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Dynamics of avian influenza
in a changing world

Virulence of three European highly pathogenic H7N1 and H7N7 avian influenza viruses in Pekin and Muscovy ducks

David Scheibner, Claudia Blaurock, Thomas C. Mettenleiter and Elsayed M. Abdelwhab

Abstract
Background: There is paucity of data on the virulence of highly pathogenic (HP) avian influenza viruses (AIV) H7 in ducks compared to HPAIV H5. Here, the virulence of HPAIV H7N1 (designated H7N1-FPV34 and H7N1-It99) and H7N7 (designated H7N7-FPV27) was assessed in Pekin and/or Muscovy ducklings after intrachoanal (IC) or intramuscular (IM) infection.
Results: The morbidity rate ranged from 60 to 100% and mortality rate from 20 to 80% depending on the duck species, virus strain and/or challenge route. All Muscovy ducklings inoculated IC with H7N7-FPV27 or H7N1-FPV34 exhibited mild to severe clinical signs resulting in the death of 2/10 and 8/10 ducklings, respectively. Also, 2/10 and 6/9 of inoculated Muscovy ducklings died after IC or IM infection with H7N1-It99, respectively. Moreover, 5/10 Pekin ducklings inoculated IC or IM with H7N1-It99 died. The level of virus detected in the oropharyngeal swabs was higher than in the cloacal swabs.
Conclusion: Taken together, HPAIV H7 cause mortality and morbidity in Muscovy and Pekin ducklings. The severity of disease in Muscovy ducklings depended on the virus strain and/or route of infection. Preferential replication of the virus in the respiratory tract compared to the gut merits further investigation.

https://doi.org/10.1186/s12917-019-1899-4

 

A brief history of bird flu

Samantha J. Lycett, Florian Duchatel and Paul Digard

Abstract
In 1918, a strain of influenzaAvirus caused a human pandemic resulting in the deaths of 50 million people. A century later, with the advent of sequencing technology and corresponding phylogenetic methods, we know much more about the origins, evolution and epidemiology of influenza epidemics. Here we review the history of avian influenza viruses through the lens of their genetic makeup: from their relationship to human pandemic viruses, starting with the 1918 H1N1 strain, through to the highly pathogenic epidemics in birds and zoonoses up to 2018. We describe the genesis of novel influenza A virus strains by reassortment and evolution in wild and domestic bird populations, as well as the role of wild bird migration in their long-range spread. The emergence of highly pathogenic avian influenza viruses, and the zoonotic incursions of avian H5 and H7 viruses into humans over the last couple of decades are also described. The threat of a new avian influenza virus causing a human pandemic is still present today, although control in domestic avian populations can minimize the risk to human health.

https://royalsocietypublishing.org/doi/10.1098/rstb.2018.0257  

A Comprehensive Model for the Quantitative Estimation of Seed Dispersal by Migratory Mallards

Erik Kleyheeg, Wolfgang Fiedler, Kamran Safi, Jonas Waldenström, Martin Wikelski and Mariëlle Liduine van Toorn

Abstract
Long-distance seed dispersal is an important ecosystem service provided by migratory animals. Plants inhabiting discrete habitats, like lakes and wetlands, experience dispersal limitation, and rely heavily on zoochory for their spatial population dynamics. Granivorous waterbirds may disperse viable seeds of wetland plants over long distances during migration. The limited knowledge of waterbird migration has long hampered the evaluation of the importance of waterbirds in seed dispersal, requiring key metrics such as realistic dispersal distances. Using recent GPS tracking of mallards during spring migration, we built a mechanistic seed dispersal model to estimate realistic dispersal distances. Mallards are abundant, partially migratory ducks known to consume seeds of >300 European plant species. Based on the tracking data, we informed a mallard migration simulator to obtain a probabilistic spring migration model for the mallard population wintering at Lake Constance in Southern Germany. We combined the spring migration model with seed retention curves to develop seed dispersal kernels. We also assessed the effects of pre-migratory fasting and the availability of suitable deposition habitats for aquatic and wetland plants. Our results show that mallards at Lake Constance can disperse seeds in the northeastern direction over median distances of 293 and 413 km for seeds with short and long retention times, respectively, assuming a departure immediately after foraging. Pre-migratory fasting strongly affected the dispersal potential, with only 1–7% of ingested seeds left for dispersal after fasting for 12 h. Availability of a suitable deposition habitat was generally <5% along the migratory flyway. The high probability of seed deposition in a freshwater habitat during the first stopover, after the mallards completed the first migratory flight, makes successful dispersal most likely to happen at 204–322 km from Lake Constance. We concluded that the directed long-distance dispersal of plant seeds, realized by mallards on spring migration, may contribute significantly to large scale spatial plant population dynamics, including range expansion in response to shifting temperature and rainfall patterns under global warming. Our dispersal model is the first to incorporate detailed behavior of migratory waterbirds and can be readily adjusted to include other vector species when tracking data are available.

