An epidemic of Newcastle disease in double-crested cormorants from Saskatchewan

Isolation and Genetic Characterization of a Novel Adenovirus Associated with Mass Mortality in Great Cormorants (Phalacrocorax carbo)

High mortality in great cormorants (Phalacrocorax carbo) was registered on the Alakol Lake in eastern Kazakhstan in 2021 when about 20% of juveniles died. High-throughput sequencing revealed the presence of a putative novel cormorant adenovirus significantly divergent from known aviadenoviruses. We suggest that this cormorant adenovirus can be considered an emerging threat to the health and conservation of this species.

Discovery of Avian Paramyxoviruses APMV-1 and APMV-6 in Shorebirds and Waterfowl in Southern Ukraine

Emerging RNA virus infections are a growing concern among domestic poultry industries due to the severe impact they can have on flock health and economic livelihoods. Avian paramyxoviruses (APMV; avulaviruses, AaV) are pathogenic, negative-sense RNA viruses that cause serious infections in the respiratory and central nervous systems. APMV was detected in multiple avian species during the 2017 wild bird migration season in Ukraine and studied using PCR, virus isolation, and sequencing. Of 4090 wild bird samples collected, mostly from southern Ukraine, eleven isolates were grown in ovo and identified for APMV serotype by hemagglutinin inhibition test as: APMV-1, APMV-4, APMV-6, and APMV-7. To build One Health's capacity to characterize APMV virulence and analyze the potential risks of spillover to immunologically naïve populations, we sequenced virus genomes in veterinary research labs in Ukraine using a nanopore (MinION) platform. RNA was extracted and amplified using a multiplex tiling primer approach to specifically capture full-length APMV-1 (n = 5) and APMV-6 (n = 2) genomes at high read depth. All APMV-1 and APMV-6 fusion (F) proteins possessed a monobasic cleavage site, suggesting these APMVs were likely low virulence, annually circulating strains. Utilization of this low-cost method will identify gaps in viral evolution and circulation in this understudied but important critical region for Eurasia.

REVENGE OF THE TREES: ENVIRONMENTAL DETERMINANTS AND POPULATION EFFECTS OF INFECTIOUS DISEASE OUTBREAKS ON A BREEDING COLONY OF DOUBLE-CRESTED CORMORANTS (PHALACROCORAX AURITUS) OVER A PERIOD OF 21 YEARS

During 16 of 21 consecutive annual breeding seasons, two diseases, Newcastle disease and avian cholera, killed approximately 50% of juvenile Double-crested Cormorants (Phalacrocorax auritus) in a large nesting colony in Canada. From 1994 to 2014, we recorded data annually on disease occurrence, causal pathogens, species and age classes affected, total number of breeding pairs of cormorants on the colony site, and other biological parameters. A mathematical model of pathogen transmission was constructed to assess the potential importance of transmission parameters and to test a hypothesis regarding the potential effect of the observed progressive loss of nest trees and the consequent shift from tree-nesting to ground-nesting behavior. The model indicated that juveniles from ground nests were 14 times more likely to die from epidemic disease (50.14% mortality) than were juveniles from nests in trees (3.57% mortality). Additive disease-related mortality of juvenile cormorants in the observed range of 40-60% would reduce a closed cormorant population over time. There was no directional change in the colony population during the study period, suggesting that immigration had compensated for disease-related mortality. Our results highlight the preeminent influence of environmental factors on pathogen transmission and the value of long-term data sets.

RNA virome abundance and diversity is associated with host age in a bird species

Despite the ongoing interest in virus discovery, little is known about the factors that shape communities of viruses within individual hosts. Here, we address how virus communities might be impacted by the age of the hosts they infect, using total RNA sequencing to reveal the RNA viromes of different age groups of Ruddy Turnstones (Arenaria interpres). From oropharyngeal and cloacal swabs we identified 14 viruses likely infecting birds, 11 of which were novel, including members of the Reoviridae, Astroviridae, and Picornaviridae. Strikingly, 12 viruses identified were from juvenile birds sampled in the first year of their life, compared to only two viruses in adult birds. Both viral abundance and alpha diversity were marginally higher in juvenile than adult birds. As well as informing studies of virus ecology, that host age might be associated with viral composition is an important consideration for the future surveillance of novel and emerging viruses.

