Avian diseases最新文献

Infections with avian metapneumoviruses (aMPVs) pose direct and indirect health problems to domesticated poultry worldwide by predisposing to secondary infections resulting in substantial economic losses. Although this primarily impacts commercial chickens, turkeys, and ducks, inducing upper respiratory disease and drops in egg production, infection of a myriad of wild bird species also contributes to the complex global epidemiology of aMPV subtypes. The functions of aMPV viral proteins have been described, with the F protein and G protein particularly important for species tropism, facilitating sequence-based epidemiological investigations and being prime targets of the host immune response. Although in vitro and in vivo studies have provided some insights into aMPV-host interactions, knowledge regarding detailed mechanisms underlying virus entry and cell-to-cell spread as well as antagonism of innate immunity in primary cells remains limited. Some information obtained from studies with the closely related human Metapneumovirus may be applicable to aMPV but requires confirmation in the context of avian models. The establishment of reverse genetics systems for the most well-characterized aMPV subtypes A, B, and C as well as primary cell and organ culture models has enabled mechanistic investigations into virus-host interactions. In this review we provide an overview of how in vitro and ex vivo models can be utilized for aMPV isolation and propagation and concomitantly to investigate innate immune responses in a more authentic context. The construction and applications of reverse genetics systems for aMPV is also discussed with respect to facilitating investigations into the function(s) of viral proteins and identifying viral molecular determinants mediating differential virulence levels in poultry species. Collectively this provides a pathway to enable progress in key areas of aMPV research with a view to mitigating the annual disease burden resulting from intra- and interspecies aMPV infections.

Avian metapneumovirus (aMPV) is a globally widespread avian disease. Infection with the virus causes respiratory illness and contributes to secondary infections, resulting in increased morbidity and mortality with serious economic losses. The virus is classified into four subtypes (A-D). Historically, the United States experienced geographically limited outbreaks of subtype C in turkeys during the late 1990s, which were eventually eradicated. In 2024, cases of aMPV subtypes A and B were reported in commercial chicken and turkey flocks, marking the first time these subtypes were detected in the United States. Although outbreaks of subtypes A and B have been detected in both chickens and turkeys, turkeys appear to be more susceptible and have a higher morbidity and mortality rate. Currently, a concern for the turkey industry is the possibility of vertical transmission of the virus from hen to poult. In these studies, we confirmed the presence of aMPV in the respiratory tract of infected commercial turkeys and then examined eggs from aMPV-positive laying hens for the presence of viral RNA that might suggest vertical transmission of the virus. Eggs from seven different aMPV-positive commercial turkey flocks were harvested and tested for aMPV subtypes A and B via quantitative real-time PCR. Results demonstrate no evidence of viral RNA in any of the egg or embryo samples tested, either inside or on the shell surface. These results provide direct evidence that vertical transmission does not appear to contribute to virus dissemination in commercial turkey flocks.

Since its first detection in turkeys in South Africa in the late 1970s, avian metapneumovirus (aMPV) has emerged as a major pathogen of concern for poultry worldwide, causing acute respiratory disease with significant economic consequences. The virus has spread throughout every continent besides Australia, with distinct subtypes (A-D) identified in different regions and hosts. In the United States, the emergence of subtype C in the mid-1990s led to widespread outbreaks in turkeys and established an endemic presence for almost a decade. Eradication efforts took years of surveillance, molecular characterization of the new subtype, concentrated region-wide eradication plans, and vaccine development before they were fully successful. The recent detection of new subtypes (subtypes A and B) in the United States in 2024, after nearly two decades of aMPV-free status, underscores the continual need for vigilant monitoring and adaptive management of this highly contagious and impactful respiratory disease. This review seeks to cover the historical emergence, progression, and eradication of aMPV subtype C (aMPV/C) in the United States, while drawing on lessons learned from the epidemic for the broader global avian industry.

