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Avian metapneumovirus (aMPV) is a highly contagious pathogen that causes acute upper respiratory tract diseases in chickens and turkeys, resulting in serious economic losses. Subtype B aMPV has recently become the dominant epidemic strain in China. We developed an attenuated aMPV subtype B strain by serial passaging in Vero cells and evaluated its safety and efficacy as a vaccine candidate. The safety test showed that after the 30th passage, the LN16-A strain was fully attenuated, as clinical signs of infection and histological lesions were absent after inoculation. The LN16-A strain did not revert to a virulent strain after five serial passages in chickens. The genomic sequence of LN16-A differed from that of the parent wild-type LN16 (wtLN16) strain and had nine amino acid mutations. In chickens, a single immunization with LN16-A induced robust humoral and cellular immune responses, including the abundant production of neutralizing antibodies, CD4+ T lymphocytes, and the Th1 (IFN-γ) and Th2 (IL-4 and IL-6) cytokines. We also confirmed that LN16-A provided 100% protection against subtype B aMPV and significantly reduced viral shedding and turbinate inflammation. Our findings suggest that the LN16-A strain is a promising live attenuated vaccine candidate that can prevent infection with subtype B aMPV.

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. [ABSTRACT FROM AUTHOR]

ABSTRACT: The clinical relevance of avian metapneumovirus (aMPV) is growing in the poultry sector, especially in broiler farming, where no vaccination is administered in Italy. Given the naïve status of the birds, a serological survey was conducted in a densely populated area of Northern Italy, to evaluate aMPV circulation. Seven farms were selected and sampled in summer/fall, then sampling was repeated in the following season (winter/spring) to assess a possible seasonal effect. In each farm, fifteen birds were blood sampled towards the end of the cycle and sera were analyzed with an ELISA test. Clinical signs were reported in 5 out of 7 farms, although all farms were positive at both sampling points, except for one, which was negative at the first sampling. The seroprevalence within farm ranged from 26.6% to 100%, and antibody titres appear to increase with age. No seasonality effect was evidenced, whereas a farm effect was more distinct. aMPV circulation appears wide in Northern Italian farms, with different clinical outcomes that could be modulated by intrinsic characteristics of the farms. In absence of vaccination, serological monitoring can be a useful tool for viral entrance monitoring, although sampling timing should be evaluated in order to spot seroconversion after late infections.

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. [ABSTRACT FROM AUTHOR]

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.

Four mutants varying the length of the G and SH genes, including a G-truncated mutant (ΔG) and three G/SH-truncated mutants (ΔSH/G-1, ΔSH/G-2, and ΔSH/G-3), were generated via serially passaging the avian metapneumovirus strain SNU21004 into the cell lines Vero E6 and DF-1 and into embryonated chicken eggs. The mutant ΔG particles resembled parental virus particles except for the variance in the density of their surface projections. G and G/SH truncation significantly affected the viral replication in chickens' tracheal ring culture and in infected chickens but not in the Vero E6 cells. In experimentally infected chickens, mutant ΔG resulted in the restriction of viral replication and the attenuation of the virulence. The mutants ΔG and ΔSH/G-1 upregulated three interleukins (IL-6, IL-12, and IL-18) and three interferons (IFNα, IFNβ, and IFNγ) in infected chickens. In addition, the expression levels of innate immunity-related genes such as Mda5, Rig-I, and Lgp2, in BALB/c mice were also upregulated when compared to the parental virus. Immunologically, the mutant ΔG induced a strong, delayed humoral immune response, while the mutant ΔSH/G-1 induced no humoral immune response. Our findings indicate the potential of the mutant ΔG but not the mutant ΔSH/G-1 as a live attenuated vaccine candidate. [ABSTRACT FROM AUTHOR]

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.

ABSTRACT: The aim of this study was to compare the effect of 2 different vaccination programs using vaccines against infection bronchitis virus (IBV) and avian metapneumovirus (aMPV) on the humoral immune response, production performance, carcass weight and composition, and the percentage of selected internal organs. During the rearing of broiler chickens, blood was collected for serum samples from randomly selected birds from each experimental group on d 1, 21, 28, and 38. Geometric mean titer (GMT) values were determined for the aforementioned diseases using serological ELISA tests, performed during routine veterinary inspections. During rearing, body weight, mortality, and feed consumption were monitored, allowing the calculation of feed consumption per kilogram of body weight gain (FCR) and the European Production Index (EPI). At the end of rearing, 20 chickens were selected for dissection, 10 birds from each group. After slaughter, the weight of the eviscerated carcass was determined, and the percentages of carcass parts and selected internal organs in the body weight were calculated. The vaccination program exerted a significant (P