Cormorants as a Potentially Important Reservoir and Carrier of Newcastle Disease Virus on the Asian Continent

Despite numerous disease prevention measures and control programs, Newcastle disease (ND) remains one of the most significant infections in poultry worldwide, especially in developing countries. It is known that wild birds, mainly of the Anseriformes order, are the main carrier of lentogenic (non-pathogenic) variants of Newcastle disease virus (NDV) in nature. But the question of the reservoir of velogenic (highly pathogenic) NDV in nature still remains open. In the 1970s, 1990s, and 2000s in North America during epizootics among cormorants, velogenic NDV strains were isolated. It was later concluded that cormorants play an important role in the maintenance and circulation of NDV in North America. New data have been obtained on the circulation of velogenic NDV strains in wild birds in Central Asia: VIIb and XIII genotype strains were isolated from cormorants for the first time in Kazakhstan. Interestingly, outbreaks of NDV registered in poultry in Central and Southern Asia were phylogenetically close to the viruses from cormorants that support the idea that cormorants can serve as the potential reservoir of velogenic NDV in developing countries of Asia. The seasonal migrations of cormorants may contribute to the distribution of the virus throughout Asia but more evidence must be obtained to confirm this hypothesis. There is increasing evidence of the introduction of NDV into the poultry farms from wild nature worldwide. This article continues the discussion on the likelihood of cormorants to serve as a reservoir and carrier of NDV on the Asian continent.

A review of virulent Newcastle disease viruses in the United States and the role of wild birds in viral persistence and spread

Newcastle disease is caused by virulent strains of Newcastle disease virus (NDV), which causes substantial morbidity and mortality events worldwide in poultry. The virus strains can be differentiated as lentogenic, mesogenic, or velogenic based on a mean death time in chicken embryos. Currently, velogenic strains of NDV are not endemic in United States domestic poultry; however, these strains are present in other countries and are occasionally detected in wild birds in the U.S. A viral introduction into domestic poultry could have severe economic consequences due to the loss of production from sick and dying birds, the cost of control measures such as depopulation and disinfection measures, and the trade restrictions that would likely be imposed as a result of an outbreak. Due to the disease-free status of the U.S. and the high cost of a potential viral incursion to the poultry industry, a qualitative risk analysis was performed to evaluate the vulnerabilities of the U.S. against the introduction of virulent strains of NDV. The most likely routes of virus introduction are explored and data gathered by several federal agencies is provided. Recommendations are ultimately provided for data that would be useful to further understand NDV on the landscape and to utilize all existing sampling opportunities to begin to comprehend viral movement and further characterize the risk of NDV introduction into the U.S.

Assessment of contemporary genetic diversity and inter-taxa/inter-region exchange of avian paramyxovirus serotype 1 in wild birds sampled in North America

BACKGROUND

Avian paramyxovirus serotype 1 (APMV-1) viruses are globally distributed, infect wild, peridomestic, and domestic birds, and sometimes lead to outbreaks of disease. Thus, the maintenance, evolution, and spread of APMV-1 viruses are relevant to avian health.

METHODS

In this study we sequenced the fusion gene from 58 APMV-1 isolates recovered from thirteen species of wild birds sampled throughout the USA during 2007-2014. We analyzed sequence information with previously reported data in order to assess contemporary genetic diversity and inter-taxa/inter-region exchange of APMV-1 in wild birds sampled in North America.

RESULTS

Our results suggest that wild birds maintain previously undescribed genetic diversity of APMV-1; however, such diversity is unlikely to be pathogenic to domestic poultry. Phylogenetic analyses revealed that APMV-1 diversity detected in wild birds of North America has been found in birds belonging to numerous taxonomic host orders and within hosts inhabiting multiple geographic regions suggesting some level of viral exchange. However, our results also provide statistical support for associations between phylogenetic tree topology and host taxonomic order/region of sample origin which supports restricted exchange among taxa and geographical regions of North America for some APMV-1 sub-genotypes.

