Evidence of avian metapneumovirus subtype C infection of wild birds in Georgia, South Carolina, Arkansas and Ohio, USA

Introduction of Avian metapneumovirus subtype A to the United States: molecular insights and implications

Avian metapneumovirus (aMPV) poses a significant threat to the poultry industry worldwide, primarily affecting turkeys and chickens. The recent detection of aMPV-A and -B subtypes in the United States marks a significant shift after a prolonged period free of aMPV following the eradication of the previously circulating subtype C. Hence, the demand for molecular diagnostic tests for aMPV has arisen due to their limited availability in the US market. In this study, we present the molecular characterization based on the complete genome sequence of aMPV subtype A, which was detected in the US for the first time. Four RT-qPCR positive samples were subjected to next-generation sequencing analysis, resulting in the assembly of one complete and one near-complete genome sequences. Phylogenetic analysis revealed that the isolated strains clustered within the aMPV-A subtype and were most closely related to recent Mexican strains. A detailed amino acid analysis identified unique mutations in the G gene of the US isolates compared to Mexican strains. Additionally, we compared the performance, cross-reactivity, and limit of detection of our revised aMPV subtype-specific RT-qPCR test with two commercial kits, demonstrating similar detection and subtyping capabilities. These findings highlight the importance of accurate diagnostic methods for disease management in the poultry industry, provide valuable insights into the epidemiology of aMPV, and underscore the need for continued vigilance and surveillance to mitigate its impact on poultry production.

Risk of invasive waterfowl interaction with poultry production: Understanding potential for avian pathogen transmission via species distribution models

Recent outbreaks of highly pathogenic avian influenza have devastated poultry production across the United States, with more than 77 million birds culled in 2022-2024 alone. Wild waterfowl, including various invasive species, host numerous pathogens, including highly pathogenic avian influenza virus (HPAIV), and have been implicated as catalysts of disease outbreaks among native fauna and domestic birds. In major poultry-producing states like Arkansas, USA, where the poultry sector is responsible for significant economic activity (>$4 billion USD in 2022), understanding the risk of invasive waterfowl interactions with domestic poultry is critical. Here, we assessed the risk of invasive waterfowl-poultry interaction in Arkansas by comparing the density of poultry production sites (chicken houses) to areas of high habitat suitability for two invasive waterfowl species, (Egyptian Goose [Alopochen aegyptiaca] and Mute Swan [Cygnus olor]), known to host significant pathogens, including avian influenza viruses. The percentage of urban land cover was the most important habitat characteristic for both invasive waterfowl species. At the 95% confidence interval, chicken house densities in areas highly suitable for both species (Egyptian Goose = 0.91 ± 0.11 chicken houses/km2; Mute Swan = 0.61 ± 0.03 chicken houses/km2) were three to five times higher than chicken house densities across the state (0.17 ± 0.01 chicken houses/km2). We show that northwestern and western Arkansas, both areas of high importance for poultry production, are also at high risk of invasive waterfowl presence. Our results suggest that targeted monitoring efforts for waterfowl-poultry contact in these areas could help mitigate the risk of avian pathogen exposure in Arkansas and similar regions with high poultry production.

Tracing the Flight: Investigating the Introduction of Avian Metapneumovirus (aMPV) A and B

Avian metapneumovirus (aMPV) has been identified as an important cause of respiratory and reproductive disease, leading to significant productive losses worldwide. Different subtypes have been found to circulate in different regions, with aMPV-A and B posing a significant burden especially in the Old World, and aMPV-C in North America, albeit with limited exceptions of marginal economic relevance. Recently, both aMPV-A and aMPV-B have been reported in the U.S.; however, the route of introduction has not been investigated. In the present study, the potential importation pathways have been studied through phylogenetic and phylodynamic analyses based on a broad collection of partial attachment (G) protein sequences collected worldwide. aMPV-B circulating in the U.S. seems the descendant of Eastern Asian strains, which, in turn, are related to European ones. A likely introduction pathway mediated by wild bird migration through the Beringian crucible, where the East Asian and Pacific American flight paths intersect, appears likely and was previously reported for avian influenza. aMPV-A, on the other hand, showed a Mexican origin, involving strains related to Asian ones. Given the low likelihood of trade or illegal importation, the role of wild birds appears probable also in this case, since the region is covered by different flight paths directed in a North-South direction through America. Since the information on the role of wild birds in aMPV epidemiology is still scarce and scattered, considering the significant practical implications for the poultry industry demonstrated by recent U.S. outbreaks, further surveys on wild birds are encouraged.

