Which diagnostic step is recommended for a cat with facial crusts to evaluate potential zoonotic infection?

Which diagnostic step is recommended for a cat with facial crusts to evaluate potential zoonotic infection?

• A. Scrape & culture cat lesions
• B. Blood culture
• C. Urinalysis
• D. Radiography

Answer: (A)

Suspected dermatophytosis (ringworm) in a cat with facial crusts raises a zoonotic risk, so obtaining a tissue sample from the lesion for culture is the most informative next step. Superficial skin scraping or hair plucking collects keratin-containing material where dermatophytes grow, and culturing these samples allows the organism to be identified definitively. This not only confirms infection but also guides treatment and informs precautions to limit transmission to people and other animals. Blood culture isn’t helpful here because dermatophytosis is a superficial fungal infection, not a bloodstream issue. Urinalysis and radiography won’t reveal the fungal cause of facial crusts and are not diagnostic for dermatophyte infection.

Suspected dermatophytosis (ringworm) in a cat with facial crusts raises a zoonotic risk, so obtaining a tissue sample from the lesion for culture is the most informative next step. Superficial skin scraping or hair plucking collects keratin-containing material where dermatophytes grow, and culturing these samples allows the organism to be identified definitively. This not only confirms infection but also guides treatment and informs precautions to limit transmission to people and other animals.

Blood culture isn’t helpful here because dermatophytosis is a superficial fungal infection, not a bloodstream issue. Urinalysis and radiography won’t reveal the fungal cause of facial crusts and are not diagnostic for dermatophyte infection.