Dear Kevin:
 
>The shelter I volunteer at (Oregon Ferret Shelter) had to do a rush rescue
>of a bunch of ferrets from a breeder in Idaho.  Of the group, most seemed
>in good health.  A few potential mommas, 1or2 seemed to have some sort of
>tumors.  Many, however, were blind.  (Some real sweethearts though!).
>
>I was wondering if the blindness could have been caused by some vitamin
>deficiency or additive.  Is it poor nutrition or would it more likely be
>genetic?
 
Without more information, it is difficult to be specific in this case.
Blindness in ferrets may be the result of a number of causes.  I am
assuming that genetic micro-ophthalmia, small and poorly developed eyes
have been ruled out, because you would notice it fairly quickly.
 
In a group of ferrets, blindness may be the result of poor nutrition,
cataracts, or a disease called retinal atrophy.
 
In this group, let's look at nutrition first.  Although not definitively
proven, it is very likely that ferrets, like cats, require taurine for
normal maintenance of the retina, as it has a role in the absorption of
biotransformation of beta-carotene, which is necessary for photoreceptor
health.  This is a large reason why ferrets can be maintained on high
quality cat food, and why ferret chows have added taurine.  Simply put,
no taurine, poor to no eyesight.  It would be interesting to find out
what this breeder was feeding these ferrets.
 
Another cause of blindness in certain lines of ferrets is cataract (lens
degeneration).  This is fairly easily diagnosed - the pupil in the eyes of
ferrets with cataracts is not balck, but a frosty white - sort of like one
of those glass bulbs which snow when you shake them up.  Cataracts in some
facilities have been shown to be inherited along family lines.
 
The third condition, retinal atrophy, is a disease that is not
well-described in ferrets.  I have seen several cases, but we don't know
if it is transmitted along familial lines yet.  As many types of retinal
disease are genetic, it is likely that this condition is as well.
 
In individual ferrets, which is probably a different situation from what
we are dealing with, trauma is probably the single most important cause of
blindness in ferrets - bad encounters with cats, protruding wires on cages,
etc.  Let's not even think about this as a possibility in multiple ferrets
from the same facility!
 
The best way to determine the cause of blindness is these ferrets is to
have a good vet do a good eye exam.  Please remember, as time comes for
these animals (and not a moment sooner), I am currently doing research on
eye diseases of ferrets - I would very much appreciate a post-mortem look
at this most interesting case.
 
With kindest regards,
Bruce Williams, dVM
[Posted in FML issue 3236]