https://doi.org/10.3389/fevo.2019.00040 

Integration of genetic and epidemiological data to infer H5N8 HPAI virus transmission dynamics during the 2016-2017 epidemic in Italy

P. Mulatti, A. Fusaro, F. Scolamacchia, B. Zecchin, A. Azzolini, G. Zamperin, C. Terregino, G. Cunial, I. Monne & S. Marangon

Abstract
Between October 2016 and December 2017, several European Countries had been involved in a massive Highly Pathogenic Avian Influenza (HPAI) epidemic sustained by H5N8 subtype virus. Starting on December 2016, also Italy was affected by H5N8 HPAI virus, with cases occurring in two epidemic waves: the first between December 2016 and May 2017, and the second in July-December 2017. Eighty-three outbreaks were recorded in poultry, 67 of which (80.72%) occurring in the second wave. A total of 14 cases were reported in wild birds. Epidemiological information and genetic analyses were conjointly used to get insight on the spread dynamics. Analyses indicated multiple introductions from wild birds to the poultry sector in the first epidemic wave, and noteworthy lateral spread from October 2017 in a limited geographical area with high poultry densities. Turkeys, layers and backyards were the mainly affected types of poultry production. Two genetic sub-groups were detected in the second wave in non-overlapping geographical areas, leading to speculate on the involvement of different wild bird populations. The integration of epidemiological data and genetic analyses allowed to unravel the transmission dynamics of H5N8 virus in Italy, and could be exploited to timely support in implementing tailored control measures.

https://doi.org/10.1038/s41598-018-36892-1

As the Duck Flies—Estimating the Dispersal of Low-Pathogenic Avian Influenza Viruses by Migrating Mallards

Mariëlle L. van Toor, Alexis Avril, Guohui Wu, Scott H. Holan and Jonas Waldenström

Abstract
Many pathogens rely on the mobility of their hosts for dispersal. In order to understand and predict how a disease can rapidly sweep across entire continents, illuminating the contributions of host movements to disease spread is pivotal. While elegant proposals have been made to elucidate the spread of human infectious diseases, the direct observation of long-distance dispersal events of animal pathogens is challenging. Pathogens like avian influenza A viruses, causing only short disease in their animal hosts, have proven exceptionally hard to study. Here, we integrate comprehensive data on population and disease dynamics for low-pathogenic avian influenza viruses in one of their main hosts, the mallard, with a novel movement model trained from empirical, high-resolution tracks ofmallardmigrations. This allowed us to simulate individualmallard migrations from a key stopover site in the Baltic Sea for the entire population and link these movements to infection simulations. Using this novel approach, we were able to estimate the dispersal of low-pathogenic avian influenza viruses by migrating mallards throughout several autumn migratory seasons and predicted areas that are at risk of importing these viruses. We found that mallards are competent vectors and on average dispersed viruses over distances of 160 km in just 3 h. Surprisingly, our simulations suggest that such dispersal events are rare even throughout the entire autumn migratory season. Our approach directly combines simulated population-level movements with local infection dynamics and offers a potential converging point for movement and disease ecology.
https://doi.org/10.3389/fevo.2018.00208 

A viral race for primacy: co-infection of a natural pair of low and highly pathogenic H7N7 avian influenza viruses in chickens and embryonated chicken eggs

Annika Graaf, Reiner Ulrich, Pavlo Maksimov, David Scheibner, Susanne Koethe, Elsayed M. Abdelwhab,
Thomas C. Mettenleiter, Martin Beer and Timm Harder

