Filaroides spp

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First-stage larva of F. osleri[1]
Adult F. osleri in a nodule, resulting in tracheal stenosis[1]

Filaroides spp are a nematode parasite of dogs in North America.

Species which are pathogenic to dogs include:

  • Filaroides osleri (formerly Oslerus osleri)
  • Filaroides hirthi

Adult F. osleri form nodules in the trachea and bronchi of dogs, where females deposit eggs that are transported via cilia and coughing into the oropharynx, where they are swallowed and pass out into the feces. The first stage larvae which develop in the soil of dog's habitat are directly infective and dogs reinfect themselves through ingestion of regurgitated stomach contents, or via feces from other dogs. Infection may also pass via oral transfer from bitches to pups during feeding. The prepatent period is 6 - 7 months[2].

These parasites commonly cause verminous tracheobronchitis[3], tracheal stenosis[4] and pneumonia[5] which can appear similar clinically to kennel cough. In younger dogs, acute onset dyspnea is common in heavy parasitism and complications with other diseases such as distemper are not uncommon[6].

Diagnosis is based on presenting clinical signs and evidence of eggs on coprological examination, which can be difficult as eggs are not always found[7]. Fecal floatation using the Baermann technique and tracheal washes appear to be more successful at identifying this parasite.

Radiography of the chest often reveals a diffuse pulmonary infiltrate throughout the lungs. Haematological abnormalities usually reflect a neutrophilia and eosinophilia[8].

A differential diagnosis would include other tracheobronchial parasites such as Angiostrongylus vasorum, Oslerus osleri and Crenosoma vulpis.

Treatment is relatively effective with ivermectin (single dose of 0.2 mg/kg)[9], selamectin or moxidectin.

References

  1. 1.0 1.1 Uni of Pennsylvania
  2. Bowman, DD (2009) Georgis' parasitology for veterinarians. Elsevier Saunders, Missouri. pp:190
  3. Yao C et al (2011) Filaroides osleri (Oslerus osleri): two case reports and a review of canid infections in North America. Vet Parasitol 179(1-3):123-129
  4. Kotani T et al (1995) Lungworm, Filaroides osleri, infection in a dog in Japan. J Vet Med Sci 57(3):573-576
  5. Caro-Vadillo A et al (2005) Verminous pneumonia due to Filaroides hirthi in a Scottish terrier in Spain. Vet Rec 157(19):586-589
  6. Carrasco L et al (1997) Massive Filaroides hirthi infestation associated with canine distemper in a puppy. Vet Rec 140(3):72-73
  7. Pinckney RD et al (1988) Filaroides hirthi infection in two related dogs. J Am Vet Med Assoc 193(10):1287-1288
  8. Torgerson PR et al (1997) Filaroides hirthi verminous pneumonia in a West Highland white terrier bred in Ireland. J Small Anim Pract 38(5):217-219
  9. Bauer C & Bahnemann R (1996) Control of Filaroides hirthi infections in Beagle dogs by ivermectin. Vet Parasitol 65(3-4):269-273