Sequestration of membrane cholesterol by cholesterol-binding proteins inhibits SARS-CoV-2 entry into Vero E6 cells.

Membrane lipids and proteins form dynamic domains crucial for physiological and pathophysiological processes, including viral infection. Many plasma membrane proteins, residing within membrane domains enriched with cholesterol (CHOL) and sphingomyelin (SM), serve as receptors for attachment and entry of viruses into the host cell. Among these, human coronaviruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), use proteins associated with membrane domains for initial binding and internalization. We hypothesized that the interaction of lipid-binding proteins with CHOL in plasma membrane could sequestrate lipids and thus affect the efficiency of virus entry into host cells, preventing the initial steps of viral infection. We have prepared CHOL-binding proteins with high affinities for lipids in the plasma membrane of mammalian cells. Binding of the perfringolysin O domain four (D4) and its variant D4E458L to membrane CHOL impaired the internalization of the receptor-binding domain of the SARS-CoV-2 spike protein and the pseudovirus complemented with the SARS-CoV-2 spike protein. SARS-CoV-2 replication in Vero E6 cells was also decreased. Overall, our results demonstrate that the integrity of CHOL-rich membrane domains and the accessibility of CHOL in the membrane play an essential role in SARS-CoV-2 cell entry.

SARS-CoV-2 molecular epidemiology in Slovenia, January to September 2021.

BackgroundSequencing of SARS-CoV-2 PCR-positive samples was introduced in Slovenia in January 2021. Our surveillance programme comprised three complementary schemes: (A) non-targeted sequencing of at least 10% of samples, (B) sequencing of samples positive after PCR screening for variants of concern (VOC) and (C) sequencing as per epidemiological indication.AimWe present the analysis of cumulative data of the non-targeted surveillance of SARS-CoV-2 and variant-dependent growth kinetics for the five most common variants in Slovenia for the first 9 months of 2021.MethodsSARS-CoV-2 PCR-positive samples, from January to September 2021, were selected for sequencing according to the national surveillance plan. Growth kinetics studies were done on Vero E6 cells.ResultsAltogether 15,175 genomes were sequenced and 64 variants were detected, of which three successively prevailed. Variant B.1.258.17 was detected in ca 80% of samples in January and was replaced, within 9 weeks, by the Alpha variant. The number of cases decreased substantially during the summer of 2021. However, the introduction of the Delta variant caused a fourth wave and completely outcompeted other variants. Other VOC were only detected in small numbers. Infection of Vero E6 cells showed higher replication rates for the variants Alpha and Delta, compared with B.1.258.17, B.1.258, and B.1.1.70, which dominated in Slovenia before the introduction of the Alpha and Delta variants.ConclusionInformation on SARS-CoV-2 variant diversity provided context to the epidemiological data of PCR-positive cases, contributed to control of the initial spread of known VOC and influenced epidemiological measures.

Transmission of SARS-CoV-2 from Human to Domestic Ferret.

We report a case of natural infection with severe acute respiratory syndrome coronavirus 2 transmitted from an owner to a pet ferret in the same household in Slovenia. The ferret had onset of gastroenteritis with severe dehydration. Whole-genome sequencing of the viruses isolated from the owner and ferret revealed a 2-nt difference.

Tear production, intraocular pressure and conjunctival bacterial flora in selected captive wild ruminants.