Avian metapneumovirus (aMPV) is a highly contagious pathogen for broilers. Its epidemiological aspects remain poorly understood in Morocco. Given that, we carried out a pilot seroepidemiological survey from December 2020 to June 2021 to define aMPV seroprevalence in Moroccan broiler flocks in different bioclimatic zones (humid to sub-humid, semi-arid, arid) during winter and spring. According to these zones, 48 flocks not vaccinated against aMPV were selected using a stratified random sampling model. With a simple random sampling strategy, fifteen to thirty sera per flock were collected then analysed using a commercial indirect ELISA kit (CIVTEST AVI TRT®, HIPRA S.A., Amer, Spain) that was able to titre antibodies against aMPV subtypes A and B. Furthermore, questionnaires were shared with veterinarians in charge of flocks to collect data and analyse it with multivariable logistic regression models to identify risk factors associated with virus circulation. From 1142 sera, 912 tested positive with the ELISA used, showing an overall aMPV seroprevalence of 79.86% in the broilers. The arid zone had the highest seroprevalences: 94.16% during winter and 84.82% during spring. Bioclimate and season seemed to contribute to aMPV seropositivity. Likewise, high stocking densities and poor hygiene scores on farms were proven to predispose birds to seropositivity. Hereby, we show the circulation of aMPV in Moroccan broiler farms is influenced by bioclimate, season, density, and hygiene conditions. The present study is the first serological evidence of aMPV in broilers in the Maghreb region.

Avian Metapneumovirus infection first emerged in South African turkeys, followed by respiratory problems in chickens with a swollen head syndrome. The etiological agent is a Metapneumovirus in the Pneumoviridae family and the first pneumovirus identified in avian species. This virus causes respiratory and reproductive affections that are worsened in the presence of other pathogens. The present review summarized the current knowledge about the virus’s properties and spread, its different subtypes, and the immunological and pathological mechanisms, especially in the broilers. The diagnostic methods are based on serology and essentially ELISA to show and titer antibodies following infection in naïve birds. Molecular tools such as PCR aim to detect and subtype avian Metapneumovirus genetic material. Besides biosecurity, prevention relies mostly on good management and vaccination.

In poultry, several respiratory viral infections lead to a drop in egg production associated with high economic losses. While the virus–host interactions at the respiratory epithelium are well studied, less is known about these interactions in the oviduct. To investigate possible differences between virus infections at these epithelial structures, we compared the interactions of two important poultry viruses on turkey organ cultures. Two members of the order Mononegavirales, the Avian Metapneumovirus (AMPV) and the Newcastle disease virus (NDV), were selected to conduct the in vitro experiments since these viruses can infect both the trachea and oviduct. In addition, we used different strains of these viruses, a subtype A and a subtype B strain for AMPV and the NDV strains Komarow and Herts'33, to detect possible differences not only between the tissues but also between different viral strains. Turkey tracheal and oviduct organ cultures (TOC and OOC) were prepared to investigate viral replication, antigen localisation, lesion development, and the expression pattern of interferon-λ and importin-α isoforms. All viruses replicated more efficiently in the oviduct than in the tracheal epithelium (p < 0.05). In addition, we observed higher expression levels of both, IFN-λ and importin-α in OOCs compared to TOCs. Our results indicated strain-dependent differences, with the AMPV-B- and Herts'33 strains being more virulent in organ cultures than the AMPV-A- and Komarow strains, based on the higher viral genome loads, more severe histological lesions, and higher upregulation of IFN-λ. Overall, our findings reveal tissue- and virus strain-dependent differences, which may have consequences for disease development in the host tissue and, subsequently, possible treatment strategies. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Preventive Veterinary Medicine / Zhongguo Yufang Shouyi Xuebao is the property of Chinese Journal of Preventive Veterinary Medicine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Newcastle disease virus (NDV) and avian metapneumovirus (aMPV) are among the most impactful pathogens affecting the turkey industry. Since turkeys are routinely immunized against both diseases, the hatchery administration of the combined respective live vaccines would offer remarkable practical advantages. However, the compatibility of NDV and aMPV vaccines has not yet been experimentally demonstrated in this species. To address this issue, an aMPV subtype B live vaccine was administered to day-old poults either alone or in combination with one of two different ND vaccines. The birds were then challenged with a virulent aMPV subtype B strain, clinical signs were recorded and aMPV and NDV vaccine replication and humoral immune response were assessed. All results supported the absence of any interference hampering protection against aMPV, with no significant differences in terms of clinical scoring. In addition, the mean aMPV vaccine viral titers and antibody titers measured in the dual vaccinated groups were comparable or even higher than in the group vaccinated solely against aMPV. Lastly, based on the NDV viral and antibody titers, the combined aMPV and NDV vaccination does not seem to interfere with protection against NDV, although further studies involving an actual ND challenge will be necessary to fully demonstrate this hypothesis. [ABSTRACT FROM AUTHOR]

Four mutants varying the length of the G and SH genes, including a G-truncated mutant (ΔG) and three G/SH-truncated mutants (ΔSH/G-1, ΔSH/G-2, and ΔSH/G-3), were generated via serially passaging the avian metapneumovirus strain SNU21004 into the cell lines Vero E6 and DF-1 and into embryonated chicken eggs. The mutant ΔG particles resembled parental virus particles except for the variance in the density of their surface projections. G and G/SH truncation significantly affected the viral replication in chickens’ tracheal ring culture and in infected chickens but not in the Vero E6 cells. In experimentally infected chickens, mutant ΔG resulted in the restriction of viral replication and the attenuation of the virulence. The mutants ΔG and ΔSH/G-1 upregulated three interleukins (IL-6, IL-12, and IL-18) and three interferons (IFNα, IFNβ, and IFNγ) in infected chickens. In addition, the expression levels of innate immunity-related genes such as Mda5, Rig-I, and Lgp2, in BALB/c mice were also upregulated when compared to the parental virus. Immunologically, the mutant ΔG induced a strong, delayed humoral immune response, while the mutant ΔSH/G-1 induced no humoral immune response. Our findings indicate the potential of the mutant ΔG but not the mutant ΔSH/G-1 as a live attenuated vaccine candidate.

