Free-ranging California Sea Lions Research Articles

Otariid gammaherpesvirus 1 in South American fur seals (Arctocephalus australis) and a novel related herpesvirus in free-ranging South American sea lions (Otaria byronia): Prevalence and effects of age, sex, and sample type.

Otariid gammaherpesvirus 1 (OtGHV1) is associated with high rates of urogenital carcinoma in free-ranging California sea lions (Zalophus californianus; CSL), and until recently was reported only in the Northern Hemisphere. The objective of this study was to survey free-ranging South American sea lions (Otaria byronia; SASL) and South American fur seals (Arctocephalus australis: SAFS) in Punta San Juan, Peru for OtGHV1 and to determine prevalence characteristics. Twenty-one percent (14/67) of urogenital swabs collected over three years (2011, 2014, 2015) from live pinnipeds of both species tested positive with a pan-herpesvirus conventional PCR. Sequencing of SAFS amplicons revealed 100% homology to OtGHV1 at the DNA polymerase, glycoprotein B, and viral bcl2-like genes. Sequencing of SASL amplicons revealed a novel related virus, herein called Otariid gammaherpesvirus 8 (OtGHV8). For comparison of sample sites, urogenital, conjunctival, and oropharyngeal swabs collected from 136 live pinnipeds of both species at Punta San Juan between 2011-2018 were then assayed using quantitative PCR for a segment of the OtGHV1/8 DNA polymerase gene using a qPCR assay now determined to cross-react between the two viruses. In total, across both species, 38.6% (51/132) of urogenital swabs, 5.6% (4/71) of conjunctival swabs, and 1.1% (1/90) of oropharyngeal swabs were positive for OtGHV1/8, with SASL only positive on urogenital swabs. Results from SASL were complicated by the finding of OtGHV8, necessitating further study to determine prevalence of OtGHV1 versus OtGHV8 using an alternate assay. Results from SAFS suggest a potential relationship between OtGHV1 in SAFS and CSL. Though necropsy surveillance in SAFS is very limited, geographic patterns of OtGHV1-associated urogenital carcinoma in CSL and the tendency of herpesviruses to cause more detrimental disease in aberrant hosts suggests that it is possible that SAFS may be the definitive host of OtGHV1, which gives further insight into the diversity and phyogeography of this clade of related gammaherpesviruses.

Mercury and selenium concentrations in lanugo of free-ranging California sea lions in the southern Gulf of California, Mexico

Total mercury ([THg]) and selenium ([TSe]) concentrations were determined in California sea lion (Zalophus californianus) lanugo from the Gulf of California in 2021 and 2022. Relationships with sex, morphometrics, and year were evaluated. Following toxicological thresholds of concern for piscivorous mammals, most pups had a [THg] < 10 ppm, one pup (2021) had a [THg] > 20 ppm, no pups had a [THg] > 30 ppm. Females had significantly higher [TSe] than males; sex did not influence [THg]. [THg] and [TSe] in 2022 were significantly higher in the general population and male cohorts compared to 2021. Significant negative correlations were observed between [THg], [TSe], and morphometrics (2021). These results indicate that, compared to other pinniped species, regional California sea lions may have a decreased likelihood of experiencing Hg-related adverse health effects. Year-related changes in element concentrations suggest continued monitoring of this population to assess pinniped, environmental, and potentially, human health.

Use of potassium chloride for low-residue euthanasia of anesthetized California sea lions (Zalophus californianus) and northern elephant seals (Mirounga angustirostris) with life-threatening injury or disease.

To demonstrate the efficacy of potassium chloride (KCl) for low-residue euthanasia of anesthetized pinnipeds in field settings for which carcass retrieval for disposal is not feasible. Stranded, free-ranging California sea lions (CSLs; Zalophus californianus; n = 17) and northern elephant seals (NESs; Mirounga angustirostris; 6) with life-threatening injury or disease between May and August 2020. Each animal was anesthetized and then received a lethal dose of KCl solution administered by IV or intracardiac injection. The effective KCl dose; durations to cardiac arrest, respiratory arrest, and pupil dilation; and presence or absence of agonal breaths, muscle fasciculations, or skeletal movements were recorded. Mean effective dose of KCl was 207.4 mg/kg (94.3 mg/lb) for the 17 CSLs and 209.1 mg/kg (95.0 mg/lb) for 5 of 6 NESs (1 outlier NES was excluded). The range in duration from the beginning of KCl injection to cardiac arrest was 0 to 6 minutes, to pupil dilation was 0 to 5 minutes, and to respiratory arrest was 0 to 5 minutes. Muscle fasciculations, skeletal movements, and agonal breaths were observed in both species during and after KCl administration. The use of KCl provides an effective, low-residue method of euthanasia in anesthetized CSLs and NESs. Our recommended dose for these species is 250 mg KCl/kg (113.6 mg KCl/lb) delivered by intracardiac injection. Compared with euthanasia by barbiturate overdose, the use of KCl reduces the potential for secondary intoxication of scavengers and is appropriate in field scenarios in which the carcass cannot be retrieved for disposal.