OBJECTIVE: Evaluation of tear production (Schirmer's tear test, STT) and measurement of intraocular pressure (IOP) were performed in a population of captive wild ungulates in a Slovenian ZOO during routine annual health check. ANIMALS STUDIED: In total, 10 fallow deer (Dama dama), 25 mouflons (Ovis aries musimon), 20 alpine ibexes (Capra ibex), and three alpine chamois (Rupicapra rupicapra) were included in the study. METHODS: Tear production was performed by Schirmer's tear test, IOP was measured with an applanation tonometer, and ophthalmological examination was conducted with slit-lamp biomicroscopy and indirect ophthalmoscopy. Conjunctival swabs were taken and submitted for aerobic bacteriology and for detection of Chlamydia spp. and Mycoplasma spp. tested by PCR. RESULTS: Average tear production (in mm/min) was 17.8 ± 3.16 for fallow deer, 17.9 ± 3.87 for mouflons, and 11.7 ± 3.87 for ibexes. Mean intraocular pressure (IOP, in mm Hg) was 14.1 ± 2.48 for fallow deer, 14.9 ± 2.20 for mouflons, and 13.1 ± 2.43 for ibexes. For chamois, average tear production and IOP were 14.5 ± 3.0 and 10.2 ± 2.5, respectively; this is the first record of STT I and IOP in chamois. Bacteriological swabs were positive for bacteria in 100% of the fallow deer, 56% of mouflons, 35% of ibexes, and 100% of chamois. Gram-positive bacteria were predominant. Moraxella spp., Chlamydia spp., and Mycoplasma spp. were not detected. CONCLUSION: The reported values were obtained in animals under manual restraint only to be applicative in similar conditions.

First Report of Marek's Disease Virus in Commercial Turkeys in Slovenia.

Marek's disease (MD), caused by Mardivirus gallidalpha 2 (GaAHV-2), also known as MD virus (MDV), is a lymphoproliferative disease that primarily affects chickens. Recently, MDV has been detected in lymphomatous tumors in turkeys in various countries. Between 2021 and 2023, three cases ranging from no to severe clinical disorders (depression, lameness, and increased mortality) occurred in commercial turkey flocks in Slovenia. In all cases, MDV was detected by PCR in DNA samples extracted from organs developing tumor infiltrations. Sequencing and phylogenetic analysis of the meq gene revealed that the GaAHV-2 detected has molecular features of a very virulent pathotype and genetic similarity with GaAHV-2 detected in chickens in Tunisia. This is the first report of MDV in commercial turkeys in Slovenia.

Herpesvirus and Subsequent Usutu Virus Infection in a Great Grey Owl (Strix nebulosa) at the Ljubljana Zoo, Slovenia.

Herpesvirus (HV) has been known to cause disease in owls, with various clinical signs and outcomes for the last several decades. The HV DNA polymerase gene was detected in oropharyngeal and cloacal swabs of a male great grey owl (Strix nebulosa) in a zoological collection in Ljubljana, Slovenia. In the following 4 months, despite continuous HV detection in swabs, no clinical signs with a clear link to HV disease were observed. Hepatoprotective and immunostimulant therapies applied during this period did not prevent HV shedding. Therefore, peroral antiviral therapy with acyclovir (150 mg/kg q24 h for seven days) was performed, and the owl tested negative at the next sampling and remained negative for the next 8 months. After that, the owl again tested positive for HV presence, and the same protocol with antiviral therapy was performed. After 3 weeks with a negative test for HV presence, without any clinical signs of illness, the owl suddenly died because of Usutu virus (USUV) infection. Among all the owls at the zoo, interestingly, only the HV-positive great grey owl died because of USUV infection. The USUV sequence detected and obtained in this study clusters together with other Europe 2 sequences detected in neighboring countries. Our study shows the potential of acyclovir therapy in the prevention of herpesvirus shedding and, moreover, lowering the possibility for spreading HV to other owls and birds. To the best of our knowledge, this is the first report of HV presence and USUV infection in a great grey owl in Slovenia.

Association of Mycoplasma canis with Fertility Disorders in Dogs: A Case Study Supported by Clinical Examination, PCR, 16S Microbiota Profiling, and Serology.

