SeaWorld San Diego has been involved in pinniped rehabilitation for release since 1964. Species involved in this program are representative of the southern California coastal populations of sea lions (Zalophus californianus), northern elephant seals (Mirounga angustirostris), and harbor seals (Phoca vitulina). Rare Guadalupe fur seals (Arctocephalus townsendi) and a single hooded seal (Cystophora cristata) have also been rehabilitated. The focus of the program has been animal rehabilitation for release with an overall release rate of 50%. Reasons for stranding and annual numbers of stranded animals have varied dramatically. Approximately 100 pinnipeds enter the program annually, with the majority of animals stranding during May and June. El Niño years yield dramatic elevations in the number of sea lions for rehabilitation and an improved release rate.
In 2003, a new program of population monitoring was initiated as part of the standard stranded animal assessment. The goal of this program was to increase the individual animal diagnostic information as well as provide samples for population survey. These results expand the stranded animal program focus to include population data as well as individual animal care. Samples gathered for assessment include free-catch urine collected within 36 hours of admission for urinalysis and domoic acid concentration determination, whole blood for complete blood count (CBC) evaluation, and serum for clinical chemistries, Leptospira serology (L. interrogans serovars canicola, grippotyphosa, hardjo, icterohaemorrhagiae, and pomona) determined by microscopic microagglutination, Toxoplasma serology determined by latex agglutination, phocine distemper and canine distemper serology determined by serum neutralization, Brucella serology determined by card and Rivinol tests, and titers for West Nile virus (WNV) determined by serum neutralization.
Over a twelve-month period, 172 pinnipeds entered rehabilitation at SeaWorld San Diego. Of these, 154 were sea lions, 11 northern elephant seals, and seven harbor seals. The overall release rate was 66%. Releases per species were 102 sea lions, four harbor seals, and eight northern elephant seals.
Intake complete blood counts suggested dehydration (elevated packed cell volume and total protein) in approximately 20% of the animals. Thirteen percent of the animals demonstrated elevated white blood cell counts and increased band neutrophil percentages interpreted as an inflammatory leukogram. Anemia was noted in seven animals.
Serology evaluations revealed no serologic evidence of exposure to Brucella sp., morbillivirus, or West Nile virus in any animals. Screening for Brucella antibodies was performed using the card and Rivinol assays. These assays may not be as specific as ELISAs currently under validation for marine mammals. However, these results contrast to positive values in 4% of stranded harbor seals on the east coast5 and positive values for various free-ranging seals and walruses.6 Morbillivirus titers in southern California pinnipeds have traditionally been negative. The results of this screening compare favorably with this data and serologic evaluations of Steller sea lions in Alaska.1 West Nile virus is an emerging pathogen in the United States. It is known to cause disease and mortality in seals2 and can be followed as it migrates across the United States. As of the fall of 2003, serologic results from this group confirm negative values for southern California animals. Comparative evaluations as the virus emerges throughout California may prove interesting.
Toxoplasma serology revealed low positive values for 11 sea lions, and 1 harbor seal. Five of the 11 northern elephant seals had toxoplasma titers. These values ranged from 1:16 to > or = to 1:2048. Samples for validation of this assay were not collected during this season. Post-mortem examinations did not demonstrate encephalitis associated with the elevated titers. In depth brain examinations were not performed; organisms may have eluded detection. Infections have been reported in harbor seals and sea lions. These are the first serologic positive results in northern elephant seals to our knowledge. Further investigations and assay validation are planned for 2004.
Leptospirosis serology was negative for all harbor seals and positive at 1:32 for L. canicola and grippotyphosa for one elephant seal. Ten sea lions demonstrated low positive (1:100 or 1:200) titers to Leptospira serovars. Of these, four were positive for L. canicola. Two animals were positive for L. pomona. All serovars tested had at least one positive animal; all age classes of sea lions were represented. Leptospirosis has been previously diagnosed in sea lions at our facility. No specific clinical or post-mortem cases were diagnosed in 2003. Animals with titers were not subsequently found infected. Leptospirosis is well described in free-ranging California sea lions.3,4 The various serovar positive results may indicate exposure to various organisms or differing cross reactivity.
Urinalysis evaluations were frequently disrupted by fecal contamination in the samples collected. Urine samples were collected from all animals regardless of presenting complaint. This proved logistically difficult and significantly increased intake animal handling. Many samples were banked and were not ultimately evaluated for domoic acid concentrations. However, these samples were especially useful in two specific instances. When a regional increase in neurologic animals was noticed at a number of stranding facilities, two affected animals had stored urine that was available for immediate evaluation for domoic acid concentration determination. Secondly, a total of twenty animals were determined to be domoic acid toxicosis suspects during rehabilitation or following post-mortem examination but not at the time of intake. Analysis of intake urine from all of these animals is underway at this time. To improve urine sample quality, a purpose specific urine cage has been designed and is in use. The value of urine specimens will be easier to evaluate with a year of the improved collection system.
Overall, the expanded diagnostics did increase personnel requirements. Population monitoring was generally performed on a small batch basis so that individual results did not heavily influence individual case management. However, these results provide a broad-based starting point for temporal population comparisons in the years to come. Changes in distribution of serologic results can now be determined based on this initial data.
The authors gratefully acknowledge the Animal Care staff of SeaWorld San Diego for the collecting samples and providing the daily care required to rehabilitate the animals. Additional thanks go to the Animal Care Laboratory personnel that tirelessly evaluated, processed, and tabulated samples and their results.
Funding for this program is provided by the National Marine Fisheries Service under the Prescott competitive grants program.
1. Burek KA, Gulland FMD, Sheffield G, Keyes E, Spraker TR, Smith AW, Skilling DE, Everman J, Stott JL, AW Trites. 2003. Disease agents in stellar sea lions in Alaska: a review and analysis of serology data from 1975-2000. Fisheries Centre Research Reports 11(4). The fisheries Centre, University of British Columbia, Vancouver.
2. Duncan A, Stremme DW, Murray SZ, Glaser AL, Stadler CK. 2003. Clinical illness in two harbor seals (Phoca vitulina) and one grey seal (Halichoerus grypus) caused by West Nile virus. Proc AAZV Minneapolis, MN.
3. Gulland FMD. 1999. Leptospirosis in marine mammals. In: Fowler, M.E. and R.E. Miller (eds.). Zoo and Wild Animal Medicine, Current Therapy 4. W. B. Saunders Co, New York. Pp. 469-471.
4. Leighton FA, Kuiken T. 2001. Leptospirosis. In: Williams, E.S. and I.K. Barker (eds.). Infectious Diseases of Wild Mammals, 3rd ed. Iowa State University Press, Iowa. Pp. 498-502.
5. Maratea J, Ewalt DR, Frasca S Jr., Dunn JL, De Guise S, Szkudlarek L, St Aubin DJ, French RA. 2003. Evidence of Brucella sp. infection in marine mammals stranded along the coast of southern New England. J Zoo Wildl Med. 34(3):256-261.
6. Nielen O, Stewart REA, Nielsen K, Measures L, Duignan P. 2001. Serologic survey of Brucella Spp. Antibodies in some marine mammals of North America. J Wild Dis. 37(1):89-100.