CONCLUSIONS

We identify previously unrecognized genetic diversity of APMV-1 in wild birds in North America which is likely a function of continued viral evolution in reservoir hosts. We did not, however, find support for the emergence or maintenance of APMV-1 strains predicted to be pathogenic to poultry in wild birds of North America outside of the order Suliformes (i.e., cormorants). Furthermore, genetic evidence suggests that ecological drivers or other mechanisms may restrict viral exchange among taxa and regions of North America. Additional and more systematic sampling for APMV-1 in North America would likely provide further inference on viral dynamics for this infectious agent in wild bird populations.

Interacting Effects of Newcastle Disease Transmission and Illegal Trade on a Wild Population of White-Winged Parakeets in Peru: A Modeling Approach

Illegal wildlife-pet trade can threaten wildlife populations directly from overharvest, but also indirectly as a pathway for introduction of infectious diseases. This study evaluated consequences of a hypothetical introduction of Newcastle disease (ND) into a wild population of Peru's most trafficked psittacine, the white-winged parakeet (Brotogeris versicolurus), through release of infected confiscated individuals. We developed two mathematical models that describe ND transmission and the influence of illegal harvest in a homogeneous (model 1) and age-structured population of parakeets (model 2). Infection transmission dynamics and harvest were consistent for all individuals in model 1, which rendered it mathematically more tractable compared to the more complex, age-structured model 2 that separated the host population into juveniles and adults. We evaluated the interaction of ND transmission and harvest through changes in the basic reproduction number (R0) and short-term host population dynamics. Our findings demonstrated that ND introduction would likely provoke considerable disease-related mortality, up to 24% population decline in two years, but high harvest rates would dampen the magnitude of the outbreak. Model 2 produced moderate differences in disease dynamics compared to model 1 (R0 = 3.63 and 2.66, respectively), but highlighted the importance of adult disease dynamics in diminishing the epidemic potential. Therefore, we suggest that future studies should use a more realistic, age-structured model. Finally, for the presumptive risk that illegal trade of white-winged parakeets could introduce ND into wild populations, our results suggest that while high harvest rates may have a protective effect on the population by reducing virus transmission, the combined effects of high harvest and disease-induced mortality may threaten population survival. These results capture the complexity and consequences of the interaction between ND transmission and harvest in a wild parrot population and highlight the importance of preventing illegal trade.

Temporal, geographic, and host distribution of avian paramyxovirus 1 (Newcastle disease virus)

Newcastle disease is caused by virulent forms of avian paramyxovirus of serotype 1 (APMV-1) and has global economic importance. The disease reached panzootic proportions within two decades after first being identified in 1926 in the United Kingdom and Indonesia and still remains endemic in many countries across the world. Here we review information on the host, temporal, and geographic distribution of APMV-1 genetic diversity based on the evolutionary systematics of the complete coding region of the fusion gene. Strains of APMV-1 are phylogenetically separated into two classes (class I and class II) and further classified into genotypes based on genetic differences. Class I viruses are genetically less diverse, generally present in wild waterfowl, and are of low virulence. Class II viruses are genetically and phenotypically more diverse, frequently isolated from poultry with occasional spillovers into wild birds, and exhibit a wider range of virulence. Waterfowl, cormorants, and pigeons are natural reservoirs of all APMV-1 pathotypes, except viscerotropic velogenic viruses for which natural reservoirs have not been identified. Genotypes I and II within class II include isolates of high and low virulence, the latter often being used as vaccines. Viruses of genotypes III and IX that emerged decades ago are now isolated rarely, but may be found in domestic and wild birds in China. Containing only virulent viruses and responsible for the majority of recent outbreaks in poultry and wild birds, viruses from genotypes V, VI, and VII, are highly mobile and have been isolated on different continents. Conversely, virulent viruses of genotypes XI (Madagascar), XIII (mainly Southwest Asia), XVI (North America) and XIV, XVII and XVIII (Africa) appear to have a more limited geographic distribution and have been isolated predominantly from poultry.

