Experimental co-infections of domestic ducks with a virulent Newcastle disease virus and low or highly pathogenic avian influenza viruses

A review of the influence of environmental pollutants (microplastics, pesticides, antibiotics, air pollutants, viruses, bacteria) on animal viruses

Microorganisms, especially viruses, cause disease in both humans and animals. Environmental chemical pollutants including microplastics, pesticides, antibiotics sand air pollutants arisen from human activities affect both animal and human health. This review assesses the impact of chemical and biological contaminants (virus and bacteria) on viruses including its life cycle, survival, mutations, loads and titers, shedding, transmission, infection, re-assortment, interference, abundance, viral transfer between cells, and the susceptibility of the host to viruses. It summarizes the sources of environmental contaminants, interactions between contaminants and viruses, and methods used to mitigate such interactions. Overall, this review provides a perspective of environmentally co-occurring contaminants on animal viruses that would be useful for future research on virus-animal-human-ecosystem harmony studies to safeguard human and animal health.

miR-155 facilitates the synergistic replication between avian leukosis virus subgroup J and reticuloendotheliosis virus by targeting a dual pathway

IMPORTANCE

The synergy of two oncogenic retroviruses is an essential phenomenon in nature. The synergistic replication of ALV-J and REV in poultry flocks increases immunosuppression and pathogenicity, extends the tumor spectrum, and accelerates viral evolution, causing substantial economic losses to the poultry industry. However, the mechanism of synergistic replication between ALV-J and REV is still incompletely elusive. We observed that microRNA-155 targets a dual pathway, PRKCI-MAPK8 and TIMP3-MMP2, interacting with the U3 region of ALV-J and REV, enabling synergistic replication. This work gives us new targets to modulate ALV-J and REV's synergistic replication, guiding future research on the mechanism.

Viral Co-Infection in Bats: A Systematic Review

Co-infection is an underappreciated phenomenon in contemporary disease ecology despite its ubiquity and importance in nature. Viruses, and other co-infecting agents, can interact in ways that shape host and agent communities, influence infection dynamics, and drive evolutionary selective pressures. Bats are host to many viruses of zoonotic potential and have drawn increasing attention in their role as wildlife reservoirs for human spillover. However, the role of co-infection in driving viral transmission dynamics within bats is unknown. Here, we systematically review peer-reviewed literature reporting viral co-infections in bats. We show that viral co-infection is common in bats but is often only reported as an incidental finding. Biases identified in our study database related to virus and host species were pre-existing in virus studies of bats generally. Studies largely speculated on the role co-infection plays in viral recombination and few investigated potential drivers or impacts of co-infection. Our results demonstrate that current knowledge of co-infection in bats is an ad hoc by-product of viral discovery efforts, and that future targeted co-infection studies will improve our understanding of the role it plays. Adding to the broader context of co-infection studies in other wildlife species, we anticipate our review will inform future co-infection study design and reporting in bats. Consideration of detection strategy, including potential viral targets, and appropriate analysis methodology will provide more robust results and facilitate further investigation of the role of viral co-infection in bat reservoirs.

Efficient and Informative Laboratory Testing for Rapid Confirmation of H5N1 (Clade 2.3.4.4) High-Pathogenicity Avian Influenza Outbreaks in the United Kingdom

During the early stages of the UK 2021-2022 H5N1 high-pathogenicity avian influenza virus (HPAIV) epizootic in commercial poultry, 12 infected premises (IPs) were confirmed by four real-time reverse-transcription-polymerase chain reaction (RRT)-PCRs, which identified the viral subtype and pathotype. An assessment was undertaken to evaluate whether a large sample throughput would challenge laboratory capacity during an exceptionally large epizootic; hence, assay performance across our test portfolio was investigated. Statistical analysis of RRT-PCR swab testing supported it to be focused on a three-test approach, featuring the matrix (M)-gene, H5 HPAIV-specific (H5-HP) and N1 RRT-PCRs, which was successfully assessed at 29 subsequent commercial IPs. The absence of nucleotide mismatches in the primer/probe binding regions for the M-gene and limited mismatches for the H5-HP RRT-PCR underlined their high sensitivity. Although less sensitive, the N1 RRT-PCR remained effective at flock level. The analyses also guided successful surveillance testing of apparently healthy commercial ducks from at-risk premises, with pools of five oropharyngeal swabs tested by the H5-HP RRT-PCR to exclude evidence of infection. Serological testing at anseriform H5N1 HPAIV outbreaks, together with quantitative comparisons of oropharyngeal and cloacal shedding, provided epidemiological information concerning the chronology of initial H5N1 HPAIV incursion and onward spread within an IP.

Viral Coinfections

In nature, viral coinfection is as widespread as viral infection alone. Viral coinfections often cause altered viral pathogenicity, disrupted host defense, and mixed-up clinical symptoms, all of which result in more difficult diagnosis and treatment of a disease. There are three major virus-virus interactions in coinfection cases: viral interference, viral synergy, and viral noninterference. We analyzed virus-virus interactions in both aspects of viruses and hosts and elucidated their possible mechanisms. Finally, we summarized the protocol of viral coinfection studies and key points in the process of virus separation and purification.