Control strategy of respiratory complex infections should address precipitating and predisposing causative agents in general and immunosuppressive agents in particular. In both clinical and subclinical forms, infectious bursal disease virus (IBDV) is one of the most immunosuppressive diseases of young chickens. This study aimed to investigate the concurrent occurrence of subclinical infectious bursal disease (IBD) and multicausal respiratory complex infections caused by Newcastle disease virus (NDV) and avian metapneumovirus (aMPV) in broilers. In this study, 800 tissue samples (e.g., trachea, cecal tonsil, bursa of Fabricius, and spleen) and 400 sera samples were collected from broilers with confirmed respiratory signs selected from 20 broiler farms in west Azerbaijan province, Iran, from October 2018 to February 2019. Pathogens in the tissue samples were detected using RT-PCR for the VP2 gene of IBDV, F gen of NDV, and N gene of aMPV. The amplified products were sequenced afterward. At the end of the husbandry period, sera samples were used to detect antibodies against IBDV, aMPV, and NDV using ELISA and HI tests. Molecular results showed that the 45% (9/20), 30% (6/20), and 15% (3/20) of tissue samples were positive for IBDV, NDV, and aMPV, respectively. Regarding co-infection, 5% (1/20) of farm isolates were positive for IBD and ND, while 10% (2/20) of farms isolates were positive for IBD and aMPV. Co-infection of IBD, ND, and aMPV was not detected in farm isolates. Serological results indicated that the IBD co-infected flocks had almost higher (P

Simple Summary: In recent years, the impact of respiratory disease resulting from Avian Metapneumovirus (aMPV) infection has been 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 in broilers located in Western France. The survey confirmed the circulation of field aMPV subtype B strains with a certain degree of genetic heterogenicity and the importance of implementation of vaccination to contain the clinical manifestations. 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. [ABSTRACT FROM AUTHOR]

Avian Metapneumovirus infection first emerged in South African turkeys, followed by respiratory problems in chickens with a swollen head syndrome. The etiological agent is a Metapneumovirus in the Pneumoviridae family and the first pneumovirus identified in avian species. This virus causes respiratory and reproductive affections that are worsened in the presence of other pathogens. The present review summarized the current knowledge about the virus's properties and spread, its different subtypes, and the immunological and pathological mechanisms, especially in the broilers. The diagnostic methods are based on serology and essentially ELISA to show and titer antibodies following infection in naïve birds. Molecular tools such as PCR aim to detect and subtype avian Metapneumovirus genetic material. Besides biosecurity, prevention relies mostly on good management and vaccination. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT: Swollen Head Syndrome (SHS) is an economically important viral disease of chickens caused by avian metapneumovirus (aMPV). The virus comprises 6 different subtypes (A,B,C,D, New-1 and New-2). To date, no information was available on the presence of the virus in Tunisian poultry.The present work aims to detect the presence of (aMPV) in broiler chicken in Tunisia, then to characterise the isolates in order to determine their subtype and to estimate their geographic origin of introduction.A total of 289 samples were collected, aMPV detection was detected by real time RT-PCR and molecular characterization was warried out by Sanger sequencing on the glycoprotein (G) gene. Phylogenetic analysis was carried out using Beast 2 software.Out of the 289 samples, 21 were revealed positive to aMPV. Only 2 isolates have been confirmed by sequencing analysis ; one isolate sampled in 2015 and another in 2019. Based on the partial G gene sequence, analysis of these 2 Tunisian isolates showed that they belong to subtype B. The isolate sampled in 2015, appeared to be phylogenetically related to derived vaccine strain. However, the one sampled in 2019 appeared to be a field strain. Phylodynamic analysis provided evidence that this field strain derived from a Spanish strain and probably the virus has been introduced from Spain to North Africa back in 2016.This study is the first that highlighted the circulation of (aMPV) in Tunisia. It is possible that aMPV has been circulating in Tunisia and neighboring countries without being detected. Also, multiple strains could be present and therefore multiple introductions have happened. Through this study, we shed the light on the importance of reinforcing farms biosecurity as well as virological surveillance.

