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

Cryopreserved tissue samples were sent for molecular analysis by genotype-discriminating quantitative real-time PCR, performed by a commercial reference laboratory (IDEXX Laboratories), as described previously. 9 The M1058L point mutation was detected in the FCoV spike gene, but the point mutation S1060A was not found. Quantitative PCR for FCoV of a peripheral blood sample yielded negative results (limit of detection: 1 × 10 3 RNA copies/ml), 10 indicating that the positive detection of FCoV in the skin lesion was not caused by contamination with virus from the peripheral blood. To improve anaemia, the cat received a blood transfusion from a donor cat with blood type A after a crossmatch test. The cat also received intravenous fluid therapy to treat dehydration. The anaemia improved temporarily after the blood transfusion (PCV 27.9%; erythrocytes 585 × 10 4 cells/µl; haemoglobin 9.6 g/dl) but worsened again owing to a relapse 28 days after the initial presentation (PCV 11.7%; erythrocytes 228 × 10 4 cells/µl; haemoglobin 3.7 g/dl). Fever and dehydration improved from day 1 after therapy and, together with the skin lesion and nasal discharge, remained stable for 10 days. The cat left the hospital at the request of the owner. A telephone interview with the owner 5 months after discharge revealed that the cat was still alive. The cat was lost to follow-up afterwards.