Infectious Bronchitis Virus Infection Increases Pathogenicity of H9N2 Avian Influenza Virus by Inducing Severe Inflammatory Response

Infectious bronchitis virus (IBV) and H9N2 avian influenza virus (AIV) are frequently identified in chickens with respiratory disease. However, the role and mechanism of IBV and H9N2 AIV co-infection remain largely unknown. Specific-pathogen-free (SPF) chickens were inoculated with IBV 2 days before H9N2 virus inoculation (IBV/H9N2); with IBV and H9N2 virus simultaneously (IBV+H9N2); with H9N2 virus 2 days before IBV inoculation (H9N2/IBV); or with either IBV or H9N2 virus alone. Severe respiratory signs, pathological damage, and higher morbidity and mortality were observed in the co-infection groups compared with the IBV and H9N2 groups. In general, a higher virus load and a more intense inflammatory response were observed in the three co-infection groups, especially in the IBV/H9N2 group. The same results were observed in the transcriptome analysis of the trachea of the SPF chickens. Therefore, IBV might play a major role in the development of respiratory disease in chickens, and secondary infection with H9N2 virus further enhances the pathogenicity by inducing a severe inflammatory response. These findings may provide a reference for the prevention and control of IBV and H9N2 AIV in the poultry industry and provide insight into the molecular mechanisms of IBV and H9N2 AIV co-infection in chickens.

Prior infection with antigenically heterologous low pathogenic avian influenza viruses interferes with the lethality of the H5 highly pathogenic strain in domestic ducks

Low and highly pathogenic avian influenza viruses (LPAIVs and HPAIVs, respectively) have been co-circulating in poultry populations in Asian, Middle Eastern, and African countries. In our avian-flu surveillance in Vietnamese domestic ducks, viral genes of LPAIV and HPAIV have been frequently detected in the same individual. To assess the influence of LPAIV on the pathogenicity of H5 HPAIV in domestic ducks, an experimental co-infection study was performed. One-week-old domestic ducks were inoculated intranasally and orally with PBS (control) or 10⁶ EID₅₀ of LPAIVs (A/duck/Vietnam/LBM678/2014 (H6N6) or A/Muscovy duck/Vietnam/LBM694/2014 (H9N2)). Seven days later, these ducks were inoculated with HPAIV (A/Muscovy duck/Vietnam/LBM808/2015 (H5N6)) in the same manner. The respective survival rates were 100% and 50% in ducks pre-infected with LBM694 or LBM678 strains and both higher than the survival of the control group (25%). The virus titers in oral/cloacal swabs of each LPAIV pre-inoculation group were significantly lower at 3-5 days post-HPAIV inoculation. Notably, almost no virus was detected in swabs from surviving individuals of the LBM678 pre-inoculation group. Antigenic cross-reactivity among the viruses was not observed in the neutralization test. These results suggest that pre-infection with LPAIV attenuates the pathogenicity of HPAIV in domestic ducks, which might be explained by innate and/or cell-mediated immunity induced by the initial infection with LPAIV.

SARS-CoV-2 coinfection with additional respiratory virus does not predict severe disease: a retrospective cohort study

Background

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) claimed over 4 million lives by July 2021 and continues to pose a serious public health threat.

Objectives

Our retrospective study utilized respiratory pathogen panel (RPP) results in patients with SARS-CoV-2 to determine if coinfection (i.e. SARS-CoV-2 positivity with an additional respiratory virus) was associated with more severe presentation and outcomes.

Methods

All patients with negative influenza/respiratory syncytial virus testing who underwent RPP testing within 7 days of a positive SARS-CoV-2 test at a large, academic medical centre in New York were examined. Patients positive for SARS-CoV-2 with a negative RPP were compared with patients positive for SARS-CoV-2 and positive for a virus by RPP in terms of biomarkers, oxygen requirements and severe COVID-19 outcome, as defined by mechanical ventilation or death within 30 days.

Results

Of the 306 SARS-CoV-2-positive patients with RPP testing, 14 (4.6%) were positive for a non-influenza virus (coinfected). Compared with the coinfected group, patients positive for SARS-CoV-2 with a negative RPP had higher inflammatory markers and were significantly more likely to be admitted (P = 0.01). Severe COVID-19 outcome occurred in 111 (36.3%) patients in the SARS-CoV-2-only group and 3 (21.4%) patients in the coinfected group (P = 0.24).

Conclusions

Patients infected with SARS-CoV-2 along with a non-influenza respiratory virus had less severe disease on presentation and were more likely to be admitted—but did not have more severe outcomes—than those infected with SARS-CoV-2 alone.

Evaluation of chickens infected with a recombinant virulent NDV clone expressing chicken IL4

BACKGROUND

There is evidence that chicken IL4 (chIL4) functions similarly to its mammalian analogue by enhancing type 2 T helper (Th2) humoral immunity and promoting protection against parasitic infections; however, no studies have been performed to assess the effect of chIL4 on the pathogenesis of Newcastle disease (ND). To assess the role of chIL4 in velogenic NDV pathogenesis we created a vNDV infectious clone expressing chIL4. We hypothesized that co-expression of chIL4 during virus replication would result in decreased inflammation caused by the Th1 response and thereby increasing survival to challenge with vNDV.

