Wild bird surveillance for highly pathogenic avian influenza H5 in North America

An early warning system for highly pathogenic viruses borne by waterbird species and related dynamics of climate change in the Caspian Sea region: Outlines of a concept

Aim. Formulation of the outlines of the concept of ViEW (Viral Early Warning) which is intended as a long term system of multidisciplinary transboundary cooperation between specialist institutions of all five Caspian region states to research, regularly monitor and share data about the generation, transmission and epidemiology of avian‐borne pathogens and their vectors in the region, and the ways climate change may affect these processes.

Material and Methods. The concept is based on the multidisciplinary experience of the authors in researching the processes incorporated in the ViEW concept and on an in‐depth survey of the literature involved.

Results. The outlines of the ViEW concept are presented in this study for review and comment by interested parties and stakeholders.

Conclusion. Review of activities and opinions of specialists and organizations with remits relating to the development, establishment and maintenance of ViEW, indicates that such a system is a necessity for global animal and human health because of the role that the Caspian region plays in the mass migration of species of waterbird known as vectors for avian influenza and the already evident impacts of climate change on their phenologies. Waterbirds frequenting the Caspian Sea littorals and their habitats together constitute a major potential global hotspot or High Risk region for the generation and transmission of highly pathogenic avian influenza viruses and other dangerous zoonotic diseases.

Using the California Waterfowl Tracker to Assess Proximity of Waterfowl to Commercial Poultry in the Central Valley of California

Migratory waterfowl are the primary reservoir of avian influenza viruses (AIV), which can be spread to commercial poultry. Surveillance efforts that track the location and abundance of wild waterfowl and link those data to inform assessments of risk and sampling for AIV currently do not exist. To assist surveillance and minimize poultry exposure to AIV, here we explored the utility of Remotely Sensed Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery in combination with land-based climate measurements (e.g., temperature and precipitation) to predict waterfowl location and abundance in near real-time in the California Central Valley (CCV), where both wild waterfowl and domestic poultry are densely located. Specifically, remotely collected MODIS and climate data were integrated into a previously developed boosted regression tree (BRT) model to predict and visualize waterfowl distributions across the CCV. Daily model-based predictions are publicly available during the winter as part of the dynamic California Waterfowl Tracker (CWT) web app hosted on the University of California's Cooperative Extension webpage. In this study, we analyzed 52 days of model predictions and produced daily spatiotemporal maps of waterfowl concentrations near the 605 commercial poultry farms in the CCV during January and February of 2019. Exposure of each poultry farm to waterfowl during each day was classified as high, medium, low, or none, depending on the density of waterfowl within 4 km of a farm. Results indicated that farms were at substantially greater risk of exposure in January, when CCV waterfowl populations peak, than in February. For example, during January, 33% (199/605) of the farms were exposed for ≥1 day to high waterfowl density vs. 19% (115/605) of the farms in February. In addition to demonstrating the overall variability of waterfowl location and density, these data demonstrate how remote sensing can be used to better triage AIV surveillance and biosecurity efforts via the utilization of a functional web app-based tool. The ability to leverage remote sensing is an integral advancement toward improving AIV surveillance in waterfowl in close proximity to commercial poultry. Expansion of these types of remote sensing methods, linked to a user-friendly web tool, could be further developed across the continental United States. The BRT model incorporated into the CWT reflects a first attempt to give an accurate representation of waterfowl distribution and density relative to commercial poultry.

Highly pathogenic avian influenza virus H5N2 (clade 2.3.4.4) challenge of mallards age appropriate to the 2015 midwestern poultry outbreak

Background

The 2015 highly pathogenic avian influenza virus (HPAIV) H5N2 clade 2.3.4.4 outbreak in upper midwestern U.S. poultry operations was not detected in wild birds to any great degree during the outbreak, despite wild waterfowl being implicated in the introduction, reassortment, and movement of the virus into North America from Asia. This outbreak led to the demise of over 50 million domestic birds and occurred mainly during the northward spring migration of adult avian populations.

