Evidence for a genetic basis of urogenital carcinoma in the wild California sea lion

Although neoplasia is a major cause of mortality in humans and domestic animals, it has rarely been described in wildlife species. One of the few examples is a highly prevalent urogenital carcinoma in California sea lions (CSLs). Although the aetiology of this carcinoma is clearly multifactorial, inbreeding depression, as estimated using levels of microsatellite multilocus heterozygosity, is identified as predictive for this neoplasia. On further analysis, this relationship appears to be largely driven by one marker, suggesting that a single locus might be associated with the occurrence of this disease in CSLs. In a case–control study, carcinoma was significantly associated with homozygosity at the Pv11 microsatellite locus. Pv11 was mapped to intron 9 of the heparanase 2 gene (HPSE2) locus, a very large gene encoding heparanase 2, which in humans is associated with multiple carcinomas. Correspondingly, immunohistochemical labelling in tissues was present in carcinoma cases within a single homozygous Pv11 genotype. To our knowledge, this is the first report of an individual locus being associated with cancer in any wildlife species. This adds emphasis to the study of HPSE2 in other species, including humans and will guide future studies on this sentinel species that shares much of its diet and environment with humans     

Common cancer in a wild animal: the California sea lion (Zalophus californianus) as an emerging model for carcinogenesis

Naturally occurring cancers in non-laboratory species have great potential in helping to decipher the often complex causes of neoplasia. Wild animal models could add substantially to our understanding of carcinogenesis, particularly of genetic and environmental interactions, but they are currently underutilized. Studying neoplasia in wild animals is difficult and especially challenging in marine mammals owing to their inaccessibility, lack of exposure history, and ethical, logistical and legal limits on experimentation. Despite this, California sea lions (Zalophus californianus) offer an opportunity to investigate risk factors for neoplasia development that have implications for terrestrial mammals and humans who share much of their environment and diet. A relatively accessible California sea lion population on the west coast of the USA has a high prevalence of urogenital carcinoma and is regularly sampled during veterinary care in wildlife rehabilitation centres. Collaborative studies have revealed that genotype, persistent organic pollutants and a herpesvirus are all associated with this cancer. This paper reviews research to date on the epidemiology and pathogenesis of urogenital carcinoma in this species, and presents the California sea lion as an important and currently underexploited wild animal model of carcinogenesis.     

A Systematic Review of Changes in Marine Mammal Health in North America, 1972-2012: The Need for a Novel Integrated Approach

Marine mammals are often cited as “sentinels of ocean health” yet accessible, synthesized data on their health changes that could effectively warn of ocean health changes are rare. The objectives of this study were to 1) perform a systematic review of published cases of marine mammal disease to determine spatial and temporal trends in disease from 1972–2012, including changes in regions and taxa affected and specific causes; and 2) compare numbers of published cases of neoplasia with known, hospital-based neoplasia records to explore the causes of discrepancy between numbers of published cases and true disease trends. Peer-reviewed literature was compiled, and data were collected from The Marine Mammal Center database in Sausalito, California for comparison of numbers of neoplasia cases. Toxicoses from harmful algal blooms appear to be increasing. Viral epidemics are most common along the Atlantic U.S. coastline, while bacterial epidemics, especially leptospirosis, are most common along the Pacific coast. Certain protozoal and fungal zoonoses appear to be emerging, such as Toxoplasma gondii in southern sea otters in California, and Cryptococcus gattii in cetaceans in the Pacific Northwest. Disease reports were most common from California where pinniped populations are large, but increased effort also occurs. Anthropogenic trauma remains a large threat to marine mammal health, through direct mortality and indirect chronic disease. Neoplasia cases were under-reported from 2003–2012 when compared to true number of cases, and over-reported in several years due to case duplication. Peer-reviewed literature greatly underestimates the true magnitude of disease in marine mammals as it focuses on novel findings, fails to reflect etiology of multifactorial diseases, rarely reports prevalence rather than simple numbers of cases, and is typically presented years after a disease first occurs. Thus literature cannot guide management actions adequately, nor inform indices of ocean health. A real-time, nationally centralized system for reporting marine mammal disease data is needed to be able to understand how marine mammal diseases are changing with ecosystem changes, and before these animals can truly be considered ‘sentinels of ocean health’.     

Antemortem diagnosis of a ventricular septal defect in a California sea lion Zalophus californianus

A yearling California sea lion Zalophus californianus stranded in poor body condition, and on physical examination a heart murmur was audible bilaterally. The sea lion was diagnosed with a left-to-right shunting membranous ventricular septal defect (VSD) using B-mode, color-flow Doppler and continuous-wave Doppler echocardiography. A left-to-right intracardiac shunting lesion was confirmed during cardiac angiographic computed tomography. The VSD defect was verified during the necropsy examination. On histologic examination concurrent mild multifocal myocarditis with focal mild ventricular free-wall myocardial necrosis were identified. A specific cause for the myocarditis and myocardial necrosis was not found, and association with the VSD and resultant myocardial dysfunction was presumed. This is the first report of the antemortem diagnosis of a VSD in a marine mammal and the first report of a VSD in a California sea lion.     

