Clinical Features and Prognostic Indices of Leptospirosis in California Sea Lions (Zalophus californianus)
The spirochete bacterium Leptospira interrogans is an enzootic pathogen in California sea lions (Zalophus californianus; CSL).1 Clinical features of leptospirosis include dehydration, polydipsia, lethargy, inappetence, and apparent abdominal pain.2 Clinical pathologic changes include azotemia, hyperphosphatemia, hypokalemia, and hypernatremia.2 We performed a retrospective review to investigate prognostic indicators for CSLs with leptospirosis treated at The Marine Mammal Center in Sausalito, CA. Cases were live-stranded animals identified after admission by clinical signs and serum chemistry and confirmed by serology or characteristic renal change on necropsy and histopathology. Of 251 cases admitted January through November 2018, 91% were male and 58% were juvenile. Survival to release was 46%. Mean rehabilitation duration was 25 days (range 18–51). Of all deaths, 44% died on mean day five (range 0–36) and 56% were euthanized on mean day seven (range 0–31). Serum chemistry parameters at admission were compared by Mann-Whitney U test between animals that survived to release and those that died. Median blood urea nitrogen, creatinine, phosphorus, sodium, bilirubin, and gamma-glutamyl transferase were significantly lower and median potassium and calcium were significantly higher in animals that survived to release (P<0.004). Survival of juveniles was higher compared to other age classes (P<0.001). There was no effect of sex. Odds of survival to release were 102 times greater for animals that ate within six days of admission (95% CI 23.8–474.3, P<0.0001). Based on these provisional findings, we propose a set of prognostic serum indicators and clinical features that can be utilized for triage of CSLs with leptospirosis.
We thank Haylie Lawson for her contributions to this project. We extend our deep gratitude to the staff and volunteers of The Marine Mammal Center for their dedicated patient care.
1. Zuerner RL, Alt DP. 2009. Variable nucleotide tandem-repeat analysis revealing a unique group of Leptospira interrogans serovar Pomona isolates associated with California sea lions. J Clin Microbiol 47:1202–1205.
2. Dierauf LA, Vandenbroek DJ, Roletto J, Koski M, Amaya L, Gage LF. 1987. An epizootic of leptospirosis in California sea lions. J Am Vet Med Assoc 187:1145–1148.