The Siberian tiger (Panthera tigris altaica) is one of the largest felines, and is mainly found in Russian Far East, northeast of China and north of Korea. Currently, there are approximately 400 wild Siberian tigers globally, with only a few of these in China (Peng et al., 2020).Therefore, they are listed as level I protected animals by the Chinese government, are included in the Convention on International Trade

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The fact that wild felines are carriers of pernicious infectious viruses should be a major concern due to the potential cross-species transmission between the felines and human or domestic animals. However, studies on the virus in the captive wild felines, especially in tigers, are thin on the ground. In this study, we screened four infectious viruses, namely, feline parvovirus (FPV), feline coronavirus (FCoV), canine distemper virus (CDV), and influenza A virus (IAV), in the blood samples of 285 captive Siberian tigers (Panthera tigris altaica) and in the spleen samples of two deceased lions (Panthera leo), which were collected from 2019 to 2021 in three Siberian Tiger Parks from the northeast of China. Nucleic acids isolated from the blood samples collected from tigers and the spleen samples collected from two deceased lions were positive for FPV by PCR, and the positive rate was 4.6% (13/285) in tigers. Furthermore, the VP2 gene of FPV was amplified by nested PCR, and the sequences of the VP2 gene from these six FPV positive strains shared 98.3–99.9% homology with the reference. The key amino acid sites of VP2 protein were consistent with that of FPV reference strains. Phylogenetic analysis based on the VP2 gene showed that in this study, FPV-positive strains were grouped within the FPV clade and closely related to the Asian strains clade. The results of this study showed that FPV circulated in the captive Siberian tigers and lions in northeastern China and provided valuable information for the study of FPV epidemiology in wild felines. Therefore, we suggest that regular antibody monitoring and booster immunization for tigers should be performed.

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Our study investigated the prevalence of feline herpesvirus-1 (FHV-1), feline calicivirus (FCV), feline immunodeficiency virus (FIV), and feline leukemia virus (FeLV) in captive Siberian tigers in Northeastern China. A total of 324 blood samples and 33 nasopharyngeal swab samples of Siberian tigers collected from 2019 to 2021 in three cities were investigated by nested PCR. The results showed that 28.1% (91/324) tigers were infected with at least one virus; the positive rates of FHV-1, FCV, and FIV were 17.3%, 13.6%, and 0.9%, respectively; and the coinfection prevalence was 13.2%.No FeLV-positive sample was detected. And we found that the blood is the best for FCV, FIV, and FeLV detection, but nasopharyngeal swabs for FHV-1. By comparing the gD genes, TK gene, and gI gene of FHV-1, the homology of the three FHV-1 positive strains in this study was found to be 91.5%-99.9% shared with tigers and domestic cats. Based on a comparison of the nucleic acid sequences of 13 FCV strains, we found that the homology of strain HB-1926 with the other strains in this study was only about 77.7%, but shared 99.3% and 98.6% homology with Urnaba strain in American cat and TG1 strain in Chinese tiger, respectively. However, the other 12 FCV strains shared 87.1%-87.5% homology compared with the Chinese domestic cats. Phylogenetic tree analysis showed that the HB-1926 strain was not in the same clade as other strains.The fragments gag-p26, pol-RT, and pol-RNAse of Siberian tiger FIV shared more than 99% homology than domestic cats FIV subtype A. This study demonstrated that captive Siberian tigers in Northeastern China were exposed to FHV-1, FCV, and FIV, and it is necessary to develop more effective vaccines and improve daily management measures.

Research on feline immunodeficiency virus (FIV) from tigers is scant throughout the world. In this study, 320 captive Siberian tigers were tested for FIV by nested PCR, and three Siberian tigers were FIV-positive. This is the first time FIV has been detected in Siberian tigers in China. The phylogenetic analysis of three FIV genes, gag-p26, pol-RT, and pol-RNAse, revealed that the Siberian tiger FIV had the minimum genetic divergence, the closest genetic relationship and the highest amino acid similarity with subtype A FIV strains from domestic cats, suggesting that the Siberian tiger FIV may have been transmitted by stray cats.