Abstract
Highly pathogenic avian influenza virus (HPAIV) infection in poultry caused devastating mortality and economic losses.
HPAIV of subtypes H5 and H7 emerge from precursor viruses of low pathogenicity (LP) by spontaneous mutation
associated with a shift in the susceptibility of the endoproteolytic cleavage site of the viral hemagglutinin protein from
trypsin- to furin-like proteases. A recently described natural pair of LP/HP H7N7 viruses derived from two spatiotemporally
linked outbreaks in layer chickens was used to study how a minority of mutated HP virions after de novo
generation in a single host might gain primacy. Co-infection experiments in embryonated eggs and in chickens were
conducted to investigate amplification, spread and transmissionof HPAIV within a poultry population that experiences
concurrent infection by an antigenically identical LP precursor virus. Simultaneous LPAIV co-infection (inoculum dose
of 106 egg-infectious dose 50% endpoint (EID50)/0.5 mL) withincreasing titers of HPAIV from 101 to 105.7 EID50/0.5 mL)
had a significant impeding impact on HP H7 replication, viral excretion kinetics, clinical signs and histopathological
lesions (in vivo) and on embryo mortality (in ovo). LP/HP co-infected chickens required a hundredfold higher virus
dose (HPAIV inoculum of 105 EID50) compared to HPAIV mono-infection (HPAIV inoculum of 103 EID50) to develop
overt clinical signs, mortality and virus spread to uninfected sentinels. Escape and spread of HP phenotypes after de
novo generation in an index host may therefore be highly precarious due to significant competition with cocirculating
LP precursor virus.
https://doi.org/10.1038/s41426-018-0204-0

The culture of primary duck endothelial cells for the study of avian influenza

Raissa L. Davis, Geunho Choi, Thijs Kuiken, Pascale Quéré, Sascha Trapp, Kirsty R. Short and Mathilde Richard

Abstract
Background:  Endothelial cells play a major role in highly pathogenic avian influenza (HPAI) virus pathogenesis in
gallinaceous poultry species (e.g. chicken, turkey and quail). Upon infection of gallinaceous poultry with HPAI viruses,
endothelial cells throughout the body become rapidly infected, leading to systemic dissemination of the virus,
disseminated intravascular coagulation, oedema and haemorrhaging. In contrast, the pathogenesis of HPAI
viruses in most wild bird species (e.g. duck, goose and gull species) is not associated with endothelial tropism.
Indeed, viral antigen is not found in the endothelial cells of most wild bird species following infection with HPAI
viruses. This differential endothelial cell tropism in avian species is poorly understood, mainly due to the absence of
appropriate cell culture systems.
Results:  Here, we describe the isolation and purification of primary duck endothelial cells from the aorta or bone
marrow of Pekin duck embryos. Cells were differentiated in the presence of vascular endothelial growth factor and, if
needed, enriched via fluorescent-activated cell sorting based on the uptake of acetylated low-density lipoprotein. The
expression of von Willebrand factor, a key marker of endothelial cells, was confirmed by polymerase chain reaction.
Monocultures of duck endothelial cells, either derived from the aorta or the bone marrow, were susceptible to infection
with an H5N1 HPAI virus but to a much lesser extent than chicken endothelial cells.
Conclusions:  The methods described herein to isolate and purify duck endothelial cells from the aorta or bone marrow
could also be applied to obtain microvascular endothelial cells from other tissues and organs, such as the lung or the
intestine, and represent a valuable tool to study the pathogenesis of avian viruses.
https://doi.org/10.1186/s12866-018-1307-4

The post-2009 influenza pandemic era: time to revisit antibody immunodominance

Kristien Van Reeth

Abstract
The current inactivated influenza vaccines rely on the induction of neutralizing antibodies against the head domain of the viral hemagglutinin (HA). The HA head contains five immunodominant antigenic sites, all of which are subject to antigenic drift, thereby limiting vaccine efficacy. Bypassing the immune system’s tendency to focus on the most variable regions of the HA may be a step toward more broadly protective influenza vaccines.
However, this requires a better understanding of the biological meaning of immunodominance, and of the hierarchy between different antigenic sites. In this issue of the JCI, Liu et al. determined the immunodominance of the five antigenic sites of the HA head in experimentally infected mice, guinea pigs, and ferrets. All three species exhibited different preferences for the five sites of the 2009 pandemic H1N1 strain. Moreover, human subjects exhibited yet a different pattern of immunodominance following immunization with the standard inactivated influenza vaccine. Together, these results have important implications for influenza vaccine design and interpretation of animal models.
https://www.jci.org/articles/view/124151

White-Tailed Sea Eagle (Haliaeetus albicilla) Die-Off Due to Infection with Highly Pathogenic Avian Influenza Virus, Subtype H5N8, in Germany

Oliver Krone, Anja Globig, Reiner Ulrich, Timm Harder, Jan Schinköthe, Christof Herrmann, Sascha Gerst, Franz J. Conraths, and Martin Beer

