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  • Caused by Stephanofilaria stilesi
  • Occurs in cattle, buffalo, goats
  • Transmitted by flies
  • Affects ventral midline (other species affect different areas of body)
  • Grossly:
    • Foci extending to large areas
    • Errect hairs, epidermal haemorrhage, serum exudate -> crusts
  • Microscopically:

Gross pathology

  • Lesions begin as small circular patches on the ventral midline with serous exudate.
  • These enlarge and coalesce producing lesions 25cm or more in diameter.
  • Hemorrhage develops along the periphery while the older, central areas develop scabs or dry crusts.
  • Healing lesions are alopecic, lichenified plaques.
  • Lesions may also occur on the flank, udder, teats, face and neck.


  • Adult parasites occur within cystic diverticula of hair follicles or free within the adjacent dermis.
    • Parasites may have lateral cords and lateral cuticular projections.
    • The thick intestine is distinctive.
    • Microfilariae within uteri is the key feature.
      • Microfilariae also occur free within the dermis, in dermal lymphatics, or in the surface exudate.
  • There is little dermal reaction to adults in cystic hair follicles, but their presence within the dermis elicits eosinophilic and mononuclear inflammation.

Differential diagnosis

  1. Pelodera strongyloides:
    • Rhabditid parasite, adults 1-1.5mm long, found in follicles
    • uteri contain eggs, not microfilaria.
  2. Dermatophytosis (Trichophyton verrucosum is most common)
  3. Mange (Chorioptes bovis)
  4. Fly bite dermatitis
  5. Contact dermatitis
  6. Zn-responsive dermatitis
  7. Other subcutaneous filarid parasites:
    • Parafilaria bovicola (adult worms 30-70mm long, found coiled in nodules in subcutaneous and intramuscular connective tissues; not seen in US)
    • Onchocerca gutterosa (adult worms 60mm long, found in nuchal ligament and subcutaneous connective tissues).