Outbreak of dermatophytosis in farmed mink in the USA

the crop (over 700 kits) developed skin lesions similar to those noted in previous years. Affected kits were in good health overall and appeared normal at birth. Multiple skin lesions became noticeable by three weeks of age, coinciding with the initial hair growth. These alopecic lesions were 1 to 5 cm in diameter and rimmed with a dry, brown-grey scale, and were believed to be somewhat pruritic. Although the lesions could be found anywhere on the body, the most common sites were the head, feet and dorsal neck (Fig 3). Dark colour phase kits were almost twice as frequently affected as dilute colour kits. Most of the litters were spared, and the distribution of affected litters within the shed appeared random. Within afflicted litters, most kits displayed lesions. The ranchers reported that raised, crusted lesions had been visible on a few of the dams just before whelping. Skin scrapings from the kits were again negative for ectoparasites. An affected kit was euthanased and submitted to the OSU VDL for postmortem examination. Grossly, the external findings were as described above and no internal abnormalities were noted. A potassium hydroxide digestion of the hair shafts demonstrated hyphal invasion of the shafts and arthrospores 3 to 5 μm in diameter. Aerobic bacterial culture of the skin yielded no significant isolates, but two colony types of Trichophyton species were again recovered on fungal culture. In addition to a positive urea test, a positive hair perforation test was obtained, as is typical of T mentagrophytes (Campbell and Stewart 1980). Histological findings included a mild to moderate orthokeratotic and parakeratotic hyperkeratosis which extended into the follicOutbreak of dermatophytosis in farmed mink in the USA