ECOLOGICAL DETERMINANTS OF AVIAN INFLUENZA VIRUS, WEST NILE VIRUS, AND AVIAN PARAMYXOVIRUS INFECTION AND ANTIBODY STATUS IN BLUE-WINGED TEAL (ANAS DISCORS) IN THE CANADIAN PRAIRIES

The Canadian prairies are one of the most important breeding and staging areas for migratory waterfowl in North America. Hundreds of thousands of waterfowl of numerous species from multiple flyways converge in and disperse from this region annually; therefore this region may be a key area for potential intra- and interspecific spread of infectious pathogens among migratory waterfowl in the Americas. Using Blue-winged Teal (Anas discors, BWTE), which have the most extensive migratory range among waterfowl species, we investigated ecologic risk factors for infection and antibody status to avian influenza virus (AIV), West Nile virus (WNV), and avian paramyxovirus-1 (APMV-1) in the three prairie provinces (Alberta, Saskatchewan, and Manitoba) prior to fall migration. We used generalized linear models to examine infection or evidence of exposure in relation to host (age, sex, body condition, exposure to other infections), spatiotemporal (year, province), population-level (local population densities of BWTE, total waterfowl densities), and environmental (local pond densities) factors. The probability of AIV infection in BWTE was associated with host factors (e.g., age and antibody status), population-level factors (e.g., local BWTE population density), and year. An interaction between age and AIV antibody status showed that hatch year birds with antibodies to AIV were more likely to be infected, suggesting an antibody response to an active infection. Infection with AIV was positively associated with local BWTE density, supporting the hypothesis of density-dependent transmission. The presence of antibodies to WNV and APMV-1 was positively associated with age and varied among years. Furthermore, the probability of being WNV antibody positive was positively associated with pond density rather than host population density, likely because ponds provide suitable breeding habitat for mosquitoes, the primary vectors for transmission. Our findings highlight the importance of spatiotemporal, environmental, and host factors at the individual and population levels, all of which may influence dynamics of these and other viruses in wild waterfowl populations.

Spatial and temporal patterns of avian paramyxovirus-1 outbreaks in double-crested cormorants (Phalacrocorax auritus) in the USA

Morbidity and mortality events caused by avian paramyxovirus-1 (APMV-1) in Double-crested Cormorant (DCCO; Phalacrocorax auritus) nesting colonies in the US and Canada have been sporadically documented in the literature. We describe APMV-1 associated outbreaks in DCCO in the US from the first reported occurrence in 1992 through 2012. The frequency of APMV-1 outbreaks has increased in the US over the last decade, but the majority of events have continued to occur in DCCO colonies in the Midwestern states. Although morbidity and mortality in conesting species has been frequently reported during DCCO APMV-1 outbreaks, our results suggest that isolation of APMV-1 is uncommon in species other than DCCO during APMV-1 outbreaks and that the cause of mortality in other species is associated with other pathogens. Populations of DCCO do not appear to have been significantly affected by this disease; however, because at least 65% of the APMV-1 outbreaks in DCCO in the US have involved APMV-1 strains classified as virulent to poultry (virulent Newcastle disease virus), its persistence and increased occurrence in DCCO warrants continued research and surveillance.

Prevalence of avian paramyxovirus 1 and avian influenza virus in double-crested Cormorants (Phalacrocorax auritus) in eastern North America

Although it is well established that wild birds, such as cormorants, carry virulent avian paramyxovirus serotype 1 (APMV-1; causative agent of Newcastle disease) and avian influenza virus (AIV), the prevalence of these viruses among Double-crested Cormorants (Phalacrocorax auritus) in the Great Lakes region of North America has not been rigorously studied. We determined the prevalences of APMV-1 and AIV in Double-crested Cormorants from the interior population of eastern North America. From 2009 to 2011, oropharyngeal and cloacal swabs and serum samples were collected from 1,957 individual Double-crested Cormorants, ranging from chicks to breeding adults, on breeding colony sites in Michigan, Wisconsin, and Mississippi, USA, and Ontario, Canada, as well as on the wintering grounds of migratory populations in Mississippi, USA. Prevalence of antibodies to APMV-1 in after-hatch year birds was consistently high across all three years, ranging from 86.3% to 91.6%. Antibody prevalences in chicks were much lower: 1.7, 15.3, and 16.4% in 2009, 2010, and 2011, respectively. Virulent APMV-1 was detected in six chicks sampled in 2010 in Ontario, Canada. Only one adult was positive for AIV-specific antibodies and five individuals were positive for AIV matrix protein, but the latter were negative for H5 and H7 AIV subtypes. We provide further evidence that Double-crested Cormorants play an important role in the maintenance and circulation of APMV-1 in the wild, but are unlikely to be involved in the circulation of AIV.