Geographical Expansion of Avian Metapneumovirus Subtype B: First Detection and Molecular Characterization of Avian Metapneumovirus Subtype B in US Poultry

Avian metapneumovirus (aMPV), classified within the Pneumoviridae family, wreaks havoc on poultry health. It typically causes upper respiratory tract and reproductive tract infections, mainly in turkeys, chickens, and ducks. Four subtypes of AMPV (A, B, C, D) and two unclassified subtypes have been identified, of which subtypes A and B are widely distributed across the world. In January 2024, an outbreak of severe respiratory disease occurred on turkey and chicken farms across different states in the US. Metagenomics sequencing of selected tissue and swab samples confirmed the presence of aMPV subtype B. Subsequently, all samples were screened using an aMPV subtype A and B multiplex real-time RT-PCR kit. Of the 221 farms, 124 (56%) were found to be positive for aMPV-B. All samples were negative for subtype A. Six whole genomes were assembled, five from turkeys and one from chickens; all six assembled genomes showed 99.29 to 99.98% nucleotide identity, indicating a clonal expansion event for aMPV-B within the country. In addition, all six sequences showed 97.74 to 98.58% nucleotide identity with previously reported subtype B sequences, e.g., VCO3/60616, Hungary/657/4, and BR/1890/E1/19. In comparison to these two reference strains, the study sequences showed unique 49-62 amino acid changes across the genome, with maximum changes in glycoprotein (G). One unique AA change from T (Threonine) to I (Isoleucine) at position 153 in G protein was reported only in the chicken aMPV sequence, which differentiated it from turkey sequences. The twelve unique AA changes along with change in polarity of the G protein may indicate that these unique changes played a role in the adaptation of this virus in the US poultry. This is the first documented report of aMPV subtype B in US poultry, highlighting the need for further investigations into its genotypic characterization, pathogenesis, and evolutionary dynamics.

Avian Metapneumovirus Infection in Poultry Flocks: A Review of Current Knowledge

Avian metapneumovirus (aMPV) is one of the respiratory viruses that cause global economic losses in poultry production systems. Therefore, it was important to design a comprehensive review article that gives more information about aMPV infection regarding the distribution, susceptibility, transmission, pathogenesis, pathology, diagnosis, and prevention. The aMPV infection is characterized by respiratory and reproductive disorders in turkeys and chickens. The disease condition is turkey rhinotracheitis in turkeys and swollen head syndrome in chickens. Infection with aMPV is associated with worldwide economic losses, especially in complications with other infections or poor environmental conditions. The genus Metapneumovirus is a single-stranded enveloped RNA virus and contains A, B, C, and D subtypes. Meat and egg-type birds are susceptible to aMPV infection. The virus can transmit through aerosol, direct contact, mechanical, and vertical routes. The disease condition is characterized by respiratory manifestations, a decrease in egg production, growth retardation, increasing morbidity rate, and sometimes nervous signs and a high mortality rate, particularly in concurrent infections. Definitive diagnosis of aMPV is based mainly on isolation and identification methods, detection of the viral DNA, as well as seroconversion. Prevention of aMPV infection depends on adopting biosecurity measures and vaccination using inactivated, live attenuated, and recombinant or DNA vaccines.

Longitudinal Survey on aMPV Circulation in French Broiler Flocks following Different Vaccination Strategies

In recent years, the impact of respiratory disease resulting from Avian Metapneumovirus (aMPV) infection has been generally rising in the broiler industry in Europe. In this context, in order to investigate aMPV contribution to the clinical picture and the potential benefits of diversified vaccination strategies compared to nonvaccination policies, a longitudinal monitoring was performed, also evaluating Infectious Bronchitis Virus (IBV) presence. Broiler flocks located in Western France, where aMPV has already proven to be a health and productivity issue, were screened by RT-PCR on rhino-pharyngeal swabs, and the viruses were genetically characterized by sequence analysis. For a more comprehensive picture of aMPV molecular epidemiology and evolution in France, aMPV subtype B strains detected from 1985 to 1998 were sequenced and included in the analysis. The survey confirmed the detection of aMPV subtype B in commercial broiler flocks in France, together with a certain heterogeneity demonstrated by the circulation of more recent and historical French field strains. No IBV field strains were detected. The implementation and evaluation of different management choices and vaccine strategies suggests once again that immunization does not prevent infection but contributes greatly to the containment of the clinical manifestations.

Molecular characterization of avian metapneumovirus subtype C detected in wild mallards (Anas platyrhynchos) in The Netherlands

Avian metapneumovirus (AMPV) represents a long-term threat to the poultry industry due to its etiological role in the induction of acute respiratory disease and/or egg drop syndrome in domestic turkeys, chickens, and ducks. Although this disease is commonly referred to as turkey rhinotracheitis, the host range of AMPV encompasses many avian species. We have screened 1323 oropharyngeal- and cloacal swab samples obtained from wild mallards in the Netherlands from 2017 to 2019 by RT-PCR using a degenerate primer pair to detect all members of the Paramyxoviridae and Pneumoviridae or an avian metapneumovirus subtype C (AMPV-C)-specific RT-qPCR assay. We identified a total of seven cases of AMPV-C infections in wild, healthy mallards (Anas platyrhynchos), of which two AMPV-C positive samples were further processed using next-generation sequencing. Phylogenetic analysis of the two complete genomes showed that the newly identified AMPV-C strains share closest sequence identity (97%) with Eurasian lineage AMPV-C strains identified in Muscovy ducks in China that presented with severe respiratory disease and egg production loss in 2011. Further analysis of G protein amino acid sequences showed a high degree of variability between the newly identified AMPV-C variants. PONDR scoring of the G protein has revealed the ectodomain of AMPV-C to be partitioned into a long intrinsically disordered and short ordered region, giving insights into AMPV G protein structural biology. In summary, we provide the first report of full-length AMPV-C genome sequences derived from wild birds in Europe. This emphasizes the need for further surveillance efforts to better characterize the host range, epidemiologic distribution, and pathogenicity of AMPV-C to determine the risk posed by cross-species jumps from wildfowl to domesticated avian species.

