Mortality trends of stranded marine mammals on Cape Cod and southeastern Massachusetts, USA, 2000 to 2006.

To understand the cause of death of 405 marine mammals stranded on Cape Cod and southeastern Massachusetts between 2000 and 2006, a system for coding final diagnosis was developed and categorized as (1) disease, (2) human interaction, (3) mass-stranded with no significant findings, (4) single-stranded with no significant findings, (5) rock and/or sand ingestion, (6) predatory attack, (7) failure to thrive or dependent calf or pup, or (8) other. The cause of death for 91 animals could not be determined. For the 314 animals that could be assigned a cause of death, gross and histological pathology results and ancillary testing indicated that disease was the leading cause of mortality in the region, affecting 116/314 (37%) of cases. Human interaction, including harassment, entanglement, and vessel collision, fatally affected 31/314 (10%) of all animals. Human interaction accounted for 13/29 (45%) of all determined gray seal Halichoerus grypus mortalities. Mass strandings were most likely to occur in northeastern Cape Cod Bay; 97/106 (92%) of mass stranded animals necropsied presented with no significant pathological findings. Mass strandings were the leading cause of death in 3 of the 4 small cetacean species: 46/67 (69%) of Atlantic white-sided dolphin Lagenorhynchus acutus, 15/21 (71%) of long-finned pilot whale Globicephala melas, and 33/54 (61%) of short-beaked common dolphin Delphinus delphis. These baseline data are critical for understanding marine mammal population health and mortality trends, which in turn have significant conservation and management implications. They not only afford a better retrospective analysis of strandings, but ultimately have application for improving current and future response to live animal stranding.

Victims or vectors: a survey of marine vertebrate zoonoses from coastal waters of the Northwest Atlantic.

Surveillance of zoonotic pathogens in marine birds and mammals in the Northwest Atlantic revealed a diversity of zoonotic agents. We found amplicons to sequences from Brucella spp., Leptospira spp., Giardia spp. and Cryptosporidium spp. in both marine mammals and birds. Avian influenza was detected in a harp seal and a herring gull. Routine aerobic and anaerobic culture showed a broad range of bacteria resistant to multiple antibiotics. Of 1460 isolates, 797 were tested for resistance, and 468 were resistant to one or more anti-microbials. 73% (341/468) were resistant to 1-4 drugs and 27% (128/468) resistant to 5-13 drugs. The high prevalence of resistance suggests that many of these isolates could have been acquired from medical and agricultural sources and inter-microbial gene transfer. Combining birds and mammals, 45% (63/141) of stranded and 8% (2/26) of by-caught animals in this study exhibited histopathological and/or gross pathological findings associated with the presence of these pathogens. Our findings indicate that marine mammals and birds in the Northwest Atlantic are reservoirs for potentially zoonotic pathogens, which they may transmit to beachgoers, fishermen and wildlife health personnel. Conversely, zoonotic pathogens found in marine vertebrates may have been acquired via contamination of coastal waters by sewage, run-off and agricultural and medical waste. In either case these animals are not limited by political boundaries and are therefore important indicators of regional and global ocean health.