Evidence of Leptospira interrogans infection in California sea lion pups from the Gulf of California

Forty-two urine and 96 blood and serum samples were obtained from California sea lion (Zalophus californianus) pups from the Gulf of California during the 2000 reproductive season. Antibody prevalence to 13 serovars of Leptospira interrogans was determined by microagglutination tests (MAT); presence of pathogenic leptospires was detected by polymerase chain reaction (PCR). Samples with antibody titers > or = 1:25 or 115 bp fragments on ethidium bromidestained 1.5% agarose gels were considered positive. Antibody prevalence was 54% overall with highest prevalence against serovar cynopteri (50% of all positive reactions). Highest antibody titers (1:50) were detected against serovars cynopteri and pomona. Polymerase chain reaction products were observed in two of 42 urine samples, six of 96 blood samples, and one of 96 serum samples. Presence of PCR products in blood and serum was demonstrated in pups that were seronegative. Kruskall-Wallis tests and corresponding post hoc Tukey tests (alpha = 0.05) showed that prevalence of leptospirosis was significantly different among all rookeries. The high seroprevalence (54%), low antibody titers (maximum 1:50), absence of pups showing clinical signs indicative of the disease, and lack of recent reports of increased mortality of sea lions in the Gulf of California are suggestive of the presence of enzootic host-adapted serovars. Crowding in rookeries as well as the presence of bats and rodents on some of the islands may explain infection by L. interrogans (sensu lato) and some of the differences in seroprevalence among reproductive rookeries.     

Evaluation of an indirect fluorescent antibody test (IFAT) for demonstration of antibodies to Toxoplasma gondii in the sea otter (Enhydra lutris)

An indirect fluorescent antibody test (IFAT) for detection of Toxoplasma gondii infection was validated using serum from 77 necropsied southern sea otters (Enhydra lutris nereis) whose T. gondii infection status was determined through immunohistochemistry and parasite isolation in cell culture. Twenty-eight otters (36%) were positive for T. gondii by immunohistochemistry or parasite isolation or both, whereas 49 (64%) were negative by both tests. At a cutoff of 1:320, combined values for IFAT sensitivity and specificity were maximized at 96.4 and 67.3%, respectively. The area under the receiver-operating characteristic curve for the IFAT was 0.84. A titer of 1:320 was used as cutoff when screening serum collected from live-sampled sea otters from California (n = 80), Washington (n = 21), and Alaska (n = 65) for T. gondii infection. Thirty-six percent (29 out of 80) of California sea otters (E. lutris nereis) and 38% (8 out of 21) of Washington sea otters (E. lutris kenyoni) were seropositive for T. gondii, compared with 0% (0 out of 65) of Alaskan sea otters (E. lutris kenyoni).     

Isolation and characterization of two parasitic protozoa from a Pacific harbor seal (Phoca vitulina richardsi) with meningoencephalomyelitis

Two species of protozoans were isolated from a harbor seal with fatal meninogoencephalitis. Serologic reactivity was detected to both Sarcocystis neurona and Toxoplasma gondii. Parasites associated with brain inflammation and necrosis reacted only with immunohistochemical stains utilizing polyclonal antisera raised against Sarcocystis neurona. However, 2 distinct parasites were observed in cell cultures derived from the seal's brain tissue. These parasites were separated by mouse passage and limiting dilution. Purified zoites from 1 isolate (HS1) reacted strongly with polyclonal antiserum to S. neurona and with the harbor seal's own serum (1:2,560 for each) on indirect immunofluorescent antibody tests (IFAT), but weakly to antisera to T. gondii and Neospora caninum (1:40). Zoites from the second isolate (HS2) reacted positively with T. gondii polyclonal antiserum (1:81,920) and with the harbor seal's own serum (1:640), but weakly to S. neurona and N. caninum antisera (1:80 or less). Amplification and sequence analysis of protozoal DNA encoding portions of the 18s ribosomal RNA (18s rDNA) and the adjacent first internal transcribed spacer (ITSI) were performed for both isolates, and resulting sequences were compared to those from similar protozoans. Based on molecular characterization, parasite morphology, serologic reactivity, histology, and immunohistochemistry, HS1 was indistinguishable from S. neurona, and HS2 was indistinguishable from T. gondii.     

Use of medetomidine-zolazepam-tiletamine with and without atipamezole reversal to immobilize captive California sea lions

From June 1998 to August 1999, 39 California sea lions (Zalophus californianus) were immobilized at a rehabilitation center in northern California (USA) using medetomidine plus zolazepam and tiletamine (MZT), alone and in combination with isoflurane, with atipamezole reversal. Animals were given 70 microg/kg medetomidine with 1 mg/kg of a 1:1 solution of tiletamine and zolazepam intramuscularly. Mean (+/-SD) time to maximal effect was 5+/-3 min. At the end of the procedure, animals were given 200 microg/kg atipamezole intramuscularly. Immobilization and recovery times were, respectively, 28+/-18 and 9+/-7 min for 15 animals maintained with MZT alone and 56+/-47 and 9+/-6 min for 18 animals intubated and maintained with isoflurane. One mortality occurred during anesthesia. Other disadvantages of the MZT combination included some prolonged ataxia, weakness and disorientation during recovery. However, the use of MZT resulted in faster induction and a more reliable plane of anesthesia that was reversible with atipamezole and safer than other previously used intramuscular agents. Physiological parameters including heart rate, respiratory rate, temperature, pulse oximeter saturation, and end-tidal carbon dioxide were monitored.