Disentangling the role of wild birds in avian metapneumovirus (aMPV) epidemiology: A systematic review and meta-analysis

Given the avian metapneumovirus (aMPV) disease burden in poultry worldwide and the evidence of a possible role played by wild birds in the virus epidemiology, the present study summarizes aMPV serological and molecular data on free-ranging avifauna available in the literature by conducting a systematic review and meta-analysis. A computerized literature research was performed on PubMed, Scopus, CAB Direct and Web of Science to identify relevant publications across the period 1990-2021, along with the screening of reference lists. A random-effect model was applied to calculate pooled prevalence estimates with 95% confidence intervals. The inconsistency index statistic (I² ) was applied to assess between-study heterogeneity. Subgroup analyses for molecular studies only were performed according to geographical area of samplings, taxonomic order, genus and migration patterns of the birds surveyed. A total of 11 publications on molecular surveys and 6 on serological ones were retained for analysis. The pooled molecular prevalence was 6% (95% CI: 1-13%) and a high between-study heterogeneity was detected (I²  = 96%, p < .01). Moderator analyses showed statistically significant differences according to geographical area studied, taxonomic order and genus. Concerning serological prevalence, a pooled estimate of 14% (95% CI: 1-39%), along with a high between-study heterogeneity, was obtained (I²  = 98%, p < .01). Moderator analysis was not performed due to the scarcity of eligible serological studies included. Overall, molecular and serological evidence suggests that some wild bird taxa could play a role in aMPV epidemiology. Particularly, wild ducks, geese, gulls and pheasants, according to scientific contributions hereby considered, proved to be susceptible to aMPV, and due to host ecology, may act as a viral carrier or reservoir. Further surveys of wild birds are encouraged for a better comprehension of the poultry/wild bird interface in aMPV epidemiology and for better characterizing the virus host breadth.

Characterization of avain metapneumovirus subgroup C isolated from chickens in Beijing, China

Avian metapneumovirus (aMPV) is an important causative agent that causes acute respiratory disease and egg-dropping in chickens and turkeys. Here, we characterized an aMPV subgroup C (aMPV/C) from 320-day-old broiler breeder chickens with severe respiratory diseases in Beijing, China, as evidenced by RT-PCR typing and confirmation of the nucleoprotein (N) gene sequence. The N gene sequence of the aMPV/C strain (designated BJ17) exhibited no deletions or insertions and possessed 94.6% to 99.6% identity to those of published aMPV/C isolates. The phylogenetic tree of the nucleotide sequences constructed using the neighbor-joining clustering method showed that the BJ17 strain formed one cluster with other aMPV/C viruses and formed one subcluster with published Chinese aMPV/C isolates regardless of Muscovy duck or chicken origins. Comparative analysis of the N proteins showed that a unique amino acid residue D at position 110 might be associated with regional distribution due to its occurrence in all the Chinese aMPV/C isolates only. Strain BJ17 was successfully isolated by cultured Vero cell passage and further inoculated in 3-wk-old specific-pathogen-free chickens for the examination of pathogenicity. Animal experimental results showed that BJ17-inoculated chickens had severe respiratory diseases and inflammatory lesions, as demonstrated by pathological changes and aMPV antigen in the nasal turbinate, tracheae, and lung tissues. These results enrich the available information regarding the epidemiology and pathogenicity of aMPV/C in chickens, which may facilitate the development of effective measures against aMPV/C infection in China.

Molecular Survey on A, B, C and New Avian Metapneumovirus (aMPV) Subtypes in Wild Birds of Northern-Central Italy

Simple Summary

Avian metapneumovirus (aMPV) is a common pathogen in poultry and has been detected in wild birds, suggesting the possible role in viral dissemination. A feature of aMPV is its genetic and antigenic variability, which has allowed the identification of various subtypes of the virus with different characteristics in terms of host tropism. Two new subtypes of aMPV were recently identified in gulls and parakeets. We aimed to explore the epidemiology of old and new aMPV subtypes in wild birds. Samples were collected in Italy during the surveillance of avian influenza in wild species and were tested with two multiplex real time RT-PCRs that were able to detect and distinguish the aMPV subtypes (A, B, C, gull, and parakeet subtypes). All of the individuals were negative, except for one mallard that was positive for aMPV subtype C. The M and G genes of this strain were molecularly characterized and revealed similarities with Chinese and European strains, including an Italian sequence that was previously detected in a widgeon. These findings confirm the susceptibility of mallards, which are closely related to domestic species, highlighting the importance of the epidemiological monitoring of aMPV circulation.