Filarial infections in California sea lions vary spatially within the Gulf of California, Mexico.

At least two species of filarial worms, Dirofilaria immitis and Acanthocheilonema (Dipetalonema) odendhali, infect otariid pinnipeds, including the California sea lion (Zalophus californianus). To date, evidence of infection in sea lions has come from dead or captive animals, and little is known about filariasis in free-living populations. We sampled 45 California sea lion adults and 197 pups captured at 12 rookeries from different ecological regions within the Gulf of California and detected and quantified D. immitis and A. odendhali microfilariae in blood smears. We investigated differences in prevalence and parasite load (intensity of infection) among ecological regions. Microfilariae were detected in the blood of 35 of the 45 (77.78%) adult females and in 1 of the 197 (0.51%) pups examined. The average burden of A. odendhali per microlitre of blood was nearly twice that of D. immitis. Prevalence and intensity of infection differed significantly among regions, being highest for colonies within the northern and northcentral regions and lowest in the southern region. Dirofilaria immitis and A. odendhali infections displayed a similar spatial pattern of prevalence. Colony density inversely predicted the prevalence of microfilariae. Based on the clinical parameters typically associated with filarial infections in carnivores and physical examinations, none of the sea lions appeared to have evidence of disease. This is a first approximation to investigate the prevalence of microfilaria infections in free-ranging California sea lions and to explore their relevance to population health.

Transcriptional Profiles of California Sea Lion Peripheral NK and CD+8 T Cells Reflect Ecological Regionalization and Infection by Oncogenic Viruses.

The California sea lion is one of the few wild mammals prone to develop cancer, particularly urogenital carcinoma (UGC), whose prevalence is currently estimated at 25% of dead adult sea lions stranded along the California coastline. Genetic factors, viruses and organochlorines have been identified as factors that increase the risk of occurrence of this pathology. Given that no cases of UGC have as yet been reported for the species along its distribution in Mexican waters, the potential relevance of contaminants for the development of urogenital carcinoma is highlighted even more as blubber levels of organochlorines are more than two orders of magnitude lower in the Gulf of California and Mexican Pacific than in California. In vitro studies have shown that organochlorines can modulate anti-viral and tumor-surveillance activities of NK and cytotoxic T-cells of marine mammals, but little is known about the activity of these effectors in live, free-living sea lions. Here, we examine leukocyte transcriptional profiles of free-ranging adult California sea lions for eight genes (Eomes, Granzyme B, Perforin, Ly49, STAT1, Tbx21, GATA3, and FoxP3) selected for their key role in anti-viral and tumor-surveillance, and investigate patterns of transcription that could be indicative of differences in ecological variables and exposure to two oncogenic viruses: sea lion type one gammaherpesvirus (OtHV-1) and sea lion papillomavirus type 1 (ZcPV-1) and systemic inflammation. We observed regional differences in the expression of genes related to Th1 responses and immune modulation, and detected clear patterns of differential regulation of gene expression in sea lions infected by genital papillomavirus compared to those infected by genital gammaherpesvirus or for simultaneous infections, similar to what is known about herpesvirus and papillomavirus infections in humans. Our study is a first approach to profile the transcriptional patterns of key immune effectors of free-ranging California sea lions and their association with ecological regions and oncogenic viruses. The observed results add insight to our understanding of immune competence of marine mammals, and may help elucidate the marked difference in the number of cases of urogenital carcinoma in sea lions from US waters and other areas of their distribution.

HYPERMUCOVISCOUS KLEBSIELLA PNEUMONIAE ISOLATES FROM STRANDED AND WILD-CAUGHT MARINE MAMMALS OF THE US PACIFIC COAST: PREVALENCE, PHENOTYPE, AND GENOTYPE.

