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. 2021 Oct 20;9(11):2188.
doi: 10.3390/microorganisms9112188.

Active Surveillance for Highly Pathogenic Avian Influenza Viruses in Wintering Waterbirds in Northeast Italy, 2020-2021

Federica Gobbo  1 , Diletta Fornasiero  2 , Maria Alessandra De Marco  3 , Bianca Zecchin  1 , Paolo Mulatti  2 , Mauro Delogu  4 , Calogero Terregino  1
Affiliations

Active Surveillance for Highly Pathogenic Avian Influenza Viruses in Wintering Waterbirds in Northeast Italy, 2020-2021

Federica Gobbo et al. Microorganisms. .

Abstract

The increasing involvement of wild waterfowl in H5 Highly Pathogenic Avian Influenza Virus (HPAIV) circulation continues to pose a threat to animal and public health worldwide. In winter 2020-2021, two field surveillance activities were carried out on a weekly basis, through virological and serological analyses, in 823 hunted and 521 trapped migratory aquatic birds in northeast Italy. Sixty Eurasian teals were recaptured several times, which allowed us to follow the progression of the HPAI H5 infection in naturally infected wild waterfowl. Oropharyngeal, cloacal, and feather swabs (OS, CS and FS) were collected from each duck and tested by real time rRT-PCR Type A influenza. The identified viruses were characterized and pathotyped by sequencing. Several viruses belonging to three different HPAI H5 subtypes were detected: H5N8, H5N5, and H5N1. High prevalence of infection with HPAI H5 clade 2.3.4.4b during November-December 2020 (up to 27.1%) was observed in captured Eurasian teals, while infection rates in hunted dabbling ducks, mainly Eurasian wigeons, showed the highest prevalence of infection in November 2020 (8.9%) and January 2021 (10.2%). All HPAI positive birds were also clinically healthy when recaptured weeks apart. The OS and FS showed the highest detection efficiency of HPAIV. Our results highlight that HPAI passive surveillance should be complemented by a targeted active surveillance to more efficiently detect novel HPAI viruses.

Keywords: HPAI H5 subtypes clade 2.3.4.4b; active surveillance; avian influenza virus; migratory aquatic bird.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the collection, analyses, or interpretation of data and in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Location of hunting sites (orange color) and capture sites (green color). V, Valle; VCPa, V. Ca Pasta (RO); VCZ, V. Ca Zuliani (RO); VD, V. Drago (VE); VSL, V. San Leonardo (RO); VC, V. Chiusa (RO); VCPi, V. Ca Pisani (RO); VM, V. Morosina (RO); VF, Valle Figheri (VE); VCa, Valle Cavallino.
Figure 2
Figure 2
HPAI epidemic curves in captured and hunted wild birds during late autumn–winter seasons 2020–2021 in northeast Italy. Upper panel: number of wild birds tested with RT-PCR; dark grey bars: HPAIV negative birds; red bars: HPAIV positive birds. Lower panel: HPAI relative prevalence.
Figure 3
Figure 3
Progression of Avian Influenza virus infections (LPAI and HPAI) in re-captured wild migratory Eurasian teals. Dotted lines: no capture occurred; pale brown bars: bird captured and virologically negative; light red bars: bird captured and virologically positive; dark red symbols: HPAIV; yellow symbols: LPAIV; grey symbols: undetermined pathotype.
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