Filaroides hirthi		Contents		Rev 01/13/2026
Lungworm of Dogs		Classification		Biology and Ecology
		Morphology and Anatomy		Life Cycle
Return to Filaroides Menu				Ecosystem Functions and Services
		Distribution		Management
Return to Filaroididae Menu		Feeding		References
		Go to Nemaplex Main Menu		Go to Dictionary of Terminology

Classification:

Chromadorea

  Rhabditia

    Rhabditida

      Metastrongyloidea

        Filaroididae

Synonyms

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Morphology and Anatomy:

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Distribution:

Filaroides hirthi is a nematode parasite within the lung parenchyma of dogs. It was prevalent in the late 1970s in major dog-breeding establishments in North America. It was found to be enzootic in all major research Beagle breeding facilities in the United States. It has also been reported in Great Britain, Ireland, Germany, Spain, Australia, and Japan (Marchiondo, 2020)

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Feeding:

Parasite within the lung parenchyma of dogs.

Biology and Ecology:

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Life Cycle:

Direct life cycle, no molluscan or annelid intermediate host required to develop to the infective stage.

• The L1 is directly infective to other dogs through ingestion in freshly passed feces; Coprophagia being the principal mechanism of transmission.
• The ingested L1 penetrates the intestinal wall, passes to the liver and then to the lungs as early as 6 h after oral ingestions
• The larvae molt in the lung parenchyma and mature to the adult stages in 5-6 weeks.
• Females deposit the thin-shelled eggs in the lungs.  Eggs develop to infective L1 which  hatch before being coughed into the intestinal tract and voided in the feces.
• Prepatent period is 32-35 days. (Marciondo, 2020)

Ecophysiological Parameters:

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Ecosystem Functions and Services:

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Management:

Identification is important. Prior to the 1970s, lesions associated with F. hirthi infection may have been confused with pathological changes induced by drugs, oncogenic influences, and other pathological organisms,  possibly leading to misinterpretations and false testing result.

In 1994 98% of Beagle dogs in toxicological studies demonstrated lungworm associated lesions associated with F. hirthi infection in Germany.

Control programs of F. hirthi in Beagle breeding colonies have been successful by treating all stud, nonpregnant, and nonlactating dogs with courses, of anthelminthics twice daily for 5 days and reperting the process after 24 weeks. (Marchiondo, 2020)

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References:

Marchiondo, A.A. 2020. Nematoda, Metastrongyloidea. Chapter 2 in Marchiondo, Cruthers and Fourie (eds) Parasiticide Screening Vol 2. Academic Pres

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Copyright © 1999 by Howard Ferris.
Revised: January 13, 2026.