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**[[Skin Glossary - Pathology|Epidermal hyperkeratosis, parakeratosis, acanthosis]], eosinophilic microabscesses and crusts
**[[Skin Glossary - Pathology|Epidermal hyperkeratosis, parakeratosis, acanthosis]], eosinophilic microabscesses and crusts
===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).
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[[Category:Integumentary System - Helminth Infections]]
[[Category:Integumentary System - Helminth Infections]]
[[Category:To_Do_-_Dermatology]][[Category:To Do - Minor]]
[[Category:To_Do_-_Dermatology]][[Category:To Do - Minor]]