Heavy Metal Exposure and Avian Influenza Infection in a Population of Ducks in Eastern North Carolina

Abstract

Highly pathogenic avian influenza (IAV) continues to circulate widely in North America, raising concerns for wildlife, livestock, and human health. Environmental contaminants, including trace metal(loid)s, may influence host immune function and susceptibility to infection. This study evaluated the relationship between feather concentrations of ten trace metal(loid)s (Se, V, Cr, Mn, Co, Cu, Zn, As, Cd, and Pb) and IAV infection status in hunter-harvested diving and dabbling ducks collected from the Chowan–Roanoke and Neuse–Pamlico watersheds of North Carolina between November 2024 and January 2025.Oropharyngeal and cloacal swabs from 428 apparently healthy ducks were tested for IAV through the USDA National Animal Health Laboratory Network. Feather samples were analyzed using inductively coupled plasma–mass spectrometry (ICP-MS). IAV prevalence and exact binomial 95% confidence intervals were calculated overall and by host and sampling characteristics. Associations between metal concentrations and IAV infection were evaluated using non-parametric tests and multivariable logistic regression adjusting for age class, duck type, watershed, and collection date. Overall IAV prevalence was 15.7% (95% CI: 12.3–19.4%). Hatch-year birds and later sampling dates were significantly associated with higher infection probability. Metal concentrations were generally low, and exceedances of established risk thresholds were uncommon (≤4% of birds for individual metals). Exploratory analyses identified a significant negative association between arsenic concentration and IAV infection (Wilcoxon p = 0.008), which persisted but was attenuated in adjusted models and did not significantly improve model fit (likelihood-ratio test p = 0.12). No consistent associations were observed for other metals. Within the exposure range observed, feather metal(loid) burdens were not strong predictors of IAV infection. Host age and seasonal timing were more influential determinants of infection risk. These findings suggest that, in this population, trace metal exposure may play a limited role in shaping IAV susceptibility relative to established ecological drivers. Further studies incorporating refined exposure assessment and longitudinal designs are needed to clarify potential contaminant–infection interactions in wild waterfowl.