Abstract

Recent insights into the genetic and antigenic variability of avian metapneumovirus (aMPV), including the discovery of two new subtypes, have renewed interest in this virus. aMPV causes a well-known respiratory disease in poultry. Domestic species show different susceptibility to aMPV subtypes, whereas sporadic detections in wild birds have revealed links between epidemiology and migration routes. To explore the epidemiology of aMPV in wild species, a molecular survey was conducted on samples that were collected from wild birds during avian influenza surveillance activity in Italy. The samples were screened in pools by multiplex real time RT-PCR assays in order to detect and differentiate subtypes A, B, C, and those that have been newly identified. All the birds were negative, except for a mallard (Anas platyrhynchos) that was positive for aMPV subtype C (sampled in Padua, in the Veneto region, in 2018). The sequencing of partial M and full G genes placed the strain in an intermediate position between European and Chinese clusters. The absence of subtypes A and B supports the negligible role of wild birds, whereas subtype C detection follows previous serological and molecular identifications in Italy. Subtype C circulation in domestic and wild populations emphasizes the importance of molecular test development and adoption to allow the prompt detection of this likely emerging subtype.

Establishment and application of a quadruple real-time RT-PCR for detecting avian metapneumovirus

In order to develop an appropriate method for high-throughput detection of avian metapneumovirus, a quadruple real-time reverse-transcription polymerase chain reaction assay was established with four pairs of specific primers and four specific probes based on the G or M gene of aMPV-A, aMPV-B, aMPV-C and aMPV-D. Its specificity and sensitivity were evaluated, and clinical samples were tested by the method. The results showed that all the four subgroups of avian metapneumovirus can be detected in the quadruple real-time RT-PCR assay simultaneously, with a detection limit of 100-1000 cRNA copies/reaction. The other common poultry viruses were negative. In the avian clinical sample detection, 39 out of 1920 clinical samples collected from 8 provinces were positive. Compared with published RT-PCR assays, the κ value of the quadruple real-time RT-PCR assay in 1920 avian clinical samples was 1.000 (P < 0.001). The established method could be used for the rapid detection of the four subgroups of avian metapneumovirus with high specificity and high sensitivity.

Zoonotic Origins of Human Metapneumovirus: A Journey from Birds to Humans

Metapneumoviruses, members of the family Pneumoviridae, have been identified in birds (avian metapneumoviruses; AMPV’s) and humans (human metapneumoviruses; HMPV’s). AMPV and HMPV are closely related viruses with a similar genomic organization and cause respiratory tract illnesses in birds and humans, respectively. AMPV can be classified into four subgroups, A–D, and is the etiological agent of turkey rhinotracheitis and swollen head syndrome in chickens. Epidemiological studies have indicated that AMPV also circulates in wild bird species which may act as reservoir hosts for novel subtypes. HMPV was first discovered in 2001, but retrospective studies have shown that HMPV has been circulating in humans for at least 50 years. AMPV subgroup C is more closely related to HMPV than to any other AMPV subgroup, suggesting that HMPV has evolved from AMPV-C following zoonotic transfer. In this review, we present a historical perspective on the discovery of metapneumoviruses and discuss the host tropism, pathogenicity, and molecular characteristics of the different AMPV and HMPV subgroups to provide increased focus on the necessity to better understand the evolutionary pathways through which HMPV emerged as a seasonal endemic human respiratory virus.

First detection of Avian metapneumovirus subtype C Eurasian Lineage in a Eurasian wigeon (Mareca penelope) wintering in Northeastern Italy: an additional hint on the role of migrating birds in the viral epidemiology

Avian metapneumovirus (aMPV) economically affects the global poultry industry causing respiratory and reproductive disorders. Considering the paucity of data on the aMPV occurrence in European free-ranging avifauna, a molecular survey was conducted on wild birds of 23 species belonging to the orders Anseriformes, Charadriiformes or Passeriformes, captured alive and sampled in Northeast Italy as part of the national Avian influenza virus (AIV) surveillance activities. A total of 492 oropharyngeal swabs, collected from 2007 to 2010, all AIV negative, were screened from aMPV by subtype-specific qRT-PCR. An aMPV-C strain, named aMPV/C/IT/Wigeon/758/07, was found in a wintering young Eurasian wigeon (Mareca penelope) sampled in November 2007. The matrix, fusion, and attachment glycoprotein genes of the detected strain were subsequently amplified by specific independent RT-PCRs, then sequenced, and compared in a phylogenetic framework with known aMPV homologous sequences retrieved from GenBank. Close genetic relationships were found between the aMPV/C/IT/Wigeon/758/07 strain and subtype C Eurasian lineage strains isolated in the late 1990s in French domestic ducks, suggesting epidemiological links. Eurasian wigeons are indeed medium to long-range migrant dabbling ducks that move along the Black Sea/Mediterranean flyway, our finding might therefore be related to migratory bridges between countries. To our knowledge, this is the first molecular evidence of the occurrence of a subtype C in Italy and backdates the aMPV-C circulation to 2007. Moreover, results suggest the susceptibility of Eurasian wigeons to aMPV. Broader investigations are needed to assess the role of wild ducks and the significance of the wildfowl/poultry interface in the aMPV-C epidemiology.

