Impact of Age, Season, and Flowingvs. Stagnant Water Habitat on Avian Influenza Prevalence in Mute Swan (Cygnus olor) in Belgium

Abstract

Due to their probable role in the spread of Asian highly pathogenic avian influenza (HPAI) H5N1 virus, and in order to explore its implication in the low pathogenic avian influenza (LPAI) virus epidemiology, mute swans represent one particular wild bird species specifically targeted in the avian influenza (AI) surveillance elaborated in Belgium. A total of 640 individual mute swans have been sampled during a 4-yr AI surveillance program (2007-2010) to determine the AI seroprevalence and viroprevalence in this species; all were analyzed through age, temporal, and habitat (flowing and stagnant water) factors. Using a nucleoprotein (NP)-based ELISA, a global antibody prevalence of 35% has been found and was characterized by two peaks in the winter and the summer that might be indicative of a greater LPAI virus circulation in the autumn than in the spring. A significantly higher antibody prevalence was detected in adult swans (53.8%) as compared to juveniles (15.5%). In contrast, a low prevalence of infection (2.7%) was found, mainly in juvenile mute swans and only during the autumn migration period. Interestingly, an impact of water habitat was observed based on the comparison of the antibody prevalence and prevalence of infection from swan populations living on stagnant water vs. flowing water, suggesting that stagnant water provides a more-favorable environment for LPAI persistence and transmission.

Antibody responses to avian influenza viruses in wild birds broaden with age

“…Studies of AIV seroprevalence have shown that ‘adult’ birds (typically individuals 1 or 2 years after hatch-year, depending on species) are more likely than ‘juvenile’ birds (sampled during or 1 year after hatch-year) to harbour antibodies targeted at AIV NP [20–27]. Here we show that not all birds defined as seropositive for AIV by NP antibody presence have equivalent levels of protection against AIV.…”

“…The prevalence of AIV in healthy wild mute swan populations is low (typically less than 3% [15,27,47,48,55]), with most infections observed in juveniles (approx. 6% prevalence) [27]. Experimental evidence in mallards ( Anas platyrhynchos ) suggests that birds are infected with approximately half of all HA types (6/11) circulating in the population within the first 2 years of life [33].…”

“…Several previous studies of AIV seroprevalence have found that male birds are less likely than females to be serologically positive for AIV [20,24,27,29]. However, other studies have shown the opposite trend [25].…”

“…LPAI H5 viruses were very common, comprising 4.9–8.4% of LPAI infections in European wild birds [47,49]. H9 viruses were rarer than H5 or H6, but were not uncommon during this period in several species and locations [27,47,48] and were interesting because of their association with protection against H5N1 HPAI infection.…”

Potential disease transmission from wild geese and swans to livestock, poultry and humans: a review of the scientific literature from a One Health perspective

“…Studies of LPAIV in swans and geese generally demonstrate very low prevalence of infection, often in the range of 0-3% in fresh faeces (Canada goose; [6] mute swan; [21,69] several species [70][71][72]). On the other hand, data on seroprevalence suggest that many swans and geese eventually do become exposed to LPAIV: 0-14% in Canada goose, [6,24,73] 45% in mute swan, [21] 63% in pink-footed goose Anser brachyrhynchus, [74] and >95% in Emperor goose Chen canagica.…”