Insights from parasite-specific serological tools in eco-immunology

Eco-immunology seeks evolutionary explanations for the tremendous variation in immune defense observed in nature. Assays to quantify immune phenotypes often are crucial to this endeavor. To this end, we suggest that more use could (and arguably should) be made of the veterinary and clinical serological toolbox. For example, measuring the magnitude and half-life of parasite-specific antibodies across a range of host taxa may provide new ways of testing theories in eco-immunology. Here, we suggest that antibody assays developed in veterinary and clinical immunology and epidemiology provide excellent tools--or at least excellent starting points for development of tools--for tests of such hypotheses. We review how such assays work and how they may be optimized for new questions and new systems in eco-immunology. We provide examples of the application of such tools to eco-immunological studies of seabirds and mammals, and suggest a decision-tree to aid development of assays. We expect that addition of such tools to the eco-immunological toolbox will promote progress in the field and help elucidate how immune systems function and why they vary in nature.

Characterization of Newcastle disease viruses isolated from cormorant and gull species in the United States in 2010

Newcastle disease virus (NDV), a member of the genus Avulavirus of the family Paramyxoviridae, is the causative agent of Newcastle disease (ND), a highly contagious disease that affects many species of birds and which frequently causes significant economic losses to the poultry industry worldwide. Virulent NDV (vNDV) is exotic in poultry in the United States; however, the virus has been frequently associated with outbreaks of ND in cormorants, which poses a significant threat to poultry species. Here, we present the characterization of 13 NDV isolates obtained from outbreaks of ND affecting cormorants and gulls in the states of Minnesota, Massachusetts, Maine, New Hampshire, and Maryland in 2010. All 2010 isolates are closely related to the viruses that caused the ND outbreaks in Minnesota in 2008, following the new evolutionary trend observed in cormorant NDV isolates since 2005. Similar to the results obtained with the 2008 isolates, the standard United States Department of Agriculture F-gene real-time reverse-transcription PCR (RRT-PCR) assay failed to detect the 2010 cormorant viruses, whereas all viruses were detected by a cormorant-specific F-gene RRT-PCR assay. Notably, NDV-positive gulls were captured on the eastern shore of Maryland, which represents a significant geographic expansion of the virus since its emergence in North America. This is the first report of vNDV originating from cormorants isolated from wild birds in Maryland and, notably, the first time that genotype V vNDV has been isolated from multiple wild bird species in the United States. These findings highlight the need for constant epidemiologic surveillance for NDV in wild bird populations and for consistent biosecurity measures to prevent the introduction of the agent into domestic poultry flocks.

Clinicopathological Characterization in Poultry of Three Strains of Newcastle Disease Virus Isolated From Recent Outbreaks

Newcastle disease is a severe threat to the poultry industry and is caused by Newcastle disease virus, a member of the genus Avulavirus, family Paramyxoviridae. The virus is rapidly evolving, and several new genotypes have been discovered in the past few years. Characterization of these strains is important to evaluate field changes, anticipate new outbreaks, and develop adequate control measures. Three Newcastle disease isolates (APMV-1/duck/Vietnam, Long Bien/78/2002, APMV-1/chicken/Australia/9809-19-1107/1998, and APMV-1/double-crested cormorant/USA, Nevada/19529-04/2005) from recent outbreaks were investigated via clinicopathological assessment, immunohistochemistry (IHC), in situ hybridization, virus isolation, and serology in experimentally infected 4-week-old chickens. Phylogenetic studies showed that Australia isolate belongs to class II genotype I, Long Bien to class II genotype VIId, and Nevada cormorant to class II genotype V. Even though all 3 viruses had a virulent fusion protein cleavage site and ICPI values greater than 1.5, they all differed in their ability to cause clinical signs, in their lesions, and in their viral distribution in body tissues. The Long Bien isolate showed the most severe clinicopathological picture and the most widespread viral distribution. The Australia and Nevada cormorant isolates had a milder pathological phenotype, with viral replication restricted to only a few organs. The variability in clinicopathological characteristics despite the similarity in ICPI suggests that full clinicopathological assessment is necessary to fully characterize new isolates and that there are differences in pathogenesis among viruses of different genotypes.

