Extrahepatic biliary tract pathologies in mammalian species of zoo animals and wildlife: a review

Mammalian species express a broad variety in the shape of their extrahepatic biliary tract. While a gall bladder is present in many species, others are lacking this organ. Evolutionary driving forces for these differences have not been determined yet, and organ-specific pathologies might present potentially influencing factors. We reviewed the literature regarding extrahepatic biliary tract pathologies reported in mammalian species of zoo animals and wildlife. Specific pathologies have been reported in the taxonomic orders Proboscidea, Chiroptera, Carnivora, Artiodactyla, Primates, Rodentia, and Lagomorpha with variable frequencies of etiological categories. While metabolic disorders with cholelith formation have been reported mainly in captive populations, parasitological infestation was found particularly in free-ranging animals. Based on the available data, we hypothesize Proboscidea, Primates, and Rodentia species to be prone to cholelithiasis. Species belonging to the Artiodactyla seem to be more susceptible to parasitological infestation while in representatives of the Carnivora infectious, metabolic, neoplastic, and parasitological disorders have been reported nearly equally. Extending our knowledge on extrahepatic biliary tract pathologies in exotic pets and wildlife will support the work of veterinary practitioners as well as scientists in evolutionary biology, making further research in this area strongly recommendable