Pasteurella multocida Infections in Yellow-eyed Penguins (Hoiho; Megadyptes antipodes) in Otago, New Zealand: Case Series of Mortalities due to Avian Cholera.

Yellow-eyed Penguins (Megadyptes antipodes; hoiho) are a unique, nationally endangered, and declining species endemic to New Zealand. Between 28 April 2023 and 28 February 2024, histopathologic examination found that six Yellow-eyed Penguins died from septicemia. A Pasteurella sp. was cultured from all six cases and confirmed as Pasteurella multocida in three cases by either MALDI-TOF (n=2) or genome sequencing (n=1). One isolate was confirmed as P. multocida type A:L3 by molecular techniques and genome sequencing. Pasteurella multocida is the causative agent of avian cholera; thus, finding P. multocida confirmed avian cholera as the cause of these deaths. A source for the bacterial infections could not be identified in these cases. Although avian cholera has been previously reported in other penguin species, to our knowledge, these are the first reported cases of P. multocida in Yellow-eyed Penguins. Yellow-eyed Penguins do not nest in dense colonies, and direct contact between birds outside of breeding pairs is irregular, making this case series an unusual presentation for avian cholera. The loss of six individuals, including three of breeding age, will have a significant impact on the mainland Yellow-eyed Penguin population, and the potential for further losses to avian cholera cannot be discounted. This case series illustrates the benefits of multiagency collaboration in monitoring for, and investigation of, potentially new and emerging diseases in threatened species.