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Description
A group of diseases affecting the epidermis caused by dermatophilus congolensis . Causes a range of conditions in large animals including rain scald in horses and strawberry foot rot in sheep. Lesions typically involve exudative dermatitis with scab formation.
Signalment
Can be seen in animals of all ages but most commonly occurs in young animals who are chronically exposed to moisture. Affets horses, sheep, cattle, goats, pigs and rarely dogs and cats.
Diagnosis
Can often make a diagnosis on history and physical exam. Impression smears can also be useful when stained with either gram stain or Giemsa and examined microscopically. Additionally it is possible to culture material from the crusts however this can be difficult due to the slow- growing nature of the pathogen.
History and Clinical signs
Lesions commonly occur followng heavy rainfall and commonly affectsthe dorsum of animals. Any previous trauma or damage to the skin can predispose to infection. Blood-sucking insects are also thought to be involved in transmission.
Equine dermatophilosis Three clinical syndromes have been documented: rain scald, Mud fever and grease heel. Tpically focal lesions develop into crusts and thick scabs covered by layers of pus. When scabs are removed the hair is taken wit them and alopecia results.
- Papules, serous, exudative matting of hair, raised crusty scabs
- Scab formation more prominent in sheep and cattle than in horses
- Lesions may resolve within weeks if dry weather, or may progress
- Treatment:
- Parenteral antibiotics e.g oxytetracycline, pr penicillin-streptomycin combinations
- Caused by Dermatophilus congolensis
- Affects cattle, horses, sheep mainly
- More common in wet and warm weather
- Transmotted from animal to animal
- Lesions tend to form on dorsal back and extremities
- Associated with skin trauma, prolonged wetting or parasites
- -> penetration of zoospores
- Bacteria proliferate in outer sheath of hair follicles and superficial epidermis
- Gram-positive, filamentous branching organisms, subdivided longitudinally and transversly
- Causing:
- Acute inflammatory response -> neutrophil migration through dermis and epidermis -> formation of microabscesses
- Further penetration of bacteria is thus prevented
- Regenerated epidermis is invaded again by remaining organisms
- Repeated reinfection -> multilaminated pustular crusts
- Grossly:
- Papules, pustules, crusts may coalesce and mat the coat
- Microscopically:
- Hyperplastic superficial perivascular dermatitis
- Multilaminated crusts, alternating keratin and inflammatory cell layers