Objectives

There have been no experimental examinations of the pathogenesis, transmission, and population impacts of this virus in adult wild waterfowl with varying exposure histories—the most relevant age class.

Methods

We captured, housed, and challenged adult wild mallards (Anas platyrhynchos) with HPAIV H5N2 clade 2.3.4.4 and measured viral infection, viral excretion, and transmission to other mallards.

Results

All inoculated birds became infected and excreted moderate amounts of virus, primarily orally, for up to 14 days. Cohoused, uninoculated birds also all became infected. Serological status had no effect on susceptibility. There were no obvious clinical signs of disease, and all birds survived to the end of the study (14 days).

Conclusions

Based on these results, adult mallards are viable hosts of HPAIV H5N2 regardless of prior exposure history and are capable of transporting the virus over short and long distances. These findings have implications for surveillance efforts. The capture and sampling of wild waterfowl in the spring, when most surveillance programs are not operating, are important to consider in the design of future HPAIV surveillance programs.

Risk mapping of highly pathogenic avian influenza H5 during 2012-2017 in Taiwan with spatial bayesian modelling: Implications for surveillance and control policies

During 2012-2017, a total of 1,144 highly pathogenic avian influenza (HPAI) H5 outbreaks were reported in Taiwan. We conjectured the current 3-km radius of the post-outbreak containment policy could fail to effectively alleviate the current ongoing epidemics of HPAI H5 in Taiwan. The high intensity of localized transmission of HPAI H5 at certain focal hotspots was identified to follow the spatial distribution of poultry-raising locations through our hotspot analyses on the HPAI H5 outbreak locations from 2015 to 2017. We then applied 3-, 5- and 7-km circular buffer zones to 15,444 registered poultry-raising locations to inspect the characteristics of the poultry-raising neighbourhood. Three spatial regression models using Bayesian inference were established to infer the risks attributable to poultry-raising characteristics in the corresponding buffer areas. The different buffer radii were treated as a sensitivity analysis of the influential range of neighbouring farms on the HPAI H5 outbreak occurrence, so as to evaluate the effective radius for post-outbreak containment. Evidence showed that the risks of outbreak occurrence were associated with increasing numbers of poultry-raising locations in both 3-km (relative risk [RR] 1.005, 95% confidence interval [CI] 1.002-1.008) and 5-km buffer areas (RR 1.005, 95% CI 1.004-1.007), whereas in the 7-km buffer model, no association between densely populated locations and increasing risks of outbreaks was observed (RR 1.000, 95% CI 0.999-1.001). Therefore, an extension to a 7-km radius for the post-outbreak containment policy (rather than a 3-km radius as in the current policy) is recommended to effectively mitigate further spreading of HPAI H5 outbreaks among neighbouring farms. Overall, we demonstrated that the densely populated locations with multiple poultry species raised in proximity as defined with 3-, 5- and 7-km buffer areas facilitated H5 HPAI outbreak diffusion and shaped the scale of HPAI H5 epidemics in Taiwan.

Avian influenza virus ecology and evolution through a climatic lens

Avian influenza virus (AIV) is a major health threat to both avian and human populations. The ecology of the virus is driven by numerous factors, including climate and avian migration patterns, yet relatively little is known about these drivers. Long-distance transport of the virus is tied to inter- and intra-continental bird migration, while enhanced viral reassortment is linked to breeding habitats in Beringia shared by migrant species from North America and Asia. Furthermore, water temperature, pH, salinity, and co-existing biota all impact the viability and persistence of the virus in the environment. Changes in climate can potentially alter the ecology of AIV through multiple pathways. Warming temperatures can change the timing and patterns of bird migration, creating novel assemblages of species and new opportunities for viral transport and reassortment. Water temperature and chemistry may also be altered, resulting in changes in virus survival. In this review, we explain how these shifts have the potential to increase viral persistence, pathogenicity, and transmissibility and amplify the threat of pandemic disease in animal and human hosts. Better understanding of climatic influences on viral ecology is essential to developing strategies to limit adverse health effects in humans and animals.

