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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
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===Gross pathology===
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*Lesions begin as small circular patches on the ventral midline with serous exudate. 
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*These enlarge and coalesce producing lesions 25cm or more in diameter. 
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*Hemorrhage develops along the periphery while the older, central areas develop scabs or dry crusts. 
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*Healing lesions are alopecic, lichenified plaques.
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*Lesions may also occur on the flank, udder, teats, face and neck.
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===Histopathology===
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*Adult parasites occur within cystic diverticula of hair follicles or free within the adjacent dermis. 
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**Parasites may have lateral cords and lateral cuticular projections. 
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**The thick intestine is distinctive.
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**Microfilariae within uteri is the key feature. 
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***Microfilariae also occur free within the dermis, in dermal lymphatics, or in the surface exudate. 
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*There is little dermal reaction to adults in cystic hair follicles, but their presence within the dermis elicits eosinophilic and mononuclear inflammation.
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===Differential diagnosis===
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# Pelodera strongyloides: 
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#*Rhabditid parasite, adults 1-1.5mm long, found in follicles
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#*uteri contain eggs, not microfilaria.
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# Dermatophytosis (Trichophyton verrucosum is most common)
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# Mange (Chorioptes bovis)
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# Fly bite dermatitis
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# Contact dermatitis
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# Zn-responsive dermatitis
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# Other subcutaneous filarid parasites: 
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#*Parafilaria bovicola (adult worms 30-70mm long, found coiled in nodules in subcutaneous and intramuscular connective tissues; not seen in US)
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#*Onchocerca gutterosa (adult worms 60mm long, found in nuchal ligament and subcutaneous connective tissues).
    
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{{unfinished}}
 
[[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]]
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