The role of Mycoplasma canis in canine fertility disorders is still poorly understood. As infection is often asymptomatic, there is an increasing need for appropriate diagnostic methods and treatment plans that would allow the reliable detection of M. canis infection and rapid alleviation of infection symptoms in affected dogs. In this study, we included 14 dogs with fertility problems and 16 dogs without fertility disorder signs. We compared clinical examination data and selected laboratory parameters (hematology and biochemistry) between the groups. We performed PCR-based detection of M. canis and 16S rRNA gene-based microbiota profiling of DNA isolated from vaginal and preputial swabs. Dog sera were tested for the presence of M. canis-specific antibodies. Hematological and selected biochemical parameters showed no differences between groups. PCR-based detection of M. canis in the samples was consistent with the results of 16S microbiota profiling. Several other bacterial taxa were also identified that could potentially be involved in different fertility disorders. Serological methods were not accurate enough since high cross-reactivity rates were observed. In the future, more accurate and efficient methods will be needed to determine the role of M. canis and its true role in the pathogenesis of specific fertility disorders in dogs.

High pathogenic avian influenza A(H5) viruses of clade 2.3.4.4b in Europe-Why trends of virus evolution are more difficult to predict.

Since 2016, A(H5Nx) high pathogenic avian influenza (HPAI) virus of clade 2.3.4.4b has become one of the most serious global threats not only to wild and domestic birds, but also to public health. In recent years, important changes in the ecology, epidemiology, and evolution of this virus have been reported, with an unprecedented global diffusion and variety of affected birds and mammalian species. After the two consecutive and devastating epidemic waves in Europe in 2020-2021 and 2021-2022, with the second one recognized as one of the largest epidemics recorded so far, this clade has begun to circulate endemically in European wild bird populations. This study used the complete genomes of 1,956 European HPAI A(H5Nx) viruses to investigate the virus evolution during this varying epidemiological outline. We investigated the spatiotemporal patterns of A(H5Nx) virus diffusion to/from and within Europe during the 2020-2021 and 2021-2022 epidemic waves, providing evidence of ongoing changes in transmission dynamics and disease epidemiology. We demonstrated the high genetic diversity of the circulating viruses, which have undergone frequent reassortment events, providing for the first time a complete overview and a proposed nomenclature of the multiple genotypes circulating in Europe in 2020-2022. We described the emergence of a new genotype with gull adapted genes, which offered the virus the opportunity to occupy new ecological niches, driving the disease endemicity in the European wild bird population. The high propensity of the virus for reassortment, its jumps to a progressively wider number of host species, including mammals, and the rapid acquisition of adaptive mutations make the trend of virus evolution and spread difficult to predict in this unfailing evolving scenario.

Effect of Mycoplasma synoviae and lentogenic Newcastle disease virus coinfection on cytokine and chemokine gene expression in chicken embryos.

Mycoplasma synoviae and Newcastle disease virus (NDV) are 2 avian pathogens that cause modulation in expression of a variety of cytokine and chemokine genes in chickens. However, there is limited data about gene modulation after coinfection with these 2 pathogens and even less data about gene modulation after infection of chicken embryos. In this study, the effect of M. synoviae type strain WVU 1853 and lentogenic LaSota vaccine strain of NDV infection on cytokine and chemokine gene expression in chicken embryos was analyzed in the liver, spleen, bursa of Fabricius, and thymus by using quantitative real-time PCR. Three types of infection were performed; infection with M. synoviae on d 10, infection with NDV on d 17; and consecutive infection with both pathogens, where M. synoviae was inoculated on d 10 and NDV on d 17. Thus, simulation of consecutive infection that may occur after NDV infection of the M. synoviae-infected host was performed. Mycoplasma synoviae infection of embryos resulted in intensive upregulation of cytokine and chemokine genes, including interferon (IFN)-γ, IL-1ß, IL-6, IL-12p40, IL-16, IL-18, MIP-1ß (CCL4), inducible nitric oxide synthase (iNOS), XCL1, and lipopolysaccharide-induced tumor necrosis factor-α factor (LITAF), with different expression profiles in the 4 organs. Inoculation of lentogenic NDV significantly upregulated IFN-γ, IL-6, and IL-16 genes in spleen and IFN-γ, IL-1ß, IL-2, IL-16, IL-21, XCL1, and MIP-1ß (CCL4) genes in the thymus, but to a lesser extent than M. synoviae. However, no genes were upregulated by NDV in the liver and bursa of Fabricius. Overall effect of NDV inoculation, regarding the number of modulated cytokine and chemokine genes and the extent of expression, was lower than M. synoviae. When NDV was introduced after on-going M. synoviae infection, most M. synoviae-induced cytokine and chemokine genes were significantly downregulated. This study provides the first evidence in chicken embryos that consecutive infection with NDV could suppress expression of cytokine and chemokine genes being significantly upregulated by the previous M. synoviae infection.

