• Microsporum canis: Most common cause in cats (90%+) and dogs (70%+)
• Microsporum gypseum: A soil-dwelling fungus; more common in dogs
• Trichophyton mentagrophytes: Less common; often from rodent exposure

Dermatophytes spread through:

• Direct contact with infected animals
• Contact with contaminated objects (fomites): brushes, bedding, collars
• Environmental contamination from infected hair and spores
• Spores can remain viable in the environment for 18+ months

Cats may show:

• Circular patches of hair loss (alopecia)
• Scaling, crusting, or flaking skin
• Broken hair shafts giving a "stubbled" appearance
• Red, irritated skin margins
• Occasionally, nodular lesions (kerions)
• Some cats are asymptomatic carriers showing no lesions

Common locations:

• Face and ears
• Paws
• Tail
• Can spread to entire body

Dogs typically show:

• Circular to irregular patches of hair loss
• Scaling and crusting
• Folliculitis (inflammation of hair follicles)
• Red, inflamed skin
• Kerions (nodular, oozing lesions)
• Onychomycosis (nail bed infection) in some cases

Common locations:

• Face and muzzle
• Ears
• Front legs and paws
• Can become generalized

Not all ringworm looks "classic":

• May mimic bacterial skin infections
• Can look like allergic dermatitis
• May cause only mild scaling without obvious hair loss
• Kerions can look like tumors or abscesses
• Some animals have subclinical infections

Animals more susceptible to infection:

• Young animals (immature immune system)
• Immunocompromised animals
• Animals in shelters or crowded environments
• Long-haired breeds
• Animals with concurrent skin disease
• Dogs: Yorkshire Terriers, Jack Russell Terriers
• Cats: Persians, Himalayans

• Uses ultraviolet light to detect fluorescence
• Positive: Apple-green fluorescence on infected hairs
• Only ~50% of M. canis strains fluoresce
• Other species typically don't fluoresce
• False positives from medications, debris, bacteria
• Useful screening tool but NOT diagnostic alone

• Pluck hairs from lesion margins
• Clear with potassium hydroxide (KOH) or use chlorphenolac
• Look for fungal spores (ectothrix or endothrix patterns) around hair shafts
• Sensitivity: 40-70% depending on technique
• Quick results but requires experience to interpret

• Dermatophyte Test Medium (DTM) or Sabouraud's agar
• Samples: plucked hairs, scale, toothbrush sample
• Color change on DTM (yellow to red) with white cottony growth
• Takes 7-21 days for results (usually 7-14 days)
• Allows species identification
• Most reliable diagnostic method

• New toothbrush brushed over entire coat for 2-3 minutes
• Excellent for screening cats (especially asymptomatic carriers)
• Toothbrush bristles cultured on fungal media
• Standard method for shelter screening

• Rapid results (same day or next day)
• Very sensitive
• Can detect dead fungal elements (may remain positive after cure)
• Available at reference laboratories
• Useful for confirming negative culture results

• May be needed for atypical presentations
• Shows fungal elements in hair follicles
• Special stains (PAS, GMS) help visualization
• Helps rule out other skin conditions

Lime Sulfur Dip (2-4%)

• Very effective; gold standard topical treatment
• Dip or sponge on entire body twice weekly
• Leave on—do not rinse
• Disadvantages: strong odor, stains light fur/fabric

Miconazole/Chlorhexidine Shampoo

• Effective combination therapy
• Use 2-3 times weekly
• Leave on for 10 minutes before rinsing
• Less effective than lime sulfur but easier to use

Enilconazole

• 0.2% rinse/dip every 3-4 days
• Not available in all countries
• Very effective

Topical Antifungal Creams

• Miconazole, clotrimazole, terbinafine creams
• Use only for localized lesions
• Not sufficient as sole treatment
• Apply to lesions 2-3 times daily

Itraconazole

• Drug of choice for many veterinarians
• Cats: 5-10 mg/kg once daily
• Dogs: 5-10 mg/kg once daily
• Pulse therapy: 1 week on, 1 week off (cats)
• Give with fatty food for absorption

Terbinafine

• Excellent efficacy; fungicidal
• Cats: 30-40 mg/kg once daily
• Dogs: 30-40 mg/kg once daily
• Can be given with or without food

Fluconazole

• Alternative option
• Good tissue penetration
• Less effective than itraconazole or terbinafine

