I would like to say something about checking complete blood cell counts for
the POSSIBLE presence of lymphoma in the ferret in response to Dr. Williams
comment that it can't be used to diagnose lymphoma.
In our practice, we recommend looking at complete blood cell counts on
ferrets starting at one year of age and at least annually thereafter. (Under
six months of age, ferrets can have a naturally occuring high lymphocyte
count) We look for a variety of things, but in particular, we check for a
high lymphocyte count.  If the lymphocyte count is high (over 60% OR over
3500 absolute count) then we recheck it in 2-4 weeks, because, as Dr.
Williams suggested, the count may be high due to other causes.  The reason we
have to look at one or the other parameter is because, in our practice, the
total white blood cell count may not be over 3500 and then we look at
percent.  In cases where the total white blood cell count is very high, then
we look at the absolute amount.  At any rate if in 2-4 weeks the high
lymphocyte count persists, then we suggest a lymph node removal (the
popliteal along the back of the thigh, only a pea sized tissue) for positive
confirmation of lymphoma.  The sad fact is in our area that 80% of the cases
that had the persistently elevated lymphocyte count turn out to be LYMPHOMA.
We have two pathologists check all our samples so there is no question that
it is pathology error, one being Dr. Susan Erdman who is doing most of the
research on this disease at M.I.T.  She is VERY picky about what she calls
lyphoma or not.  We diagnose it EVERY WEEK in our practice (our 4 man
strictly exotic animal practice sees about 18% of all its patients as
ferrets).  I realize that there may be a regional difference in how much
lymphoma is seen, but it is out there.
The other 20% turn out to be hyperplastic, but the sad thing is that as we
follow their complete blood cell counts over the next year or two, we have
had at least 50% of those become positive for lymphoma at a later date
when we check another lymph node.
I would agree with Dr. Williams, that there are certainly other reasons that
the lymph nodes can be overactive or "hyperplastic" and the chronic infection
with Helicobacter is certainly high on the list.
Therefore, I think, after screening ferrets this way for over 3 years, that
the CBC is a very valuable tool to look for lymphoma, but NOT TO DIAGNOSE  IT
ALONE.  It is about the only tool we have right now, as there is no test
specifically for lymphoma.  We find that the cases that respond to
chemotherapy the best are those that are caught early with screening before
they have serious clinical signs.  Most of these ferrets that we are finding
this way range in age from 8 months to 3 years of age (in older ferrets we
usually see obvious clinical signs) with no clinical signs.  Scary, but true.
Just thought I would throw in my two cents worth.
Susan Brown, D.V.M.
 
[Posted in FML issue 0731]