Abstract

Leptospirosis, a zoonosis caused by pathogenic species of the spirochete genus Leptospira, was first reported in California sea lions (Zalophus californianus; CSL) in 1970.^1,2 Since the early 1980s, The Marine Mammal Center (TMMC) has treated CSL stranding along the California coast during recurrent, seasonal epizootics.^3-7 TMMC treatment of leptospirosis in CSL consists of supportive care and antibiotics; however, due to the severity of resulting renal disease, roughly 70% die.⁵ The goals of antibiotic therapy in CSL are to improve survival and eliminate shedding of the infectious leptospires in the urine (the primary mode of transmission). Guided by protocols used in other species^8-10, current antibiotic therapy in CSL is a 9–14 day course of penicillin and sometimes includes tetracyclines.

In 2010–11, we assessed leptospiruria (using real-time PCR) and survival in antibiotic-treated CSL. Twenty-eight stranded CSL with serum chemistry values indicative of clinical leptospirosis (BUN > 100 mg/dl and creatinine > 2 mg/dl)⁵ were followed until release (N = 14, range = 30–92 days, median = 59 days) or death (N = 14, range = 2–34 days, median = 7 days). All 28 CSL received a course of antibiotics upon admission to TMMC that consisted of penicillin G (30,000 units/kg IM every 48 hours) when animals were inappetant and amoxicillin tetrahydrate (22 mg/kg PO every 12 hours) when eating. Duration of antibiotic therapy was 9–16 days in CSL that survived and 1–16 days in CSL that died. In addition, antibiotics to treat other conditions (e.g., verminous pneumonia and skin infections) were used in 11/28 CSL and consisted of one or more of the following: enrofloxacin, ciprofloxacin, doxycycline, oxytetracycline, and ceftiofur. In CSL that survived to release, leptospires were detected in all urine samples collected within 14 days of admission and at least once in each CSL. In CSL that died, leptospiruria was detected in all but 3 samples: one CSL had no urine collected for testing until 20 days after admission and then again at death, and was negative in both instances; another CSL was positive 6 days post-admission, but not at death. In the 14 CSL that survived, 9 were leptospiruric at release and 8/10 evaluated at 6 weeks (42 days) were leptospiruric. Five of the 14 CSL that survived were treated with only penicillin G/amoxicillin (duration 9–14 days) and all 5 were leptospiruric at release (30–61 days from stranding). Twelve of the 14 CSL that died were treated with only penicillin G/amoxicillin (duration 1–13 days) and 11/12 were shedding at the time of death (death occurred 2–20 days from stranding; median = 8 days). Results are summarized in Table 1.

From these preliminary data we conclude that current antibiotic therapy is not sufficient to eliminate leptospiruria in the majority of CSL stranding with leptospirosis. The data are insufficient to determine whether antibiotic choice influences survival, although there is a pattern suggestive of greater survival rates in CSL that received additional antibiotics. Identification of a treatment regimen that optimizes survival and elimination of leptospiruria in CSL stranding with leptospirosis will require a prospective, case-controlled study in which multiple antibiotic protocols are evaluated.

Table 1. Numbers of California sea lions shedding leptospires at death or release by antibiotic treatment

Antibiotics: Penicillin G (PG), Amoxicillin (A), Oxytetracycline (O), Doxycycline (D), Ciprofloxacin (C), Enrofloxacin (E), Ceftiofur (CR).

Acknowledgements

The authors wish to thank all of the volunteers and staff from the Marine Mammal Center in Sausalito who helped in sample collection from both stranded and wild-caught California sea lions. We would also like to thank the Prescott Grant Program, the Hellman Family Foundation, and the De Logi Chair in Biological Sciences for their financial support.

* Presenting author

Literature Cited

1.  McIlhattan TJ, Martin JW, Wagner RJ, Iversen JO. 1971. Isolation of Leptospira pomona from a naturally infected California sea lion, Sonoma county, California. Journal of Wildlife Diseases 7:195–197.

2.  Vedros NA, Smith AW, Schonewald J, Migaki G, Hubbard RC. 1971. Leptospirosis epizootic among California sea lions. Science 172:1250–1251.

3.  Dierauf LA, Vandenbroek DJ, Roletto J, Koski M, Amaya, L, Gage LJ. 1985. An epizootic of leptospirosis in California sea lions. J Am Vet Med Assoc 187:1145–1148.

4.  Gerber JA, Roletto J, Morgan LE, Smith DM, Gage LJ. 1993. Findings in pinnipeds stranded along the central and northern California coast, 1984–1990. Journal of Wildlife Diseases 29:423–433.

5.  Gulland F, Koski M, Lowenstine LJ, Colagross A, Morgan L, Spraker T. 1996. Leptospirosis in California sea lions (Zalophus californianus) stranded along the central California coast, 1981–1994. Journal of Wildlife Diseases 32:572–580.

6.  Greig DJ, Gulland F, Kreuder C. 2005. A decade of live California sea lion (Zalophus califorianus) strandings along the central California coast: causes and trends, 1991–2000. Aquatic Mammals 33:11–22.

7.  Lloyd-Smith JO, Greig DJ, Hietala S, Ghneim GS, Palmer L, St Leger J, Grenfell BT, Gulland F. 2007. Cyclical changes in seroprevalence of leptospirosis in California sea lions: endemic and epidemic disease in one host species? BMC Infectious Diseases 7:125–136.

8.  Griffith ME, Hospenthal DR, Murray CK. 2006. Antimicrobial therapy of leptospirosis. Curr Opin Infect Dis 19:533–537.

9.  Suputtamongkol Y, Pongtavornpinyo W, Lubell Y, Suttinont C, Hoontrakul S, Phimda K, Losuwanaluk K, Suwancharoen D, Silpasakorn S, Chierakul W, Day N. 2010. Strategies for Diagnosis and Treatment of Suspected Leptospirosis: A Cost-Benefit Analysis. Plos Neglected Tropical Diseases 4:

10. Watt G, Padre LP, Tuazon ML, Calubaquib C, Santiago E, Ranoa CP, Laughlin LW. 1988. Placebo-controlled trial of intravenous penicillin for severe and late leptospirosis. Lancet 1:433–435.