Research Note: Detection of Avian metapneumovirus subgroup C specific antibodies in a mallard flock in Italy

Avian metapneumovirus (aMPV) is a viral pathogen that causes respiratory signs and drops in egg production most notably in turkeys but also affects chickens, ducks and other species. Four subgroups (aMPV-A, -B, -C and -D) have been characterized to date, which differ genetically, antigenically and in terms of geographic distribution and host range. Despite the rising awareness towards aMPV, many aspects of its epidemiology are still poorly understood.

In this pilot study, a serological survey was carried out to assess the possible circulation of subgroups A, B, and C in intensively raised ducks in Northern Italy. A total of 220 sera from 10 Pekin duck flocks and one mallard flock were collected at slaughter and tested by subgroup-specific aMPV-A, B, and C indirect ELISA assays. None of the tested birds had been vaccinated against aMPV and no symptoms had been reported. No aMPV-A, B or C antibodies were detected in any bird of the Pekin duck flocks, whereas the entire mallard flock tested positive for aMPV-C antibodies. This is the first report of aMPV-C antibodies in ducks in Italy, where only aMPV-B has been reported to circulate in recent years. Further research efforts will be targeted towards the screening of a larger panel of samples, in the hope of obtaining positive samples from which full length genome sequences and infectious viruses can be isolated for virus characterization. Finally, the demonstration of aMPV-C specific antibodies in the serum of all sampled mallards indirectly suggests that this species is readily infected by aMPV-C and supports a possible role of wild anatids as a transmission vector of the virus.

Novel Inactivated Subtype B Avian Metapneumovirus Vaccine Induced Humoral and Cellular Immune Responses

Avian metapneumovirus (aMPV), a highly contagious agent, is widespread and causes acute upper respiratory tract disease in chickens and turkeys. However, currently, there is no vaccine licensed in China. Herein, we describe the development of an inactivated aMPV/B vaccine using the aMPV/B strain LN16. Combined with a novel adjuvant containing immune-stimulating complexes (ISCOMs), the novel vaccine could induce high virus-specific and VN antibodies. In addition, it activated B and T lymphocytes and promoted the expression of IL-4 and IFN-γ. Importantly, boosting vaccination with the inactivated aMPV/B vaccine could provide 100% protection against aMPV/B infection with reduced virus shedding and turbinate inflammation. The protection efficacy could last for at least 6 months. This study yielded a novel inactivated aMPV/B vaccine that could serve as the first vaccine candidate in China, thus contributing to the control of aMPV/B and promoting the development of the poultry industry.

Proteome Analysis in a Mammalian Cell line Reveals that PLK2 is Involved in Avian Metapneumovirus Type C (aMPV/C)-Induced Apoptosis

Avian metapneumovirus subtype C (aMPV/C) causes an acute respiratory disease that has caused serious economic losses in the Chinese poultry industry. In the present study, we first explored the protein profile in aMPV/C-infected Vero cells using iTRAQ quantitative proteomics. A total of 921 of 7034 proteins were identified as significantly altered by aMPV/C infection. Three selected proteins were confirmed by Western blot analysis. Bioinformatics GO analysis revealed multiple signaling pathways involving cell cycle, endocytosis, and PI3K-Akt, mTOR, MAPK and p53 signaling pathways, which might participate in viral infection. In this analysis, we found that PLK2 expression was upregulated by aMPV/C infection and investigated whether it contributed to aMPV/C-mediated cellular dysfunction. Suppressing PLK2 attenuated aMPV/C-induced reactive oxygen species (ROS) production and p53-dependent apoptosis and reduced virus release. These results in a mammalian cell line suggest that high PLK2 expression correlates with aMPV/C-induced apoptosis and viral replication, providing new insight into the potential avian host cellular response to aMPV/C infection and antiviral targets.

Discovery and Characterization of Novel RNA Viruses in Aquatic North American Wild Birds

Wild birds are recognized viral reservoirs but our understanding about avian viral diversity is limited. We describe here three novel RNA viruses that we identified in oropharyngeal/cloacal swabs collected from wild birds. The complete genome of a novel gull metapneumovirus (GuMPV B29) was determined. Phylogenetic analyses indicated that this virus could represent a novel avian metapneumovirus (AMPV) sub-group, intermediate between AMPV-C and the subgroup of the other AMPVs. This virus was detected in an American herring (1/24, 4.2%) and great black-backed (4/26, 15.4%) gulls. A novel gull coronavirus (GuCoV B29) was detected in great black-backed (3/26, 11.5%) and American herring (2/24, 8.3%) gulls. Phylogenetic analyses of GuCoV B29 suggested that this virus could represent a novel species within the genus Gammacoronavirus, close to other recently identified potential novel avian coronaviral species. One GuMPV-GuCoV co-infection was detected. A novel duck calicivirus (DuCV-2 B6) was identified in mallards (2/5, 40%) and American black ducks (7/26, 26.9%). This virus, of which we identified two different types, was fully sequenced and was genetically closest to other caliciviruses identified in Anatidae, but more distant to other caliciviruses from birds in the genus Anas. These discoveries increase our knowledge about avian virus diversity and host distributions.

