Canis ISSN: 2398-2942

Filaroides hirthi

Synonym(s): F. hirthi

Contributor(s): Stephen Barr




  • Superfamily: Metastrongyloidea.
  • Genus: Filaroides.
  • Species: Hirthi.

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Clinical Effects



  • Adults, eggs and larvae in lung alveolar and bronchial spaces.
  • L1 in sputum and feces.


  • See lifecycle diagram.
    • Adult.
    • 1st stage larva.


Transmission from bitch to puppies
  • L1 in respiratory secretions is carried out of the mouth with partly digested food that is being regurgitated to feed the pups.
  • Coprophagy and licking also relevant.
Transmission to other dogs
  • L1 passed in the feces or vomitus are fully infective if these are eaten relatively fresh.
Internal autoinfection
  • L1 are swallowed and, in immunosuppressed dogs, are able to migrate directly from the intestine back to the lungs.

Pathological effects

  • In hyperinfected dogs, worms, eggs and L1 are distributed throughout the lung parenchyma.
  • Interstial and nodular infiltrates around worms (but particularly around eggs and L1), form granulomata that appear grossly as small grayish nodules that may coalesce to form masses.


Control via animal

  • Anthelmintic treatment.
  • Separation of dogs so that they have no access to feces or vomitus.
  • Derive puppies by Caesarean section and hand rear them in separate kennels. However, it is not known whether or not prenatal transmission could occur in dogs with auto-infection.

Control via chemotherapies

  • Albendazole Albendazole : (25 mg/kg bid for 5 days) (not licensed for use in dogs).
  • Ivermectin Ivermectin or millbemycins might be tried. Ivermectin (at 50 mcg/kg), is reported to have effect.
  • Fenbendazole Fenbendazole : (50 mg/kg/day for 14 days) (unlicenced use).

Control via environment

  • Removal of all feces immediately when passed.
  • Larvae are rapidly killed by desiccation.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Bahnemann R & Bauer C (1994) Lungworm infection in a Beagle colony - Filaroides hirthi, a common but not well known companion. Experimental Toxicol Pathol 46 (1), 55-62 PubMed.
  • Bourdeau P & Ehm J P (1992) Filaroides sp. infection in dogs. A case report and an update on filaroidosis caused by Filaroides hirthi Georgi and Anderson 1975. Recueil de Medicine Veterinaire 168 (5), 315-321 CABI.
  • Georgi J R (1986) Parasites of the respiratory tract. Vet Clin N Am Small Anim Pract 17 (6), 1421-1442 PubMed.