The present invention relates to ivermectin formulations for administration to pet and domestic animals. These formulations provide long term protection against Dirofilaria parasites, without the risks for secondary adverse of conventional formulations. Preferred formulations are collars, collar strips, or medallions, attachments for collars, ear tags, bands which are affixed to limbs or parts of the body, adhesive strips and films, and peel-off films, or spot-on or pour-on forms which are administered at least twice a year up to around once a year.
