Abstract

The California sea lion (Zalophus californianus) population is affected by Leptospira interrogans serovar Pomona annually, causing low levels of infection year-round and recurrent, cyclical outbreaks of disease. The microscopic agglutination test (MAT) is the standard diagnostic tool to detect anti-Leptospira antibodies (an indication of prior exposure) in serum, whereas polymerase chain reaction (PCR) can be used to detect Leptospira DNA in urine (leptospiruria; an indication of current infection and active shedding). While urine needs to be collected aseptically from anesthetized or deceased animals, serum is much easier to collect and anti-Leptospira antibody titers to serovar Pomona are surprisingly good predictors of shedding status.¹ Here we investigate how prediction of shedding in stranded and wild-caught California sea lions can be enhanced using additional data on demographics, kidney health and environmental factors. Using LASSO regression, we find that shedding predictions based on MAT titers are improved by information on kidney function and seasonality, and that accurate predictions can be made without MAT by including additional demographic data. Our findings indicate that we can expand our studies of shedding to include animals lacking PCR data, and even to animals lacking MAT data, offering potential to enrich our understanding of Leptospira transmission dynamics in this system.

Acknowledgements

The authors wish to thank The Marine Mammal Center (TMMC; Sausalito, CA, USA) and the Marine Mammal Laboratory (MML; Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA, USA) for their contributions to this study in the form of biological sampling in both stranded (TMMC) and wild-caught (MML) sea lions.

References

1.  Prager KC, Buhnerkempe MG, Greig DJ, Orr AJ, Jensen ED, Gomez F, Galloway RL, Wu Q, Gulland FMD, Lloyd-Smith JO. 2020. Linking longitudinal and cross-sectional biomarker data to understand host-pathogen dynamics: Leptospira in California sea lions (Zalophus californianus) as a case study. PLoS Negl Trop Dis. 14(6).