Rehoming and Other Refinements and Replacement in Procedures Using Golden Hamsters in SARS-CoV-2 Vaccine Research.

Effective vaccines are needed to fight the COVID-19 pandemic. Forty golden hamsters were inoculated with two promising vaccine candidates and eighteen animals were used in pilot trials with viral challenge. ELISA assays were performed to determine endpoint serum titres for specific antibodies and virus neutralisation tests were used to evaluate the efficacy of antibodies. All tests with serum from vaccinated hamsters were negative even after booster vaccinations and changes in vaccination protocol. We concluded that antibodies did not have sufficient neutralising properties. Refinements were observed at all steps, and the in vitro method (virus neutralisation test) presented a replacement measure and ultimately lead to a reduction in the total number of animals used in the project. The institutional animal welfare officer and institutional designated veterinarian approved the reuse or rehoming of the surplus animals. Simple socialization procedures were performed and ultimately 19 animals were rehomed, and feedback was collected. Recently, FELASA published recommendations for rehoming of animals used for scientific and educational purposes, with species-specific guidelines, including mice, rats, and rabbits. Based on our positive experience and feedback from adopters, we concluded that the rehoming of rodents, including hamsters, is not only possible, but highly recommended.

Encephalitozoon cuniculi Infection of Domestic Rabbits (Oryctolagus cuniculus) in Slovenia between 2017 and 2021.

Encephalitozoon cuniculi is a microsporidial parasite that primarily infects domestic rabbits (Oryctolagus cuniculus). It is the causative agent of encephalitozoonosis, a disease with an internationally recognized seroprevalence among rabbits. This study determines the presence, clinical manifestation, and serological status of encephalitozoonosis in pet rabbits in Slovenia using various diagnostic procedures. From 2017 to 2021, 224 pet rabbit sera were collected and tested for encephalitozoonosis with the indirect immunofluorescence assay. Immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against E. cuniculi were confirmed in 160 (65.6%) cases. Most seropositive rabbits suffered from neurological clinical signs or signs of gastrointestinal disorders such as recurrent hypomotilities, chronic weight loss, cachexia, or anorexia, and fewer showed clinical signs related to the urinary system or phacoclastic uveitis. A quarter of the positively tested rabbits presented without clinical signs. Hematological and biochemical blood analysis confirmed that seropositive animals had elevated globulin and deviated albumin levels in comparison to the normal reference values of non-infected animals. Furthermore, rabbits with neurological clinical signs showed statistically significant higher levels of globulins and total protein. Sixty-eight whole-body radiographs and thirty-two abdominal ultrasound reports were analyzed, looking for changes in the shape or size of the urinary bladder, presence of urinary sludge or uroliths, and any abnormalities related to the kidneys (shape, size, or nephrolites). The results suggest that neurological defects in the urinary bladder caused by E. cuniculi lead to a distended urinary bladder and consequently dysuria, incontinence, urine scalding, and sludgy urine.

Molecular characterization of atypical Chlamydia and evidence of their dissemination in different European and Asian chicken flocks by specific real-time PCR.