Emergent hypermucoviscous (HMV) strains of Klebsiella pneumoniae have been reported in multiple marine mammal species; however, there is limited information regarding the epidemiology and pathogenesis of this infection in these species. We determined the prevalence of HMV K. pneumoniae in wild-caught and stranded marine mammal populations on the US Pacific Coast. Samples were collected from 270 free-ranging California sea lions (CSLs; Zalophus californianus) captured at three discrete sampling sites and from 336 stranded marine mammals of various species. We recovered HMV K. pneumoniae only from CSLs, with a prevalence of 1.5% (4 of 275) in stranded animals, compared with 1.1% (3 of 270) in wild-caught animals. We assessed the phenotypic and genotypic variability of recovered HMV K. pneumoniae isolates recovered from CSLs ( n=11) and of archival HMV and non-HMV isolates from stranded marine mammals ( n=19). All but two HMV isolates were of the K2 serotype, whereas none of the non-HMV isolates belonged to this serotype. Of the HMV isolates, 96% (24 of 25) were PCR positive for the HMV-associated gene p- rmpA, whereas 92% (23 of 25) were PCR positive for p- rmpA2. Genetic fingerprinting by repetitive extragenic palindromic PCR showed four discrete clusters, demonstrating genotypic variability that loosely correlated with phenotype. Antimicrobial susceptibility testing revealed all isolates from stranded CSLs were susceptible to ceftiofur, indicating this antimicrobial agent is an appropriate choice for treatment of HMV K. pneumoniae infections in stranded CSLs. Our culture assay could reliably detect HMV K. pneumoniae from concentrations as low as 102 colony-forming units per milligram of feces. We identified the presence of HMV K. pneumoniae in both wild-caught and stranded CSLs from the US Pacific Coast and highlight the need for further studies to evaluate the potential impact of this pathogen on marine mammal health.

Flipper stroke rate and venous oxygen levels in free-ranging California sea lions.

The depletion rate of the blood oxygen store, development of hypoxemia and dive capacity are dependent on the distribution and rate of blood oxygen delivery to tissues while diving. Although blood oxygen extraction by working muscle would increase the blood oxygen depletion rate in a swimming animal, there is little information on the relationship between muscle workload and blood oxygen depletion during dives. Therefore, we examined flipper stroke rate, a proxy of muscle workload, and posterior vena cava oxygen profiles in four adult female California sea lions (Zalophus californianus) during foraging trips at sea. Flipper stroke rate analysis revealed that sea lions minimized muscle metabolism with a stroke-glide strategy when diving, and exhibited prolonged glides during the descent of deeper dives (>100 m). During the descent phase of these deep dives, 55±21% of descent was spent gliding, with the longest glides lasting over 160 s and covering a vertical distance of 340 m. Animals also consistently glided to the surface from 15 to 25 m depth during these deeper dives. Venous hemoglobin saturation (SO2 ) profiles were highly variable throughout dives, with values occasionally increasing during shallow dives. The relationship between SO2 and flipper stroke rate was weak during deeper dives, while this relationship was stronger during shallow dives. We conclude that (1) the depletion of oxygen in the posterior vena cava in deep-diving sea lions is not dependent on stroke effort, and (2) stroke-glide patterns during dives contribute to a reduction of muscle metabolic rate.

Use of Acoustic Transmitter-Equipped Remote Sedation to Aid in Tracking and Capture of Entangled California Sea Lions (Zalophus californianus).

Free-ranging California sea lions ( Zalophus californianus ) with marine debris entanglements were darted with a combination of medetomidine, butorphanol, and midazolam by using acoustic transmitter-equipped darts. Of the 15 animals sedated, 13 (87%) reentered the water and were tracked by using a unidirectional hydrophone. Sea lions that entered the water continued to surface and breathe postsedation. There were three mortalities (20%) during the course of this study due to the following: suspected drowning caused by entrapment under a dock, overdose due to inaccurate weight estimation, and trauma caused by a dart puncturing the animal's abdomen. The drug combination, new dart design, and tracking techniques allowed for successful remote sedation and capture of California sea lions in high-risk situations and improved our ability to determine the final outcome for all cases. These methods allow targeting and capture of individual animals, while minimizing disturbance to other animals.

Transformation of the genital epithelial tract occurs early in California sea lion development.

