Ponds: with ponds a more likely infectious concern would be giardia,
same as with aquaria.  It's not unusual for ferrets to get giardia from
fish tanks and so on.  There would be other things to weigh, too, for
instance, the eating of some types of cyanobacter (commonly called
Bluegreen "algae" though it is closer to bacteria) over time has been
linked to later liver and intestinal illnesses including malignancies.
 
In relation to West Nile (which they can potentially get as per below):
http://fhl.sonic-weasel.org/browse.php?msg=SG800
 
>While ferrets can potentially contract it, no cases have been reported
>as far as I can tell.  Ferrets likely do not come in contact with
>Culex mosquitoes terribly commonly.  Birds appear to be the most likely
>reservoir of infection, with humans and horses serving as dead-end
>hosts.  This is classic or many of the other arboviruses like VEE and
>WEE, and ferrets really play no part in the spread of those
>encephalitides either.
>
>Not something that should keep you up at night.
>
>With kindest regards,
>
>Bruce Williams, DVM
 
Syringe feeding: due to encountering too many cases of aspiration
pneumonia the vets who post to the FHL usually advise NOT syringe
feeding, BUT when it is unavoidable the rule of thumb is to *have
the treating vet or one of the vet's trusted techs give hands on
instruction*.  Aspiration pneumonia can be fatal.  There are multiple
tricks for helping a sick ferret eat -- especially patient finger
feeding while softly speaking or singing to the ferret -- which should
be tried first.
 
-- Sukie (not a vet)
Ferret Health List
http://www.smartgroups.com/groups/ferrethealth
FHL Archives
http://fhl.sonic-weasel.org
International Ferret Congress
http://www.ferretcongress.org
[Posted in FML issue 4950]