Avian Clade Research Articles

Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming

Abstract Characterizing heat tolerance is critical for predicting an organism's vulnerability to climate warming. Recent studies of ectotherms report that impacts of climate warming are expected to be greater in the tropics, where ectotherms tend to have lower heat tolerances and experience air temperatures closer to their heat tolerance limits than their temperate counterparts. However, similar comparisons of heat tolerance are largely lacking for endotherms, and it remains an open question whether climate warming will also disproportionately affect tropical endotherms. To address this empirical gap, we measured thermoregulatory responses to acute heat stress in 81 bird species (23 temperate, 58 tropical), assembling the largest comparative dataset of endothermic heat tolerances to date. After controlling for body mass and experimental chamber humidity, temperate species had significantly higher heat tolerance limits (ΔHTL = 2.2°C; 45.2 vs. 43.0°C) and upper critical temperatures (ΔUCT = 1.1°C; 38.7 vs. 37.6°C) on average than tropical species. Importantly, however, these differences do not appear to impact vulnerability to climate warming, as neither thermal safety margins [i.e. the difference between upper critical temperature (UCT) and maximum air temperature, Tmax] nor warming tolerances [the difference between heat tolerance limit (HTL) and Tmax] differed between temperate and tropical species. We also observed substantial variation in heat tolerance among avian orders, with pigeons and doves (Columbiformes) being among the most heat tolerant species in our dataset. Overall, our results suggest that, from a physiological standpoint, tropical birds may not be systematically more susceptible to climate warming than temperate birds, contrasting previous studies of ectotherms. Furthermore, we show that certain avian clades may be more resilient to warming irrespective of local climate. However, because we only sampled at one temperate and one tropical site, we caution that replication from other habitats and localities are needed to evaluate the generality of our findings. A free Plain Language Summary can be found within the Supporting Information of this article.

The Female-Specific W Chromosomes of Birds Have Conserved Gene Contents but Are Not Feminized.

Sex chromosomes are unique genomic regions with sex-specific or sex-biased inherent patterns and are expected to be more frequently subject to sex-specific selection. Substantial knowledge on the evolutionary patterns of sex-linked genes have been gained from the studies on the male heterogametic systems (XY male, XX female), but the understanding of the role of sex-specific selection in the evolution of female-heterogametic sex chromosomes (ZW female, ZZ male) is limited. Here we collect the W-linked genes of 27 birds, covering the three major avian clades: Neoaves (songbirds), Galloanserae (chicken), and Palaeognathae (ratites and tinamous). We find that the avian W chromosomes exhibit very conserved gene content despite their independent evolution of recombination suppression. The retained W-linked genes have higher dosage-sensitive and higher expression level than the lost genes, suggesting the role of purifying selection in their retention. Moreover, they are not enriched in ancestrally female-biased genes, and have not acquired new ovary-biased expression patterns after becoming W-linked. They are broadly expressed across female tissues, and the expression profile of the W-linked genes in females is not deviated from that of the homologous Z-linked genes. Together, our new analyses suggest that female-specific positive selection on the avian W chromosomes is limited, and the gene content of the W chromosomes is mainly shaped by purifying selection.

Structure and possible ventilatory function of unusual, expanded sternal ribs in the Early Cretaceous bird Jeholornis