METHODS

To evaluate the effect of chIL4 during early infection with velogenic Newcastle disease virus (NDV) in chickens, recombinant NDV clones expressing either chIL4 (rZJ1-IL4) or a control expressing green fluorescent protein (rZJ1-GFP) were created by inserting an expression cassette in an intergenic region of the NDV genome. The pathogenesis of rZJ1-IL4 was assessed in 4-week-old specific pathogen free chickens. The extent of virus replication was evaluated by titration in mucosal secretions and immunohistochemistry in multiple tissues. Expression of chIL4 was confirmed in tissues using immunohistochemistry.

RESULTS

Infection of birds with the rZJ1-IL4 resulted in successful viral replication in vivo and in vitro and generation of the chIL4 in tissues. All birds were clinically normal 2 DPI, with one bird in each group showing conjunctival swelling and enlarged spleens grossly. At 5 DPI, moderate or severe depression was observed in birds infected with rZJ1-GFP or rZJ1-IL4, respectively. Neurological signs and thymic atrophy were observed in one bird infected with rZJ1-IL4. Grossly, conjunctival swelling, mottled spleen and proventricular hemorrhages were observed at 5 DPI in one bird from each group. At 5 DPI, severe necrosis in the spleen, bursa and cecal tonsils were observed in birds infected with rZJ1-GFP, along with minimal evidence of chIL4 expression. In contrast, splenic atrophy, and moderate necrosis in the bursa and cecal tonsils were observed in birds infected with rZJ1-IL4. In addition, chIL4 signal was found in all tissues of rZJ1-IL4 birds at 5DPI.

CONCLUSIONS

The production of chIL4 by a recombinant NDV strain resulted in the activation of the positive feedback loop associated with IL4 production. Insertion of chIL4 into NDV may decrease necrosis to lymphoid organs while increasing the severity of lymphoid atrophy and prolonged disease. However, with a low number of birds it is difficult to determine whether these results are significant to disease outcome.

Therapeutic Exploitation of Viral Interference

Viral interference, originally, referred to a state of temporary immunity, is a state whereby infection with a virus limits replication or production of a second infecting virus. However, replication of a second virus could also be dominant over the first virus. In fact, dominance can alternate between the two viruses. Expression of type I interferon genes is many times upregulated in infected epithelial cells. Since the interferon system can control most, if not all, virus infections in the absence of adaptive immunity, it was proposed that viral induction of a nonspecific localized temporary state of immunity may provide a strategy to control viral infections. Clinical observations also support such a theory, which gave credence to the development of superinfection therapy (SIT). SIT is an innovative therapeutic approach where a non-pathogenic virus is used to infect patients harboring a pathogenic virus. For the functional cure of persistent viral infections and for the development of broad- spectrum antivirals against emerging viruses a paradigm shift was recently proposed. Instead of the virus, the therapy should be directed at the host. Such a host-directed-therapy (HDT) strategy could be the activation of endogenous innate immune response via toll-like receptors (TLRs). Superinfection therapy is such a host-directed-therapy, which has been validated in patients infected with two completely different viruses, the hepatitis B (DNA), and hepatitis C (RNA) viruses. SIT exerts post-infection interference via the constant presence of an attenuated non-pathogenic avian double- stranded (ds) RNA viral vector which boosts the endogenous innate (IFN) response. SIT could, therefore, be developed into a biological platform for a new "one drug, multiple bugs" broad-spectrum antiviral treatment approach.

Development and application of a triplex real-time PCR assay for simultaneous detection of avian influenza virus, Newcastle disease virus, and duck Tembusu virus

Background

Pathogens including duck-origin avian influenza virus (AIV), duck-origin Newcastle disease virus (NDV) and duck Tembusu virus (DTMUV) posed great harm to ducks and caused great economic losses to the duck industry. In this study, we aim to develop a triplex real-time polymerase chain reaction (PCR) assay to detect these three viruses as early as possible in the suspicious duck flocks.

Results

The detection limit of the triplex real-time PCR for AIV, NDV, and DTMUV was 1 × 10¹ copies/μL, which was at least 10 times higher than the conventional PCR. In addition, the triplex assay was highly specific, and won’t cross-react with other duck pathogens. Besides, the intra-day relative standard deviation and inter-day relative standard deviation were lower than 4.44% for these viruses at three different concentrations. Finally, a total of 120 clinical samples were evaluated by the triplex real-time PCR, the conventional PCR and virus isolation, and the positive rates for these three methods were 20.83, 21.67, 19.17%, respectively. Taking virus isolation as the gold standard, the diagnostic specificity and positive predictive value of the three viruses were all above 85%, while the diagnostic sensitivity and negative predictive value of the three viruses were all 100%.

Conclusion

The developed triplex real-time PCR is fast, specific and sensitive, and is feasible and effective for the simultaneous detection of AIV, NDV, and DTMUV in ducks.