Griseofulvin

• Older drug, still effective
• Higher side effect potential
• Not recommended in pregnant animals or breeding animals
• Avoid in FIV+ cats (bone marrow suppression)

• Minimum 6-8 weeks of systemic therapy
• Continue until clinical cure PLUS negative fungal cultures
• Typically need two consecutive negative cultures 2-4 weeks apart
• Stopping early leads to relapse

• Dermatophyte spores can survive in the environment for 18+ months
• Reinfection from contaminated environment is common
• Environmental treatment reduces treatment duration
• Prevents spread to other animals and humans

Step 1: Remove Organic Material

• Vacuum thoroughly (dispose of bags/empty canisters outdoors)
• Remove all pet hair from surfaces
• Wash all bedding, blankets, and fabric items
• Dispose of heavily contaminated items that can't be cleaned

Effective disinfectants:

• Dilute bleach (1:10 to 1:32): Most accessible and effective
• Accelerated hydrogen peroxide: Excellent efficacy
• Enilconazole: Environmental antifungal spray
• F10 disinfectant: Veterinary-grade option

Areas to Treat

• Floors, especially cracks and crevices
• Furniture
• Cat trees and scratching posts (consider disposal)
• Carriers, crates, and cages
• Grooming tools (replace brushes and combs)
• HVAC filters
• Vehicles if pet travels in them

• Clean and disinfect at least twice weekly during treatment
• More frequently in multi-animal households
• Continue until pet is culture-negative

• Confine infected animals to one easily cleaned room
• Use hard, non-porous surfaces when possible
• Limit contact between infected and non-infected animals
• Wear protective clothing when handling infected animals
• Wash hands thoroughly after contact

Clinical Cure

• Resolution of all skin lesions
• Hair regrowth in affected areas
• No new lesions appearing

Mycological Cure

• Two consecutive negative fungal cultures
• Cultures taken 2-4 weeks apart
• Clinical signs may resolve before cultures become negative

• Stopping treatment when lesions resolve (cultures may still be positive)
• Not treating the environment
• Not treating all animals in household
• Using topical therapy alone
• Inadequate treatment duration

If ringworm recurs:

• Re-evaluate for resistant strains
• Check for underlying immunocompromise
• Ensure all in-contact animals were treated
• Intensify environmental decontamination
• Consider underlying disease workup

Ringworm from pets typically causes:

• Circular, red, scaly lesions on skin (tinea corporis)
• Intensely itchy patches
• Can affect any body area, commonly arms, face
• Usually responds well to treatment

More susceptible to infection:

• Children
• Elderly individuals
• Immunocompromised people (HIV/AIDS, chemotherapy, transplant recipients)
• People with damaged skin

• Wash hands after handling infected animals
• Wear gloves and long sleeves when treating
• Change and wash clothes after contact
• Don't allow infected animals on beds/furniture
• Keep infected animals away from high-risk individuals
• Seek medical attention if skin lesions develop

• Consult a physician or dermatologist
• Treatment usually involves topical antifungal cream
• Severe or widespread cases may need oral medication
• Treat all infected family members simultaneously
• Continue treating the pet to prevent reinfection

• Inform owners of zoonotic risk at diagnosis
• Provide written instructions for protection
• Recommend handwashing and protective measures
• Advise seeking medical care if lesions develop

Shelters face unique challenges:

• High animal turnover
• Crowded conditions
• Stressed, immunocompromised animals
• Limited resources for treatment
• Risk of outbreak spread

• Screen all incoming cats (especially long-haired breeds)
• Toothbrush culture technique for all new arrivals
• Quarantine until culture results available
• Wood's lamp screening (but remember 50% false negative rate)

If ringworm is detected:

• Immediately isolate affected animals
• Identify all potentially exposed animals
• Culture all exposed animals
• Implement intensive cleaning protocols
• Establish dedicated ringworm treatment area

• Treat affected animals in designated area
• Use dedicated staff or volunteers for ringworm room
• Ensure adequate training for staff
• Document all treatments and culture results
• Consider foster placement for treatment

• Can adopt out with informed consent
• Provide treatment supplies and instructions
• Schedule follow-up cultures
• Ensure adopters understand commitment
• Written contract about treatment completion

• Adequate space per animal
• Good ventilation
• Regular screening of new arrivals
• Prompt isolation of suspicious cases
• Routine environmental cleaning
• Stress reduction measures