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

Comparative pathogenicity of three A(H5N1) clade 2.3.4.4b HPAI viruses in blue-winged teal and transmission to domestic poultry

Long-distance migratory ducks play a critical role in the maintenance and dissemination of A(H5N1) viruses. Comparative pathogenicity studies were conducted on blue-winged teal (BWTE; Anas discors) using three distinct genotypes of A(H5N1) clade 2.3.4.4b viruses (A1, B1.3, and B4.1) isolated from wild ducks in Canada. Twenty-four hours post-intranasal infection of BWTE, contact turkeys and chickens were introduced into each of the groups to evaluate viral transmission. The levels of viral shedding in BWTE increased from 3 to 7 days post-infection (dpi) and continued at lower levels until 14 dpi. The A1 genotype virus (MALL/NS/22) was found to be the least pathogenic to BWTE compared to the reassortant genotypes, B4.1 (RBME/BC/22) and B1.3 (BWTE/MB/22). The B1.3 genotype was the most virulent to BWTE and caused 66.7% mortality compared to 12.5% mortality caused by the B4.1 genotype. The extent of transmission from infected BWTE to contact turkeys and chickens showed variations. Turkeys housed with BWTE infected with either virus died within 6 to 10 days post-contact (dpc). Conversely, the transmission and mortality among contact chickens varied. The highest mortality (3 out of 5) occurred in chickens exposed to BWTE infected with the B1.3 genotype. Whilst in the B4.1 genotype, 2 out of 6 chickens died, none of the chickens in the A1 genotype succumbed to infection. No shedding or seroconversion was noted in all surviving chickens. This research underscores variations in the pathogenic traits and transmissibility among the different genotypes of A(H5N1) clade 2.3.4.4b viruses. This finding is vital for understanding the role of migratory birds in the epidemiology of A(H5N1) and the need for continuous monitoring of these viruses.

IMPORTANCE

The recurrent incursions of A(H5N1) clade 2.3.4.4b viruses into North America have resulted in the emergence of reassortant virus genotypes. These genotypes exhibit variations in pathogenicity and host ranges. Blue-winged teal (BWTE) are the most common dabbling ducks in North America and play a crucial role in maintaining and dispersing influenza A viruses (IAVs). In some areas, the migratory pathways of BWTE overlap with densely populated commercial poultry facilities. Despite this, the role of BWTE in the maintenance and spread of A(H5N1) is not well understood, and there is limited data on their susceptibility to A(H5N1) clade 2.3.4.4b viruses. Our study demonstrates differences in BWTE susceptibility to distinct genotypes of A(H5N1) clade 2.3.4.4b viruses. The virus transmission from infected BWTE and lethality in turkeys and chickens were also influenced by the virus genotypes. The findings suggest that BWTE could contribute to the maintenance and spread of highly pathogenic avian influenza (HPAI) viruses, and active surveillance in BWTE is essential.

Avian influenza antibody prevalence increases with mercury contamination in wild waterfowl

Environmental contamination is widespread and can negatively impact wildlife health. Some contaminants, including heavy metals, have immunosuppressive effects, but prior studies have rarely measured contamination and disease simultaneously, which limits our understanding of how contaminants and pathogens interact to influence wildlife health. Here, we measured mercury concentrations, influenza infection, influenza antibodies and body condition in 749 individuals from 11 species of wild ducks overwintering in California. We found that the odds of prior influenza infection increased more than fivefold across the observed range of blood mercury concentrations, while accounting for species, age, sex and date. Influenza infection prevalence was also higher in species with higher average mercury concentrations. We detected no relationship between influenza infection and body fat content. This positive relationship between influenza prevalence and mercury concentrations in migratory waterfowl suggests that immunotoxic effects of mercury contamination could promote the spread of avian influenza along migratory flyways, especially if influenza has minimal effects on bird health and mobility. More generally, these results show that the effects of environmental contamination could extend beyond the geographical area of contamination itself by altering the prevalence of infectious diseases in highly mobile hosts.

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.

Waterfowl occurrence and residence time as indicators of H5 and H7 avian influenza in North American Poultry

Avian influenza (AI) affects wild aquatic birds and poses hazards to human health, food security, and wildlife conservation globally. Accordingly, there is a recognized need for new methods and tools to help quantify the dynamic interaction between wild bird hosts and commercial poultry. Using satellite-marked waterfowl, we applied Bayesian joint hierarchical modeling to concurrently model species distributions, residency times, migration timing, and disease occurrence probability under an integrated animal movement and disease distribution modeling framework. Our results indicate that migratory waterfowl are positively related to AI occurrence over North America such that as waterfowl occurrence probability or residence time increase at a given location, so too does the chance of a commercial poultry AI outbreak. Analyses also suggest that AI occurrence probability is greatest during our observed waterfowl northward migration, and less during the southward migration. Methodologically, we found that when modeling disparate facets of disease systems at the wildlife-agriculture interface, it is essential that multiscale spatial patterns be addressed to avoid mistakenly inferring a disease process or disease-environment relationship from a pattern evaluated at the improper spatial scale. The study offers important insights into migratory waterfowl ecology and AI disease dynamics that aid in better preparing for future outbreaks.