End-point and real-time avian metapneumovirus (AMPV) RT-PCRs have been developed to detect one or two of the four recognized subgroups (A,B,C, and D) simultaneously or for broad range AMPV detection. Current subgroup specific tests target variable areas of the genome which makes these PCRs sensitive to specificity defects as recently documented. In the current study, a single five-plex digital droplet RT-PCR targeting the conserved viral polymerase gene of AMPV, which is less prone to genetic drift, has been designed. This digital droplet RT-PCR was capable of identifying each of the four AMPV subgroups. Each subgroup was identified according to a specifically assigned fluorescent amplitude. Specificity, which was tested including 31 AMPV strains, non-AMPV avian viruses and closely related human respiratory viruses, was 100%. The specific limit of detection for extracted viral RNA was estimated between 1 and 3 copies/μl. This tool simplifies the number of tests required for AMPV genotype diagnostics and should be theoretically less effected by viral genome evolution due to its target region. Ultimately, application of this test will contribute to an improved understanding of the global geographic distribution and subgroup host range of field strains.

In this study, avian coronavirus infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), avian metapneumovirus (AMPV), and avian reovirus (ARV) were evaluated in broiler and layer flocks. For this purpose, tracheal swabs from 48 broiler and 45 layer flocks with respiratory signs were inoculated SPF embryonated chicken eggs for virus isolation. The viruses were identified by real-time PCR. Results showed that the most common virus in both broiler and layer farms was IBV with incidence rates of 58.33% and 46.67%, respectively. ILTV, AMPV, and ARV incidences in the samples were found to be 22.22%, 13.33%, and 4.44% in layer flocks while 2.08%, 8.33%, and 20.83% in broilers, respectively. The numbers of IBV+AMPV and IBV+ARV coinfections were 5 (11.11%) and 1 (2.22%) in layers, whereas, 1 (2.08%) and 5 (10.42%) broilers, respectively. In addition, 2 broiler flocks (4.17%) had triple infection with IBV, AMPV, and ARV. ILTV was detected always alone from the samples of layer and broiler flocks. Sequencing of S1 gene of selected IBV TR/L45 and TR/B42 isolates showed similarities with IS/1494/06 (HM131453) at the rates of 98.98% and 99.69%, respectively, while TR/L37, TR/L38, and TR/L39 isolates were identical to 4/91 (KF377577) vaccine strain at the rates of 99.01%, 99.01%, and 98.76%, respectively. Sequencing analysis of the ICP4 and TK genes of ILTV isolates revealed that they were all field strains with low virulence. The present data represent actual information on the genotypes of IBV and ILTV circulating in poultry flocks in Türkiye. [ABSTRACT FROM AUTHOR]

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. 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. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Preventive Veterinary Medicine / Zhongguo Yufang Shouyi Xuebao is the property of Chinese Journal of Preventive Veterinary Medicine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Control strategy of respiratory complex infections should address precipitating and predisposing causative agents in general and immunosuppressive agents in particular. In both clinical and subclinical forms, infectious bursal disease virus (IBDV) is one of the most immunosuppressive diseases of young chickens. This study aimed to investigate the concurrent occurrence of subclinical infectious bursal disease (IBD) and multicausal respiratory complex infections caused by Newcastle disease virus (NDV) and avian metapneumovirus (aMPV) in broilers. In this study, 800 tissue samples (e.g., trachea, cecal tonsil, bursa of Fabricius, and spleen) and 400 sera samples were collected from broilers with confirmed respiratory signs selected from 20 broiler farms in west Azerbaijan province, Iran, from October 2018 to February 2019. Pathogens in the tissue samples were detected using RT-PCR for the VP2 gene of IBDV, F gen of NDV, and N gene of aMPV. The amplified products were sequenced afterward. At the end of the husbandry period, sera samples were used to detect antibodies against IBDV, aMPV, and NDV using ELISA and HI tests. Molecular results showed that the 45% (9/20), 30% (6/20), and 15% (3/20) of tissue samples were positive for IBDV, NDV, and aMPV, respectively. Regarding co-infection, 5% (1/20) of farm isolates were positive for IBD and ND, while 10% (2/20) of farms isolates were positive for IBD and aMPV. Co-infection of IBD, ND, and aMPV was not detected in farm isolates. Serological results indicated that the IBD co-infected flocks had almost higher (P<0.05) antibody titers against IBD; however, IBDV-NDV co-infected flocks and IBDV-aMPV co-infected flocks had lower antibody titer against NDVand aMPV, respectively. It can be concluded that lower antibody titer against ND and aMPV in IBD-ND and IBD-aMPV co-infections indicated suppressive effects of IBD on these diseases. Therefore, vaccination against IBD even in regions without clinical form of IBD is inevitable for the reduction of immunosuppressive effects of subclinical IBD on immune responses against these diseases. [ABSTRACT FROM AUTHOR]

The clinical relevance of avian metapneumovirus (aMPV) is growing in the poultry sector, especially in broiler farming, where no vaccination is administered in Italy. Given the naïve status of the birds, a serological survey was conducted in a densely populated area of Northern Italy, to evaluate aMPV circulation. Seven farms were selected and sampled in summer/fall, then sampling was repeated in the following season (winter/spring) to assess a possible seasonal effect. In each farm, fifteen birds were blood sampled towards the end of the cycle and sera were analyzed with an ELISA test. Clinical signs were reported in 5 out of 7 farms, although all farms were positive at both sampling points, except for one, which was negative at the first sampling. The seroprevalence within farm ranged from 26.6% to 100%, and antibody titres appear to increase with age. No seasonality effect was evidenced, whereas a farm effect was more distinct. aMPV circulation appears wide in Northern Italian farms, with different clinical outcomes that could be modulated by intrinsic characteristics of the farms. In absence of vaccination, serological monitoring can be a useful tool for viral entrance monitoring, although sampling timing should be evaluated in order to spot seroconversion after late infections. [ABSTRACT FROM AUTHOR]

