Descriptive epidemiology and test characteristics of cats diagnosed with Microsporum canis dermatophytosis in a Northwestern US animal shelter

Abstract

Objectives The aims of this descriptive study were to identify risk factors for feline Microsporum canis infection at shelter intake, to describe screening test accuracy, and to refine confirmatory testing time frames. Methods Database records for the general feline population and intake data, medical records and fungal culture logs for cats diagnosed with M canis at a limited admissions shelter were accessed retrospectively for a period of 2 years. Results The feline population at the study shelter had a prevalence of M canis of 1.8% (95% confidence interval [CI] 1.6–2.0%). Kittens were eight (95% CI 4.8–13.5) times more likely to present with dermatophytosis than adults. Although more cats presented with M canis during summer and autumn, season was not significant when the model was controlled for age. Owner-surrendered cats were half as likely (95% CI 0.41–0.77) as transported cats to be diagnosed with M canis. Wood’s lamp examinations had a sensitivity of 66.8% (95% CI 60.2–73.4) and a specificity of 74.8% (95% CI 64.2–85.1) compared with dermatophyte test medium (DTM) culture. In 78.8% (95% CI 61–91) of littermate or household groups with mixed Wood’s lamp results, all cats were DTM culture positive. Under consistent incubation conditions, 202/202 diagnostic DTM plates for M canis-infected cats showed recognizable colony growth before 7 days (median 4 days), and 19/19 fomite carrier cat cultures showed growth before 12 days (median 5 days). Conclusions and relevance Applying the results of this study to shelter protocols could optimize diagnostic approaches and shorten the length of stay for shelter cats and kittens, resulting in streamlined shelter operations and improved feline welfare.

A review: the prevalence of dermatophytosis on cats in Indonesia and Turkey

“…Based on the age of the sampled animals, the prevalence of feline dermatophytosis in this study from the highest to the lowest was 36/181 (19.9%) for cats younger than one year, 9/136 (6.6%) for cats between one and three years of age, and 7/111 (6.3%) for cats older than three years of age (Table 2). As reported by [17], 11/17 (64.7%) of dermatophytepositive cats were younger than one year, while [3,18] reported that cats aged 6 months and younger were more likely to have greater prevalence. Increased susceptibility to dermatophytosis in kittens can be impaired by a variety of causes, including immaturity of the immune system, insufficiency of past immunity, skin micro trauma induced by siblings or ectoparasites, and frequent close contact with other cats during socialization [3,17].…”

“…As reported by [17], 11/17 (64.7%) of dermatophytepositive cats were younger than one year, while [3,18] reported that cats aged 6 months and younger were more likely to have greater prevalence. Increased susceptibility to dermatophytosis in kittens can be impaired by a variety of causes, including immaturity of the immune system, insufficiency of past immunity, skin micro trauma induced by siblings or ectoparasites, and frequent close contact with other cats during socialization [3,17]. The present study found a moderately higher incidence of dermatophytes (13.4%) in female cats than in male cats (10.7%), as compared to a study in Eastern India that recorded a higher prevalence of male cats than female cats and the disparity in prevalence between female and male cats may be due to unequal number of samples of each sex [7].…”

“…Dermatophytosis or commonly known as ringworm is a fungal infection on the superficial layer of the skin primarily caused by dermatophytes that have the capability to invade the stratum corneum of the epidermis and the keratinized tissues such as nails and hairs of the infected animals [1][2] . While feline dermatophytosis is clinically mild and self-limiting, this disease has caused concern because it is highly contagious, zoonotic and environmentally difficult [3]. Microsporum canis were the most isolated pathogen of the dermatophytepositive cats while other species such as Microsporum gypseum, Microsporum pericolor and Trichophyton sp.…”

“…Previously, [3] concluded that based on several studies, cats seem to be more vulnerable towards dermatophytes when they aged younger than one year old, cats with long-haired coats, Persian breeds, cats diagnosed with feline immunodeficiency virus (FIV) and few exposure factors such as cats living in cattery or shelters or living outside, warm or humid climate and warm season. Humidity and temperature are examples of environmental factors that give the dermatophytes a beneficial atmosphere to grow and infect hosts.…”

Comparison of Adhesive Tape Impression Cytology, Hair Plucks, and Fungal Culture for the Diagnosis of Dermatophytosis in Dogs and Cats

“…It can possibly be attributed to an increased fungal load on kittens’ and cats’ haircoats and to an outbreak of infection due to skin microtrauma. In this study, most of the feline patients were kittens, and skin traumas in this group can occur, as queens overzealously groom their kittens with their keratinous tongue papillae, or during fighting or playing with their littermates [ 33 ]. Additionally, kittens have reduced grooming tendencies and therefore the fungal elements are not mechanically removed, leading to an increase in fungal elements.…”