Detection of Leptospira kirschneri in a short-beaked common dolphin (Delphinus delphis delphis) stranded off the coast of southern California, USA

• Published in: BMC Veterinary Research
• Main Authors: K. C. Prager, Kerri Danil, Elyse Wurster, Kathleen M. Colegrove, Renee Galloway, Niesa Kettler, Rinosh Mani, Ryelan F. McDonough, Jason W. Sahl, Nathan E. Stone, David M. Wagner, James O. Lloyd-Smith
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2024
• Subjects: Leptospira; Cetacean; Marine mammal; Common dolphin; Delphinus delphis; Northeastern Pacific; Veterinary medicine; SF600-1100; Elephant Seal
• Online Access: https://doi.org/10.1186/s12917-024-04111-x; https://doaj.org/article/bd2d4e15ddc6457ab67f06f91580f17a

Abstract Background Pathogenic Leptospira species are globally important zoonotic pathogens capable of infecting a wide range of host species. In marine mammals, reports of Leptospira have predominantly been in pinnipeds, with isolated reports of infections in cetaceans. Case presentation On 28 June 2021, a 150.5 cm long female, short-beaked common dolphin (Delphinus delphis delphis) stranded alive on the coast of southern California and subsequently died. Gross necropsy revealed multifocal cortical pallor within the reniculi of the kidney, and lymphoplasmacytic tubulointerstitial nephritis was observed histologically. Immunohistochemistry confirmed Leptospira infection, and PCR followed by lfb1 gene amplicon sequencing suggested that the infecting organism was L. kirschneri. Leptospira DNA capture and enrichment allowed for whole-genome sequencing to be conducted. Phylogenetic analyses confirmed the causative agent was a previously undescribed, divergent lineage of L. kirschneri. Conclusions We report the first detection of pathogenic Leptospira in a short-beaked common dolphin, and the first detection in any cetacean in the northeastern Pacific Ocean. Renal lesions were consistent with leptospirosis in other host species, including marine mammals, and were the most significant lesions detected overall, suggesting leptospirosis as the likely cause of death. We identified the cause of the infection as L. kirschneri, a species detected only once before in a marine mammal – a northern elephant seal (Mirounga angustirostris) of the northeastern Pacific. These findings raise questions about the mechanism of transmission, given the obligate marine lifestyle of cetaceans (in contrast to pinnipeds, which spend time on land) and the commonly accepted view that Leptospira are quickly killed by salt water. They also raise important questions regarding the source of infection, and whether it arose from transmission among marine mammals or from terrestrial-to-marine spillover. Moving forward, surveillance and sampling must ...