Many specimens of the basal bird Jeholornis from the Early Cretaceous Jehol Biota of northeast China include one or two distinctive paddle-shaped skeletal elements preserved in the thoracic region. These ossifications have generally been identified as lateral trabeculae, paired processes of the sternum that are common within the derived avian clade Ornithothoraces. In extant birds, lateral trabeculae define membrane-filled embayments or fenestrae in the caudal portion of the sternum that contribute to the area available for attachment of the pectoralis musculature, which drives the downstroke in flight. The presence of lateral trabeculae in Jeholornis would thus suggest a proportionally larger M. pectoralis, and a more powerful downstroke, than in other non-ornithothoracine avians. However, previously undescribed specimens of Jeholornis reveal that the paddle-shaped elements are actually anomalously expanded sternal ribs, the caudalmost of four pairs in the ribcage. Accordingly, lateral trabeculae are absent in Jeholornis, dovetailing with other evidence that basal birds lack many components of the sophisticated flight apparatus typical of ornithothoracines. The expanded sternal ribs represent a striking, and somewhat functionally enigmatic, autapomorphy of Jeholornis. In many pterosaurs the sternal ribs bear multiple small prominences, the sternocostapophyses, that probably improved the mechanical advantage of ribcage musculature involved in ventilation and increased the area for muscle attachment. The sternal rib expansions seen in Jeholornis presumably served a similar purpose, and are among a suite of derived features of this taxon that appear to represent adaptations for the demands of powered flight but only partially parallel those independently acquired by ornithothoracines.

The hummingbird syrinx morphome: a detailed three-dimensional description of the black jacobin\u2019s vocal organ

BackgroundThe ability to imitate sounds depends on a process called vocal production learning, a rare evolutionary trait. In addition to the few mammalian groups that possess this ability, vocal production learning has evolved independently in three avian clades: songbirds, parrots, and hummingbirds. Although the anatomy and mechanisms of sound production in songbirds are well understood, little is known about the hummingbird’s vocal anatomy.ResultsWe use high-resolution micro-computed tomography (μCT) and microdissection to reveal the three-dimensional structure of the syrinx, the vocal organ of the black jacobin (Florisuga fusca), a phylogenetically basal hummingbird species. We identify three features of the black jacobin’s syrinx: (i) a shift in the position of the syrinx to the outside of the thoracic cavity and the related loss of the sterno-tracheal muscle, (ii) complex intrinsic musculature, oriented dorso-ventrally, and (iii) ossicles embedded in the medial vibratory membranes.ConclusionsThe extra-thoracic placement of the black jacobin’s syrinx and the dorso-ventrally oriented musculature likely aid to uncoupling syrinx movements from extensive flight-related thorax constraints. The syrinx morphology further allows for vibratory decoupling, precise control of complex acoustic parameters, and a large motor redundancy that may be key biomechanical factors leading to acoustic complexity and thus facilitating the occurrence of vocal production learning.

The earliest Tyrannida (Aves, Passeriformes), from the Oligocene of France

Passeriformes is the most diverse bird order. Nevertheless, passerines have a remarkably poor early fossil record. In addition, high osteological homoplasy across passerines makes partial specimens difficult to systematically assign precisely. Here we describe one of the few earliest fossil passerines, from the early Oligocene (ca 30 Ma) of southern France, and one of the best preserved and most complete. This fossil can be conservatively assigned to Tyrannida, a subclade of the New World Tyranni (Suboscines), i.e. of the Tyrannides. A most probably stem-representative of Tyrannida, the new fossil bears strong resemblance with some manakins (Pipridae), possibly due to plesiomorphy. Furthermore, it yields a new point of calibration for molecular phylogenies, already consistent with the age of the fossil. Tyrannida, and the more inclusive Tyrannides, are today confined to the New World. Therefore, the new fossil calls for scenarios of transatlantic crossing during or near the Oligocene. Later, the European part of the distribution of the Tyrannida disappeared, leading to a relictual modern New World distribution of this clade, a pattern known in other avian clades. The history of Tyrannida somehow mirrors that of the enigmatic Sapayoa aenigma, sole New World representative of the Eurylaimides (Old World Tyranni), with transatlantic crossing probably caused by similar events.

Highly pathogenic avian influenza subtype H5Nx clade 2.3.4.4 outbreaks in Dutch poultry farms, 2014-2018: Clinical signs and mortality.

