Influenza A viruses (IAV) cause persistent epidemics and occasional human pandemics, leading to considerable economic losses. The ecology and epidemiology of IAV are very complex and the emergence of novel zoonotic pathogens is one of the greatest challenges in the healthcare. IAV are characterized by genetic and antigenic variability resulting from a combination of high mutation rates and a segmented genome that provides the ability to rapidly change and adapt to new hosts. In this context, available scientific evidence is of great importance for understanding the epidemiology and evolution of influenza viruses. The present review summarizes original research papers and IAV infections reported in dogs all over the world. Reports of interspecies transmission of equine influenza viruses (EIV) H3N2 from birds to dogs, as well as double and triple reassortant strains resulting from reassortment of avian, human and canine strains have amplified the genetic variety of canine influenza viruses. A total of 146 articles were deemed acceptable by PubMed and the Google Scholar database and were therefore included in this review. The largest number of research articles (n=68) were published in Asia, followed by the Americas (n=44), Europe (n=31), Africa (n=2) and Australia (n=1). Publications are conventionally divided into three categories. The first category (largest group) included modern articles published from 2011 to the present (n=93). The second group consisted of publications from 2000 to 2010 (n=46). Single papers of 1919, 1931, 1963, 1972, 1975, and 1992 were also used, which was necessary to emphasize the history of the study of the ecology and evolution of the IAV circulating among various mammalian species. The largest number of publications occurred in 2010 (n=18) and 2015 (n=11), which is associated with IAV outbreaks observed at that time in the dog population in America, Europe and Asia. In general, these findings raise concerns that dogs, may mediate the adaptation of IAVs to zoonotic transmission and therefore serve as alternative hosts for genetic reassortment of these viruses. The global concern and significant threat to public health from the present COVID-19 pandemic confirms the necessity for active surveillance of zoonotic viral diseases with pandemic potential.
Influenza and other acute respiratory viral infections are the most common contemporary infectious diseases resulting in prominent harm to human health and great economic damage. At least five groups of viruses including more than 300 subtypes are currently referred to ARVI pathogens. Such infectious agents are characterized by variability resulting in their altered antigenic characteristics, increased contagiousness, "evasion from immune response and resistance to antivirals. Relevance of influenza and other ARVIs is also accounted for by rapid development of bacteria-associated respiratory diseases. Continuous variability of influenza viruses and emergence of new ARVI pathogens pose a serious threat. In recent years, a simultaneous circulation of subtype A (H1N1) and A (H3N2) influenza viruses with a predominance of a pandemic strain as well as type B viruses have been observed. Among the causative agents of non-influenza ARVIs, respiratory syncytial virus, rhino- and adenoviruses, and I/III parainfluenza viruses are recorded most often. Here we present the data of virology and serological examination of clinical samples collected during the 2018 – 2019 epidemic season in the Republic of Kazakhstan. For this, 2794 clinical samples (2530 nasopharyngeal swabs and 264 blood serums) were collected from patients diagnosed with ARVI, ARI, bronchitis, and pneumonia. Analysis of nasopharyngeal swabs for detection of influenza by RT-PCR demonstrated that mixed etiology influenza viruses with predominance of A/H1N1pdm virus circulated in Kazakhstan. The genetic fingerprints of influenza virus were found in 511 swabs (20.20% of total examined samples). Influenza A virus RNA was detected in 508 biological samples: A/H1N1 – in 289, A/H3N2 – in 209, and unidentified virus subtype in 10 samples. Type B influenza virus was detected in 3 samples. Study of 264 serum samples by HAI assay and ELISA showed emergence of antibodies against influenza A/H1N1, A/H3N2, and B viruses in residents from various regions of Kazakhstan that indirectly confirmed co-circulation of these viruses. 42 influenza virus strains were isolated in chicken embryos, from which 28 were assigned to A/H1N1pdm virus, 13 to A/H3N2 virus, and one isolate was identified as influenza B virus. Laboratory diagnostics of clinical samples for ARVIs established that among identified non-influenza agents respiratory syncytial virus dominated, while rhinoviruses and adenoviruses were less common. Metapneumoviruses, bocaviruses, coronaviruses, and type I parainfluenza viruses were detected in few cases. Comparison of study data with those obtained after examining circulation of influenza viruses during the 2017 – 2018 epidemic season showed that in 2018 – 2019 in Kazakhstan similar to the previous epidemic season, influenza A and B viruses continued to circulate, with prevalence of A/H1N1pdm virus. Identification of non-influenza viruses causing respiratory infections in 2018 – 2019 showed predominance of respiratory syncytial virus, which correlated with data on the 2017 – 2018 epidemic season.
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