Chlamydia psittaci is a zoonotic pathogen associated primarily with avian chlamydiosis. New chlamydial agents with suspected zoonotic potential were recently detected from domestic poultry in Germany and France indicating that the spectrum of Chlamydiaceae encountered in birds is not confined to a single chlamydial species. For further characterization, a specific real-time PCR targeting the conserved 16S rRNA gene was developed and validated for a specific detection of these atypical Chlamydiaceae. In order to address the epidemiological importance of the new chlamydial agents and their distribution, Chlamydiaceae-positive chicken samples collected from flocks from five different countries were examined. The results confirmed that C.psittaci is not the predominant chlamydial species among chickens examined and suggested that the new chlamydial agents could putatively be widespread in poultry flocks (France, Greece, Croatia, Slovenia and China at least) justifying their systematic investigation when poultry samples are submitted to laboratories for avian chlamydiosis diagnosis. Besides, 16S rRNA-based dendrogram, including sequences from both isolates of the new chlamydial agents or positive samples as well as representative sequences from species belonging to the order Chlamydiales, showed the new chlamydial agents to form a distinct line of descent separated from those of other chlamydial species, but clearly grouped within the family Chlamydiaceae. Finally, the phylogenetic tree inferred from the multi-locus sequence typing based on four housekeeping fragments (gatA, gidA, enoA and hflX) and the ompA-based dendrogram showed an almost identical topology of the new chlamydial agents with that recovered by 16S rRNA-based dendrogram. Interestingly, partial ompA gene sequences displayed considerable diversity among isolates.

Prevalence of pigeon circovirus infections in feral pigeons in Ljubljana, Slovenia.

Pigeon circovirus (PiCV) was detected by real-time PCR in cloacal swabs, pharyngeal swabs, and serum samples taken from 74 feral pigeons (Columba livia var. domestica) that were caught at various locations in the city of Ljubljana, Slovenia. PiCV infections were detected in the majority of the tested birds. The highest (74.3%) detection rate was observed in the cloacal swabs and the lowest (31.1%) in serum samples. PiCV DNA was more readily detected in the cloacal swabs, pharyngeal swabs, and serum samples of birds younger than 1 yr. Molecular analysis of partial open reading frame V1 sequences showed that PiCV strains detected in feral pigeons share high nucleotide and amino acid sequence identities with PiCV strains detected in ornamental, racing, meat, and feral pigeons.

Surveillance of influenza A viruses in wild birds in Slovenia from 2006 to 2010.

Within the framework of the surveillance program for the early detection of H5 and H7 subtypes of avian influenza (AI) viruses, samples from 2547 wild birds of different species that were collected between 2006 and 2010 were examined by PCR-based methods. AI viruses of various subtypes were detected in 4.4% of birds from four different orders: Anseriformes, Ciconiiformes, Charadriiformes, and Pelecaniformes. Highly pathogenic avian influenza (HPAI) H5N1 viruses were detected only in 2006. HPAI H5N1 virus was confirmed in 1.9% of birds from four different species. Comparison of nucleotide sequences of the H5N1 hemagglutinin gene indicated that two different HPAI H5N1 viruses from the European-Middle Eastern-African clade 1 had been introduced into Slovenia, despite the relatively short duration of the HPAI outbreak. Low pathogenic avian influenza (LPAI) viruses were detected in 2.5% of birds during a 5-yr period. The subtypes H1, H2, H3, H4, H5, H7N7, H8, H10, H11, and H13N6 were determined in 18 out of 64 cases. The highest prevalence (81%) of LPAI viruses, including the H5 subtype, were found in birds sampled as a part of the "active" surveillance system.

Detection of Herpesviruses in Wild Bird Casualties in Slovenia.

