Epizootiological aspects of swine influenza in Ukraine for the period 2021–2025
Abstract
Swine influenza is one of the most common respiratory viral infections in swine farming, causing significant ec o nomic losses and posing a potential threat to public health due to the ability of influenza A viruses to undergo inte r species transmission and genetic reassortment. Pigs play an important role in the emergence of new virus variants, as they can be infected by swine, human, and avian strains alike. Given the pandemic and the emergence of new zoon o tic variants of influenza viruses, continuous epizootiological surveillance of the swine population is a crucial comp o nent of the biosecurity system and early warning system for pandemic threats. The objective s of the study was to assess the prevalence of influenza A virus among Ukraine’s pig population in 2021–2025 and to determine the cha r acteristics of its circulation based on the results of molecular and serological studies. The data for the analysis were derived from diagnostic tests conducted by the Centre of Veterinary Diagnostics LTD , a commercial research center (Kyiv city). The Real-Time RT-PCR method was used to detect viral RNA, and enzyme-linked immunosorbent assay (ELISA) was used to determine specific antibodies. Statistical and epizootiological analyses of the obtained data were conducted. During the study period, 132 swine farms and 587 samples of pathological and biological material were tested using Real-Time RT-PCR . Influenza A virus RNA was detected o n 33 farms (25.0%) and in 69 samples (11.8%). The proportion of PCR-positive samples gradually decreased from 16.5% in 2021 to 6.1% in 2025. Serolo g ical studies covered 173 farms and 7308 blood sera. Antibodies to the influenza A virus were detected o n 118 farms (68.2%), and the overall seropositivity rate was 40.5% (2959 positive samples). The highest seropositivity rates were recorded in the Sumy (82.6%), Volyn (79.0%), Ternopil (69.9%), and Lviv (51.2%) oblast s, while the highest rates of viral RNA detection were observed in the Ivano-Frankivsk, Kharkiv, and Kirovohrad oblast s . The results indicate a significantly wider spread of the infection than can be assessed based solely on the results of direct virus detection. It was found that the level of seropositivity exceeded the frequency of detection of viral RNA by more than three times (40.5% versus 11.8%), which indicates long-term circulation of the virus in the pig population and significant spread of infection even in the absence of active virus excretion . The study results confirm the enzootic nature of influenza A virus circulation in the pig population of Ukraine. The combination of high seropositivity with a relatively low fr e quency of viral RNA detection indicates the long-term persistence of the infection on farms and the development of post infection immunity. The data obtained justify the need for further comprehensive molecular and serological mon i toring of the swine influenza virus as an important element in preventing economic losses in swine farming and mi n imizing the risks of the emerg ence of new zoonotic variants of the virus.References
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