P‐82 Mycosis fungoides in a cow with bovine leukosis virus

Abstract

Mycosis fungoides (MF) is a cutaneous manifestation of a T‐cell lymphoma, which has been diagnosed in various species including one case in a 10‐month‐old calf. However, we are not aware of a case report of MF in an adult bovine or of this disease being associated with bovine leukosis virus infection. We report a case of a cow diagnosed with MF‐like disease and bovine leukosis virus. A 6‐year‐old Holstein cow was presented with a history of cutaneous masses, anorexia, weight loss and reduced milk production. This cow had delivered a healthy calf 49 days before admission. Two days before parturition, the owner had observed the first skin nodules, which had progressively enlarged. Physical examination revealed multiple alopecic hyperpigmented tumors, ranging from 2 to 7 cm in diameter, which were painful on palpation. Some of the lesions were ulcerated, although most were covered by dry and rough epidermis. No abnormality other than the skin lesions and emaciation was detected on clinical examination. Complete blood count revealed leukocytosis (23,450/μL), lymphocytosis (17,588/μL) and atypical lymphocytes. Plasma protein concentration was 6.8 g/dL. Agar gel immunodiffusion test for bovine leukosis virus was positive. Histopathological findings included a diffuse dermal lymphocytic infiltration and epitheliotropism. Immunohistochemistry revealed that neoplastic lymphocytes were CD3+ and CD79a– cells. Due to the poor prognosis, the cow was euthanized. This report describes a rare MF d’emblée‐like condition in a cow with bovine leukosis virus. Funding: Self‐funded.