The complete host range of avian herpesviruses in wild birds is unknown, and information about nucleotide sequences is available only in limited cases. The aim of this study was to detect the presence of herpesviruses in wild birds and to gain more information about their phylogenetic relationship. Oropharyngeal and cloacal swabs from 447 wild birds from 15 different orders presented as wildlife casualties were examined for herpesvirus presence with PCR targeting a fragment of the DNA polymerase gene. Herpesviruses were detected in oropharyngeal and/or cloacal swabs in 34 (7.5%) birds belonging to 11 species from six different avian orders: Accipitriformes, Charadriiformes, Columbiformes, Falconiformes, Passeriformes, and Strigiformes. The results of phylogenetic analysis showed that various herpesviruses sequences are present in the wild bird population. Some herpesviruses are host species-specific, whereas in some cases very similar sequences were detected through different avian orders, which confirms findings that herpesviruses are not always restricted to bird species. It seems that herpesvirus transmission could occur by predation from avian prey, and even by superpredation-for example, large owls, such as the Eurasian eagle owl (Bubo bubo) or Ural owl (Strix uralensis), preying on smaller raptors. This can lead to greater infection exposure and is in line with the fact that raptors were the most infected species group. Nevertheless, the individual or simultaneous detection of herpesviruses in oropharyngeal and cloacal swabs shows that both swab samples should be used for herpesvirus detection in wild birds.

Novel adenoviruses from captive psittacine birds in Slovenia.

To assess the prevalence of adenoviruses in psittacine birds kept in Slovenia, 258 cloacal swabs were collected from different psittacine species and screened by a nested PCR with degenerate, consensus primers targeting the adenoviral DNA polymerase gene. Forty-two samples were found to be positive. By sequencing, 28 samples from 10 different parrot species were identified as the formerly described siadenovirus, psittacine adenovirus 2 (PsAdV-2). A second siadenovirus, a variant of PsAdV-5 (described earlier from Pacific parrotlet, sun parakeet, cockatiel and budgerigar) was found in seven budgerigars, two cockatiels and an amazon parrot species. A variant of Meyer's parrot adenovirus (aviadenovirus, proposed PsAdV-8) was identified in an African grey parrot and a cockatiel. Two novel atadenoviruses were revealed in cockatiel (PsAdV-9) and rose-ringed parakeet (PsAdV-10). These results support the earlier finding that many PsAdVs can cross the species barrier among psittacines, especially effectively in the case of PsAdV-2.

Variation of vlhA gene in Mycoplasma synoviae clones isolated from chickens.

Mycoplasma synoviae synthesizes haemagglutinin VlhA, which cleaves into the N-terminal part, a lipoprotein MSPB, and a C-terminal part MSPA. Previous studies have shown that the 3'-end of the expressed vlhA gene can recombine with vlhA pseudogenes in a process called gene conversion, but there have been no data about diversification of the expressed vlhA gene in M. synoviae populations replicating in chickens. Following intratracheal inoculation with the M. synoviae strain ULB 02/T6, which showed only minor vlhA gene variation prior to inoculation, we investigated temporal changes in MSPB epitopes defined by monoclonal antibodies (mAbs) 3B4 and 50, as well as diversification of the vlhA gene sequence in M. synoviae populations recovered from chicken tracheas. In cultures isolated 8 and 18 days post inoculation (p.i.), most colonies showed variation of MSPB epitopes for mAbs 3B4 and 50. They also changed 3'-end vlhA gene sequences. Further diversity of the vlhA gene occurred in cultures isolated 8 weeks and 5 months p.i. The vlhA gene sequences from isolated cultures shared only 65 to 80% sequence identity with vlhA gene of the inoculated ULB 02/T6 culture. Notably, in most of those cultures their vlhA gene sequences contained stop codons potentially causing premature terminations of translation. Interestingly, in one culture isolated 8 weeks p.i. (clone T6-8W/IT2A) the 3'-vlhA gene sequence was identical in the last 1140 bases to that of the first vlhA pseudogene positioned the most far (upstream) of the expressed vlhA gene. This is the first demonstration of temporal diversity of the vlhA gene in M. synoviae populations isolated from chicken tracheas.

Circulation of infectious bronchitis virus strains from Italy 02 and QX genotypes in Slovenia between 2007 and 2009.

