Difference between revisions of "Stephanofilaria stilesi"
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==Stephanofilaira stilesi== | ==Stephanofilaira stilesi== | ||
Revision as of 16:18, 22 September 2008
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Stephanofilaira stilesi
- Dermall lesions of cattle in USA
Lifecycle
- The infective larvae develop in the horn fly - Haematobia irritans
- Flies ingest microfilaria as they feed on cutaneous lesions.
- Microfilaria develop into L3 larvae in the hornfly over 18-21 days.
- Infective L3 larva are deposited into the skin when the fly bites again, where they grow into adult worms.
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.
Histopathology
- 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
- Pelodera strongyloides:
- Rhabditid parasite, adults 1-1.5mm long, found in follicles
- uteri contain eggs, not microfilaria.
- Dermatophytosis (Trichophyton verrucosum is most common)
- Mange (Chorioptes bovis)
- Fly bite dermatitis
- Contact dermatitis
- Zn-responsive dermatitis
- 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).
Stephanofilaria assamensis
- 'Humpsore'
- Bos indicus in India