First Molecular Characterization of Avian Metapneumovirus (aMPV) in Turkish Broiler Flocks

Viral respiratory diseases, including avian metapneumovirus (aMPV), have a significant economic impact on poultry industries. The frequency and genotype diversity of aMPV in Turkish broiler flocks is not known at present. The aim of this study was to report the first molecular identification and phylogeny of aMPV, which is circulating in Turkish broiler flocks. Trachea tissue samples and tracheal swabs were collected from 110 broiler flocks distributed in different geographical regions in Turkey between March 2017 and March 2018. Detection of aMPV was confirmed with the use of universal reverse transcriptase (RT) PCR, and eight (7.2%) broiler farms were positive for aMPV. Sequence analysis of the G gene revealed the exclusive presence of subtype B viruses. Three field isolates clustered closely with a 2002 Israel isolate, indicating a potential transmission route between these two countries and through the Middle East. The remaining five field isolates were closely related to a vaccine strain, even though broiler flocks in Turkey are not routinely vaccinated against aMPV. Therefore, we speculate these five isolates could have originated from nearby vaccinated turkey farms. Additionally, the presence of some nucleotide substitutions compared to the reference vaccine sequence suggests prolonged circulation and evolution of the original vaccine virus or a vaccine subpopulation was selected under field conditions. This evidence emphasizes the need for further detailed and more systemic approaches to evaluate aMPV spread and evolution in order to design effective control strategies.

Avian Metapneumovirus circulation in Italian broiler farms

With increasing frequency, avian Metapneumovirus (aMPV) is reported to induce respiratory signs in chickens. An adequate knowledge of current aMPV prevalence among Italian broilers is lacking, with little information available on its economical and health impact on the poultry industry. In order to collect preliminary data on the epidemiological context of aMPV in broiler flocks, a survey was performed in areas of Northern Italy with high poultry density from 2014 to 2016. Upper respiratory tract swabs were collected and processed by A and B subtype-specific multiplex real-time reverse transcription PCR (RT-PCR). Samples were also screened for infectious bronchitis virus (IBV) by generic RT-PCR and sequencing. Productive data and respiratory signs were detailed where possible. The high prevalence of aMPV was confirmed in broilers older than 26 d and also attested in IBV-negative farms. All aMPV detections belonged to subtype B. Italian strain genetic variability was evaluated by the partial attachment (G) gene sequencing of selected strains and compared with contemporary turkey strains and previously published aMPV references, revealing no host specificity and the progressive evolution of this virus in Italy.

A Reverse Genetics Approach for the Design of Methyltransferase-Defective Live Attenuated Avian Metapneumovirus Vaccines

Avian metapneumovirus (aMPV), also known as avian pneumovirus or turkey rhinotracheitis virus, is the causative agent of turkey rhinotracheitis and is associated with swollen head syndrome in chickens. aMPV belongs to the family Paramyxoviridae which includes many important human pathogens such as human respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and human parainfluenza virus type 3 (PIV3). The family also includes highly lethal emerging pathogens such as Nipah virus and Hendra virus, as well as agriculturally important viruses such as Newcastle disease virus (NDV). For many of these viruses, there is no effective vaccine. Here, we describe a reverse genetics approach to develop live attenuated aMPV vaccines by inhibiting the viral mRNA cap methyltransferase. The viral mRNA cap methyltransferase is an excellent target for the attenuation of paramyxoviruses because it plays essential roles in mRNA stability, efficient viral protein translation and innate immunity. We have described in detail the materials and methods used to generate recombinant aMPVs that lack viral mRNA cap methyltransferase activity. We have also provided methods to evaluate the genetic stability, pathogenesis, and immunogenicity of live aMPV vaccine candidates in turkeys.

Methyltransferase-defective avian metapneumovirus vaccines provide complete protection against challenge with the homologous Colorado strain and the heterologous Minnesota strain

Avian metapneumovirus (aMPV), also known as avian pneumovirus or turkey rhinotracheitis virus, is the causative agent of turkey rhinotracheitis and is associated with swollen head syndrome in chickens. Since its discovery in the 1970s, aMPV has been recognized as an economically important pathogen in the poultry industry worldwide. The conserved region VI (CR VI) of the large (L) polymerase proteins of paramyxoviruses catalyzes methyltransferase (MTase) activities that typically methylate viral mRNAs at guanine N-7 (G-N-7) and ribose 2'-O positions. In this study, we generated a panel of recombinant aMPV (raMPV) Colorado strains carrying mutations in the S-adenosyl methionine (SAM) binding site in the CR VI of L protein. These recombinant viruses were specifically defective in ribose 2'-O, but not G-N-7 methylation and were genetically stable and highly attenuated in cell culture and viral replication in the upper and lower respiratory tracts of specific-pathogen-free (SPF) young turkeys. Importantly, turkeys vaccinated with these MTase-defective raMPVs triggered a high level of neutralizing antibody and were completely protected from challenge with homologous aMPV Colorado strain and heterologous aMPV Minnesota strain. Collectively, our results indicate (i) that aMPV lacking 2'-O methylation is highly attenuated in vitro and in vivo and (ii) that inhibition of mRNA cap MTase can serve as a novel target to rationally design live attenuated vaccines for aMPV and perhaps other paramyxoviruses.