Avian metapneumovirus (aMPV) is a contagious respiratory disease affecting mainly turkeys and chickens, causing respiratory problems along with reproductive disorders such as egg drop. In the United States, the recent introduction of the aMPV subgroup B initially and later subgroup A in poultry farms resulted in significant economic losses. To isolate aMPV-B, 22 clinical samples from chicken and turkey farms that tested strongly positive by real-time RT-PCR were inoculated in four different cell lines, including turkey tracheal cells (TT cells), the Japanese quail fibrosarcoma cell line (QT35), chicken embryo fibroblasts, and Vero E6 cells. After five blind passages, successful isolation was achieved in one tracheal sample pool inoculated on TT cells. Real-time RT-PCR, indirect immunofluorescence assay, and next-generation sequencing confirmed the successful isolation. After primary isolation, successful adaptation and propagation in Vero E6 cells was achieved. The whole-genome sequence-based molecular characterization of this isolate (TT P6) revealed 100% identity with the field strain sequence of the source sample (ADRDL-6). The TT P6 isolate and all newly detected U.S. aMPV-B isolates showed >99% identity and clustered separately from previously reported Asian, European, and South American sequences, based on whole-genome and individual-gene analyses. The highest heterogeneity was detected in the G protein, which exhibited unique amino acid substitutions, and the SH protein. Interestingly, TT P6 possessed unique threonine157isoleucine (Thr157Ile) and isoleucine322threonine (Ile322Thr) substitutions compared to all other U.S. aMPV-Bs. However, turkey origin isolate NC 23734-GA showed maximum identity with TT P6 isolate (chicken origin), including a unique Ile322Thr mutation. Complete Vero cell adaptation and in-depth molecular characterization of TT P6 isolate make it a suitable candidate for pathogenesis study and vaccine development. The distinct phylogenetic clustering and unique amino acid changes of U.S. aMPV-Bs, particularly in the G protein, suggest the possibility of new variant emergence in the United States, requiring further genetic and in vivo studies.

Avian metapneumovirus (aMPV) poses a significant threat to poultry health, causing respiratory disease, reduced egg production, and substantial economic losses. Despite its global importance, data on aMPV circulation in North Africa remain limited. This study investigated the prevalence and genetic diversity of aMPV in wild birds in Morocco, with a focus on migratory species. Molecular testing detected aMPV in 12% of samples (131 birds, 254 samples), with subtype B comprising 73% of positive cases and subtype A accounting for 27%. Phylogenetic analysis revealed close genetic relationships between Moroccan strains and European reference strains, including vaccine-related sequences. Strains isolated from different bird species clustered into distinct phylogenetic groups, suggesting potential host-specific adaptations. These findings underscore the role of migratory birds in the dissemination of aMPV and highlight the urgent need for enhanced surveillance to guide control strategies for both wild and domestic bird populations.

The recent ongoing outbreak of avian metapneumovirus subgroup B (aMPV-B) in the United States represents a serious threat to turkey and chicken production. In this study, we used the aMPV-B/chicken/USA/SD-24/P6 isolate to test pathogenicity and to establish a challenge model in chickens and turkeys. Two studies were conducted in both species: in 7- and 14-day-old chickens and in 1-, 7-, and 14-day-old turkeys. We inoculated two challenge doses: 10³ and 10⁵ 50% tissue culture infectious doses. All challenged birds were monitored for clinical signs, gross lesions, histopathologic lesions, as well as virus shedding for 7 days postchallenge (DPC). Each challenged chicken and turkey showed clear clinical signs, as well as gross and histopathologic lesions, along with virus shedding with no noticeable variations related to age or challenge dose. The inoculated virus demonstrated high pathogenicity in both chickens (the host of origin) and turkeys, indicating no host specificity. The highest virus shedding occurred at 3 and 5 DPC in all challenge groups across both species. To our knowledge, this study is the first in the United States to fulfill the Koch's postulates for aMPV-B by experimentally reproducing clinical disease in both chickens and turkeys using a U.S. field strain, followed by successful reisolation of the virus from infected tissues. These challenge models will be helpful for evaluation of the efficacy of imported and new vaccines.

Avian metapneumovirus (aMPV) is a highly contagious pathogen that has caused enormous economic losses worldwide and recently to the U.S. poultry industry. It results in upper respiratory disease, which worsens with secondary bacterial infection. The infection may also spread to the reproductive tract, impacting both egg quality and quantity. Based on the genetic heterogeneity of the G gene, four subtypes, A, B, C, and D, have been identified for aMPVs, with two new, unclassified subtypes detected in North America. Genetic structure and molecular characterization are crucial for understanding genetic diversity, viral epidemics, host range, geographical distribution, and the determinants of pathogenicity and virulence. Additionally, genetic data guide infection control, such as the selection of vaccine strains. This review article provides valuable insights into the genomic characterization of aMPVs, particularly considering the recent introduction and rapid spread of subtypes A and B in the United States. The review highlights the outlines for future control plans based on the molecular characterization of recently emerging aMPVs in U.S. poultry.

