Published Date: 2011-11-10 18:13:12
Subject: PRO/AH/EDR> Infectious salmon anemia - Canada (03): (BC)
Archive Number: 20111110.3335
INFECTIOUS SALMON ANEMIA - CANADA (03): (BRITISH COLUMBIA)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Thu 3 Nov 2011
Source: Mainstream Canada [edited]
Independent tests at one of the world's top ISA [infectious salmon
anemia] virus research labs reanalyzed 48 samples of Pacific salmon
and did not find conclusive evidence that any of the fish had ISA.
This week [of 31 Oct 2011], Dr Are Nylund at the University of Bergen
(Norway) reanalyzed tests done last month [October 2011] on 48 Pacific
salmon by Dr Fred Kibenge at the University of Prince Edward Island
(UPEI). After extensive re-testing, Nylund did not find conclusive
evidence that the fish had the infectious salmon anemia (ISA) virus.
Sampling for this virus is extremely sensitive, so Dr Nylund tested
and retested the samples. One of the samples was tested 33 times; in
that sample he found one weak positive result and 32 negative results.
In a recent interview, of which Mainstream has obtained a copy [see
http://tinyurl.com/66kljmy], Dr Nylund explained, "The test material
we received was of poor quality, and all tests were negative except
the one which was weakly positive. This means that I could not confirm
the results from Kibenge, since he found 2 clearly positive findings
and concluded that this had European origin."
Dr Nylund continued, "This also means that a virus having genetic
similarities with ISA or something totally different may be picked up
by the test. Therefore we need to sequence/genotype the virus to
provide serious comment on the origin." He said the findings could
represent a previously unknown type of Pacific Ocean virus. "Not all
ISA-type findings are described, and there are surely many we have not
yet discovered," he said.
Nylund said that it's possible any newly discovered virus could have
its origins in ancient evolution. "Today there are several examples of
pathogens that are related and which have a North Pacific and a North
Atlantic type. One example of this is the paramyxovirus," he said.
"The reason for this is that the salmon and some of its pathogens in
the Pacific and Atlantic once had the same origin, but they have
developed differently as they have been geographically isolated over a
Thousands of farmed and wild salmon have been tested for the
infectious salmon anemia virus (ISAV), in British Columbia, including
more than 1200 in 2011 alone. All of those tests were negative and
they show that to date, there is no ISAV in our fish, farmed or wild.
But 2 weeks ago anti-aquaculture activist Alexandra Morton claimed
Pacific salmon collected by Simon Fraser University researchers had
been infected with the European ISA virus. She made the claim before
the tests were even concluded, spreading fear and concern without any
basis in fact.
The fish were sent for re-testing to one of the world's top ISA virus
research labs at the University of Bergen in Norway and those results
do not support Dr Kibenge's findings, nor do they give conclusive
findings on the origin of the virus.
We are glad these tests were done, as they provide a good scientific
control for the results announced publicly 2 weeks ago.
Another new lab report published by Ms Morton indicates that Kibenge
tested another batch of samples she submitted, and one of the 20
apparently showed a weak positive result. However, Kibenge cautioned
in his report that "the presence of ISA virus sequences in the tissue
samples does not imply that the subject fish had ISA or that ISA is
present in the area where the subject fish were collected from."
Further genetic testing is again necessary to determine if the latest
results from UPEI mean anything, or if the results were also skewed
because of poor-quality samples.
Canadian Food Inspection Agency (CFIA) is doing proper tests now to
determine whether it can reach the same conclusions and will be
investigating the chain of custody (scientific procedure for
collecting and storing samples to prevent contamination). We believe
that it is more important than ever to wait for the lead agency on
this file to give the final word on this issue, and for them to
complete their battery of tests before jumping to any conclusions. We
urge the CFIA scientists to quickly conclude their investigation and
publish their findings.
Mainstream, along with the rest of the BC salmon farming industry, has
offered to provide further samples for testing by CFIA and are
advocating for more sampling and testing of our region's wild fish and
for continuation of the surveillance program.
For more information please contact
Grant Warkentin, Communications Officer, Mainstream Canada
David E Starling, DVM
Aqueterinary Services R, PC
Veterinary Medicine for Aquatic Animals
Ames, IA 50014
[Infectious salmon anemia virus (ISAV) is a member of the genus
_Isavirus_ in the family Orthomyxoviridae. It is an RNA virus which
renders its genetic material more fragile and RT-PCR tests might turn
out negative if the sample is not adequately preserved. This is a
highly contagious influenza virus and further collection of fish
should provide with new evidence if the disease is propagating among
wild salmonids. Apparently there is new evidence of infected fish
besides the 2 out of 48 mentioned (see ProMED post 20111108.3321). The
results on new sampling efforts and sequencing of the eventually
positive samples would clarify the situation. See also