First identification of a single amino acid change in the spike protein region of feline coronavirus detected from a coronavirus-associated cutaneous nodule in a cat

Osumi, Takafumi; Mitsui, Ikki; Leutenegger, Christian M; Okabe, Ryo; Ide, Kaori; Nishifuji, Koji

Three studies have reported cutaneous manifestations in cats with FIP. [4] [5] [6] Two of those cases had clinical signs of the non-effusive form of FIP, with ocular and/or kidney involvement, whereas the third case had clinical signs of the mixed form of FIP, with ocular and renal involvement as well as pleural effusion. All three cats in these studies were <2 years old, and they developed papular-to-nodular skin lesions. Histopathologically, the skin lesions reported previously were characterised by a perivascular pyogranulomatous inflammatory reaction in the dermis to subcutis. The presence of coronavirus antigen in macrophages within the skin lesions was confirmed by immunohistochemistry in all three cases. However, genetic evidence of mutated FCoV in the cutaneous lesions of FIP has not been reported. Here, we describe a feline case in which a nucleotide mutation in the FCoV spike gene was identified by real-time reverse transcription (RT)-PCR in a coronavirus-associated cutaneous nodule. The mutation was consistent with previous FCoV mutations commonly associated with FIP. 7