Avian metapneumovirus (aMPV) is a disease that has become economically significant in commercial poultry worldwide. This virus has been reported to affect ducks, layers, broilers, and turkeys and causes upper respiratory disease, drops in egg quality and production, and increases in secondary infections. aMPV subtype C was the only subtype previously reported in the United States from 1997 to 2007. However, in October 2023, the California Animal Health and Food Safety Lab (CAHFS) received the first reported case of aMPV subtype A in the country. Since then, aMPV subtype A has been found in commercial broiler and turkey operations throughout California and has more recently spread to Midwestern states. Given the potential economic impact on commercial poultry operations, this case series aims to determine patterns in poultry type, age, location, temporal distribution, and comorbidities of poultry diagnosed with aMPV subtype A throughout the CAHFS system. During the period October 2023 to March 2024, 93 submissions were tested for aMPV subtype A, which comprised 33 commercial meat turkey cases and 60 chicken cases (broiler: 57/60, layer: 2/60, backyard: 1/60). Of those cases tested, 58.1% (54/93) were positive for aMPV subtype A via reverse transcription polymerase chain reaction and included 29 broiler cases and 25 meat turkey cases. The age of affected meat turkeys ranged from 16 to 105 days with a median age of 42 days. The top three most common comorbidities were colibacillosis (96.0%, 24/25), salmonellosis (20.0%, 5/25), and Ornithobacterium rhinotracheale (ORT) infection (20.0%, 5/25), with some turkeys being infected by more than one of these pathogens. The age of affected broiler chickens ranged from 25 to 70 days with a median age of 37 days, and the most common comorbidities were colibacillosis (93.1%, 27/29), infectious bronchitis virus infection (58.6%, 17/29), and ORT infection (37.9%, 11/29). Coinfection with more than one pathogen was also noted in chickens. Statistical analysis showed a significant difference in comorbidity frequency in commercial broilers during the outbreak period when compared to the year prior to the outbreak (P < 0.001). Ultimately, this case report provides baseline information on the first detection of aMPV subtype A in California and aids in our understanding of this emerging disease in the United States.

Avian metapneumovirus (aMPV) is an important global respiratory pathogen for poultry, primarily affecting turkeys and chickens. Until recently, subtype C was the only aMPV ever detected in the United States, which was considered an aMPV-free country for poultry since the eradication of the last cases of aMPV-C in the early 2000s. However, aMPV subtypes A and B were both detected in the United States in 2023-2024, with outbreaks reported in many states. The rapid spread of aMPVs in poultry, despite increased biosecurity practices driven by the avian influenza threat, highlights a gap in our epidemiological knowledge regarding these viruses, making effective preventative measures difficult to establish. To improve our understanding of the genetic characteristics and the transmission of aMPV strains circulating in the United States, 43 RT-qPCR-positive oropharyngeal swabs collected between February and June 2024 from 32 chicken farms belonging to 18 poultry production companies across the state of Georgia were subjected to next-generation sequencing analysis. Forty-two complete or nearly complete aMPV genomes were obtained from the sequencing data, all identified as subtype B, and sharing high genetic similarity among themselves and to other recent North and South American aMPV-B viruses. The combination of phylogenetic analysis and the available metadata revealed genetic clustering by production company and by proximity between farms. Additionally, a comprehensive single-nucleotide polymorphism (SNP) analysis showed the maximum genetic divergence (45 SNPs) between aMPVs from different companies, suggesting multiple viral introduction events into Georgia, likely from other U.S. sources. Overall this work helps characterize aMPV-B strains circulating in the United States and genetic connections that will inform the affected companies to adapt their biosafety measures for aMPV containment.

Avian metapneumovirus (aMPV) is a highly contagious upper respiratory pathogen of poultry globally that emerged in the United States in January 2024 and rapidly spread to flocks throughout North America. In turkeys, the disease (turkey rhinotracheitis) initiates as an upper respiratory infection with high morbidity and frequent complication by bacterial coinfection that can lead to high mortality and significant economic loss. In chickens (swollen head syndrome), uncomplicated clinical disease is less severe than in turkeys. Chickens are less susceptible to the virus, although, once infected, bacterial complication is common. This results in cellulitis and fasciitis of the head and face giving rise to the "swollen head" presentation, often accompanied by neurological signs and elevated mortality. In turkey breeders, broiler breeders, and laying hens, aMPV causes a decrease in egg production, which may become permanent in turkey breeders and may affect eggshell quality causing significant economic impact. Given its similar clinical appearance to other respiratory pathogens, definitive diagnosis requires identification of the virus by isolation, RT-PCR/RT-qPCR, immunohistochemical staining, or in situ hybridization. Exposure to vaccinal- or wild-type aMPV can be monitored using ELISA and virus neutralization. Stringent biosecurity and vaccination protocols along with accurate diagnosis and epidemiological surveillance are required for control of aMPV.