Besides ivomec/Heartgard there are 2 other heartworm preventative options.
Interceptor, the brown 0-10 pound dog size, can be used.  It is given once
a month orally.  The other option is Revolution.  The 5-15 pound cat size
can be used.  This is applied once a month over the shoulder blades.  I
also use the Interceptor tablets for my ferrets.  They both will actually
eat the beef flavored tablet on their own.
 
Hope that helps,
Jerry Murray, DVM
[Posted in FML issue 3625]