Flea is the common name for insects of the order Siphonaptera (classification: phylum Arthropoda, class Insecta) which are wingless insects with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living by hematophagy off the blood of mammals.

Ticks are blood feeding external parasites of mammals, birds, and reptiles throughout the world. Approximately 850 species have been described worldwide There are two well established families of ticks, the Ixodidae (hard ticks), and Argasidae (soft ticks).

Worms are the most common endoparasites of companion animals and infestations rank among the most critical of parasitic infestations in cats, dogs, and horses. There are two main classes of worms that affect companion animals: tapeworms and roundworms.