Furry hosts and fungal guests: Investigating dermatophyte carriage in shelter and clinic cats and dogs of northern Portugal

Dermatophytosis is a widespread fungal infection affecting both animals and humans, commonly known as ringworm. Dermatophytosis results in the breakdown of keratin, leading to skin, hair, and claw lesions, and has an important global prevalence that is often underestimated. While typically self-limiting, dermatophytosis can pose a severe risk due to its contagious nature, particularly in shelters. This study aimed to assess the prevalence of dermatophytes in the fur of dogs and cats in animal shelters and pet clinics, shedding light on the importance of understanding and managing this infectious disease in both animal and human populations. To better understand the epidemiology of dermatophytes in Portugal, a study was conducted from March to May 2022. The prevalence of dermatophyte isolation in culture was evaluated. A total of 341 animals, 286 (83.9%) dogs and 55 (16.1%) cats were studied, and 45.0% (n=157) of the animals were from shelters, while 54.0% (n=184) were from clinics. Twenty-eight (8.2%) animals had skin lesions, and of these, four (14.3%) tested positive for dermatophytes. Dermatophytes were isolated from 12/341 studied animals. The prevalence of Microsporum canis was 3.2% (confidence interval [CI] 95%: 1.6-5.7%), and the prevalence of Microsporum audouinii was 0.3% (CI 95%: 0.0-1.6%). Healthy dogs and cats without clinical signs were found to carry dermatophytes, stressing the potential for these animals to act as subclinical carriers and emphasizing the importance of pet-owner awareness regarding zoonotic risks and the need for ongoing research and surveillance to mitigate the risks associated with fungal infections.