Abstract

Sera from 225 California sea lions (Zalophus californianus) that presented to one of three participating California coast marine mammal rehabilitation centers in 1996 were evaluated for antibodies to Leptospira pomona using a microscopic agglutination test (MAT). Any animal with a titer of 1:100 or greater was considered positive. The overall prevalence was 38.22% (86/225), although the prevalence at each center varied from 100% (38/38) at the Marine Mammal Care Center (MMCC) at Fort MacArthur to 27.75% (48/173) at The Marine Mammal Center (TMMC) to 0% (0/14) at Sea World, San Diego. At TMMC, the majority of seropositive animals were subadults and adults; males were 4.67 times more likely to be seropositive to L. pomona than females; and the highest proportion of seropositive animals presented during the winter and autumn months.

Evaluation of the sensitivity and specificity of the MAT as a method for detection of exposure to L. pomona in California sea lions was also performed using sera from individuals with visible leptospires in kidney sections as positive controls and negative control captive individuals. Our results indicate that the MAT has 100% sensitivity and specificity for detection of L. pomona antibodies in California sea lions. Therefore, the MAT previously developed for cattle is a useful test for determining exposure to L. pomona in California sea lions, and exposure may be more common in all regions of California than previously expected.

Acknowledgements

The authors would like to thank Ocean Park Corporation, Japan and the participating California marine mammal rehabilitation centers, The Marine Mammal Center, Sausalito, Marine Mammal Care Center, San Pedro, and Sea World, San Diego for their cooperation in obtaining serum samples. Funding for MAT analysis was provided by The Marine Mammal Center, Sausalito.