Revolution, in the right amount, provides protection against
heartworms. I have one study (with separate results for many different
pets, including ferrets) that suggests that 18 mg. of selemectin per
month for a 1-kg ferret should provide protection against heartworms.
Of course, this assumes that the ferret is not already infected.

Revolution for cats sized 5-15 lbs. has 45 mg of selemectin per 0.75 ml
vial. I divide one vial equally between two ferrets once a month, so
each gets 22-23 mg. of selemectin per month. I do this from April --
October, the time of year that mosquitos are around here in CT.

If anyone wants a copy of that study, which is in PDF format, email me
privately.

Jeff
In Loving Memory of Neo, Trinity, Morphy, Possum, Pip, Pop, Sabrina,
Minnie Mouse, Hunny, Misty, Frodo, Baggins, and Mr. Parker
Caring for Luna, Baby Girl, Dozer, Boomer, and Zoomer 

[Posted in FML 7119]