Abstract
In contrast to previous incursions of highly pathogenic avian influenza (HPAIV) H5 viruses, H5N8 clade 2.3.4.4b viruses caused numerous cases of lethal infections in white-tailed sea eagles (Haliaeetus albicilla) affecting mainly young eagles (younger than five years of age) in Germany during winter 2016/2017. Until April 2017, 17 HPAIV H5N8-positive white-tailed sea eagles had been detected (three found alive and 14 carcasses) by real-time RT-PCR and partial nucleotide sequence analyses. Severe neurological clinical signs were noticed which were corroborated by immunohistopathology revealing mild to moderate, oligo- to multifocal necrotizing virus-induced polioencephalitis. Lethal lead (Pb) concentrations, a main factor of mortality in sea eagles in previous years, could be ruled out by atomic absorption spectrometry. HPAIV H5 clade 2.3.4.4b reportedly is the first highly pathogenic influenza virus known to induce fatal disease in European white-tailed see eagles. This virus strain may become a new health threat to a highly protected species across its distribution range in Eurasia. Positive cloacal swabs suggest that eagles can spread the virus with their faeces.
https://doi.org/10.3390/v10090478

A novel European H5N8 influenza A virus has increased virulence in ducks but low zoonotic potential

Christian Grund, Donata Hoffmann, Reiner Ulrich, Mahmoud Naguib, Jan Schinköthe, Bernd Hoffmann, Timm Harder, Sandra Saenger, Katja Zscheppang, Mario Tönnies, Stefan Hippenstiel, Andreas Hocke, Thorsten Wolff, Martin Beer

Abstract
We investigated in a unique setup of animal models and a human lung explant culture biological properties, including zoonotic potential, of a representative 2016 highly pathogenic avian influenza virus (HPAIV) H5N8, clade 2.3.4.4 group B (H5N8B), that spread rapidly in a huge and ongoing outbreak series in Europe and caused high mortality in waterfowl and domestic birds. HPAIV H5N8B showed increased virulence with rapid onset of severe disease and mortality in Pekin ducks due to pronounced neuro- and hepatotropism. Cross-species infection was evaluated in mice, ferrets, and in a human lung explant culture model. While the H5N8B isolate was highly virulent for Balb/c mice, virulence and transmissibility were grossly reduced in ferrets, which was mirrored by marginal replication in human lung cultures infected ex vivo. Our data indicate that the 2016 HPAIV H5N8B is avian-adapted with augmented virulence for waterfowl, but has low zoonotic potential. The here tested combination of animal studies with the inoculation of human explants provides a promising future work flow to evaluate zoonotic potential, mammalian replication competence and avian virulence of HPAIV.
https://rdcu.be/3chT

Integrating animal movement with habitat suitability for estimating dynamic migratory connectivity

Marielle L. van Toor, Bart Kranstauber, Scott H. Newman, Diann J. Prosser, John Y. Takekawa, Georgios Technitis, Robert Weibel, Martin Wikelski, Kamran Safi

Abstract
Context High-resolution animal movement data are becoming increasingly available, yet having a multitude of empirical trajectories alone does not allow us to easily predict animal movement. To answer ecological and evolutionary questions at a population level, quantitative estimates of a species’ potential to link patches or populations are of importance.
Objectives We introduce an approach that combines movement-informed simulated trajectories with an environment-informed estimate of the trajectories’ plausibility to derive connectivity. Using the example of bar-headed geese we estimated migratory connectivity at a landscape level throughout the annual cycle in their native range.
Methods We used tracking data of bar-headed geese to develop a multi-state movement model and to estimate temporally explicit habitat suitability within the species’ range. We simulated migratory movements between range fragments, and calculated a
measure we called route viability. The results are compared to expectations derived from published literature.
Results Simulated migrations matched empirical trajectories in key characteristics such as stopover duration. The viability of the simulated trajectories was similar to that of the empirical trajectories. We found that, overall, the migratory connectivity was higher within the breeding than in wintering areas, corroborating previous findings for this species.
Conclusions We show how empirical tracking data and environmental information can be fused for meaningful predictions of animal movements throughout the year and even outside the spatial range of the available data. Beyond predicting migratory connectivity, our framework will prove useful for modelling ecological processes facilitated by animal movement, such as seed dispersal or disease ecology.
https://link.springer.com/article/10.1007/s10980-018-0637-9