An unusually high prevalence of metastatic urogenital carcinoma has been observed in free-ranging California sea lions stranded off the coast of California in the past two decades. No cases have been reported for sea lions in the relatively unpolluted Gulf of California. We investigated occurrence of genital epithelial transformation in 60 sea lions (n=57 pups and 3 adult females) from the Gulf of California and examined whether infection by a viral pathogen previously found to be associated with urogenital carcinoma accounted for such alterations. We also explored the contribution of MHC class II gene expression on transformation. Cellular alterations, such as squamous cell atypia (ASC), atypical squamous cells of undetermined significance (ASCUS) and low-grade squamous intraepithelial lesions were observed in 42% of the pups and in 67% of the adult females. Normal genital epithelium was more common in male than female pups. ASC was five times more likely to occur in older pups. Epithelial alterations were unrelated to infection by the potentially oncogenic otarine type I gammaherpesvirus (OtHV-1), but ASCUS was more common in pups with marked and severe inflammation. Expression of MHC class II DRB loci (Zaca DRB-D) by peripheral antigen-presenting leucocytes showed a slightly ‘protective’ effect for ASC. We propose that transformation of the California sea lion genital epithelium is relatively common in young animals, increases with age and is probably the result of infection by an unidentified pathogen. Expression of a specific MHC class II gene, suggestive of presentation of specific antigenic peptides to immune effectors, appears to lower the risk of transformation. Our study provides the first evidence that epithelial transformation of the California sea lion genital tract is relatively common, even from an early age, and raises questions regarding differences in sea lion cancer-detection and -repair success between geographical regions.

Detection and characterization of diverse coccidian protozoa shed by California sea lions.

Tissue-cyst forming coccidia in the family Sarcocystidae are etiologic agents of protozoal encephalitis in marine mammals including the federally listed Southern sea otter (Enhydra lutris). California sea lions (Zalophus californianus), whose coastal habitat overlaps with sea otters, are definitive hosts for coccidian protozoa provisionally named Coccidia A, B and C. While Coccidia A and B have unknown clinical effects on aquatic wildlife hosts, Coccidia C is associated with severe protozoal disease in harbor seals (Phoca vitulina). In this study, we conducted surveillance for protozoal infection and fecal shedding in hospitalized and free-ranging California sea lions on the Pacific Coast and examined oocyst morphology and phenotypic characteristics of isolates via mouse bioassay and cell culture. Coccidia A and B were shed in similar frequency, particularly by yearlings. Oocysts shed by one free-ranging sea lion sampled at Año Nuevo State Park in California were previously unidentified in sea lions and were most similar to coccidia infecting Guadalupe fur seals (Arctocephalus townsendi) diagnosed with protozoal disease in Oregon (USA). Sporulated Coccidia A and B oocysts did not replicate in three strains of mice or in African green monkey kidney cells. However, cultivation experiments revealed that the inoculum of fecally-derived Coccidia A and B oocysts additionally contained organisms with genetic and antigenic similarity to Sarcocystis neurona; despite the absence of detectable free sporocysts in fecal samples by microscopic examination. In addition to the further characterization of Coccidia A and B in free-ranging and hospitalized sea lions, these results provide evidence of a new role for sea lions as putative mechanical vectors of S. neurona, or S. neurona-like species. Future work is needed to clarify the distribution, taxonomical status, and pathogenesis of these parasites in sea lions and other marine mammals that share their the near-shore marine environment.

Asymptomatic and chronic carriage of Leptospira interrogans serovar Pomona in California sea lions (Zalophus californianus)

Since 1970, periodic outbreaks of leptospirosis, caused by pathogenic spirochetes in the genus Leptospira, have caused morbidity and mortality of California sea lions (Zalophus californianus) along the Pacific coast of North America. Yearly seasonal epizootics of varying magnitude occur between the months of July and December, with major epizootics occurring every 3-5 years. Genetic and serological data suggest that Leptospira interrogans serovar Pomona is the infecting serovar and is enzootic in the California sea lion population, although the mechanism of persistence is unknown. We report asymptomatic carriage of Leptospira in 39% (33/85) of wild, free-ranging sea lions sampled during the epizootic season, and asymptomatic seroconversion with chronic asymptomatic carriage in a rehabilitated sea lion. This is the first report of asymptomatic carriage in wild, free-ranging California sea lions and the first example of seroconversion and asymptomatic chronic carriage in a sea lion. Detection of asymptomatic chronic carriage of Leptospira in California sea lions, a species known to suffer significant disease and mortality from the same Leptospira strain, goes against widely-held notions regarding leptospirosis in accidental versus maintenance host species. Further, chronic carriage could provide a mechanism for persistent circulation of Leptospira in the California sea lion population, particularly if these animals shed infectious leptospires for months to years.