Effect of Newcastle disease and infectious bronchitis live vaccines on the immune system and production parameters of experimentally infected broiler chickens with H9N2 avian influenza

H9N2 Avian influenza (AI) is an infectious disease which considered to have low pathogenic virulence, but in the case of coinfection with other pathogens it has the potential to become a major threat to the poultry industry. Infectious bronchitis (IB) and Newcastle diseases (ND) are other common problems to the poultry industry, which there are an extensive vaccination program against these viral pathogens. To investigate the effects of administration of infectious bronchitis and Newcastle disease live vaccines (IBLVs and NDLVs) in the presence of H9N2 AI infection on the immune system and some production parameters, 180 one-day-old broiler chicks were randomly allocated into six groups with different vaccination programs including H120 IBLV, 4/91 IBLV, B1 NDLV and LaSota NDLV. At the age of 20 days, all birds of the experimental groups except the negative control group, were inoculated intra-nasally (at dose of 106 EID50) with H9N2 AIV. After the inoculation, gross and microscopic lesions of the immune organs, serological changes and some production parameters were examined. The findings of this study showed that coinfection of H9N2 AI with NDLVs exacerbated the gross and microscopic injuries in the immune organs; especially the bursa of Fabricius. LaSota + AIV group had the most severe lesion in the bursa of Fabricius, spleen and thymus. Furthermore, the birds of LaSota + AIV group consumed the least amount of feed and water and their final body weight were significantly (P ≤ 0.05) lower in comparison with the other groups. Interestingly, in the context of this experiment both 4/91 and H120 IB live vaccines enhanced the HI antibody titers against H9N2 AIV, but the 4/91 showed the most significant (P ≤ 0.05) increase compared to the other experimental groups.

Naturally Avian Influenza Virus-Infected Wild Birds Are More Likely to Test Positive for Mycobacterium spp. and Salmonella spp

Wild birds often harbor infectious microorganisms. Some of these infectious microorganisms may present a risk to domestic animals and humans through spillover events. Detections of certain microorganisms have been shown to increase host susceptibility to infections by other microorganisms, leading to coinfections and altered host-to-host transmission patterns. However, little is known about the frequency of coinfections and its impact on wild bird populations. In order to verify whether avian influenza virus (AIV) natural infection in wild waterbirds was related to the excretion of other microorganisms, 73 AIV-positive samples (feces and cloacal swabs) were coupled with 73 AIV-negative samples of the same sampling characteristics and tested by real-time PCR specific for the following microorganisms: West Nile virus, avian avulavirus 1, Salmonella spp., Yersinia enterocolitica, Yersinia pseudotuberculosis, Mycobacterium avium subspecies, Mycobacterium tuberculosis complex, and Mycobacterium spp. Concurrent detections were found in 47.9% (35/73) of the AIV-positive samples and in 23.3% (17/73) of the AIV-negative samples (P = 0.003). Mycobacterium spp. and Salmonella spp. were found to be significantly more prevalent among the AIV-positive samples than among the AIV-negative samples (42.9% vs. 22.8%; P = 0.024 and 15.2% vs. 0.0%; P = 0.0015, respectively). Prevalence of concurrent detections differed significantly among sampling years (P = 0.001), host families (P = 0.002), host species (P = 0.003), AIV subtypes (P = 0.003), and type of sample (P = 0.009). Multiple concurrent detections (more than one of the tested microorganisms excluding AIV) were found in 9.6% (7/73) of all the AIV-positive samples, accounting for 20% (7/35) of the concurrent detection cases. In contrast, in AIV-negative samples we never detected more than one of the selected microorganisms. These results show that AIV detection was associated with the detection of the monitored microorganisms. Further studies of a larger field sample set or under experimental conditions are necessary to infer causality in these trends.

Laboratory Methods for Assessing and Licensing Influenza Vaccines for Poultry

Avian influenza (AI) vaccines for poultry are based on hemagglutinin (HA) proteins, and protection is specific to the subtype. An estimated 313 billion doses have been used between 2002 and 2018 for high pathogenicity AI control. No universal vaccines are currently available. The majority of AI vaccines are inactivated whole influenza viruses that are grown in embryonating chicken eggs, emulsified in oil adjuvant systems, and injected subcutaneously or intramuscularly. Live virus-vectored vaccines such as recombinant viruses of fowl pox, Newcastle disease, and herpesvirus of turkeys containing inserts of AI virus HA genes have been used on a more limited basis. Also, vaccines have been licensed or registered based on baculovirus and defective replicating alphavirus (RNA particles) expressing HA protein or DNA vaccine with HA gene insert. In studies to evaluate vaccine efficacy and potency, the protocol design and its implementation should address the biosafety level needed for the work, provide information required for approval by Institutional Biosafety and Animal Care Committees, contain information on seed strain selection, provide needed information on animal subjects and their relevant parameters, and address the selection and use of challenge viruses. Various metrics have been used to directly measure vaccine-induced protection, including prevention of death, clinical signs, and lesions; prevention of decreases in egg production and alterations in egg quality; quantification of the reduction in virus replication and shedding from the respiratory tract and gastrointestinal tracts; and prevention of contact transmission in in vivo poultry experiments. In addition, indirect measures of vaccine potency and protection have been developed and validated against the direct measures and include serological assays in vaccinated poultry and the assessment of the content of HA antigen in the vaccine. These indirect assessments of protection are useful in determining if vaccine batches have a consistent ability to protect. For adequate potency, vaccines should contain 50 mean protective doses of antigen per dose, which corresponds to 0.3-7.8 μg of HA protein in inactivated vaccines, depending on immunogenicity and antigenic relatedness of individual seed strains.

Molecular survey and interaction of common respiratory pathogens in chicken flocks (field perspective)

Aim:

The present study was designed for the detection of the most prevalent respiratory infections in chicken flocks and clarifying their interaction and impact on flock health.

