Sane and sound: a serologic and molecular survey for selected infectious agents in neozootic Egyptian geese (Alopochen aegyptiacus) in Germany

Aquatic birds can act as vectors and reservoir hosts for pathogens relevant for wild birds and poultry as well as human health. In this study, we address the questions (1) if the Egyptian goose (Alopochen aegyptiacus), as one of the most successful neozootic bird species in Europe, carry infectious agents that are relevant for poultry and wild birds and (2) if seasonal prevalences of these infectious agents differ from those of native geese species. In 2015 and 2016, up to 190 Egyptian geese from Western Germany were investigated serologically for antibodies (Ab) against influenza A viruses (IAV), Avian avulavirus 1 (AAvV-1), aviadenoviruses, Duck atadenovirus A (syn.: egg drop syndrome 1976 virus) (EDSV), and West Nile virus (WNV). Ab were detected against IAV in 6.1% (10/164), against AAvV-1 in 2.4% (4/165), against EDSV in 15.2% (16/105), and against aviadenoviruses in 0.86% (1/116) of the geese blood samples, respectively. None of the birds had Ab against WNV (0/84). PCR-based techniques (cloacal and/or pharyngeal swabs) were applied for the presence of IAV, AAvV-1, Mycoplasma spp., and Riemerella anatipestifer. Riemerella DNA was detected in the pharyngeal swabs with an overall prevalence of 70.3% (104/148). Neither Mycoplasma DNA nor IAV or AAvV-1 RNA could be detected in the pharynx or cloaca of the examined birds. Our study shows that Egyptian geese are frequent carriers of Riemerella anatipestifer and furthermore provides serological evidence of exposure to IAV, AAvV-1, and EDSV. It is one of very few studies on infectious agents of neozootic bird species. Comparing our results from a neozootic non-migratory goose species with published results from native migratory geese species (bean goose (Anser fabalis) and white-fronted goose (A. albifrons)) and another neozootic non-migratory goose species (Canada goose (Branta canadensis)), we found differences in the seroprevalence of viral pathogens. Native goose species show higher seroprevalences of IAV and AAvV-1, whereas neozootic non-migratory geese reveal higher seroprevalences for EDSV. The findings are discussed in the frame of seasonal variations in selected infectious agents, differences in sampling periods, and contrasting movement ecology of the different geese species.