I managed to reach Dr. Susan Erdman by phone to discuss the findings from
her research.  Here are the highlights:
 
(1) The evidence points very strongly to a viral cause of adult
    lymphosarcoma.
(2) A retrovirus is the leading suspect. A retrovirus has been discovered in
    lymphosarcoma tissue in ferrets but this isn't nailed down 100% yet.
    The retrovirus could just be hanging out and some other virus is at
    fault.  Dr. Erdman is working to determine the RNA sequence of this
    retrovirus to see if it is related to other known retroviruses like HIV
    or FeLV.  That could take several years, unfortunately.  Deciphering the
    genetic sequence of this virus could help develop diagnostic tests or
    markers to determine which ferrets are most likely to get cancer or when.
(3) Juvenile lymphosarcoma appears to be a different entity.  The time
    required for tumor development is much different and the type of cells
    and the way the cells grow is different.  Dr. Erdman hasn't specifically
    studied juvenile lymphoma in ferrets, but it's definitely not the same
    as adult cancers.  Thus, the cause for these juvenile tumors remains
    uncertain.
(4) The method by which any virus is transmitted from ferret to ferret is
     unknown. Not much help, I know.
(5) The ferrets with lymphosarcoma studied came from a variety of breeders,
    commercial and hobby breeders. No clues there.
(6) I asked about adrenal cortical tumors and insulinoma, and she hasn't
    studied these cancers specifically.  She had no speculation about
    insulinoma but said that the existing evidence leads her to believe
    that the most suspect cause for adrenal cancers may be early neutering,
    perhaps complicated by disruption of light-dark cycles with artificial
    light.
 
So, there's the latest.  The studies will continue, but in the meantime,
none of this really gives ferret owners a way yet to keep ferrets from
getting lympho.  But, perhaps knowing that this is a transmissible disease,
ferret owners can rely on their experience to come up with some theories.
If you've had the unfortunate experience to have suffered through more than
one ferret with lymphosarcoma, maybe you can provide the clue that leads to
a way to prevent other ferrets from getting this cancer.  Think back about
what was different between the ferrets that got sick and those that didn't
get sick.
 
As for treatment, perhaps knowing that this may be a retrovirus-associated
cancer may point to a therapy, but I wouldn't be too encouraging.
Retroviruses are very difficult to treat because the virus inserts itself
into the host's own chromosomes.  Unlike viruses or bacteria that are on the
outside of the host cells, it's very difficult to fight an invader that
hides out in the host's own genome.  *If* this is a retrovirus, prevention,
rather than treatment will be where the emphasis should go.
 
Finally, just a correction on an earlier post of mine where I mentioned
there are five known human hepatitis viruses.  There are six.  I forgot
hepatitis G--the most recent...just wanted to set the record straight.
 
--Jeff Johnston ([log in to unmask])
[Posted in FML issue 1724]