RISK FACTORS ASSOCIATED WITH PERIANESTHETIC MORTALITY OF STRANDED FREE-RANGING CALIFORNIA SEA LIONS (ZALOPHUS CALIFORNIANUS) UNDERGOING REHABILITATION

The objective of this study was to identify risk factors associated with perianesthetic mortality of stranded free-ranging California sea lions (Zalophus californianus) undergoing rehabilitation. Hospital records of California sea lions that underwent heavy sedation or general anesthesia from 2004 through 2008 were reviewed, including records from 419 anesthetic events. Procedures that resulted in death during or in the subsequent 72 hr of anesthesia were classified as cases (n = 15). Procedures in which the animal survived were classified as controls (n = 334). Procedures that resulted in euthanasia (n = 70) were removed from subsequent analysis. The following risk factors were reviewed: gender, age class, health status, duration of anesthetic period, atropine premedication, induction protocols, maintenance protocols, and history of prior anesthesia. The prevalence of fatalities during anesthesia was 3.4% (n = 12) over the 5-yr period. With the inclusion of animals that died within 72 hr after anesthesia, the total mortality prevalence rose to 4.3% (n = 15). The most common time of death was during anesthetic maintenance. Health status was the single best predictor of anesthetic outcome, and sea lions premedicated with atropine had increased odds of anesthetic-related death.

IMMUNOMODULATORY EFFECTS UPON IN VITRO EXPOSURE OF CALIFORNIA SEA LION AND SOUTHERN SEA OTTER PERIPHERAL BLOOD LEUKOCYTES TO DOMOIC ACID

During red tide bloom events, the marine diatom Pseudo-nitzschia produces the toxin domoic acid (DA), which has been associated with stranding and mortality events involving California sea lions (Zalophus californianus) and southern sea otters (Enhydra lutris). In addition to these well-documented DA-induced neurotoxic events, there is increasing concern that DA may exert chronic effects, such as immunomodulation, which may potentially increase an individual's susceptibility to a number of opportunistic infections following nonlethal exposure. We investigated the effects of DA on innate (phagocytosis and respiratory burst) and adaptive (mitogen-induced lymphocyte proliferation) immune functions with the use of peripheral blood leukocytes collected from healthy California sea lions and southern sea otters upon in vitro exposure to 0 (unexposed control), 0.0001, 0.001, 0.01, 0.1, 1.0, 10, and 100 microM DA. Domoic acid did not significantly modulate phagocytosis or respiratory burst in either species. For California sea lions, DA significantly increased ConA-induced T-lymphocyte proliferation upon exposure to DA concentrations ranging from 0.0001 to 10 microM, resulting in a nonlinear dose-response curve. There was no effect on lymphocyte proliferation at the highest concentration of DA tested. No effects on lymphocyte proliferation were observed in southern sea otters. Importantly, the in vitro DA concentrations affecting T-cell proliferation were within or below the range of DA in serum measured in free-ranging California sea lions following natural exposure, suggesting a risk for immunomodulation in free-ranging animals. Understanding the risk for immunomodulation upon DA exposure will contribute in the health assessment and management of California sea lions and southern sea otters, as well as guide veterinarians and wildlife rehabilitators in caring for and treating afflicted animals.

Tumor Morphology and Immunohistochemical Expression of Estrogen Receptor, Progesterone Receptor, p53, and Ki67 in Urogenital Carcinomas of California Sea Lions (Zalophus californianus)

Metastatic carcinoma of urogenital origin is a common cause of mortality in free-ranging California sea lions (Zalophus californianus). The etiology of this cancer is likely multifactorial, with viral infection, genetic factors, and exposure to environmental organochlorine contaminants possible contributing factors. In this study, expression of estrogen receptor alpha (ER alpha), progesterone receptor (PR), p53, and Ki67 were evaluated by immunohistochemistry in 12 sea lions with metastatic carcinoma, genital epithelial dysplasia, and intraepithelial neoplasia; 4 with genital epithelial dysplasia and intraepithelial neoplasia without metastases; and 6 control animals. Dysplastic and neoplastic lesions were identified in multiple areas of the cervix, vagina, penis, prepuce, and urethra in affected animals, suggesting multicentric development. Lesions were graded according to degree of epithelial dysplasia and infiltration and lesions of different grades were evaluated separately. Estrogen receptor expression was lower in intraepithelial lesions compared with normal genital epithelium, and expression in metastatic lesions was completely absent. There was progesterone receptor expression in neoplastic cells in intraepithelial lesions of all grades and in metastases, with no significant difference between lesion grades or between control and affected epithelium. Ki67 index and p53 expression increased with lesion grade and were higher in lesions than normal epithelium. Metastatic tumors exhibited highly variable morphology; however, proliferation index, ER alpha, PR, and p53 expression were similar in tumors with different patterns of growth. These results suggest that endogenous hormones, environmental contaminants that interact with steroid hormone receptors, and alterations in p53 may play a role in urogenital carcinogenesis in California sea lions.