IMPORTANCE

Paramyxoviruses include many economically and agriculturally important viruses such as avian metapneumovirus (aMPV), and Newcastle disease virus (NDV), human pathogens such as human respiratory syncytial virus, human metapneumovirus, human parainfluenza virus type 3, and measles virus, and highly lethal emerging pathogens such as Nipah virus and Hendra virus. For many of them, there is no effective vaccine or antiviral drug. These viruses share common strategies for viral gene expression and replication. During transcription, paramyxoviruses produce capped, methylated, and polyadenylated mRNAs. Using aMPV as a model, we found that viral ribose 2'-O methyltransferase (MTase) is a novel approach to rationally attenuate the virus for vaccine purpose. Recombinant aMPV (raMPV) lacking 2'-O MTase were not only highly attenuated in turkeys but also provided complete protection against the challenge of homologous and heterologous aMPV strains. This novel approach can be applicable to other animal and human paramyxoviruses for rationally designing live attenuated vaccines.

Molecular comparisons of full length metapneumovirus (MPV) genomes, including newly determined French AMPV-C and -D isolates, further supports possible subclassification within the MPV Genus

Four avian metapneumovirus (AMPV) subgroups (A-D) have been reported previously based on genetic and antigenic differences. However, until now full length sequences of the only known isolates of European subgroup C and subgroup D viruses (duck and turkey origin, respectively) have been unavailable. These full length sequences were determined and compared with other full length AMPV and human metapneumoviruses (HMPV) sequences reported previously, using phylogenetics, comparisons of nucleic and amino acid sequences and study of codon usage bias. Results confirmed that subgroup C viruses were more closely related to HMPV than they were to the other AMPV subgroups in the study. This was consistent with previous findings using partial genome sequences. Closer relationships between AMPV-A, B and D were also evident throughout the majority of results. Three metapneumovirus "clusters" HMPV, AMPV-C and AMPV-A, B and D were further supported by codon bias and phylogenetics. The data presented here together with those of previous studies describing antigenic relationships also between AMPV-A, B and D and between AMPV-C and HMPV may call for a subclassification of metapneumoviruses similar to that used for avian paramyxoviruses, grouping AMPV-A, B and D as type I metapneumoviruses and AMPV-C and HMPV as type II.

Viral replication and lung lesions in BALB/c mice experimentally inoculated with avian metapneumovirus subgroup C isolated from chickens

Avian metapneumovirus (aMPV) emerged as an important respiratory pathogen causing acute respiratory tract infection in avian species. Here we used a chicken aMPV subgroup C (aMPV/C) isolate to inoculate experimentally BALB/c mice and found that the aMPV/C can efficiently replicate and persist in the lungs of mice for at least 21 days with a peak viral load at day 6 postinoculation. Lung pathological changes were characterized by increased inflammatory cells. Immunochemical assay showed the presence of viral antigens in the lungs and significant upregulation of pulmonary inflammatory cytokines and chemokines including MCP-1, MIP-1α, RANTES, IL-1β, IFN-γ, and TNF-α were detected following inoculation. These results indicate for the first time that chicken aMPV/C may replicate in the lung of mice. Whether aMPV/C has potential as zoonotic pathogen, further investigation will be required.

The pathogenicity of avian metapneumovirus subtype C wild bird isolates in domestic turkeys

Background

Avian metapneumovirus subtype C (aMPV/C) causes severe upper respiratory disease in turkeys. Previous report revealed the presence of aMPV/C in wild birds in the southeast regions of the U.S.

Methods

In this study, aMPV/C positive oral swabs from American coots (AC) and Canada geese (CG) were passaged three times in the respiratory tract of specific pathogen free (SPF) turkeys and used as aMPV/C P3 virus isolates in subsequent studies.

Results

Wild bird P3 isolates showed similar growth characteristics when compared to virulent aMPV/C in chicken embryo fibroblast ( CEF) cell cultures and their glycoprotein G gene sequence was closely related to the G gene of aMPV/C Colorado reference virus. Three-day-old commercial or SPF turkeys were inoculated oculonasally with wild bird aMPV/C P3 isolates. At 5 and 7 days post-inoculation (DPI), severe clinical signs were observed in both of the AC and CG virus-exposed groups. Viral RNA was detected in tracheal swabs by reverse transcriptase polymerase chain reaction (RT-PCR). In addition, immunohistochemistry showed virus replication in the nasal turbinate and trachea. All virus-exposed turkeys developed positive antibody response by 14 DPI.

Conclusions

Our data demonstrate that aMPV/C wild bird isolates induced typical aMPV/C disease in the domestic turkeys.

