Karen Eggert, Public Affairs Specialist APHIS reported on August 17, 2007 that VHS test results on samples of Cyprinus carpio provided by Cornell University were in from the National Veterinarian Services laboratory. NVSL could not verify the results, which were then deemed negative.
Eggert then emailed back several answers to specific questions on how to interpret the results of the tests at NVSL.
Question: Does the NVSL negative results mean that Cyprinus carpio do not test positive for vhs or that the sample tested did not?
“We can only go on the samples we get and could not speak for the future tests we'd run on the species. In this particular die-off, samples were sent to us and we tested them, on virus isolation they came back negative. What I mean is we can't say that this species will never be affected by VHS. But at this point, we have no evidence suggesting that they need to be added to our VHS-susceptible species list. But as I said earlier, we can never rule out any action we might take in the future.
Karen Eggert
Public Affairs Specialist
301.734.7280
karen.m.eggert@aphis.usda.gov”
Question: Is there any possibility of further action by APHIS with regard to Cyprinus carpio? Do these findings essentially serve as a demonstration that Cyprinus carpio will not now or in the future be added to the list of vhs effected species? This is good news for koi hobbyists if so.
“We only take regulatory action if the samples test positive on virus isolation, since they didn't, we won't be taking any further actions. We can never rule out any actions we might take in the future. If we were to ever get positive results on virus isolation for any species, we'd take regulatory action.
Karen Eggert
Public Affairs Specialist
301.734.7280
karen.m.eggert@aphis.usda.gov”
Furthermore, we contacted the New York Department of Environmental Conservation, which initially broke the story of the Cornell laboratory findings and Cornell’s fisheries science laboratory directly.
This was an emailed response from the head of the Cornell laboratory:
"Fm: Dr. Paul R. Bowser
Re: Carp and VHSV
With regard to your question below, we did have a Common Carp submitted to our laboratory for diagnostic processing with the resultant isolation of VHSV in cell culture. We followed that up with RT-PCR and quantitative RT-PCR assays to confirm the specific identity of the virus as VHSV. Fluid from the positive cell culture was forwarded to a colleague at another fish research laboratory where an independent RT-PCR testing confirmed the identity of the virus as VHSV. That laboratory also performed partial genetic sequencing of the virus, again confirming the identity of the virus as VHSV.
We subsequently forwarded original tissue from the fish as well as cell culture fluid from the VHSV-positive cell culture to the NSVL. It is my understanding that they obtained positive results for VHSV from the cell culture fluid, but were unable to isolate the virus from the original tissues. The inconsistency of the results may have been due to the fact that we were dealing with a single fish and those tissues had been frozen and thawed more than once during the handling involved with preparation for transport from one lab to another. We make every attempt to minimize the number of times tissues are frozen and thawed. Freezing and thawing is known to adversely impact this virus and that could have been the case with these samples.
As you are probably aware, VHSV has been found in a large diversity of fish species. Several of the fish species are in the minnow family, Cyprinidae; the fish family that contains such species as the minnows, goldfish and carp. I realize that for the official purposes of USDA APHIS, they consider a positive diagnosis to require isolation of the virus in cell culture followed by a subsequent RT-PCR test to confirm the specific identity of the virus as VHSV; both of which must be performed in their NSVL laboratory. Given their regulatory responsibilities, this course of action is appropriate for them.
However, given the broad host range of VHSV in so many different fish species, I believe that the koi hobbyist should practice good fish health management for this virus just as they do for any other disease of fish.
P. R. Bowser
Professor of Aquatic Animal Medicine"
Dr. Geoffory Groocock took our call that afternoon and stated, “We need to be cautious. We have only tested one carp and we know this virus effects many species.” Groocock noted that they did detect the virus in carp tissue and replicated it in cell culture and that the negative result at NVSL was likely a result of its being damaged in freezing and/or due to the limited sample availability. Groocock noted that as a veterinarian dealing with aquaculture he senses the industry being where the livestock and poultry industries were nearly a decade ago in dealing with pathogens that had the potential to cause devastation not only to their animals, but their bottom line. However, he noted there was hope in that after a period of adjustment for those industries those that met the regulatory challenges and were proactive could demonstrate not only the health benefits in their best management practices, but benefited on their bottom lines. He noted those in the koi industry and hobby that best isolated their prized collections from untested fish would be most capable to ward off such disease threats.
Neither Cornell nor APHIS have stated nor will they state that the news of the negative test results at NVSL amount to a refractory status for Cyprinus carpio (koi/carp). The scientific community is urging “caution.” Interpretation of what caution means vary. If this disease does affect koi prior to a positive test confirmed by the NVSL laboratory those fish managed by those who proactively treated them as susceptible will benefit.