Prevalence, co-infection, and spatiotemporal patterns of five feline upper respiratory tract pathogens in domestic cats in China, 2021–2024

Abstract Background Feline upper respiratory tract disease (URTD) is one of the most common infectious diseases affecting domestic cats globally. The primary etiological agents include feline herpesvirus 1 (FHV-1), feline calicivirus (FCV), Mycoplasma felis, Bordetella bronchiseptica, and Chlamydia felis. Although these pathogens are well recognized, large-scale nationwide epidemiological data on their prevalence, co-infection patterns, temporal-spatial distribution, and age/sex correlates in China remain limited. This study aimed to characterize the epidemiological features of the five major feline respiratory pathogens based on four-year nationwide clinical detection data. Results A retrospective analysis was conducted on clinical samples collected across China from January 2021 to December 2024, using the InCycle fully automated nucleic acid testing system and a 5-plex real-time PCR assay. Among the 732,124 specimens tested, FCV showed the highest overall detection rate (41.22%), followed by M. felis (31.01%), FHV-1 (15.31%), B. b (9.68%), and C. felis (5.62%). Mixed infections were common, with FCV- M. felis dual co-infection being the most frequent combination. Temporal analysis revealed that total positive cases remained low in 2021, increased sharply thereafter, and peaked in March 2024. FCV exhibited the highest positive rate (35.50%-45.80%) with three distinct peaks, while M. felis prevalence showed a gradual downward trend over the study period. FHV-1 displayed seasonal fluctuations, B. b had a single prevalence peak in 2022–2023, and C. felis prevalence declined steadily. Regionally, FCV and M. felis were the dominant pathogens across all six geographic regions, with the East region reporting the highest absolute number of positive cases, and B. b showing a north-to-south prevalence gradient. No clinically significant sex-based differences in pathogen prevalence were observed. Highly significant age-specific differences were identified for all pathogens (*p* < 0.001, ***): FCV, M. felis , B. b , and C. felis were most prevalent in cats ≤ 6 months of age, whereas FHV-1 prevalence peaked in cats > 10 years old. Conclusions This study provides a comprehensive overview of the prevalence, co-infection patterns, temporal and regional distributions, and age/sex associations of the five major feline respiratory pathogens in China. The findings offer critical epidemiological insights to inform evidence-based clinical diagnosis, prevention, and control strategies for feline URTD in the country.