Localization of a region in the fusion protein of avian metapneumovirus that modulates cell-cell fusion

The genus Metapneumovirus within the subfamily Pneumovirinae of the family Paramyxoviridae includes two members, human metapneumovirus (hMPV) and avian metapneumovirus (aMPV), causing respiratory tract infections in humans and birds, respectively. Paramyxoviruses enter host cells by fusing the viral envelope with a host cell membrane. Membrane fusion of hMPV appears to be unique, in that fusion of some hMPV strains requires low pH. Here, we show that the fusion (F) proteins of aMPV promote fusion in the absence of the attachment protein and low pH is not required. Furthermore, there are notable differences in cell-cell fusion among aMPV subtypes. Trypsin was required for cell-cell fusion induced by subtype B but not subtypes A and C. The F protein of aMPV subtype A was highly fusogenic, whereas those from subtypes B and C were not. By construction and evaluation of chimeric F proteins composed of domains from the F proteins of subtypes A and B, we localized a region composed of amino acid residues 170 to 338 in the F protein that is responsible for the hyperfusogenic phenotype of the F from subtype A. Further mutagenesis analysis revealed that residues R295, G297, and K323 in this region collectively contributed to the hyperfusogenicity. Taken together, we have identified a region in the aMPV F protein that modulates the extent of membrane fusion. A model for fusion consistent with these data is presented.

Detection of and phylogenetic studies with avian metapneumovirus recovered from feral pigeons and wild birds in Brazil

The aim of the present study was to determine whether avian metapneumovirus (aMPV)-related viruses were present in wild and synanthropic birds in Brazil. Therefore, we analysed samples from wild birds, feral pigeons and domestic chickens in order to perform a phylogenetic comparison. To detect the presence of aMPV, a nested reverse transcriptase-polymerase chain reaction was performed with the aim of amplifying a fragment of 270 bases for subtype A and 330 bases for subtype B, comprising the gene coding the G glycoprotein. Positive samples for aMPV subtypes A and B were found in seven (13.2%) different asymptomatic wild birds and pigeons (50%) that had been received at the Bosque dos Jequitibás Zoo Triage Center, Brazil. Also analysed were positive samples from 15 (12.9%) domestic chickens with swollen head syndrome from several regions of Brazil. The positive samples from wild birds, pigeons and domestic chickens clustered in two major phylogenetic groups: some with aMPV subtype A and others with subtype B. The similarity of the G fragment nucleotide sequence of aMPV isolated from chickens and synanthropic and wild avian species ranged from 100 to 97.5% (from 100 to 92.5% for the amino acids). Some positive aMPV samples, which were obtained from wild birds classified in the Orders Psittaciformes, Anseriformes and Craciformes, clustered with subtype A, and others from the Anas and Dendrocygma genera (Anseriformes Order) with subtype B. The understanding of the epizootiology of aMPV is very important, especially if this involves the participation of non-domestic bird species, which would add complexity to their control on farms and to implementation of vaccination programmes for aMPV.

Viral respiratory diseases (ILT, aMPV infections, IB): are they ever under control?

1.

The use of vaccines is the main approach to control of the economically important poultry viral respiratory diseases infectious laryngotracheitis (ILT), avian metapneumovirus (aMPV) infections and infectious bronchitis (IB). This paper appraises the current methods of vaccine control in the light of the nature of each virus and epidemiological factors associated with each disease.

2.

Infectious laryngotracheitis virus (ILTV) exists as a single type with a wide range of disease severity. It is a serious disease in certain regions of the world. Recent work has distinguished molecular differences between vaccine and field strains and vaccine virus can be a cause of disease. Vaccines have remained unaltered for many years but new ones are being developed to counter vaccine side effects and reversion and reactivation of latent virus.

3.

Avian metapneumoviruses, the cause of turkey rhinotracheitis and respiratory disease in chickens exists as 4 subtypes, A, B, C and D. A and B are widespread and vaccines work well provided that accurate doses are given. Newer vaccine developments are designed to eliminate reversion and possibly counter the appearance of newer field strains which may break through established vaccine coverage.

4.

IB presents the biggest problem of the three. Being an unstable RNA virus, part of the viral genome that codes for the S1 spike gene can undergo mutation and recombination so that important antigenic variants can appear irregularly which may evade existing vaccine protection. While conventional vaccines work well against homologous types, new strategies are needed to counter this instability. Molecular approaches involving tailoring viruses to suit field challenges are in progress. However, the simple use of two genetically different vaccines to protect against a wide range of heterologous types is now a widespread practice that is very effective.

5.

None of the three diseases described can claim to be satisfactorily controlled and it remains to be seen whether the newer generations of vaccines will be more efficacious and cost effective. The importance of constant surveillance is emphasised and the testing of novel vaccines cannot be achieved without the use of vaccine-challenge experiments in poultry.

Population dynamics and rates of molecular evolution of a recently emerged paramyxovirus, avian metapneumovirus subtype C

We report the existence of two distinct sublineages of avian metapneumovirus (MPV) subtype C, a virus which has caused serious economic loss in commercial turkey farms in the United States. This subtype is closely related to human MPV, infects multiple avian species, and is globally distributed. The evolutionary rates of this virus are estimated to be 1.3 x 10(-3) to 7 x 10(-3) substitutions per site per year, and coalescent estimates place its emergence between 1991 and 1996. The four genes examined show a concordant demographic pattern which is characterized by a rapid increase in population size followed by stable population grown until the present.