BACKGROUND: Avian Metapneumovirus (AMPV) causes mild to acute contagious infection of the upper respiratory tract in turkey and chicken with different mortality rate. OBJECTIVES: This study was aimed to molecular detection and subtyping of AMPV infection in broiler flocks using RT-PCR method in Semnan province on samples from 2016 to2020. METHODS: Sampling was carried out from the upper part of the trachea, choana, and sinuses of broiler chickens from the 85 broiler flocks. All flocks were more than 3 weeks of age. In total 10 swabs were taken from each flock, while each 5 were pooled as one sample (total two samples per flock). The samples were transferred to the laboratory for RNA extraction and RT-PCR amplification. RESULTS: Out of 85 tested broiler flocks, 30 (35.3%) were positive for AMPV using the Nd/Nx primer set. In addition, 28 positive samples were found to be of subtype B using the Ga/G12 primer set and 2 remaining positive samples were non-subtype B, probably A, C or D subtypes. CONCLUSIONS: Since AMPV vaccination was not performed in Semnan province, it can be concluded that some cases were infected with the natural viruses. Therefore, vaccination could be effective in controlling AMPV-induced respiratory distress.

In poultry, several respiratory viral infections lead to a drop in egg production associated with high economic losses. While the virus–host interactions at the respiratory epithelium are well studied, less is known about these interactions in the oviduct. To investigate possible differences between virus infections at these epithelial structures, we compared the interactions of two important poultry viruses on turkey organ cultures. Two members of the order Mononegavirales, the Avian Metapneumovirus (AMPV) and the Newcastle disease virus (NDV), were selected to conduct the in vitro experiments since these viruses can infect both the trachea and oviduct. In addition, we used different strains of these viruses, a subtype A and a subtype B strain for AMPV and the NDV strains Komarow and Herts’33, to detect possible differences not only between the tissues but also between different viral strains. Turkey tracheal and oviduct organ cultures (TOC and OOC) were prepared to investigate viral replication, antigen localisation, lesion development, and the expression pattern of interferon-λ and importin-α isoforms. All viruses replicated more efficiently in the oviduct than in the tracheal epithelium (p < 0.05). In addition, we observed higher expression levels of both, IFN-λ and importin-α in OOCs compared to TOCs. Our results indicated strain-dependent differences, with the AMPV-B- and Herts’33 strains being more virulent in organ cultures than the AMPV-A- and Komarow strains, based on the higher viral genome loads, more severe histological lesions, and higher upregulation of IFN-λ. Overall, our findings reveal tissue- and virus strain-dependent differences, which may have consequences for disease development in the host tissue and, subsequently, possible treatment strategies.

Newcastle disease virus (NDV) and avian metapneumovirus (aMPV) are among the most impactful pathogens affecting the turkey industry. Since turkeys are routinely immunized against both diseases, the hatchery administration of the combined respective live vaccines would offer remarkable practical advantages. However, the compatibility of NDV and aMPV vaccines has not yet been experimentally demonstrated in this species. To address this issue, an aMPV subtype B live vaccine was administered to day-old poults either alone or in combination with one of two different ND vaccines. The birds were then challenged with a virulent aMPV subtype B strain, clinical signs were recorded and aMPV and NDV vaccine replication and humoral immune response were assessed. All results supported the absence of any interference hampering protection against aMPV, with no significant differences in terms of clinical scoring. In addition, the mean aMPV vaccine viral titers and antibody titers measured in the dual vaccinated groups were comparable or even higher than in the group vaccinated solely against aMPV. Lastly, based on the NDV viral and antibody titers, the combined aMPV and NDV vaccination does not seem to interfere with protection against NDV, although further studies involving an actual ND challenge will be necessary to fully demonstrate this hypothesis.

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. [ABSTRACT FROM AUTHOR]

Avian metapneumovirus (aMPV) causes respiratory disease and drops in egg production in chickens, and is routinely controlled by vaccination. However, the host's immune response to virulent challenge in vaccinated or unvaccinated broiler chickens is poorly characterized. We show that subtype B vaccination offers heterologous (subtype A challenge) and homologous (subtype B challenge) protection. Subtype B challenge caused significantly greater humoral antibody titres in vaccinated and unvaccinated chickens. In turbinate and lung tissues of unvaccinated-challenged chickens, IgA and IgY mRNA transcription was significantly up-regulated after subtype B challenge compared to subtype A. Cellular immunity (CD8-α and CD8-β) gene transcripts were significantly up-regulated during early and later stages of infection from subtype B or subtype A, respectively. Immune gene transcriptional responses (IL-1β, IL-6 and IL-18) were significantly up-regulated after challenge. Gene transcription results showed that mRNA expression levels of CD8-α, CD8-β, TLR3 and IL-6, particularly in turbinate and trachea tissues, are useful parameters to include in future aMPV vaccination-challenge studies. [ABSTRACT FROM AUTHOR]

