Role of Free-Ranging Synanthropic Egyptian Geese (Alopochen aegyptiaca) as Natural Host Reservoirs for Salmonella spp. in Germany

SIMPLE SUMMARY: Salmonella is worldwide one of the most common and pathogenic bacteria causing severe gastroenteritis in humans and animals. As such, birds are natural carriers of different zoonotic-relevant Salmonella serovars. Consistently, Anseriformes transmit Salmonella spp. to humans and manifest clinical Salmonellosis. The Egyptian goose (EG; Alopochen aegyptiaca) represents a fast-spreading alien species in Europe, North America and Asia. This alien species prefers urban habitats such as parks, urban ponds, public swimming pools, riversides or golf courses, thereby having frequent contact with humans, wildlife and domestic pets. Increased environmental EG faecal contamination in cities brings up the question of potential anthropozoonotic pathogen spill-overs to humans, including Salmonella. To the best of our knowledge, this is the first study to investigate the role of the EG as a natural host reservoir of Salmonella but also to discuss transmission routes of salmonellosis to humans in chlorinated public swimming pools. ABSTRACT: Salmonella is one of the most common and pathogenic bacteria worldwide, causing severe enteritis in humans and representing a relevant intestinal illness in One Health for young, old and immunosuppressed patients. Various Salmonella serovars have been described to be responsible for human Salmonellosis. Birds represent natural carriers of different zoonotic-relevant Salmonella serovars and Anseriformes can not only transmit Salmonella spp. to humans but also manifest clinical Salmonellosis. In this study, 138 scat samples (n = 138) of free-ranging Egyptian geese (EG; Alopochen aegyptiaca) were collected in Germany, including 83 scat samples from city parks, 30 samples from 14 public swimming pools and 25 fresh caecal samples of dead EG. Collected EG scat samples were examined for the presence of Salmonella spp. according either to the ISO 6579 (2017) norm or to a combination of bacterial pre-enrichment and specific PCR for detection of Salmonella DNA. All 138 analysed EG faecal samples resulted Salmonella-negative. Furthermore, the survival of Salmonella enterica subsp. enterica Serovar Anatum in spiked EG droppings was tested in four different concentrations of chlorinated pool water. In vitro testing demonstrated that S. Anatum-spiked EG droppings were still infectious for up to six hours in chlorinated pool water according to current German regulations for public swimming pools. This study is to be considered as a baseline investigation to clarify the role of synanthropic EG as natural carriers of zoonotic Salmonella in cities; nonetheless, large-scale epidemiological studies, including higher numbers of samples as well as more urban locations, are needed for final conclusions on the occurrence of this intestinal bacteria in neozootic EG.