Materials and Methods:

A total of 359 serum samples were collected from 55 backyard chickens and tested using commercial enzyme-linked immunosorbent assay kits to determine the seroprevalence of Newcastle disease virus (NDV), infectious bronchitis virus (IBV), influenza type A, Mycoplasma gallisepticum (MG), and Mycoplasma synoviae (MS). Molecular prevalence of NDV, IBV, low pathogenic avian influenza virus (LPAIV) H9N2, MG, and MS was carried out on swab, and tissue samples collected from 55 backyard flocks and 11 commercial broiler flocks suffered from respiratory infections using polymerase chain reaction (PCR) and reverse transcription-PCR.

Results:

Seroprevalence of NDV, IBV, Influenza type A virus, MG, and MS in chicken backyard flocks was 56.4%, 50.9%, 12.7%, 14.5%, and 3.6%, respectively. Specific antibodies against one or more respiratory viruses and mycoplasma were detected in 36.4% of backyard flocks, indicating concurrent viral infections. The molecular survey showed that 90.9% of chicken backyard flocks were infected with common respiratory viruses (NDV, IBV, and LPAIV H9N2) while 81.8% of commercial broiler flocks were infected. The molecular prevalence rate of NDV, IBV, and LPAIV H9N2 was 46.97%, 56.1%, and 19.7% in backyard flocks, respectively. Combined viral and bacterial infection represented 40% and 63.6% of the respiratory infections, resulting in enhanced pathogenicity and increased mortalities of up to 87.5% and 27.8% in backyard and commercial flocks, respectively. Mixed infection of IBV, LPAIV H9N2, and/or Escherichia coli is the most prevalent mixed infection in broiler flocks, inducing severe clinical outcomes. Avian pathogenic E. coli was, respectively, isolated from 40% of backyard flocks and 81.82% of broiler flocks. Staphylococcus aureus was isolated from three backyard chicken flocks mixed with other respiratory pathogens with elevated mortality. Mixed infection of E. coli and MG reported in 9.1% of broiler flock. MG was detected in 14.5% of backyard flocks and 9.1% of broiler flocks while MS was detected only in 3.6% of backyard chickens mixed with E. coli, and other viruses.

Conclusion:

Our results confirm that mixed infections are more commonly prevalent and associated with dramatic exacerbation in clinical outcomes than a single infection. Bidirectional synergistic interaction between these concurrently interacted respiratory pathogens explains the severe clinical impact and high mortality rate. The high prevalence of IBV (either as a single or combined infection) with LPAIV H9N2 and/or E. coli, in spite of intensive use of commercial vaccines, increases the need for revising vaccination programs and the application of standard biosecurity measures. Backyard chickens impose a great risk and threaten commercial flocks due to the high prevalence of viral respiratory pathogens.

Quantitative evaluation of viral interference among Egyptian isolates of highly pathogenic avian influenza viruses (H5N1 and H5N8) with the lentogenic and velogenic Newcastle disease virus genotype VII in specific pathogen-free embryonated chicken eggs model

Background and Aim

Mixed infections of the highly pathogenic avian influenza virus (HPAIV) and Newcastle disease virus (NDV) are considered the most distressing problem of the poultry industry. The problem arises due to the influence of a hidden virus on the replication of another suspected virus. Consequently, misdiagnosis of the real cause of disease may become a source of infection for other healthy stock by transmission and dissemination of the hidden virus. This study aimed to determine the impact of HPAIV and NDV on each other in a specific pathogen-free embryonated chicken egg (SPF-ECE) model.

Materials and Methods

HPAIVs (H5N1 and H5N8) and NDVs [avirulent NDV [avNDV] and velogenic NDV [vNDV]) were inoculated into the allantois cavity of SPF-ECE with graded titers (2, 3, and 4 log₁₀ EID50) at 24 and 48 h of incubation, followed by the collection of allantoic fluid. A quantitative reverse transcription real-time polymerase chain reaction was used to determine the viral RNA copies of both viruses.

Results

Obvious interference was reported on the growth of NDVs when co-inoculated with AIVs. NDV RNA titers reduction ranged from <3 to 5 log₁₀ to complete suppression, but slight interference with the growth of AIVs occurred. H5N1 RNA titers showed <1-2 log₁₀ reduction when co-inoculated with vNDV compared with the H5N1 control. The interference impact of H5N8 was more powerful than that of H5N1, while vNDV showed more resistance for interference than the avNDV strain. On the other hand, interference of AIVs was not observed except when vNDV was inoculated before H5N1. The interfering impact was increased after 48 h of inoculation, whereas no titer of avNDV was detectable.

Conclusion

AIV strains had a powerful effect on NDV growth, regardless of which infection occurred first.

