Infectious bronchitis virus (IBV) is one of the most important poultry pathogens, leading significant economic losses worldwide. IBV is characterised by highly genetic, serotype, and pathotypic variability. Despite extensive immunoprophylaxis strategies, the emergence of new genetic lineages is frequently observed in the field, causing disease control to be more complicated. In the last decade, the spread of variants assigned to the GI-23 lineage of IBV (formerly known as Var2) started from Middle-Eastern countries and reached Europe in the last few years. Recently, the introduction and fast spread of Var2-like IBVs in Poland was reported. In this study, the virulence properties and efficacy of different vaccination programmes were evaluated against infection with the IBV GI-23 strain gammaCoV/Ck/Poland/G052/2016. The pathogenicity of the Var2 isolate was conducted in one-day-old and three-week-old SPF chickens and showed that the course of the disease is age dependent. Seven vaccination programmes using Mass, 793B, QX alone or in combination, and Var2 live vaccines were tested against the GI-23 infectious bronchitis virus challenge. All groups were scored according to the ciliostasis test at 5 days post challenge. Two immunoprophylaxis strategies generated full protection against gammaCoV/Ck/Poland/G052/2016 infection—Var2 and Mass used in one-day-old chickens boosted by a combination of the QX and 793B vaccine (both with a ciliostasis score of 0 and 100% protection).

The only knowledge of the molecular structure of European turkey coronaviruses (TCoVs) comes from France. These viruses have a quite distinct S gene from North American isolates. The aim of the study was to estimate the prevalence of TCoV strains in a Polish turkey farm during a twelve-year period, between 2008 and 2019, and to characterize their full-length S gene. Out of the 648 flocks tested, 65 (10.0%, 95% CI: 7.9–12.6) were positive for TCoV and 16 of them were molecularly characterized. Phylogenetic analysis showed that these strains belonged to two clusters, one formed by the early isolates identified at the beginning of the TCoV monitoring (from 2009 to 2010), and the other, which was formed by more recent strains from 2014 to 2019. Our analysis of the changes observed in the deduced amino acids of the S1 protein suggests the existence of three variable regions. Moreover, although the selection pressure analysis showed that the TCoV strains were evolving under negative selection, some sites of the S1 subunit were positively selected, and most of them were located within the proposed variable regions. Our sequence analysis also showed one TCoV strain had recombined with another one in the S1 gene. The presented investigation on the molecular feature of the S gene of TCoVs circulating in the turkey population in Poland contributes interesting data to the current state of knowledge.

The epidemiological situation in Poland for IBV GII (formerly known as D1466) has seemed stable over the years, but an increase in such infections has been recently reported. In this study, genetic characterization of the representatives of this genotype was performed in order to determine whether the new epidemic wave of GII IBV was responsible for changes in this status quo. Genotyping based on the complete S1 coding region of eight Polish IBV field strains from 2011 to 2021 confirmed that they belonged to genotype II, with two of them clustered in the two previously identified GII-1 and GII-2 lineages. In turn, the S1 coding region sequences of the next six Polish strains are very different from the previous ones and form a separate group on the phylogenetic tree. However, comprehensive analysis of all complete S1 coding regions of GII strains did not fulfill all parameters needed to create the separate GII lineage, and they all seem to belong to the GII-1 lineage. Further analysis of the partial S1 sequence of 15 IBV GII strains showed their genetic distinctiveness and indicates the ongoing evolution of this virus genotype. Considering the results of our study and the recent outbreaks of GII-2 in Western Europe, it appears that infections with GII virus strains mainly affect egg-producing, long-lived chickens, commercial layers, and breeders. Furthermore, due to the high diversity of these viruses, their circulation in the poultry population may remain undetected, and for this reason, the observed production problems in laying flocks may be attributed to other, unrelated factors.

In June 2023, Poland experienced an unprecedented outbreak of highly pathogenic avian influenza (HPAI) H5N1 virus infections in cats, raising concerns about the role of cats in HPAI H5N1 virus ecology and potential public health implications. We describe the clinical course and molecular findings in a cat designated as cat No. 14 during this outbreak, with emphasis on the viral load detected in various organs and tissues. The cat was initially examined for recurrent dermatological problems, although the owner also reported reduced activity. Over the following five days, the disease rapidly progressed, with systemic and neurological signs unresponsive to treatment. Blood analyses revealed no major haematological abnormalities, whereas serial serum biochemistry showed progressive abnormalities. Due to the poor prognosis, the cat was humanely euthanized five days after the initial veterinary examination. Tissue samples from major internal organs and lymph nodes, together with tracheal and rectal swabs and bile, were collected for real-time RT-PCR. Viral RNA was detected in all analysed samples except the intestines, mesenteric lymph nodes, rectal swab, and bile, with the highest viral loads observed in the cerebellum and brain. This case provides molecular evidence of widespread HPAI H5N1 viral RNA distribution across tissues, complemented by detailed haematological and biochemical findings, further characterizing the systemic nature of infection.