Fourteen infectious bronchitis viruses (IBVs) detected in broiler, broiler breeder, and layer flocks in Slovenia between 2007 and 2009 were molecularly analyzed by reverse transcription-PCR and direct sequencing of the S1 gene. Phylogenetic analyses based on partial S1 gene sequences revealed that seven strains were classified as the Italy 02 genotype, a genetic group of IBV that has not previously been detected in Slovenia. Another seven strains were classified as the QX genotype. The results of phylogenetic analyses and epidemiologic investigations revealed that the genetic classification correlates with the geographic origins of the IBV strains. Greater genetic variability (maximum nucleotide and amino acid divergences were 4.8% and 9.9%, respectively) was observed within the Slovenian strains from the Italy 02 genotype detected between 2007 and 2009 than within strains from the QX genotype isolated in 2008 and 2009 (1.2% and 1.3%, respectively). The Slovenian strains classified as the Italy 02 genotype form a separate genetic cluster. These strains shared five specific amino acid substitutions that became fixed during the period of surveillance. Strains from the QX genotype that shared one specific amino acid substitution also form a separate genetic cluster.

Field efficacy of different vaccines against infectious bursal disease in broiler flocks.

A field study was performed to determine the efficacy of three commercially available vaccines against infectious bursal disease (IBD) in commercial broilers raised in a high IBD virus (IBDV) risk area. Live attenuated intermediate and intermediate plus vaccines were used in four flocks. Birds were vaccinated orally at the estimated vaccination time. Three broiler flocks were vaccinated subcutaneously with a turkey herpesvirus (HVT)-IBD vector vaccine at one day old. Evaluation of the efficacy of different vaccines was focused on humoral immune response, bursa/body weight (B/Bw) ratio, molecular detection of IBDV in ileocaecal tonsils and bursa of Fabricius, and production parameters. The serological results showed that although the uptake of all three vaccine strains was confirmed in the lymphoid organs, no significant antibody response to vaccination was detected in flocks vaccinated with intermediate and intermediate plus vaccines. A significant increase in antibody titres detected in flocks vaccinated with the vector vaccine indicated its ability to induce an immune response in birds with a high level of maternally derived antibodies. Observations obtained in this field trial did not confirm the expected reduction of the B/Bw ratio in flocks vaccinated with less attenuated vaccines. No significant differences were observed between birds vaccinated with the vector vaccine and those immunised with the intermediate plus vaccine. Very virulent IBDV was confirmed in the flock vaccinated with the intermediate vaccine. The infection induced reduced B/Bw and moderate mortality but did not affect the production parameters. Field infection was not detected in broilers vaccinated with the intermediate plus vaccine and the vector vaccine.

Herpesvirus Infection in a Breeding Population of Two Coexisting Strix Owls.

Birds are a frequent host of a large variety of herpesviruses, and infections in them may go unnoticed or may result in fatal disease. In wild breeding populations of owls, there is very limited information about the presence, impact, and potential transmission of herpesvirus. The herpesvirus partial DNA polymerase gene was detected using polymerase chain reaction in oropharyngeal swabs of 16 out of 170 owls examined that were captured in or near nest boxes. Herpesvirus was detected in Ural owls (Strix uralensis), in both adults and young, but not in tawny owls (Strix aluco). In yellow-necked mice (Apodemus flavicollis), as the main prey of tawny owls and Ural owls in the area, herpesvirus was detected in the organs of 2 out of 40 mice captured at the same locations as the owls. Phylogenetic analysis showed that the herpesvirus sequences detected in the Ural owls differed from the herpesvirus sequences detected in the yellow-necked mice. The results indicate that herpesvirus infection exists in the breeding wild Ural owl population. However, herpesvirus-infected owls did not show any clinical or productivity deviances and, based on a phylogenetic comparison of detected herpesvirus sequences and sequences obtained from Genbank database, it seems that mice and other rodents are not the source of owl infections. The most probable transmission pathway is intraspecific, especially from adults to their chicks, but the origin of herpesvirus in owls remains to be investigated.