Dirofilaria repens (Nematoda: Filaroidea, Onchocercidae) is a whitish and filariform worm (male 5-7 cm, female 6-17cm) localized as adult in the subcutaneous connective of the dog. Other animals affected are the red fox (Vulpes vulpes) and more rarely the cat. The microfilariae are found in peripheral blood, waiting to be picked up by a mosquito (see website link below for lifecycle). The main representative of the genus Dirofilaria is D. immitis, commonly called heartworm and infectious agent of  heartworm disease.