Newcastle disease (ND), infectious laryngotracheitis (ILT) and avian metapneumovirus (aMPV) can be similar making it critical to quickly differentiate them. Herein, we adapted pre-existing molecular-based diagnostic assays for NDV and ILTV, and developed new assays for aMPV A and B, for use under synchronized thermocycling conditions. All assays performed equivalently with linearity over a 5 log10 dynamic range, a reproducible (R² > 0.99) limit of detection of ≥ 10 target copies, and amplification efficiencies between 86.8%– 98.2%. Using biological specimens for NDV and ILTV showed 100% specificity. Identical amplification conditions will simplify procedures for detection in diagnostic laboratories. [ABSTRACT FROM AUTHOR]

Abstract Avian Metapneumovirus (aMPV) has been recognized as a respiratory pathogen of turkey and chickens for a long time. Recently, a crescent awareness of aMPV, especially subtype B, clinical and economic impact has risen among European researchers and veterinarians. Nevertheless, the knowledge of its epidemiology and evolution is still limited. In the present study, the broadest available collection of partial G gene sequences obtained from European aMPV-B strains was analyzed using different phylodynamic and biostatistical approaches to reconstruct the viral spreading over time and the role of different hosts on its evolution. After aMPV-B introduction, approximatively in 1985 in France, the infection spread was relatively quick, involving the Western and Mediterranean Europe until the end of the 1990s, and then spreading westwards at the beginning of the new millennium, in parallel with an increase of viral population size. In the following period, a wider mixing among aMPV-B strains detected in eastern and western countries could be observed. Most of the within-country genetic heterogeneity was ascribable to single or few introduction events, followed by local circulation. This, combined with the high evolutionary rate herein demonstrated, led to the establishment of genetically and phenotypically different clusters among countries, which could affect the efficacy of natural or vaccine-induced immunity and should be accounted for when planning control measure implementation. On the contrary, while a significant strain exchange was proven among turkey, guinea fowl and chicken, no evidence of differential selective pressures or specific amino-acid mutations was observed, suggesting that no host adaptation is occurring.

Despite vaccination against avian metapneumoviruses (aMPV), cases of turkey rhinotracheitis (TRT) caused by aMPV field strains are frequently reported. Differences have been shown in the level of immune system stimulation after aMPV vaccination between turkeys that do and do not possess specific anti-aMPV maternally derived antibodies (MDA). The article describes the influence of MDA on the production of IFNγ in the spleen of aMPV-vaccinated turkeys.

SUMMARY: Avian metapneumovirus (AMPV) is an important pathogen for chicken and turkey, responsible for acute upper respiratory tract infection and swollen head syndrome. The disease is highly contagious and causes significant economic losses in chicken and turkey flocks, particularly when associated with secondary infections. In the present study, we performed a serological survey in chicken sera collected from Bangladesh during the period 2014 to 2016. Of 1929, chicken sera examined by indirect enzyme-linked immunosorbent assay, 1,028 (53.29%) were positive. The incidence of AMPV antibodies was higher in broiler breeder flocks aged over 41 wk. The seropositive rate was higher in Gazipur and Mymensingh district and during rainy and winter seasons. This is the first report of serologic evidence of AMPV in Bangladesh. Our results indicate that commercial poultry in Bangladesh is exposed to AMPV.

SUMMARY: Avian metapneumovirus (aMPV) is a major respiratory pathogen in poultry worldwide, causing an acute and highly contagious infection of the upper respiratory tract in turkeys (turkey rhinotracheitis) and many other avian species, including chickens (swollen head syndrome). Since its first description in late 1970s in South Africa, 6 subtypes (A, B, C, D, and 2 new subtypes) have been identified. Infected animals develop local and systemic immunity. However, maternal derived antibodies do not correlate with protection. In intensive flocks, infection spreads rapidly between birds. Wild birds can be infected and they are suggested as probable links. Affected turkeys exhibit nonspecific symptoms and lesions dominated by an acute inflammation of the upper respiratory tract. The virus can induce a decrease in egg production and poor eggshell quality that cause huge economic losses to the poultry industry. Diagnosis of aMPV infection is performed by ELISA tests and molecular methods (RT-PCR). Application of rigorous biosecurity and vaccination programs are crucial and effective for the control of turkey rhinotracheitis. Different types of vaccines are used, with satisfactory protection offered by live attenuated and inactivated vaccines. In addition, new vaccines are being developed and tested which seem to give convincing results.

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.

Avian Metapneumovirus (aMPV) is a causative agent of respiratory disease complex in turkeys and chickens that has recently been detected in Vietnam. Due to its novelty, this study was conducted to elucidate the distribution of aMPV in several provinces in northern Vietnam. By the application of Enzyme-Linked Immunosorbent Assay (ELISA) and nested Reverse Transcription-Polymerase Chain Reaction (RT-PCR), this study demonstrated the circulation of aMPV in 12 out of 14 cities/provinces with positive rates of 37.6% and 17.2%, respectively. All nested RT-PCR positive samples were aMPV subgroup B. By pairing the detection results with age groups, it was observed that aMPV infections occurred in chickens of all ages. Additionally, by genetic characterization, aMPV strains were demonstrated to not be attenuated vaccine viruses and to belong to at least two genetic clades. Overall, the obtained results provided insights into the prevalence of aMPV and indicated a greater complexity of respiratory diseases in chickens in Vietnam. [ABSTRACT FROM AUTHOR]

ABSTRACT: 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.

