3.1. Prevalence of FCoV in southwest China
From May 2017 to December 2020, 23 FIP-suspected samples of ascites fluid and 150 diarrheal fecal samples from veterinary hospitals and catteries in southwest China were tested using RT-nPCR amplification. Of the 173 samples, 139 (80.35%, 95 % CI; 73.6%–86%) were positive for FCoV (Table 1), including the positive rates of FCoV in FIP-suspected cat; the rates in diarrheal cats were 95.65% (22/23, 78.1%–99.9%) and 78% (117/150, 95% CI; 70.5%–84.3%), respectively. As shown in Table 2, the positive rates of FCoV in multi-cat environments and single-cat households were 85% (79/93, 95% CI: 76%–91.5%) and 66.67% (38/57, 95% CI: 52.9%–78.6%), respectively. These results suggest that FCoV is highly prevalent in southwest China. The detection rate of FCoV was significantly associated with the cat’s living environment (p = 0.014) and clinical symptoms (p = 0.05).
The 139 positive samples were typed using type I and II FCoV typing primers. Of the 127 successfully typed FCoV-positive samples, type I FCoV was predominant, accounting for 87.77% (122/139, 95% CI: 81.1%–92.7%), and type II FCoV accounting for 41.01% (57/139, 95% CI: 32.7%–49.7%). Eleven other samples failed typing, possibly due to the low viral load in samples or the potential mismatching between primers and templates. Interestingly, co-infection with type I and II FCoV were detected in 51 samples (36.69%, 95% CI: 28.7%–45.3%), the first such report in mainland China, and the detection rate of co-infection with types I and II FCoV were significantly higher in the multi-cat environment than in the single-cat environment (p< 0.01; Table 2).