Seroepidemiology of parapoxvirus infections in captive and free-ranging California sea lions Zalophus californianus

Cutaneous nodular lesions caused by parapoxvirus infections are commonly observed in stranded pinnipeds following their arrival at rehabilitation facilities. An indirect enzyme-linked immunosorbent assay (ELISA) was developed and validated to determine exposure to parapoxviruses in California sea lions Zalophus californianus in captivity and in the wild. The diagnostic performance of this assay was evaluated using receiver-operating characteristic analysis. At a selected cut-off value, the calculated sensitivity was 100% (95% CI = 86 to 100%) and the specificity was 100% (95% CI = 87 to 100%). Analysis of sera collected from 26 affected sea lions during various stages of the disease revealed anti-parapoxvirus antibodies in all affected sea lions prior to the development of cutaneous pox lesions. This indicated that previous exposure to a parapoxvirus does not confer protection against clinical disease. In at least 7 cases, exposure to the virus occurred during hospitalization. Analysis of paired sera from 74 unaffected sea lions indicated subclinical infections in at least 3 animals. Finally, the prevalence of anti-parapoxviral antibodies in 761 free-ranging California sea lions captured and tested was 91% (95% CI = 89 to 93%). This indicated that infection with a parapoxvirus is a common occurrence in the wild and that the release of captive sea lions infected with parapoxvirus into the wild should not increase the risk of a parapoxvirus outbreak in free-ranging sea lions.

Diagnosis and seroprevalence of leptospirosis in California sea lions from coastal California.

The sensitivity and specificity of the microscopic agglutination test (MAT) as a method for detection of exposure to Leptospira spp. in California sea lions (Zalophus californianus) were determined. Sera came from individuals that demonstrated clinical signs of renal disease, had lesions suggestive of leptospirosis at necropsy, and had visible leptospires in silver stained kidney sections as positive controls. Sera from unexposed captive individuals were used as negative controls. The test was 100% sensitive at 1:3,200 for confirming renal infection and 100% specific at negative < 1:100 for detection of Leptospira interrogans scrovar pomona antibodies by MAT in California sea lions. Leptospira interrogans serovar pomona was used as a screening serovar because it has been isolated previously from the kidneys and placentas of California sea lions, and there appears to be cross-reactivity between serovar pomona and other serovars. Sera from 225 free-ranging California sea lions presented to one of three participating California (USA) coastal marine mammal rehabilitation centers in 1996 were then evaluated for antibodies to serovar pomona using the MAT. The overall seroprevalence was 38.2% (86/225), although the prevalence varied among locations from 100% (38/38) in animals at the Marine Mammal Care Center (Fort MacArthur, California, USA) to 0% (0/14) at SeaWorld California (San Diego, California). At The Marine Mammal Center (Sausalito, California) [prevalence 27.8% (48/173)], the majority of seropositive animals were subadults and adults, and males were 4.7 times more likely to be seropositive to serovar pomona than females. When combining results from all three centers, subadult and adult animals were more likely to be seropositive than pups and juvenile sea lions, and the highest proportion of seropositive animals presented during the autumn months. Serum elevations of blood urea nitrogen, creatinine, phosphorus, and/or calcium were associated with seropositivity to serovar pomona. We found no association between potassium or sodium levels and seropositivity.

Coccidioidomycosis in free-living California sea lions (Zalophus californianus) in central California.

Coccidioidomycosis is described in seven California sea lions (Zalophus californianus) admitted to The Marine Mammal Center, Sausalito, California (USA), between January 1986 and December 1994. Diagnoses were confirmed by histology in all seven cases, culture in three cases, and serology in one case. These are believed to be the first published cases of coccidioidomycosis in free-ranging California sea lions.