In recent years, different subtypes of highly pathogenic avian influenza (HPAI) viruses caused outbreaks in several poultry types worldwide. Early detection of HPAI virus infection is crucial to reduce virus spread. Previously, the use of a mortality ratio threshold to expedite notification of suspicion in layer farms was proposed. The purpose of this study was to describe the clinical signs reported in the early stages of HPAI H5N8 and H5N6 outbreaks on chicken and Pekin duck farms between 2014 and 2018 in the Netherlands and compare them with the onset of an increased mortality ratio (MR). Data on daily mortality and clinical signs from nine egg‐producing chicken farms and seven Pekin duck farms infected with HPAI H5N8 (2014 and 2016) and H5N6 (2017–2018) in the Netherlands were analysed. In 12 out of 15 outbreaks for which a MR was available, MR increase preceded or coincided with the first observation of clinical signs by the farmer. In one chicken and two Pekin duck outbreaks, clinical signs were observed prior to MR increase. On all farms, veterinarians observed clinical signs of general disease. Nervous or locomotor signs were reported in all Pekin duck outbreaks, but only in two chicken outbreaks. Other clinical signs were observed less frequently in both chickens and Pekin ducks. Compared to veterinarians, farmers observed and reported clinical signs, especially respiratory and gastrointestinal signs, less frequently. This case series suggests that a MR with a set threshold could be an objective parameter to detect HPAI infection on chicken and Pekin duck farms at an early stage. Observation of clinical signs may provide additional indication for farmers and veterinarians for notifying a clinical suspicion of HPAI infection. Further assessment and validation of a MR threshold in Pekin ducks are important as it could serve as an important tool in HPAI surveillance programs.

Speciation Associated with Shifts in Migratory Behavior in an Avian Radiation.

Migratory animals move up to thousands of kilometers every year [1]. Losses of migration (i.e., migratory drop-offs) occur when individuals of a migratory species stop migrating and establish founder sedentary populations, a phenomenon documented in birds [2-5] and butterflies [6]. In theory, losses-and also gains-of migration might promote speciation if sedentary and migratory populations become reproductively isolated [7-9]. Because migratory and sedentary strategies involve alternative physiological, behavioral, and morphological traits [10-13], divergence along multiple axes of organismal function is expected to accompany switches in migratory behavior, potentially accelerating speciation. We present evidence of speciation driven by a migratory drop-off in the fork-tailed flycatcher (Tyrannus savana) resulting in reproductive isolation likely driven by changes in breeding schedules (allochronic speciation [13-15]) and geographic isolation of breeding grounds (allopatric speciation [16]). Phylogenetic analyses across New World flycatchers (Tyrannidae) showed that an association between speciation and drop-offs is also observable at a macroevolutionary scale. Loss of migration was significantly more frequent than its gain, and speciation rates of migratory and partially migratory lineages (i.e., species having both migratory and sedentary populations) exceeded those of sedentary lineages. Models of trait evolution indicated that partial migration is an intermediate step between migratory and sedentary states in this family. Given that partial migration is widespread across migratory animals (e.g., of all migratory birds, ca. 51% are partially migratory [5]), speciation via switches in migratory behavior might be an important yet overlooked mechanism of animal diversification.

Pandemic potential of highly pathogenic avian influenza clade 2.3.4.4 A(H5) viruses.

SummaryThe panzootic caused by A/goose/Guangdong/1/96‐lineage highly pathogenic avian influenza (HPAI) A(H5) viruses has occurred in multiple waves since 1996. From 2013 onwards, clade 2.3.4.4 viruses of subtypes A(H5N2), A(H5N6), and A(H5N8) emerged to cause panzootic waves of unprecedented magnitude among avian species accompanied by severe losses to the poultry industry around the world. Clade 2.3.4.4 A(H5) viruses have expanded in distinct geographical and evolutionary pathways likely via long distance migratory bird dispersal onto several continents and by poultry trade among neighboring countries. Coupled with regional circulation, the viruses have evolved further by reassorting with local viruses. As of February 2019, there have been 23 cases of humans infected with clade 2.3.4.4 H5N6 viruses, 16 (70%) of which had fatal outcomes. To date, no HPAI A(H5) virus has caused sustainable human‐to‐human transmission. However, due to the lack of population immunity in humans and ongoing evolution of the virus, there is a continuing risk that clade 2.3.4.4 A(H5) viruses could cause an influenza pandemic if the ability to transmit efficiently among humans was gained. Therefore, multisectoral collaborations among the animal, environmental, and public health sectors are essential to conduct risk assessments and develop countermeasures to prevent disease and to control spread. In this article, we describe an assessment of the likelihood of clade 2.3.4.4 A(H5) viruses gaining human‐to‐human transmissibility and impact on human health should such human‐to‐human transmission occur. This structured analysis assessed properties of the virus, attributes of the human population, and ecology and epidemiology of these viruses in animal hosts.

