Abstract

An epizootic of sequential clinical illness occurred in a small group of California sea lions, Zalophus californianus, at a large marine animal theme park. Four of six sub-adult to adult male sea lions, ages 5-30 years, presented a variety of clinical signs including anorexia, lethargy, abdominal discomfort and diarrhea. Two of those four animals also experienced vomiting or regurgitation. In addition, late in the series of illnesses, a fifth animal presented with vesicular lesions on the dorsal surface of the foreflippers but had no signs of gastrointestinal disease. Fecal samples of three out of the four clinically ill sea lions tested positive for San Miguel sea lion virus (SMSLV) using PCR and sequencing. SMSLV was also detected in the vesicular fluid, as well as a fecal sample collected from the fifth affected sea lion. Blood analyses conducted within two days of the first clinical signs from two of the four clinically affected animals showed marked leukopenia, lymphopenia and thrombocytopenia uncharacteristic of previous reports of calicivirus infection in sea lions. The sea lions were treated empirically with antibiotics and supportive care with all recovering uneventfully within 5-14 days. Interestingly, one of the six exposed sea lions never developed clinical signs of vesicular or gastrointestinal disease and no SMSLV was detected on fecal PCR.

Early diagnosis with fecal PCR enabled the clinicians to manage the cases accordingly. These cases highlight the variability of disease manifestation and viral shedding following calicivirus infection beyond the more common vesicular disease to include gastrointestinal disease and moderate bone marrow suppression.