Infectious bursal disease virus suppresses H9N2 avian influenza viral shedding in broiler chickens

1. Infectious bursal disease virus (IBDV) causes immunosuppression in chickens, increasing their susceptibility to other infectious diseases and resulting in vaccination failure. Here, we investigated the immune-depressing effect of IBDV on H9N2 avian influenza viral infection in the broiler chickens. 2. For this purpose, chickens were divided into four groups. In group A, chickens were inoculated with IBDV at 21 days of age and H9N2 avian influenza virus (AIV) 5 days later. Groups B and C only received AIV at 26 days of age and IBDV at 21 days, respectively. The control group (D) were inoculated with normal saline at the same times. Tissue samples from different organs were collected on the days 1, 3, 6, 9, and 12 after H9N2 infection. 3. Macroscopic observation showed IBD lesions in groups A and C, including swollen bursa with the presence of gelatinous exudates, haemorrhages in the thigh muscle, edema, and nephritis. 4. Reverse Transcription-PCR was used to study H9N2 AIV dissemination, and qRT-PCR to determine viral genome copy number in different organs. A considerable titre of AIV was found in the trachea, lungs, cecal tonsils, spleens, and feces of infected chickens. The genome copy number of the virus in the trachea and lungs of group A was significantly higher than that in group B on the first day after inoculation. But in the other days post inoculation, RT-PCR did not detect the AIV genome in group A. Although there might have been some immunosuppression in group A, IBDV could interfere with AIV replication in the chickens of this group. 5. In conclusion, we propose that pre-exposure to IBDV at 3 weeks of age reduces the replication and shedding of H9N2 in broiler chicken.

Viral interference between H9N2-low pathogenic avian influenza virus and avian infectious bronchitis virus vaccine strain H120 in vivo

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AIV and IBV co-infection led to decreased growth of both viruses.

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During super-infection, the second virus decreased the growth of the first virus.

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ELISA antibody titers, depending on the experimental conditions.

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Histopathological findings showed important lesions.

The interaction between a low pathogenic avian influenza virus (A/CK/TUN/145/2012), a H9N2 Tunisian isolate, and a vaccine strain (H120) of avian infectious bronchitis, administered simultaneously or sequentially three days apart to chicks during 20 days, was evaluated using ELISA antibody levels, quantitative reverse transcription–polymerase chain reaction (qRT-PCR) analyses and histopathology examination. First, the in vivo replication interference of avian influenza virus (AIV) and infectious bronchitis virus (IBV) was evaluated using qRT-PCR to detect accurately either AIV or IBV genomes or viral copy numbers during dual infections. Second, we have determined the amount of specific antibodies in sera of chick’s infected with AIV alone, IBV alone, mixed AIV + IBV, IBV then AIV or AIV IBV 3 days later using an ELISA test. Finally, histopathological analyses of internal organs from inoculated chicks were realized. Quantitative results of AIV and IBV co-infection showed that interferences between the two viruses yielded decreased viral growth. However, in the case of super-infection, the second virus, either AIV or IBV, induced a decrease in the growth of the first inoculated virus. According to our results, vaccine application was safe and do not interfere with AIV H9N2 infection, and does not enhance such infection. In conclusion, co-infection of chicks with AIV and IBV, simultaneously or sequentially, affected the clinical signs, the virus replication dynamics as well as the internal organ integrity. The results proposed that infection with heterologous virus may result in temporary competition for cell receptors or competent cells for replication, most likely interferon-mediated.

Development and application of multiplex PCR method for simultaneous detection of seven viruses in ducks

BACKGROUND

Major viruses, including duck-origin avian influenza virus, duck-origin Newcastle disease virus, novel duck parvovirus, duck hepatitis A virus, duck Tembusu virus, fowl adenovirus, and duck enteritis virus, pose great harm to ducks and cause enormous economic losses to duck industry. This study aims to establish a multiplex polymerase chain reaction (m-PCR) method for simultaneous detection of these seven viruses.

RESULTS

Specific primers were designed and synthesized according to the conserved region of seven viral gene sequences. Then, seven recombinant plasmids, as the positive controls, were reconstructed in this study. Within the study, D-optimal design was adopted to optimize PCR parameters. The optimum parameters for m-PCR were annealing temperature at 57 °C, Mg²⁺ concentration at 4 mM, Taq DNA polymerase concentration at 0.05 U/μL, and dNTP concentration at 0.32 mM. With these optimal parameters, the m-PCR method produced neither cross-reactions among these seven viruses nor nonspecific reactions with other common waterfowl pathogens. The detection limit of m-PCR for each virus was 1 × 10⁴ viral DNA copies/μL. In addition, the m-PCR method could detect a combination of several random viruses in co-infection analysis. Finally, the m-PCR method was successfully applied to clinical samples, and the detection results were consistent with uniplex PCR.

CONCLUSION

Given its rapidity, specificity, sensitivity, and convenience, the established m-PCR method is feasible for simultaneous detection of seven duck-infecting viruses and can be applied to clinical diagnosis of viral infection in ducks.

Study of the underlying mechanisms and consequences of pathogenicity differences between two in vitro selected G1-H9N2 clones originating from a single isolate