Incorporating heterogeneous sampling probabilities in continuous phylogeographic inference - Application to H5N1 spread in the Mekong region.

The potentially low precision associated with the geographic origin of sampled sequences represents an important limitation for spatially explicit (i.e. continuous) phylogeographic inference of fast-evolving pathogens such as RNA viruses. A substantial proportion of publicly available sequences is geo-referenced at broad spatial scale such as the administrative unit of origin, rather than more precise locations (e.g. geographic coordinates). Most frequently, such sequences are either discarded prior to continuous phylogeographic inference or arbitrarily assigned to the geographic coordinates of the centroid of their administrative area of origin for lack of a better alternative. We here implement and describe a new approach that allows to incorporate heterogeneous prior sampling probabilities over a geographic area. External data, such as outbreak locations, are used to specify these prior sampling probabilities over a collection of sub-polygons. We apply this new method to the analysis of highly pathogenic avian influenza H5N1 clade data in the Mekong region. Our method allows to properly include, in continuous phylogeographic analyses, H5N1 sequences that are only associated with large administrative areas of origin and assign them with more accurate locations. Finally, we use continuous phylogeographic reconstructions to analyse the dispersal dynamics of different H5N1 clades and investigate the impact of environmental factors on lineage dispersal velocities. Our new method allowing heterogeneous sampling priors for continuous phylogeographic inference is implemented in the open-source multi-platform software package BEAST 1.10. Supplementary data are available at Bioinformatics online.

A skeleton of a small bird with a distinctive furcula morphology, from the Rupelian of Poland, adds a new taxon to early Oligocene avifaunas

A partial skeleton of a new small avian species is reported from marine sediments of the Rupelian locality Jamna Dolna 2 in southeast Poland. Carpathiavis meniliticus gen. et sp. nov. is characterized by an unusual furcula morphology with stout shafts (scapi clavicularum) and a long, rodshaped furcular apophysis. With regard to furcula shape and the proportions of the wing bones, the new species shows a resemblance to the taxon Eocuculus, which occurs in the late Eocene of North America and the early Oligocene of France. However, there are some distinct differences to Eocuculus, and in overall morphology C. meniliticus is also similar to the late Paleocene/early Eocene taxon Songzia, which is a putative representative of the Ralloidea (rails and allies). Even though a wellfounded phylogenetic assignment of the new species is impeded by the poor preservation of the skeleton, Carpathiavis clearly represents a distinctive new taxon that has not previously been reported from the Rupelian of Europe. In its skeletal morphology, the new taxon differs from all extant avian clades and substantiates previous evidence that in the early Oligocene morphologically distinctive representatives of extinct clades lived alongside essentially moderntype representatives of extant avian groups.

Pathogenicity and genomic changes of a 2016 European H5N8 highly pathogenic avian influenza virus (clade 2.3.4.4) in experimentally infected mallards and chickens

Highly pathogenic avian influenza H5N8 clade 2.3.4.4 virus caused outbreaks in poultry and unusually high mortality in wild birds in 2016–2017. The pathobiology of one of these viruses was examined in mallards and chickens. High mortality and transmission to direct contacts were observed in mallards inoculated with medium and high doses of the virus. However, in chickens, high mortality occurred only when birds are given the high virus dose and no transmission was observed, indicating that the virus was better adapted to mallards. In comparison with the virus inoculum, viral sequences obtained from the chickens had a higher number of nucleotide changes but lower intra-host genomic diversity than viral sequences obtained from the mallards. These observations are consistent with population bottlenecks occurring when viruses infect and replicate in a host that it is not well adapted to. Whether these observations apply to influenza viruses in general remains to be determined.

