Aside from usage in many other beasts beyond dogs, ivermectin has a fairly wide and possibly growing range of applications, eg used externally to treat rosacea, internally for river blindness, etc. It has anthelmintic effects on many roundworms, but not flatworms. It's an acaricide and generally effective in treating scabies; also lice and bedbugs. Definitely keep pet spiders away from ivermectin! I've seen nothing (yet) indicating antifungal properties. Anyone considering self administration (a commenter somewhere above) should note the hepatotoxicity of the drug.
Edit note:
I am pretty sure ivermectin is the active ingredient in Revolution, an extremely popular medicine for dogs... and cats, combatting both heartworm and fleas and maybe more.
