Post-mortem examination and histopathological analysis of tissues collected from infant eastern cottontail rabbits (Sylvilagus floridanus) in rehabilitation

Young eastern cottontail rabbits (Sylvilagus floridanus) are commonly admitted to wildlife rehabilitation centers and often carry a guarded prognosis, even those who appear healthy on admission. For this research, necropsies and histopathological analysis were performed to attempt to determine the cause of death of infant eastern cottontails who died suddenly in care without clinical signs of illness. A total of 26 cadavers were collected in 2022 and 2023, with an average body weight on admission of 76.8 ± 4.4 g. Freeze-thaw artifacts and cell autolysis limited findings in the tissues. However, pre-mortem lesions were found in the heart (n = 5), liver (n = 5), large intestine (n = 1), small intestine (n = 2), and lungs (n = 3). These were mostly inflammatory or bacterial in nature. An unexpected but important finding was that six of the cadavers had milk present in their lungs, likely the result of tube-feeding errors, which may have resulted in the deaths of these rabbits. Other results suggest a systemic response to bacteria and inflammation, and dysbiosis could not be ruled out in some cases.