A Model for Determining Infectivity of Zoonotic .

To better understand public health implications of waterfowl as reservoirs for zoonotic sources of in recreational waters, we developed a (chick) model of infection to assess the pathogenicity of environmental isolates of . This method involved exposure of 1-day-old chicks through ingestion of water, the natural route of infection. Viable from laboratory-infected animals were monitored by using a modified non-invasive sampling of fresh chick excreta followed by a passive polycarbonate-filter migration culture assay. The method was used to evaluate the infectivities of three laboratory strains of spp. (, and ), three clinical isolates of , and four environmental spp. isolated from California gulls (). The results revealed that chicks were successfully infected with all laboratory and clinical isolates of spp. through ingestion of -spiked water, with infection rates ranging from <10 to >90% in a dose-dependent manner. More importantly, exposure of chicks with spp. isolated from excreta also resulted in successful establishment of infection (≤90%). Each monitored spp. contained ≥7.5 × 10 CFU⋅g of feces 7 days post-exposure. These results suggest that a model can be used to assess infectivity of isolates, including gull and human clinical isolates. Use of an avian animal model can be applied to assess the importance of birds, such as the , as potential contributors of waterborne-associated outbreaks of campylobacteriosis.