Aggressive Cancer in Sea Lions Linked to Ocean Pollution and Herpesvirus Precursor, Implications for Human Health

January 11, 2021 | California sea lions (Zalophus californianus) are experiencing high rates of urogenital carcinoma (UGC) cancer incidence from the combined effect of toxic “legacy” pesticides like DDT and the viral infection Otarine herpesvirus-1 (OtHV1), according to a study in Frontiers in Marine Science. Previous research documents the role herpesvirus infection, genotype, and organochlorine pesticides play in sea lion cancer development. However, synergism (collaboration) between a viral infection and toxic chemical exposure increases cancer development odds. Pollution of the oceans with toxic chemicals lacks adequate regulation, is widespread and only getting worse. More than 80 percent of ocean pollution comes from land-based, anthropological activities. A recent study, published in Annals of Public Health, finds toxic chemicals from pesticides, heavy metals, plastics, and other sources readily contaminate the ocean, especially near coastal regions where chemical inputs occur in higher concentrations. Scientists for this study assess cancer incidence among 394 California sea lions for 20 years. Using a stepwise regression model, scientists find herpesvirus condition, exposure to contaminants, and blubber depth aid in UGC cancer development, but not the genotype. The risk of developing UGC is nearly 44 times higher in sea lions with herpesvirus infections. Furthermore, UGC risk increases 1.48-fold per every unit of contaminant concentration within blubber. [Gulland, Frances et al. Persistent Contaminants and Herpesvirus OtHV1 Are Positively Associated with Cancer in Wild California Sea Lions (Zalophus californianus). Frontiers in Marine Science. December 2020.]