Lorikeet Magic: Examining Lorikeet Enteritis through the Microbiota David Minich 1*, Christopher Madden 1*, Kristen French-Kim 1, Morgan V. Evans 1,2, Gregory A. Ballash 1, Margaret Martinez 1, Jennifer Hausmann 3, Randall E. Junge 4, Vanessa L. Hale 1 1 The Ohio State University College of Veterinary Medicine, Columbus, OH 2 Environmental Health Sciences, The Ohio State University College of Public Health, Columbus, OH 3 Denver Zoo, Denver, CO 4 Columbus Zoo and Aquarium, Columbus, OH *Contributed equally Necrotizing enteritis is one of the most common causes of morbidity and mortality in lorikeets under human care, and recurrent outbreaks of enteritis have been reported in lorikeet flocks at multiple zoological institutions across North America. Etiologic agents underlying the enteritis can be difficult to diagnose due to inconsistent or inconclusive culture results. In this study, we examine the microbiota in two lorikeet flocks (Columbus Zoo and Aquarium – CZA - and Denver Zoo - DZ) that have a history of enteritis. Since 2012, the CZA lorikeet flock has experienced repeated outbreaks of enteritis despite extensive diet, husbandry, and exhibit modifications. In 2018, both CZA and DZ observed a spike in enteritis. Healthy lorikeets (n=67) at CZA were sampled 3 times over 3 seasons during flock health surveys. Healthy lorikeets (n=38) at DZ were sampled a single time. Lorikeets with enteritis (CZA n=33; DZ n= 16) were opportunistically sampled between November 2018 and September 2019. We employed 16S rRNA sequencing to characterize the cloacal microbiota associated with healthy lorikeets, lorikeets with enteritis, and lorikeets susceptible to enteritis. “Susceptible” was defined as any bird with a history of enteritis or any bird that presented with enteritis after being sampled as a “healthy” bird during a flock health survey. We identified Clostridium perfringens as the likely agent in these outbreaks, and we observed reduced microbial diversity and significantly higher levels of C. perfringens in lorikeets with enteritis as compared to healthy lorikeets. We further identified the toxin-type and antimicrobial susceptibility profiles of C. perfringens isolates obtained from intestinal contents. Additionally, we examined histopathologic changes in the intestines of lorikeets with and without enteritis. Our results identify lorikeets at high risk for Clostridial infection, which could allow targeted therapeutic applications to prevent outbreaks of enteritis, promote antimicrobial stewardship, and enhance lorikeet health.