Avian metapneumoviruses (aMPV) are a causative agent of turkey rhinotracheitis (TRT). Despite vaccination, cases of TRT outbreaks are frequently reported. Considering that there are aMPV-free areas, a part of turkey poults possess (MDA+) or do not possess (MDA−) maternally derived antibodies (MDA) in the first weeks of life, which is the time of TRT vaccination. Study was undertaken to establish the level of protection against homologue aMPV/A infection, in MDA+ and MDA− turkeys, vaccinated against TRT at the 0 or 14th d of life and infected 14 d later. With the use of ELISA test and qPCR techniques, we have established the level of immune system stimulation after the vaccination and how does it correlate with the level of protection against the aMPV infection. Vaccination of MDA+ turkeys (especially at 0 d of life) resulted in weaker IgA production in upper respiratory tract. In addition, we have demonstrated differences in both humoral and cell-mediated immunity stimulation after infection of vaccinated turkeys. Despite these differences, we have shown that all vaccinated birds were protected against the disease which was determined based on the clinical and histopathological scoring, as well as the level of aMPV/A replication and shedding. Nonvaccinated groups of turkeys displayed typical signs of TRT after infection which indicates that MDA alone are incapable of preventing the disease. Differences in TRT course were recorded between different age groups of nonvaccinated birds. Birds infected at the 28th d of life (especially MDA− birds) developed more severe signs, and the level of aMPV replication was higher than that in birds infected on the 14th d of life. Despite the minor role in alleviating TRT course, MDA seems not to interfere with the vaccination efficacy. It is hard to predict whether the observed immune system stimulation differences between MDA+ and MDA− birds after vaccination can influence the outcome of vaccination efficacy under the field conditions.

Background: Avian metapneumovirus (aMPV) infection has significant economic impacts on the poultry industry all around the world. Aims: The aim of this study is molecular investigations of different types of aMPV in broiler farms in different provinces of Iran from 2016 to 2018. Methods: Tracheal and oropharyngeal swabs were collected from two hundred broiler chickens with respiratory signs in ten provinces of Iran, including Kurdistan, West Azerbaijan, Semnan, Esfahan, Sistan and Baluchistan, Qazvin, Khuzestan, Fars, Gilan, and Khorasan Razavi from February 2016 to December 2018. After RNA extraction, the presence of aMPV was confirmed using N gene special primers. Then, subtype-specific primers were utilized to differentiate the specific subtype. All positive samples were sequenced. Results: As a general trend, the percentage of aMPV positive chickens increased gradually over time. All samples were clustered together and placed in the subtype B aMPV group. Although 2 samples from 2016 and 2 samples from 2018 were placed in a separate branch, most of the current study samples of 2016, 2017, and 2018 revealed six segregated subbranches, and they were placed close to other isolates of 2011 and 2013 from Iran. Conclusion: The current field study indicated the presence of aMPV in a considerable number of areas in Iran. Thus, the role of this virus in broiler respiratory complex should not be neglected. [ABSTRACT FROM AUTHOR]

In the present study, one hundred and sixteen partial G gene sequences of Avian metapneumovirus (aMPV) subtype B, obtained during routine diagnostics in different European Countries in the last few years (2014–2019), were analysed by sequence and phylogenetic analyses in order to draw an updated picture of the molecular characteristics of circulating strains. Nucleotide sequences were compared with other sequences of European and non‐European aMPV‐Bs collected prior to that period or retrieved from GenBank. Phylogenetic relationships among the aMPV‐B strains, reconstructed using the maximum likelihood method implemented in MEGA X, demonstrated that aMPV‐B has evolved in Europe from its first appearance, frequently displaying a clear relation with the geographic area of detection. The 40% of aMPV‐B viruses analysed were classified as vaccine‐derived strains, being phylogenetically related, and showing high nucleotide identity with live commercial vaccine strains licensed in Europe. The remaining 60% were classified as field strains since they clustered separately and showed a low nucleotide identity with vaccines and vaccine‐derived strains. The phylogenetic tree showed that the virus has continued to evolve from its first appearance in the '80s since more recently detected strains belonged to clades phylogenetically distant from the older strains. Unlike vaccine‐derived strains, field strains tended to cluster according to their geographic origin and irrespective of the host species where the viruses had been detected. In conclusion, the molecular characterization of aMPV‐B and the differentiation between vaccines and field strains through G gene sequence analysis can be a useful tool towards correct diagnosis and should be routinely applied in order to better address the control strategies. [ABSTRACT FROM AUTHOR]

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.