New Fossil Birds from the Earliest Eocene of Mongolia

Understanding of the Asian early Paleogene avifauna is limited relative to that of North American and European avifauna of the same period. While major patterns of mammalian faunal exchange among these three regions across the Paleocene/Eocene boundary have been described, much less is known about the dynamics of bird diversity over the same time interval. Here, we report bird fossils from the earliest Eocene Bumban Member of the Naranbulag Formation in central Mongolia that add to the known record from Asia from just after this boundary. Most of this material, collected by the joint American Museum of Natural History/ Mongolia Academy of Sciences expeditions, is referable to a previously described taxon in Presbyornithidae (Anseriformes). However, five isolated elements are identified as comprising at least four species from at least three other major avian clades. While further inclusive phylogenetic analyses of each of these clades are necessary, the new remains represent possible earliest occurrences in Asia of these clades. The material includes a humerus and a furcula from shorebirds (Pan-Charadriiformes), a quadrate from a stem member of the flamingo-grebe lineage (Pan-Mirandornithes), and a coracoid from a stem galliform (Pangalliformes). We also report a humerus with uncertain phylogenetic affinities but with similarities to core Gruiformes. These new fossils expand our knowledge of the Asian avifauna during this time and have the potential to further inform our understanding of the early biogeography of these clades. The shorebird and flamingo-grebe material indicate that both these lineages were present in Asia by the earliest Eocene. The pan-mirandornithine quadrate provides insight into the early feeding ecology of the flamingo-grebe clade.

A Phylogenomic Supertree of Birds

It has long been appreciated that analyses of genomic data (e.g., whole genome sequencing or sequence capture) have the potential to reveal the tree of life, but it remains challenging to move from sequence data to a clear understanding of evolutionary history, in part due to the computational challenges of phylogenetic estimation using genome-scale data. Supertree methods solve that challenge because they facilitate a divide-and-conquer approach for large-scale phylogeny inference by integrating smaller subtrees in a computationally efficient manner. Here, we combined information from sequence capture and whole-genome phylogenies using supertree methods. However, the available phylogenomic trees had limited overlap so we used taxon-rich (but not phylogenomic) megaphylogenies to weave them together. This allowed us to construct a phylogenomic supertree, with support values, that included 707 bird species (~7% of avian species diversity). We estimated branch lengths using mitochondrial sequence data and we used these branch lengths to estimate divergence times. Our time-calibrated supertree supports radiation of all three major avian clades (Palaeognathae, Galloanseres, and Neoaves) near the Cretaceous-Paleogene (K-Pg) boundary. The approach we used will permit the continued addition of taxa to this supertree as new phylogenomic data are published, and it could be applied to other taxa as well.

Phenotypic Diversity Arises from Secondary Signal Loss in the Elaborate Visual Displays of Toucans and Barbets.

Complexity and diversity are fundamental characteristics of life, but the relationship between the two remains murky. For example, both gaining and losing complexity can support diversity-so how exactly does complexity influence the emergence of unique phenotypes? Here we address this question by examining how complexity underlies the diversity of elaborate visual displays in the avian clade Ramphastides (toucans and barbets). These species communicate in part by using body movement and colorful ornaments on the tail. We find that sexual size dimorphism predicts the evolution of one specific signal, the tail-cock gesture, implying that tail cocking is more likely to evolve under stronger sexual selection. We also discover process-level constraints on the evolution of complexity: signals are gained along a strict order of operations, where the tail-cock gesture arises before other colors and gestures. Yet virtually any signal can be lost at any time. As a result, many extant phenotypes were more likely to arise through loss of complexity, highlighting the importance of secondary signal loss to phenotypic diversity. Collectively, our results demonstrate how sexual selection catalyzes the evolution of complex phenotypes, which indirectly support diversity by allowing different traits to be modified or lost in the future.

