Dermatophytosis, usually caused by Microsporum canis, is the most common fungal infection in cats worldwide and one of the most important infectious skin diseases in this species. The diagnosis is challenging and the use of fungal cultures is quite useful but requires laboratorial experience and needs at least 21 days to get the result.

The aim of this study was to develop and evaluate the diagnostic efficacy of enzyme immunoassays ELISA (enzyme-linked immunosorbent assay) and Western blot (WB) for the diagnosis of feline dermatophytosis caused by M. canis. Seventy cats of various ages were divided into three groups: S (symptomatic, n=20), AS (asymptomatic, n=30), and N (negative, n=20). All animals were submitted to mycological cultivation and blood samples for carrying out the serological tests. A significant difference (p<0.05, Kruskal-Wallis) was found between IgG-specific levels of sera of M. canis positives (symptomatic and asymptomatic) and negatives. There was no statistical difference between symptomatic and asymptomatic groups. The test ELISA has good sensitivity (94%) and high specificity (75%). The sensitivity is higher than that of direct microscopic hair examination and similar to that of fungal culture. The WB technique detected 13 bands and the 50 kDa protein was considered the most immunogenic protein, observing reactivity in 83.3% in the symptomatic group and 66.6% in the asymptomatic group. The study concludes that the ringworm induces clear humoral immune response and the ELISA and WB techniques are effective for the diagnosis of dermatophytosis caused by M. canis in symptomatic and asymptomatic cats.