The G1-H9N2 avian influenza virus (AIV) has caused significant economic losses in the commercial poultry industry due to reduced egg production and increased mortality. The field observations have shown that H9N2 viruses circulate and naturally mix with other pathogens and these simultaneous infections can exacerbate disease. To avoid an incorrect virus characterization, due to co-infection, isolates were purified by in vitro plaque assays. Two plaque purified G1-H9N2 clones, selected on different cell types, named MDCK-and CEF-clone in regards to the cell culture used, were studied in vivo, revealing two different virulence phenotypes. Subsequently, the underlying mechanisms were studied. Specifically, the phenotypical outcome of SPF bird infection by the two clones resulted in completely different clinical outcomes. These differences in clinical outcome were used to study the factors behind this output in more detail. Further studies demonstrated that the more severe disease outcome associated with the MDCK-clone involves a strong induction of pro-inflammatory cytokines and a lack of type I interferon production, whereas the mild disease outcome associated with the CEF-clone is related to a greater antiviral cytokine response. The immunosuppressive effect of the MDCK-clone on splenocytes was further demonstrated via ChIFN-γ lack production after ex vivo mitogenic stimulation. Genome sequencing of the two clones identified only four amino acid differences including three in the HA sequence (HA-E198A, HA-R234L, HA-E502D-H9 numbering) and one in the NA sequence (NA-V33M). In the present study, valuable insights on the mechanisms responsible for AI pathogenicity and molecular mechanisms of H9N2 infections in chicken were obtained while highlighting the impact of the cells viruses are grown on their virulence.

Interaction between avian influenza subtype H9N2 and Newcastle disease virus vaccine strain (LaSota) in chickens

BACKGROUND

H9N2 avian influenza virus is endemic in Egyptian poultry flocks. The role of the live viral vaccines such as LaSota in exaggeration of the clinical picture of H9N2 infection under field conditions is significantly important leading to severe economic losses due to higher mortality and lower growth performance. This experiment was designed to identify the possible interaction between experimental infection with H9N2 virus and NDV live vaccine (LaSota strain) in broiler chickens. Six groups each of 20 broiler chicks were used. Three groups (G1-3) were infected with H9N2 and vaccinated with LaSota, 3 days before, at the same day or 3 days post vaccination (dpv), while the remaining groups (G4-6) were non-vaccinated infected, vaccinated non-infected and non-vaccinated non-infected.

RESULTS

The highest mortality rate (37.5%) was noticed in chickens of G1 (H9N2 infected 3 days prior LaSota vaccination). Also, this bird group had the most severe clinical signs, histopathological lesions and the longest viral shedding for 9 days post infection (dpi). In the 2nd and 3rd groups, the mortality rate was the similar (31.2%) with less pronounced clinical signs, histopathological lesions and H9N2 shedding was for only 6 dpi with the least shedding quantity in chickens of G3. The control non-vaccinated infected chickens (G4) had 18.7% mortality with the least degree of clinical signs, lesions and the highest viral shedding quantity but only for 6 dpi. At 35 days of age, there was a statistical significant decrease (P < 0.05) in chicken's body weight of all H9N2 infected groups from G1 to G4 compared to non-infected control groups, G5 and G6 respectively.

CONCLUSION

It was clear that laSota vaccination significantly affect H9N2 infection in broiler chickens regarding clinical signs, mortality rate, lesions, performance and viral shedding.

Pathobiology of Avian avulavirus 1: special focus on waterfowl

Avian avulaviruses serotype 1 (abbreviated as APMV-1 for the historical name avian paramyxovirus 1) are capable of infecting a wide spectrum of avian species with variable clinical symptoms and outcomes. Ease of transmission has allowed the virus to spread worldwide with varying degrees of virulence depending upon the virus strain and host species. The emergence of new virulent genotypes from global epizootics, and the year-to-year genomic changes in low and high virulence APMV-1 imply that distinct genotypes of APMV-1 are simultaneously evolving at different geographic locations across the globe. This vast genomic diversity may be favoured by large variety of avian species susceptibility to APMV-1 infection, and by the availability of highly mobile wild birds. It has long been considered that waterfowls are not sensitive to APMV-1 and are unable to show any clinical signs, however, outbreaks from the 90's contradict these concepts. The APMV-1 isolates are increasingly reported from the waterfowl. Waterfowl have strong innate immune responses, which minimize the impact of virus infection, however, are unable to prevent the viral shedding. Numerous APMV-1 are carried by domestic waterfowl intermingling with terrestrial poultry. Therefore, commercial ducks and geese should be vaccinated against APMV-1 to minimize the virus shedding and for the prevention the transmission. Genetic diversity within APMV-1 demonstrates the need for continual monitoring of viral evolution and periodic updates of vaccine seed-strains to achieve efficient control and eradication of APMV-1 in waterfowls.

Virological and Immunological Outcomes of Coinfections

Coinfections involving viruses are being recognized to influence the disease pattern that occurs relative to that with single infection. Classically, we usually think of a clinical syndrome as the consequence of infection by a single virus that is isolated from clinical specimens. However, this biased laboratory approach omits detection of additional agents that could be contributing to the clinical outcome, including novel agents not usually considered pathogens. The presence of an additional agent may also interfere with the targeted isolation of a known virus. Viral interference, a phenomenon where one virus competitively suppresses replication of other coinfecting viruses, is the most common outcome of viral coinfections. In addition, coinfections can modulate virus virulence and cell death, thereby altering disease severity and epidemiology. Immunity to primary virus infection can also modulate immune responses to subsequent secondary infections. In this review, various virological mechanisms that determine viral persistence/exclusion during coinfections are discussed, and insights into the isolation/detection of multiple viruses are provided. We also discuss features of heterologous infections that impact the pattern of immune responsiveness that develops.