Climatic shifts drove major contractions in avian latitudinal distributions throughout the Cenozoic

Many higher level avian clades are restricted to Earth's lower latitudes, leading to historical biogeographic reconstructions favoring a Gondwanan origin of crown birds and numerous deep subclades. However, several such "tropical-restricted" clades (TRCs) are represented by stem-lineage fossils well outside the ranges of their closest living relatives, often on northern continents. To assess the drivers of these geographic disjunctions, we combined ecological niche modeling, paleoclimate models, and the early Cenozoic fossil record to examine the influence of climatic change on avian geographic distributions over the last ∼56 million years. By modeling the distribution of suitable habitable area through time, we illustrate that most Paleogene fossil-bearing localities would have been suitable for occupancy by extant TRC representatives when their stem-lineage fossils were deposited. Potentially suitable habitat for these TRCs is inferred to have become progressively restricted toward the tropics throughout the Cenozoic, culminating in relatively narrow circumtropical distributions in the present day. Our results are consistent with coarse-scale niche conservatism at the clade level and support a scenario whereby climate change over geological timescales has largely dictated the geographic distributions of many major avian clades. The distinctive modern bias toward high avian diversity at tropical latitudes for most hierarchical taxonomic levels may therefore represent a relatively recent phenomenon, overprinting a complex biogeographic history of dramatic geographic range shifts driven by Earth's changing climate, variable persistence, and intercontinental dispersal. Earth's current climatic trajectory portends a return to a megathermal state, which may dramatically influence the geographic distributions of many range-restricted extant clades.

A NOVEL ORTHOREOVIRUS ASSOCIATED WITH EPIZOOTIC NECROTIZING ENTERITIS AND SPLENIC NECROSIS IN AMERICAN CROWS (CORVUS BRACHYRHYNCHOS)

Epizootic mortalities in American Crows (Corvus brachyrhynchos) during the winter months, referred to as winter mortality of crows, have been recorded in North America for almost two decades. The most common postmortem findings include necrotizing enteritis, colitis, and fibrinous splenic necrosis. These findings are proposed to be due to infection with a Reovirus sp. Our objectives were to characterize the pathology and seasonality of the epizootics in New York State (NYS), confirm the causative role of an Orthoreovirus sp., and determine its phylogeny. On the basis of our proposed case definition for reovirosis, we examined case data collected by the NYS Wildlife Health Program for 16 yr. A total of 558 cases of reovirosis were recorded between 2001 and 2017. Reovirosis had a clear seasonal presentation: cases occurred almost exclusively in winter months (71% in December-January). Detailed data from a 2-yr period (2016-17) demonstrated that reovirosis caused up to 70% of all recorded crow deaths during epizootic months. Crows with positive orthoreovirus isolation from the spleen or intestine were 32 times more likely to die with characteristic histologic lesions of enteritis or enterocolitis and splenic necrosis than crows with negative isolation results. An in situ hybridization probe specific to virus isolated from NYS crow reovirosis cases demonstrated a direct association between viral presence and characteristic histologic lesions. Sigma C (capsid protein) sequences of isolates from NYS crows showed high homology with Tvärminne avian virus, recently proposed as a novel Corvus orthoreovirus clade, and only distantly related to the avian orthoreovirus clade. Our study indicated that a novel orthoreovirus was the cause of winter mortality (or reovirosis) of American Crows and placed the NYS isolates in the newly proposed genus of Corvid orthoreovirus.

