Dermatology

What are the main functions of bovine skin?

• Provides shape and form

• Acts as an enclosing barrier

• Regulates temperature

• Produces adnexa (hair, glands)

• Serves as a reservoir

• Contributes to immunoregulation

• Responsible for sensory perception

What causes dermatophytosis in cattle, and how is it spread?

• Ringworm → Caused by Trichophyton verrucosum and T. mentagrophytes

• Very common in cattle

• Transmission: direct animal-to-animal contact and fomites

What conditions predispose cattle to ringworm infections?

• Young animals

• Overcrowding

• Poor nutrition

• Indoor housing

• Warm, humid environments

How does dermatophytosis develop, and how does it present?

• Fungus invades fully keratinized tissue (non-living)

• Typically affects head and trunk

• Appearance: multifocal alopecia, heavy crusting, possible ring pattern

• Erythema may be absent or hidden under crusts

What diagnostic methods are used for dermatophytosis?

• Direct microscopy: skin scraping or hair-shaft exam

• Fungal culture: use broken hairs, avoid large crusts, use specialized media

How is dermatophytosis treated?

• Topicals: lime sulfur, enilconazole, miconazole/ketoconazole shampoos, 3–4% chlorhexidine

• Vaccines available for T. verrucosum and T. mentagrophytes
  (Also often self-limiting)

What organism causes dermatophilosis and under what conditions does it proliferate?

• Caused by Dermatophilus congolensis

• Requires moisture + skin damage → zoospores germinate → penetrate epidermis

• Spread by direct contact or mechanical vectors; chronic carriers are common

Where do lesions commonly appear, and what do they look like?

• Sites: distal limbs, dorsum, muzzle, pinnae

• Lesions: encrusted, proliferative dermatitis; papules, ulcerations, pus-filled crusts; alopecia
  (“Paintbrush” lesions)

What key diagnostic finding is characteristic for dermatophilosis?

• Impression smear showing railroad-track cocci

• Can also use bacterial culture, histopathology, PCR

What is the recommended treatment approach?

• Remove animals from moisture

• Remove crusts

• Topicals: iodophors, lime sulfur

• Systemic therapy only if severe: penicillin, TMS, long-acting oxytetracycline

Which species are commonly affected by papillomas and what is the typical course?

• Cattle: very common; appear <2 yrs; often regress; problematic on teats, penis, interdigital space, GI

  • Bovine papillomavirus (BPV)

  • Carcinogenic, double-stranded DNA

  • Generally species-specific (one exception exists)

  • Site-specific; >20 types; 5 major subgroups

• Goats: rare; head/neck or mammary

• Sheep: rare

What are the five morphologic types of papillomas?

1. Typical — cauliflower

2. Pedunculated — narrow base

3. Atypical — flat, broad base

4. Filamentous — thin base, keratinized

5. Rice-form — very small

How do papillomas spread and how are they diagnosed?

• Transmission: direct contact, fomites (dehorning, tagging tools)

• Diagnosis: clinical appearance, biopsy, serology, PCR

What are the management and treatment options for papillomas?

• “Benign neglect” (most regress)

• Crushing, surgical removal, cryotherapy

• Autogenous vaccines

• Prevention: isolate, disinfect shared equipment, commercial/autogenous vaccines

What are the key identifying features of pseudocowpox?

• Cause: parapoxvirus

• Distribution: teats (most common), sometimes udder or scrotum

• Lesion progression: 2–3 mm papules → crust → circular spread → horseshoe/ring-shaped scabs in ~10 days

• Zoonotic (“milker’s nodules” on hands)

What virus causes Bovine Herpes Mammillitis and what lesions develop?

• Caused by Bovine Herpesvirus-2 (BHV-2)

• May be epidemic or endemic

• Distribution: oral, udder, or generalized

• Lesions: edema, pain, vesicles → ulcers → scabs

How is Bovine Herpes Mammillitis diagnosed and managed?

• Diagnosis: virus isolation, serum neutralization, histology

• Treatment: ulcers heal in 3–10 weeks; topical or systemic antimicrobials for secondary infection

• Management: segregate(wean), milk last, disinfect equipment, hand hygiene

What are the two forms of Bovine Cutaneous lymphosarcoma noted in cattle?

• Systemic lymphoma — BLV positive; may involve skin secondarily

• Cutaneous form — very rare; <3 years old; BLV negative

What does cutaneous lymphosarcoma look like and how is it treated?

• Distribution: neck, shoulders, back, croup

• Appearance: intradermal plaques with white-gray scabs

• Diagnosis: biopsy

• Treatment: may regress spontaneously; returns if systemic lymphoma develops; supportive care

What are the three types of photosensitization in cattle?

• Type I: ingestion of photodynamic agent

• Type II: congenital porphyrin metabolism abnormality

• Type III: liver disease → phylloerythrin accumulation

• Requirements: photodynamic agent, lightly pigmented skin, UV-A exposure

What areas are affected and what lesions are seen?

• Distribution: hairless or lightly pigmented skin

• Lesions: erythema, edema, painful skin → blisters, exudation → thickening, fissures → necrosis & sloughing

• Clinical signs may also reflect liver disease (if Type III)

How is photosensitization diagnosed and treated?

• Diagnosis: characteristic lesions, plant exposure history, elevated liver enzymes, liver biopsy, post-mortem

• Treatment: remove toxin source, avoid sunlight, wound management, feed low-quality grass hay or cereal hay (reduce chlorophyll intake)