Pathology and Etiology of Marine Mammals Causing Sudden Death in Republic of Korea

Abstract

In Korea, there are wide range of marine mammals including spotted seals, Northern fur Seals, common dolphins and finless porpoises. Northern fur seals are usually found by one or two off the coast of Gyeongsangbuk-do, and spotted seals around Baengnyeong Island, the West Coast, the Southern Ocean in East and East Sea Coast area. There are also minke whales, Pacific white-sided dolphins, common dolphins, and Indo-Pacific bottlenose dolphins in the coast of Korea. Recently, the reports on marine mammal diseases increase worldwide. Although there are many marine mammals in Republic of Korea, a few study on the marine mammal diseases to date, and thus we started to research on bacterial diseases of marine mammals. First of all, bacterial examination of the tissues of a male finless porpoise, Neophocaena asiaeorientalis, found dead in February 2010 in Tongyeong, Republic of Korea, was performed, and Dietzia cinnamea and Clostridium tertium were isolated from lung and intestine, respectively. C. tertium is a non-toxin producing clostridia, but damages gastrointestinal mucosa by direct colonization, and causes abscessation, osteomyelitis, and death in a dolphin. However, we could not determine whether these organisms resulted in any clinical symptoms of the finless porpoise. In the winter of 2012, an adult female Steller sea lion was found dead at Biyang-do, a small island near Jeju-do in Republic of Korea. As a result of bacterial examination, Streptococcus phocae and Streptococcus halichoeri were isolated, which were known as pathogenic bacteria of marine mammals. However, we could not prove if their infection contributed to the death of the Steller sea lion. A total of 44 long-beaked common dolphins, Delphinus capensis, 21 females and 23 males, were taken in the South and East Seas coast of Republic of Korea. They were bycaught in sotw nets on anchors from February 2012 to August 2013. Twenty-one spcies of bacteria were cultured from tissue samples of long-beaked common dolphins. Among the isolates, several bacteria are known as bacterial pathogen to marine mammals and humans. Histopathological examination could not reveal pathogenicity of the isolates on the death of dolphins. As a result of analysis of antimicrobial resistance in the bacteria isolated from marine mammals, Streptococcus spp. and Staphylococcus spp. were sensitive to all tested antibiotics. Fifty-four percent were resistant to at least one antibiotic, while 17% were resistant to multiple antibiotics.

Key words: antimicrobial resistance, bacteria, Delphinus capensis, Eumetopias jubatus, finless porpoise, long-beaked common dolphin, marine mammals, Neophocaena asiaeorientalis, Steller Sea Lion, Republic of Korea