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Volume 28, Number 12—December 2022
Dispatch

Mass Mortality Caused by Highly Pathogenic Influenza A(H5N1) Virus in Sandwich Terns, the Netherlands, 2022

Jolianne M. Rijks1Comments to Author , Mardik F. Leopold1, Susanne Kühn, Ronald in ‘t Veld, Fred Schenk, Allix Brenninkmeijer, Sander J. Lilipaly, Mónika Z. Ballmann, Leon Kelder, Job W. de Jong, Wouter Courtens, Roy Slaterus, Erik Kleyheeg, Sandra Vreman, Marja J.L. Kik, Andrea Gröne, Ron A.M. Fouchier, Marc Engelsma, Mart C.M. de Jong, Thijs Kuiken, and Nancy Beerens
Author affiliations: Dutch Wildlife Health Centre, Utrecht University, Utrecht, the Netherlands (J.M. Rijks, M.J.L. Kik, A. Gröne); Wageningen Marine Research, Den Helder, the Netherlands (M.F. Leopold, S. Kühn); Staatsbosbeheer Zuid-Hollandse Delta, Numansdorp, the Netherlands (R. in ’t Veld); Stichting Het Zeeuwse Landschap, Wilhelminadorp, the Netherlands (F. Schenk); Province of Groningen, Groningen, the Netherlands (A. Brenninkmeijer); Deltamilieu Projecten, Vlissingen, the Netherlands (S.J. Lilipaly, M.Z. Ballmann); Staatsbosbeheer Beheereenheid de Kop, Schoorl, the Netherlands (L. Kelder); Bureau Waardenburg, Culemborg, the Netherlands (J.W. de Jong); Research Institute for Nature and Forest, Brussels, Belgium (W. Courtens); Sovon Dutch Centre for Field Ornithology, Nijmegen, the Netherlands (E. Kleyheeg, R. Slaterus); Wageningen Bioveterinary Research, Lelystad, the Netherlands (S. Vreman, M. Engelsma,, N. Beerens); Department of Viroscience, Erasmus MC, Rotterdam, the Netherlands (R.A.M. Fouchier, T. Kuiken); Wageningen University and Research, Quantitative Veterinary Epidemiology group, Wageningen, the Netherlands (M.C.M. de Jong)

Main Article

Table

Mortality, fledgling success, carcass removal, and estimated fraction of Sandwich tern breeding population that died or disappeared in 10 breeding colonies, the Netherlands, 2022

Breeding colony no. Date mortality first observed Fledgling success (no. fledglings produced/no. initial breeding pairs) Dead adults found Dead chicks found Abandoned eggs Carcass removal Estimated percentage of breeding population that died or disappeared from colony*
Colony 1 2022 May 30 1% (20/2,100) 342 425 Yes, all 700 late nests Yes, with a 12-d delay, on 10 of next 18 d, adults and chicks 99%
Colony 2 2022 Jun 21 0% (0/150) 107 0 Yes, all 150 late nests Once, with a 3-d delay, adults only 100%
Colony 3† 2022 Jun 4 0% (0/1,176) 170 Hundreds Yes, many Yes, with a 6-d delay, on 6 of next 18 d, adults only 100%
Colony 4† 2022 May 26 0.1% (5/3,374) 3,316 Thousands Unknown Twice, once 19 d after start, then 16 d later, adults only 99.8%
Colony 5 2022 May 29 0% (0/220) 400 0 Unknown Once, 17 d after deaths started, adults only 100%
Colony 6 2022 May 31 Low (Few/3,016)‡ 941 Thousands Yes, all 245 late nests Yes, without delay, on 15 of next 36 d, adults only >92%
Colony 7 2022 May 31 11.1% (45/404) 115 Unknown Yes, many of 40 late nests Yes, without delay, on 14 of next 36 d, adults only 78%
Colony 8 2022 Jun 14 47.4% (65/137) 2 0 No (also no late nests) No 5% or not applicable§
Colony 9 2022 Jun 6 9.5% (665/6,974) 2,368 3,122 No, there is activity above 400 late nests Yes, with an 8-d delay, on 14 of next 27 d, adults and chicks 81%
Colony 10¶
 2022 Jun 14
 0% (0/600)
 240
 12
 Unknown, 150 + 450 late nests
 Yes, with a 7-d delay, on 3 of next 15 d, adults and chicks
 100%
Overall Low (Few/18,151 pairs) 8,001 (22% of breeding birds) Thousands

*Calculated by subtracting the ratio of fledgling success in 2022 over average fledgling success in previous years (0.5 fledgling per pair) from 100%. †After colony 3 and colony 4 were decimated, a very late colony of 600 breeding pairs was established in July on Texel midway between these 2 colonies (53.022°N, 4.819°E), and this very late colony yielded 300 fledglings in September 2022. ‡Exact number not recorded. §Because no carcass was examined, it is unclear if the 2 dead birds observed in this colony died from other causes or the cause of death was HPAI H5N1 but further infections in the colony were aborted. ¶In this colony, some very late birds did end up producing some fledglings (around 155) in August (Appendix 1 Table 1).

Main Article

1These authors contributed equally to this article.

Page created: October 21, 2022
Page updated: November 22, 2022
Page reviewed: November 22, 2022
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