Campylobacter spp. are a potential cause of gastrointestinal disease in dogs, and Campylobacter jejuni is most frequently implicated as the etiology of canine campylobacteriosis. Clinical signs include diarrhea, lethargy, anorexia, and occasionally fever and vomiting. However, dogs presenting with this clinical history are rarely tested for Campylobacter infection. Campylobacter jejuni is also a zoonotic pathogen and leading cause of acute bacterial enteritis in people. Our overarching objective is to evaluate our hypothesis that Campylobacter jejuni is underdiagnosed as a cause of enteric disease in dogs, and multidrug-resistant strains implicated in recent human disease outbreaks are also circulating in canine populations. This will be achieved through the following specific aims: (1) Estimate the prevalence of Campylobacter jejuni infection among apparently healthy dogs vs. dogs presenting with acute diarrhea; (2) Identify risk factors for Campylobacter jejuni infection among dogs; and (3) Characterize the Campylobacter jejuni isolates to evaluate potential public health risk, with emphasis on estimating the background prevalence of multidrug-resistant Campylobacter shedding in dogs. We will collect fecal samples from dogs presenting to Cornell University’s Small Animal Community Practice (SACP) over a 1-year period, including apparently healthy dogs and dogs with acute diarrhea. Fecal samples will also be collected from dogs presenting to the Emergency and Critical Care (ECC) Service with acute diarrhea over this duration. Relevant data corresponding to each sampled dog will be collected to identify and quantify risk factors for infection, such as dietary factors, recent drug administration, and exposure to other animals. Campylobacter jejuni will be identified using PCR screening of samples followed by culture. Confirmed Campylobacter jejuni isolates will be characterized through whole-genome sequencing (WGS) and phenotypic antimicrobial susceptibility testing, and we will utilize these results to evaluate the risk and implications of zoonotic transmission.