This article describes a series of animal studies for the development of an avian metapneumovirus (aMPV) live vaccine. Although aMPV causes continual economic loss in the poultry industry, there are no live aMPV vaccines available in Korea. Furthermore, information is limited with respect to standard field practices for vaccinations at an early age. Here, the development of an aMPV live vaccine was attempted, and its efficacy was investigated with respect to the vaccination route and age to develop a method for controlling aMPV. Before vaccine development, an animal challenge model was established using the aMPV field isolate to identify the most effective time and site for collecting samples for evaluation. After attenuation of the virulent aMPV in Vero cells, a safety and efficacy test was conducted for the vaccine candidate. As a novel aMPV live vaccine candidate, aMPV K655/07HP displayed sufficient safety in day-old chicks with 10 vaccine doses. The efficacy test using 1-week-old chicks showed weaker humoral immune response than that in 4-week-old chicks. However, the candidate vaccine provided complete protection against infection caused by the challenge virus for all ages of vaccinated chicks. In conclusion, an effective aMPV challenge model was established for studying aMPV in chickens, which offered important, insightful information. The safety and efficacy study suggested that the new aMPV candidate vaccine could be used to effectively reduce the economic losses incurred because of aMPV infection.

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.

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After experimental inoculation of broiler chickens with subtype A avian metapneumovirus isolate, mild clinical signs were observed on days 6-14 after inoculation. The infected chickens demonstrated slight increase of T-helpers activity in blood, poor specific antibody response, development of specific secretory antibodies. Subtype B avian metapneumovirus isolate caused a somewhat more obvious specific clinical signs in chickens compared with subtype A on days 5-15 after inoculation, however, in both experiments, clinical signs completely disappeared in 14-15 days after infection. The increase of relative number of cytotoxic T lymphocytes in blood and in spleen, specific antibody response in 50-70% of chickens and activation of local immune response in 50% of chickens were observed in inoculated chickens.

Experimental infection of 7-day-old chicks with the isolate of avian metapneumovirus Subtype В induced mild signs of respiratory infection and swelled infraorbital sinuses in 5-15 days post infection. Lesions in tissues of trachea, nasal passages and primary lymphoid organs were reported. Using real-time RT-PCR avian metapneumovirus genome was detected in the upper part of the respiratory tract, infraorbital sinuses and Harderian gland within 2-12 days post infection. The immune response was characterized by formation of humoral and local antibodies in 7-21 days post infection. In 3 days post infection increased percentage of CD8a+ T-cell subpopulation was reported in blood and spleen of the infected chicks.

Respiratory pathogens are a health threat for poultry. Co-infections lead to the exacerbation of clinical symptoms and lesions. Mycoplasma gallisepticum (M. gallispeticum) and Avian Metapneumovirus (AMPV) are two avian respiratory pathogens that co-circulate worldwide. The knowledge about the host–pathogen interaction of M. gallispeticum and AMPV in the chicken respiratory tract is limited. We aimed to investigate how co-infections affect the pathogenesis of the respiratory disease and whether the order of invading pathogens leads to changes in host–pathogen interaction. We used chicken tracheal organ cultures (TOC) to investigate pathogen invasion and replication, lesion development, and selected innate immune responses, such as interferon (IFN) α, inducible nitric oxide synthase (iNOS) and IFNλ mRNA expression levels. We performed mono-inoculations (AMPV or M. gallispeticum) or dual-inoculations in two orders with a 24-h interval between the first and second pathogen. Dual-inoculations compared to mono-inoculations resulted in more severe host reactions. Pre-infection with AMPV followed by M. gallispeticum resulted in prolonged viral replication, more significant innate immune responses, and lesions (p < 0.05). AMPV as the secondary pathogen impaired the bacterial attachment process. Consequently, the M. gallispeticum replication was delayed, the innate immune response was less pronounced, and lesions appeared later. Our results suggest a competing process in co-infections and offer new insights in disease processes.

Avian Metapneumovirus (aMPV) has been recognized as a respiratory pathogen of turkey and chickens for a long time. Recently, a crescent awareness of aMPV, especially subtype B, clinical and economic impact has risen among European researchers and veterinarians. Nevertheless, the knowledge of its epidemiology and evolution is still limited. In the present study, the broadest available collection of partial G gene sequences obtained from European aMPV-B strains was analyzed using different phylodynamic and biostatistical approaches to reconstruct the viral spreading over time and the role of different hosts on its evolution. After aMPV-B introduction, approximatively in 1985 in France, the infection spread was relatively quick, involving the Western and Mediterranean Europe until the end of the 1990s, and then spreading westwards at the beginning of the new millennium, in parallel with an increase of viral population size. In the following period, a wider mixing among aMPV-B strains detected in eastern and western countries could be observed. Most of the within-country genetic heterogeneity was ascribable to single or few introduction events, followed by local circulation. This, combined with the high evolutionary rate herein demonstrated, led to the establishment of genetically and phenotypically different clusters among countries, which could affect the efficacy of natural or vaccine-induced immunity and should be accounted for when planning control measure implementation. On the contrary, while a significant strain exchange was proven among turkey, guinea fowl and chicken, no evidence of differential selective pressures or specific amino-acid mutations was observed, suggesting that no host adaptation is occurring. [ABSTRACT FROM AUTHOR]