North American wintering mallards infected with highly pathogenic avian influenza show few signs of altered local or migratory movements

Abstract

Avian influenza viruses pose a threat to wildlife and livestock health. The emergence of highly pathogenic avian influenza (HPAI) in wild birds and poultry in North America in late 2021 was the first such outbreak since 2015 and the largest outbreak in North America to date. Despite its prominence and economic impacts, we know relatively little about how HPAI spreads in wild bird populations. In January 2022, we captured 43 mallards (Anas platyrhynchos) in Tennessee, USA, 11 of which were actively infected with HPAI. These were the first confirmed detections of HPAI H5N1 clade 2.3.4.4b in the Mississippi Flyway. We compared movement patterns of infected and uninfected birds and found no clear differences; infected birds moved just as much during winter, migrated slightly earlier, and migrated similar distances as uninfected birds. Infected mallards also contacted and shared space with uninfected birds while on their wintering grounds, suggesting ongoing transmission of the virus. We found no differences in body condition or survival rates between infected and uninfected birds. Together, these results show that HPAI H5N1 clade 2.3.4.4b infection was unrelated to body condition or movement behavior in mallards infected at this location during winter; if these results are confirmed in other seasons and as HPAI H5N1 continues to evolve, they suggest that these birds could contribute to the maintenance and dispersal of HPAI in North America. Further research on more species across larger geographic areas and multiple seasons would help clarify potential impacts of HPAI on waterfowl and how this emerging disease spreads at continental scales, across species, and potentially between wildlife and domestic animals.

HPAIV outbreak triggers short-term colony connectivity in a seabird metapopulation

“…Long-distance movements are only relevant for disease transmission if the moving animal is infectious at the time of movement. The limited evidence currently available on the effect of HPAIV infection on movement is ambiguous: a recent study on griffon vultures, Gyps vulvus , shows that infected individuals were more lethargic or even immobile thus probably reducing the reducing transmission risks 34 while movements of infected mallards, Anas platyrhynchos , did not differ from unaffected individuals whilst sharing space with the latter, suggesting that movements of infected birds contributed to the maintenance and dispersal of HPAI 35 . We do not have information on the disease status for our GPS-tracked animals since they were captured well before the disease outbreak.…”

Geographic, ecological, and temporal patterns of seabird mortality during the 2022 HPAI H5N1 outbreak on the island of Newfoundland

“…A wide range of birds and a number of mammalian species have been found to be infected with HPAIVs, though mortality rates depend in part on differences in taxa- and species-specific traits (European Food Safety Authority et al 2023a; Teitelbaum et al 2023; Alkie et al 2023). For example, unusual mortality among dabbling ducks has not been largely attributed to HPAIV despite its detection in apparently healthy birds, though some species of diving ducks, such as Tufted Ducks ( Aythya fuligula ), are particularly susceptible to HPAIVs and often exhibit high mortality rates (Keawcharoen et al 2008; Kleyheeg et al 2017; Caliendo et al 2022).…”