Molecular epidemiological investigation of viruses in Amur tigers in Northeast China

A systematic molecular epidemiology survey was conducted on ten viruses in 226 captive and two wild Amur tigers from Northeast China. The target viruses were: feline panleukopenia virus (FPV), feline herpesvirus-1 (FHV-1), feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), canine distemper virus (CDV), feline coronavirus (FCoV), feline calicivirus (FCV), influenza A virus (IAV), hepatitis E virus (HEV), and rotavirus A (RVA). The overall infection prevalence in captive tigers was 45.6% (103/226), with FPV (25.2%) and FHV-1 (20.4%) identified as the dominant pathogens. Other viruses detected at lower frequencies were FIV (3.1%), CDV (1.8%), FCoV (0.9%), and FeLV (0.4%); FCV, IAV, HEV, and RVA were not detected. This study reports the first detection of FeLV in this subspecies. Infection prevalence exhibited marked age and regional dependence, being highest in juveniles (56.5%) and in the facilities of Shenyang (55.8%) and Harbin (52.6%). Phylogenetic analysis of partial VP2 sequences indicated that FPV strains from captive tigers formed a distinct, well-supported monophyletic clade (bootstrap = 99). In contrast, the VP2 sequence from the wild tiger (YINGCHUN) did not group within the captive tiger clade; instead, it occupied a separate position within the broader FPV cluster. FIV strains from tigers were phylogenetically interspersed with strains from domestic cats in China. Despite existing vaccination protocols, the persistent high prevalence of FPV and FHV-1 indicates suboptimal immunoprotection. These findings clarify the current viral pathogen profile in captive Amur tigers and underscore the necessity for optimizing disease management strategies, including age-stratified immunization, enhanced biosecurity, and the establishment of transboundary surveillance.