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Dirofilaria immitis

Dirofilaria immitis

Dirofilaria immitis


  • Kingdom Animalia
  • Phylum Nematoda
  • Class Secernentea
  • Order Spirurida
  • Superfamily Filarioidea
  • Family Onchocercidae
  • Genus Dirofilaria

Final host

  • Dog, fox, wild canids
  • Occasionally cat (Human as accidental host, the life cycle is not completed)


  • Adults: long, slender, white worms (≈ 12-31 cm long, according to sex)
  • The mail tail has the typical loose spiral of Spirurids and the tail bears small lateral alae with several pairs of papillae
  • The two spicules are unequal in size and form (long and pointed the left one smaller and blunt-ended the right one)
  • The vulva is situated at the end of the oesophagus in the female
  • The microfilariae (≈ 218-340 µm long) are not ensheathed and have a tapered anterior end and blunt posterior end
  • Microfilariae show enzymatic (acid phosphatase) activity at the anal and excretory pores


  • Indirect, with mosquitoes (Culicidae) as intermediate hosts (vectorial transmission)


  • Cardiovascular system (right ventricle and pulmonary artery)


  • Haematophagous


  • L1 (microfilariae) in bloodstream


  • L3 (vectorial transmission)