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Comparative Study
. 2021 Dec;10(1):97-108.
doi: 10.1080/22221751.2020.1868274.

Comparative pathogenicity and environmental transmission of recent highly pathogenic avian influenza H5 viruses

Nancy Beerens  1 , Evelien A Germeraad  1 , Sandra Venema  1 , Eline Verheij  1 , Sylvia B E Pritz-Verschuren  1 , Jose L Gonzales  1
Affiliations
Comparative Study

Comparative pathogenicity and environmental transmission of recent highly pathogenic avian influenza H5 viruses

Nancy Beerens et al. Emerg Microbes Infect. 2021 Dec.

Abstract

Strategies to control spread of highly pathogenic avian influenza (HPAI) viruses by wild birds appear limited, hence timely characterization of novel viruses is important to mitigate the risk for the poultry sector and human health. In this study we characterize three recent H5-clade 2.3.4.4 viruses, the H5N8-2014 group A virus and the H5N8-2016 and H5N6-2017 group B viruses. The pathogenicity of the three viruses for chickens, Pekin ducks and Eurasian wigeons was compared. The three viruses were highly pathogenic for chickens, but the two H5N8 viruses caused no to mild clinical symptoms in both duck species. The highest pathogenicity for duck species was observed for the most recent H5N6-2017 virus. For both duck species, virus shedding from the cloaca was higher after infection with group B viruses compared to the H5N8-2014 group A virus. Higher cloacal virus shedding of wild ducks may increase transmission between wild birds and poultry. Environmental transmission of H5N8-2016 virus to chickens was studied, which showed that chickens are efficiently infected by (fecal) contaminated water. These results suggest that pathogenicity of HPAI H5 viruses and virus shedding for ducks is evolving, which may have implications for the risk of introduction of these viruses into the poultry sector.

Keywords: Eurasian wigeons; H5N6; H5N8; Highly pathogenic avian influenza; ducks; environmental transmission; pathogenicity; virus shedding.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Survival of 6-week-old SPF chickens (blue), Pekin ducks (orange) and Eurasian (EA) wigeons (green) after intratracheal/intranasal infection (doses 105.3 EID50/bird) with (A) H5N8-2014, (B) H5N8-2016, and (C) H5N6-2017 viruses. Per group 10 birds were monitored for 10 days for clinical symptoms and mortality. The pathogenicity score was calculated based on OIE criteria for IVPI, and ranges from 0.0 (no pathogenicity) to 3.0 (highest pathogenicity). The pathogenicity scores for the viruses are listed in the legend.
Figure 2.
Figure 2.
Mean virus shedding (log10 EID50/ml) after infection with (A) H5N8-2014, (B) H5N8-2016, and (C) H5N6-2017 viruses. Virus shedding was measured in oropharyngeal (OP) and cloacal (CL) swabs collected from chickens (blue), Pekin ducks (orange), and Eurasian (EA) wigeons (orange) during 10 days after infection. The detection limit of 1.7 log10 EID50/ml is marked by a black line.
Figure 3.
Figure 3.
Survival of 6-week-old chickens after exposure to water (blue line) or bedding material (orange line) contaminated by Eurasian wigeons infected with H5N8-2016 virus.
Figure 4.
Figure 4.
Virus shedding of chickens exposed to contaminated water (w1–w10) for 7 days, measured in (A) oropharyngeal (OP) swabs and (B) cloacal (CL) swabs.
Figure 5.
Figure 5.
Persistence of virus in water and bedding material in the two control cages. The viability of the virus was tested by inoculation into four embryonated eggs (columns), and the amount of viral RNA was determined by real-time RT-PCR (line graph). Samples of water and bedding material were tested pre-collection (P) in the pen housing the Eurasian wigeons, and at days 0, 1, 2, and 5 of the environmental transmission experiment. Water samples were also tested on day 6. WP: water pre-collection, WC1: water control cage 1, WC2: water control cage 2, BP: bedding pre-collection BC1: bedding control cage 1, BC2: bedding control cage 2.
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