Comparative Epidemiology of Human Fatal Infections with Novel, High (H5N6 and H5N1) and Low (H7N9 and H9N2) Pathogenicity Avian Influenza A Viruses

This study aimed to assess the mortality risks for human infection with high (HPAI) and low (LPAI) pathogenicity avian influenza viruses. The HPAI case fatality rate (CFR) was far higher than the LPAI CFR [66.0% (293/444) vs. 68.75% (11/16) vs. 40.4% (265/656) vs. 0.0% (0/18) in the cases with H5N1, H5N6, H7N9, and H9N2 viruses, respectively; p < 0.001]. Similarly, the CFR of the index cases was greater than the secondary cases with H5N1 [100% (43/43) vs. 43.3% (42/97), p < 0.001]. Old age [22.5 vs. 17 years for H5N1, p = 0.018; 61 vs. 49 years for H7H9, p < 0.001], concurrent diseases [18.8% (15/80) vs. 8.33% (9/108) for H5N1, p = 0.046; 58.6% (156/266) vs. 34.8% (135/388) for H7H9, p < 0.001], delayed confirmation [13 vs. 6 days for H5N1, p < 0.001; 10 vs. 8 days for H7N9, p = 0.011] in the fatalities and survivors, were risk factors for deaths. With regard to the H5N1 clusters, exposure to poultry [67.4% (29/43) vs. 45.2% (19/42), p = 0.039] was the higher risk for the primary than the secondary deaths. In conclusion, old age, comorbidities, delayed confirmation, along with poultry exposure are the major risks contributing to fatal outcomes in human HPAI and LPAI infections.

Surveillance for Eurasian-origin and intercontinental reassortant highly pathogenic influenza A viruses in Alaska, spring and summer 2015

BACKGROUND

Eurasian-origin and intercontinental reassortant highly pathogenic (HP) influenza A viruses (IAVs) were first detected in North America in wild, captive, and domestic birds during November-December 2014. Detections of HP viruses in wild birds in the contiguous United States and southern Canadian provinces continued into winter and spring of 2015 raising concerns that migratory birds could potentially disperse viruses to more northerly breeding areas where they could be maintained to eventually seed future poultry outbreaks.

RESULTS

We sampled 1,129 wild birds on the Yukon-Kuskokwim Delta, Alaska, one of the largest breeding areas for waterfowl in North America, during spring and summer of 2015 to test for Eurasian lineage and intercontinental reassortant HP H5 IAVs and potential progeny viruses. We did not detect HP IAVs in our sample collection from western Alaska; however, we isolated five low pathogenic (LP) viruses. Four isolates were of the H6N1 (n = 2), H6N2, and H9N2 combined subtypes whereas the fifth isolate was a mixed infection that included H3 and N7 gene segments. Genetic characterization of these five LP IAVs isolated from cackling (Branta hutchinsii; n = 2) and greater white-fronted geese (Anser albifrons; n = 3), revealed three viral gene segments sharing high nucleotide identity with HP H5 viruses recently detected in North America. Additionally, one of the five isolates was comprised of multiple Eurasian lineage gene segments.

CONCLUSIONS

Our results did not provide direct evidence for circulation of HP IAVs in the Yukon-Kuskokwim Delta region of Alaska during spring and summer of 2015. Prevalence and genetic characteristics of LP IAVs during the sampling period are concordant with previous findings of relatively low viral prevalence in geese during spring, non-detection of IAVs in geese during summer, and evidence for intercontinental exchange of viruses in western Alaska.

Highly pathogenic avian influenza viruses H5N2, H5N3, and H5N8 in Taiwan in 2015

A severe epidemic, affecting mainly goose populations, broke out in early January 2015. The causative agents were identified as novel H5 avian influenza viruses carrying N2, N3, and N8 subtypes of the neuraminidase gene. From January 8 to February 11, 766 waterfowl and poultry farms were invaded by the H5 viruses, and more than 2.2 million geese died or were culled. Phylogenetic analysis suggested that these avian influenza viruses derived from the H5 viruses of clade 2.3.4.4 which were emerging in 2014 in East Asia, West Europe, and North America.