Ultraconserved elements resolve genus-level relationships in a major Australasian bird radiation (Aves: Meliphagidae)

ABSTRACT The honeyeaters are the most species-rich clade of birds east of Wallace’s Line. They occupy a wide range of habitats, from desert to rainforest, and occur throughout Australia, New Guinea, and oceanic islands across Wallacea and the Pacific. Honeyeater natural history is well characterised, but comparative studies of this group are hampered by the lack of a well-supported phylogeny. Here, we infer the first genome-scale, genus-level phylogeny of the honeyeaters using 4397 ultraconserved elements from 57 species. We analysed the data using concatenated and species-tree approaches, and we found support for novel clades previously undetected in analyses of single- or multi-locus datasets. Despite sequencing thousands of loci, phylogenetic relationships of the New Caledonian Crow Honeyeater (Gymnomyza aubryana) remain equivocal. This study provides a new phylogenetic framework from which to study the ecology and evolution of one of Australasia’s most iconic avian clades.

Skeletons from the early Oligocene of Poland fill a significant temporal gap in the fossil record of upupiform birds (hoopoes and allies)

ABSTRACT Upupiformes is the avian clade including extant hoopoes (Upupidae) and wood hoopoes (Phoeniculidae). Upupiform birds are abundantly represented in some Eocene fossil sites and are also known from early Miocene localities, but the fossil record in between is surprisingly scant. This gap of over 25 million years is bridged by two skeletons from the early Oligocene of Poland. One of the fossils is described as a new species, ?Laurillardia smoleni, sp. nov., the other is tentatively referred to Laurillardia munieri Flot, 1891. We detail that these stem group Upupiformes are more closely related to the crown group than are the Eocene Messelirrisoridae. The specimens show that very small upupiform birds coexisted with passerines (Passeriformes) for at least ten million years and challenge previous hypotheses that the arrival of passerines in Europe led to the demise of small non-passeriform arboreal birds. It remains elusive, why small upupiform birds became extinct in the Northern Hemisphere. Even though these insectivorous birds may not have found enough food after the emergence of cold Northern Hemispheric winters, it is an open question why very small-sized upupiform birds do not occur in the tropical regions of Asia but are today restricted to Africa south of the Sahara. http://www.zoobank.org/urn:lsid:zoobank.org:pub:A90B22E7-C3EC-4EAE-A757-F073EAF521F3

Historical and geographical patterns of new HPAIV emergences and association with spatial factors

Historical and geographical patterns of new HPAIV emergences and association with spatial factors

Protective efficacy of an inactivated chimeric H5 avian influenza vaccine against H5 highly pathogenic avian influenza virus clades 2.3.4.4 and 2.3.2.1.

The H5 subtype of highly pathogenic avian influenza (HPAI) viruses pose a serious challenge to public health and the poultry industry in China. In this study, we generated a chimeric QH/KJ recombinant virus expressing the entire haemagglutinin (HA)-1 region of the HPAI virus A/chicken/China/QH/2017(H5N6) (clade 2.3.4.4) and the HA2 region of the HPAI virus A/chicken/China/KJ/2017(H5N1) (clade 2.3.2.1). The resulting chimeric PR8-QH/KJ virus exhibited similar in vitro growth kinetics as the parental PR8-QH and PR8-KJ viruses. The chimeric PR8-QH/KJ virus induced specific, cross-reactive haemagglutination-inhibition and serum-neutralizing antibodies against both QH and KJ viruses, although PR8-QH and PR8-KJ exhibited no cross-reactivity with each other. Furthermore, the chimeric PR8-QH/KJ vaccine significantly reduced virus shedding and completely protected chickens from challenge with HPAI H5N6 and H5N1 viruses. However, the Re-8 vaccine against clade 2.3.4.4 viruses provided specific-pathogen-free chickens only partial protection when challenged with QH virus. Our results suggest that the antigenic variation of these epidemic viruses occurred and they can escape the current vaccine immunization. The Re-8 vaccine needs an update. The chimeric PR8-QH/KJ vaccine is effective against H5 HPAI virus clades 2.3.4.4 and 2.3.2.1 in chickens.