Evolutionary changes affecting rapid identification of 2008 Newcastle disease viruses isolated from double-crested cormorants

A morbidity-mortality event involving virulent Newcastle disease virus (NDV) in wild double-crested cormorants (Phalacrocorax auritus) occurred in North America in the summer of 2008. All 22 viruses isolated from cormorants were positively identified by the USDA-validated real-time reverse transcription-PCR assay targeting the matrix gene. However, the USDA-validated reverse transcription-PCR assay targeting the fusion gene that is specific for virulent isolates identified only 1 of these 22 isolates. Additionally, several of these isolates have been sequenced, and this information was used to identify genomic changes that caused the failure of the test and to revisit the evolution of NDV in cormorants. The forward primer and fusion probe were redesigned from the 2008 cormorant isolate sequence, and the revised fusion gene test successfully identified all 22 isolates. Phylogenetic analyses using both the full fusion sequence and the partial 374-nucleotide sequence identified these isolates as genotype V, with their nearest ancestor being an earlier isolate collected from Nevada in 2005. Histopathological analysis of this ancestral strain revealed morphological changes in the brain consistent with that of the traditional mesogenic pathotypes in cormorants. Intracerebral pathogenicity assays indicated that each of these isolates is virulent with values of >0.7 but not more virulent than earlier isolates reported from Canada.

The avian neurologic examination and ancillary neurodiagnostic techniques: a review update

The purpose of this article is to guide the avian clinician in the assessment of neurologic function in birds. Physical and neurologic examinations that evaluate cranial nerves, postural reactions, and spinal reflexes identify neurologic dysfunction and the corresponding anatomic location of the lesion. Ancillary diagnostic tests, such as cerebrospinal fluid analysis, diagnostic imaging, muscle and nerve histology, and electrodiagnostics, are tools to confirm and clarify conclusions from the neurologic examination and to identify the cause of disease. Once the disease location and pathologic process have been identified, appropriate treatment and prognosis may be provided.

Historical perspective and future directions in training of veterinary pathologists with an emphasis on zoo and wildlife species

This article discusses the history of the field of zoo and wildlife pathology, training opportunities for veterinary students and graduate veterinarians, and current and future job opportunities. The niches occupied by veterinarians in this field and their contributions to animal and human health are also highlighted. The field of zoo and wildlife, or "non-traditional" species, pathology has its roots in comparative anatomy, zoology, wildlife biology, and medical pathology in the mid- to late nineteenth century. The initial emphasis was on comparisons between animal and human diseases or on management of game animals. Veterinarians became increasingly involved during the twentieth century, gradually changing the emphasis to improvement of conservation strategies, captive care, and elucidation of diseases of concern for the animals themselves. Currently there are several zoos and wildlife agencies in the United States employing full-time veterinary pathologists. Private and government diagnostic laboratories, veterinary schools, and other academic institutions in the United States with pathology departments are other employers. The field requires post-DVM training by means of a residency program leading to board certification, graduate school (MS or PhD degrees), or both. Veterinary students can gain valuable experience in the field through externships and, at some schools, through elective courses in the curriculum. Current concerns about ecosystem health, bioterrorism, and the recognition that captive and free-ranging wildlife can serve as sentinel species will increase the demand for veterinary pathologists choosing this very rewarding career path specializing in non-traditional species.

Molecular characterization of avian paramyxovirus 1 isolates collected from cormorants in Canada from 1995 to 2000

Sequences encompassing cleavage sites of fusion protein genes were obtained for avian paramyxovirus 1 isolates from cormorants in Canada. All isolates have the virulent cleavage site SRGRRQKR*FVG. They form a distinct cluster within isolates obtained around the world and may represent a novel genotype closely related to genotype V.