Avian Respiratory Coinfection and Impact on Avian Influenza Pathogenicity in Domestic Poultry: Field and Experimental Findings

The avian respiratory system hosts a wide range of commensal and potential pathogenic bacteria and/or viruses that interact with each other. Such interactions could be either synergistic or antagonistic, which subsequently determines the severity of the disease complex. The intensive rearing methods of poultry are responsible for the marked increase in avian respiratory diseases worldwide. The interaction between avian influenza with other pathogens can guarantee the continuous existence of other avian pathogens, which represents a global concern. A better understanding of the impact of the interaction between avian influenza virus and other avian respiratory pathogens provides a better insight into the respiratory disease complex in poultry and can lead to improved intervention strategies aimed at controlling virus spread.

Effect of Infection with a Mesogenic Strain of Newcastle Disease Virus on Infection with Highly Pathogenic Avian Influenza Virus in Chickens

Little is known on the interactions between avian influenza virus (AIV) and Newcastle disease virus (NDV) when coinfecting the same poultry host. In a previous study we found that infection of chickens with a mesogenic strain of NDV (mNDV) can reduce highly pathogenic AIV (HPAIV) replication, clinical disease, and mortality. This interaction depended on the titer of the viruses used and the timing of the infections. To further explore the effect of mNDV infectious dose in protecting chickens against HPAIV infection, 2-wk-old birds were inoculated with different doses of mNDV (10(4), 10(6), or 10(7) 50% embryo infective dose [EID50]) 3 days before inoculation with a HPAIV (10(5) or 10(6) EID50). Although birds coinfected with the higher mNDV doses (10(6) or 10(7)) survived for longer than birds inoculated only with HPAIV (10(5)), we did not observe the same protection with the lower dose of mNDV (10(4)) or when given the higher dose of HPAIV (10(6)), indicating that the relation between the titer of the two coinfecting viruses is determinant in the outcome. In a similar experiment, a higher number of 4-wk-old birds survived, and for longer, even when given higher HPAIV doses (10(6.3) and 10(7.3) EID50). In addition, we also examined the duration of protection provided by mNDV (10(7) EID50) on a HPAIV infection. Five-week-old chickens were inoculated with mNDV followed by inoculation with 10(6) EID50 of an HPAIV given at 2, 4, 6, or 9 days after the mNDV. HPAIV replication was affected and an increase in survival was found in all coinfected groups when compared to the HPAIV single-inoculated group, but the mortality in coinfected groups was high. In conclusion, previous inoculation with mNDV can affect HPAIV replication in chickens for at least 9 days, but this viral interference is titer dependent.

Hemato-biochemical and pathological changes on avian influenza in naturally infected domestic ducks in Egypt

AIM

Few studies have been made in regard to avian influenza (AI) in ducks, thus the aim of this work was planned to investigate the hematological, biochemical, and pathological changes in domestic Egyptian ducks naturally infected with AI.

MATERIALS AND METHODS

30 duck from private backyards 3-month-old 15 were clinically healthy (Group 1) and the other fifteen (Group 2) were naturally diseased with AI (H5N1). The disease was diagnosed by polymerase chain reaction as H5N1.

RESULTS

Duck showed cyanosis, subcutaneous edema of head and neck with nervous signs (torticollis). Hematological studies revealed a microcytic hypochromic anemia. Biochemical studies revealed a significant decrease in total protein, albumin and globulin concentration with significant increase of activities of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, Υ-glutamyl transpeptidase, lactic acid dehydrogenase and creatine phsphokinase. Prominent increase in creatinine and uric acid in addition to hypocalcemia and hyperphosphatemia were significantly detected in the infected ducks. Histopathological finding confirm these investigations.

CONCLUSION

The highly pathogenic AIV (A/H5N1) became more severe infectious to ducks than before and causes nervous manifestations and blindness which were uncommon in ducks. Besides the significant increases of hepatic enzymes, brain, heart, and renal markers as a response to virus damage to these organs.

Previous infection with virulent strains of Newcastle disease virus reduces highly pathogenic avian influenza virus replication, disease, and mortality in chickens

Highly pathogenic avian influenza virus (HPAIV) and Newcastle disease virus (NDV) are two of the most important viruses affecting poultry worldwide and produce co-infections especially in areas of the world where both viruses are endemic; but little is known about the interactions between these two viruses. The objective of this study was to determine if co-infection with NDV affects HPAIV replication in chickens. Only infections with virulent NDV strains (mesogenic Pigeon/1984 or velogenic CA/2002), and not a lentogenic NDV strain (LaSota), interfered with the replication of HPAIV A/chicken/Queretaro/14588-19/95 (H5N2) when the H5N2 was given at a high dose (10^6.9 EID₅₀) two days after the NDV inoculation, but despite this interference, mortality was still observed. However, chickens infected with the less virulent mesogenic NDV Pigeon/1984 strain three days prior to being infected with a lower dose (10^5.3–5.5 EID₅₀) of the same or a different HPAIV, A/chicken/Jalisco/CPA-12283-12/2012 (H7N3), had reduced HPAIV replication and increased survival rates. In conclusion, previous infection of chickens with virulent NDV strains can reduce HPAIV replication, and consequently disease and mortality. This interference depends on the titer of the viruses used, the virulence of the NDV, and the timing of the infections. The information obtained from these studies helps to understand the possible interactions and outcomes of infection (disease and virus shedding) when HPAIV and NDV co-infect chickens in the field.