[Using geo-intelligence to estimate risk of introduction of influenza type A in MexicoCenário de risco de introdução do vírus da influenza A no México estimado com o uso de inteligência geográfica]

Objetivo.

Estimar el escenario potencial probabilístico de introducción del agente causal de la influenza tipo A en México mediante geointeligencia sanitaria.

Métodos.

Estudio ecológico en el que consideran 1 973 brotes de influenza con alto grado de patogenicidad en el mundo durante el período 2014-2016. Se desarrolló un modelado geoespacial con herramientas de la geointeligencia, como la representación espacial, modelo de conexidad, caracterización espacial de la fuente de inoculo con el modelo de máxima entropía y la curva característica de operación receptora (COR) mediante la evaluación espacial multicriterio y se validó con el índice de Moran y la regresión geográficamente ponderada.

Resultados.

Se estimaron las isocronas de riesgo sanitario con una distancia de 548 km y su crecimiento exponencial; hasta la cuarta isócrona se identificaron las costas este y oeste de Estados Unidos de América (EEUU) y una porción de América Central como posible superficie que favorece la introducción del patógeno. Se obtuvo, también, una curva COR = 0,923, se identificaron dos períodos de riesgo de introducción (setiembre-marzo) y (abril-agosto) con trayectorias de norte-sur y sur-norte respectivamente, con alta autocorrelación positiva para el modelado geoespacial, y se estimó un escenario donde más de la mitad de México se encuentra en un riesgo alto de introducción, con 78 millones de personas expuestas. Se identificó una asociación positiva entre las áreas de riesgo significativo (P < 0,001).

Conclusión.

Se evidencia que más de 50% del territorio mexicano se encuentra en riesgo de introducción del agente causal de la influenza tipo A, con aproximadamente 70% de la población expuesta.

Flaviviruses in migratory passerines during spring stopover in a desert oasis

Bird migration has long been hypothesized as the main mechanism for long-distance dispersal of flaviviruses, but the role of migratory birds in flaviviruses spillover is not well documented. In this study, we investigated the eco-epidemiology of West Nile virus (WNV) and Usutu virus (USUV) in trans-Saharan passerines during their spring stopover in southern Tunisian oases. To do, we combined oral swab analysis and serological tools to assess whether migratory birds could be reaching these stopover sites while infectious or have been previously exposed to viruses. All sampled birds tested negative for oral swab analysis. However, anti-WNV and anti-USUV antibodies were detected in 32% and 1% of tested birds, respectively. Among WNV-seropositive species, the Golden oriole (Oriolus oriolus) showed the highest anti-WNV occurrence probability. In this species, anti-WNV occurrence was twice larger in males than females. Inter-specific and intraspecific morphological, physiological and behavioural differences could explain these results. Although our findings did not show evidence for passerines migrating while infectious, they did not exclude an existing enzootic WNV transmission cycle in Tunisian oases. Further investigations including larger samples of migratory birds are needed for a better understanding of this issue.

The ecology of avian influenza viruses in wild dabbling ducks (Anas spp.) in Canada

Avian influenza virus (AIV) occurrence and transmission remain important wildlife and human health issues in much of the world, including in North America. Through Canada’s Inter-Agency Wild Bird Influenza Survey, close to 20,000 apparently healthy, wild dabbling ducks (of seven species) were tested for AIV between 2005 and 2011. We used these data to identify and evaluate ecological and demographic correlates of infection with low pathogenic AIVs in wild dabbling ducks (Anas spp.) across Canada. Generalized linear mixed effects model analyses revealed that risk of AIV infection was higher in hatch-year birds compared to adults, and was positively associated with a high proportion of hatch-year birds in the population. Males were more likely to be infected than females in British Columbia and in Eastern Provinces of Canada, but more complex relationships among age and sex cohorts were found in the Prairie Provinces. A species effect was apparent in Eastern Canada and British Columbia, where teal (A. discors and/or A. carolinensis) were less likely to be infected than mallards (A. platyrhynchos). Risk of AIV infection increased with the density of the breeding population, in both Eastern Canada and the Prairie Provinces, and lower temperatures preceding sampling were associated with a higher probability of AIV infection in Eastern Canada. Our results provide new insights into the ecological and demographic factors associated with AIV infection in waterfowl.

Characterization of avian paramyxovirus type 6 isolated from a Eurasian teal in the intersection of migratory flyways in Russia

The complete genome sequence was determined for avian paramyxovirus (APMV-6) serotype 6 strain teal/Chany/455/2009, isolated from a teal (Anas crecca) in Siberia. Siberia is crossed by four major migration flyways and represents the major breeding area for many wild bird species in the Palearctic. Strain teal/Chany/455/2009 is genetically closely related to Kazakh and Chinese strains and belongs to the genetic group of duck/Hong Kong/18/199/77-like APMV-6 viruses. We show that the virus has low pathogenic potential according to genetic markers and animal model experiments.