) web-site, accessed 6 Jun 2004 [edited]
[The expressed views of political campaigners regarding IPN, and fish-farming, in Scotland call for the posting of an excerpt from the original document cited above: "Final report of the Aquaculture Health Joint Working Group subgroup on infectious pancreatic necrosis in Scotland. 95 pages. Aberdeen, December 2003". Interested readers may refer to the URL for the full text of the Report. (FRS is an agency of the Scottish Executive Environment and Rural Affairs Department). - Mod.AS].
Chapter 3.4: A description of the regional and temporal patterns of IPN virus prevalence in Scottish salmon farms 1996-2002: conclusions ----------------------------------------------- IPN virus became widespread on Scottish salmon farms during the period 1996-2002. Prevalence shows a large variation, IPN virus being the most common (88 percent prevalence), in Shetland marine sites in 2002, while remaining undetected in fresh water sites in the Outer Hebrides for several years. Prior to 2001, this variation was largely controlled by differences between regions, with the effect of differences between fresh water and sea water environments, and year-to-year differences, being of secondary significance.
Recently, the role of regional differences has declined, while that of inter-annual variation has increased. Seasonal differences in IPN virus prevalence are small in spite of large differences in case numbers.
Year-to-year differences are highly significant in that, except in the southern mainland, this variance reflects a trend of increasing IPN virus prevalence at an annual rate of 3 percent in fresh water and 7.6 percent in sea water, but local increases sometimes happen faster than this.
In Orkney, the northern mainland, and, particularly, the Outer Hebrides, these increases were from low to moderately high levels. However, in Shetland, the initial prevalence was not low, so IPN virus had become almost ubiquitous in sea water by 2000. By 2002, very high prevalence had been reached in marine waters in almost all areas. In fresh water sites, the prevalence of IPN virus also shows rapid increase, which is faster in Shetland fresh water sites than in fresh water sites elsewhere. More statistical analysis of the data for 1996-2001 is available elsewhere.
This analysis is a description of the FRS Fish Health Inspectorate's data set, and biases with respect to real IPN virus prevalence may result from the different purposes for which these data were collected. However, levels of prevalence correspond closely to the number of farms under movement restriction. Moreover, the patterns obtained from these data should be buffered against such biases, being dependent on relative prevalence. These patterns of declining regional variation, and, a general, but not universal, increase in prevalence of IPN virus, are striking.
-- ProMED-mail
[Our moderator, MHJ, has added the following remark: "It is worth noting that there are striking markers for climate change in the UK in recent years, from birds, to butterflies, to, in this case, fish diseases, and the possibility of WNV".
Though using FMD terminology in relation to IPN does not reflect an overly scientific attitude, the campaigners' concern is understandable. We shall be glad to obtain and post first-hand data on IPN's evolution in Scotland during 2003 and the current year 2004. - Mod.AS].
Patricia A. Doyle, PhD Please visit my "Emerging Diseases" message board at: Zhan le Devlesa tai sastimasa Go with God and in Good Health



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