Serological surveillance of Influenza A virus and Highly pathogenic avian influenza H5N1 in ruminants in Ukraine, 2015‒2026
Abstract
This article provides a concise review of the current literature on the circulation of influenza A viruses in cattle and the unprecedented emergence of highly pathogenic avian influenza (HPAI) H5N1 infection in this species. Particular attention is paid to the ecological and biological aspects of influenza A virus cross-species transmission, as well as to the potential implications of these events for veterinary medicine, livestock production, and public health. The study presents the results of the first pilot serological investigation conducted at the National Scientific Center ‘Institute of Experimental and Clinical Veterinary Medicine’, providing evidence of the potential circulation of influenza A virus among ruminants in Ukraine. A total of 510 serum samples collected from cattle and small ruminants in different regions of Ukraine between 2015 and 2026 were tested using an enzyme-linked immunosorbent assay (ELISA). Three (0.59%) seropositive cattle serum samples, collected in 2023 and 2026, were identified, whereas all serum samples obtained from small ruminants tested negative. Overall, the seroprevalence of antibodies against influenza A virus was low, ranging from 1.67% to 5.0%, depending on the year of sampling and the geographical region. Further serological characterization of all influenza A virus-positive sera for antibodies against highly pathogenic avian influenza H5N1 yielded negative results. Thus, the findings do not support the circulation of HPAI H5N1 among the examined ruminant population in Ukraine. Nevertheless, given the remarkable evolutionary plasticity of influenza A viruses, their ability to overcome species barriers, and their potential to establish novel transmission pathways, continued serological, virological, and molecular surveillance of ruminants is warranted. Such monitoring is essential for the early detection of cross-species transmission events, changes in virus ecology, and the emergence of novel biological properties