Date: 2002-02-08 17:43:00 UTC
Subject: Re: Confirmatory tests for Aleutian disease
--- In Ferret-Health-list@y..., "dr_bruce_williams" wrote:
> So, once and for all - a positive serologic test means that
> animal is exposed, but it will take additional tests to show
> animal truly has Aleutian Disease. Serologically positive
> are certainly at high risk for development of the disease
> and for shedding the virus, but it does not equate with
> having the disease itself.
While I would agree with this statement in regard to the CEP
test, one of the selling points of the Avecon tests, according
to Avecon, is that they do not give false positives.
According to the Avecon website, and to the talk Dr. Stephon
gave at the Pittsburgh ferret show last June, the ELISA and
POCT tests are testing for a protein found in the antibodies
only when the virus is replicating. According to the
literature, those tests will therefore only show a positive
result when the ferret actually has the virus, and not when
there are merely antibodies due to exposure only. The down
side is that if the virus goes into a dormant state, it may be
possible for the test to give a false negative.
I am not a medical professional, so I do not have the ability
to determine whether or not these claims are correct.
I have stated before that I personally prefer the United CEP
test. That test looks for several different proteins in the
antibodies, and gives a positive result if any of the proteins
are found. I feel there is less chance of a false negative
with the CEP, but that is my personal opinion, and may not be
As I have also said before, no test is 100% accurate, and it
is best to retest at least once, several weeks after the first
test, especially if a positive result is obtained. There are
other tests that can help confirm that a positive ADV test
result does indeed mean the ferret has ADV, but it may take
time for the other tests to show the abnormalities associated
with ADV. So, if a ferret with a positive CEP or ELISA test
result has normal gammaglobulin levels, it is not safe to
assume that the ADV test was a false positive. Any positive
ADV test result should be regarded as a potential case of ADV.
I have 9 ferrets that test positive for ADV, and have for over
2 1/2 years. Of the 9, only one had abnormal bloodtest
results in the first 6 months. That one, within a few months
of becoming positive, had elevated liver enzymes and high
levels of gammaglobulins. Over the course of time, his
gammaglobulin levels have continued to increase.
Three of the remaining 8 started to show elevated
gammaglobulin levels after about a year. For the first year
after they started to test positive, though, their protein
levels stayed well within normal limits. The remaining 5 have
only started to show elevated protein levels within the last 6
months, and at this time, their levels are just slightly over
normal limits. Except for the one that showed problem early
on, all of the others have otherwise normal blood values, with
no indication of liver or kidney problems.
Over the last 2 1/2 years I have had well over 100 tests for
ADV run on my ferrets. Frequently, I will draw samples and
send them to United, Avecon and Dr. Stevenson at the same
time. In the majority of cases, the results from all 3
sources agree. I have had false negative results from both
the Avecon ELISA and the United CEP, though. With the CEP, it
happened early in the course of the infection, when the
antibody titers were low. With the ELISA, it happened twice
in a 3 month period in a ferret whose titers (according the
Dr. Stevenson's tests) were at a level of 1024, which is
considered high. The second set of ELISA tests were run on
both blood and saliva. However, subsequent ELISA tests run on
samples from this ferret have all been positive.
One more point - do not assume because a ferret tests positive
with a low titer that the ferret will not be shedding the
disease. I have had ferrets with titer levels of 16 and 64
(both considered low) have a positive PCR result on both their
blood and urine samples. And, I have ferrets with high titers
that have never had a positive PCR result. The antibody
concentration does not seem to have any correlation to the
presence of the actual virus in the bodily fluids, from the
tests that have been run on my ferrets. Granted, my kids are
a small sample, and do not constitute a statistically valid
sample, but that is what I have observed.
ADV - If your ferret hasn't been tested, you don't know!
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