Pádraig J. Duignan
Ecosystem and Public Health, University of Calgary Veterinary Medicine, Calgary, Alberta T2N 4Z6, Canada
Abstract
The objective of this presentation is to review and discuss recent advances in the field of marine mammal health in the Oceania region, largely focusing on the territorial waters of New Zealand and Australia. By "recent" I mean investigations conducted since the turn of the millennium. I intend to focus on disease/health issues that could be regarded as emerging diseases with potentially significant consequences for population dynamics and conservation (e.g. morbillivirus infection, brucellosis, Klebsiella pneumoniae), zoonosis or anthropozoonosis (K. pneumoniae, tuberculosis), or simply weird and wonderful entities that currently lack definitive answers but could be of significance for local populations (eg. fulminating ulcerative dermatitis in dolphins, alopecia in fur seals).
Since the late 1980's morbilliviruses have been implicated in several mass mortality events involving pinnipeds and cetaceans in the northern hemisphere. However, reports of the presence of a similar virus in the South Pacific and Indian Oceans, either based on serology or pathology, are rare and sporadic.1,2 The first confirmation of morbillivirus mortality came from an offshore bottlenose dolphin (Tursiops truncatus) found stranded on Stradbroke Is. off the Queensland coast in October 2009.3 It was soon followed by a second confirmed case from Fraser Is. in March 2010.4 A previous study had reported that a sero-positive individual of this species had stranded in Tasmania in 1997.2 Retrospective serology on a limited sample size of stranded, entangled, and captive cetaceans in Queensland suggested that the virus may have been present in Australian waters at least since the mid 1980's and with a level of seroprevalence in melon headed whales (Peponocephala electra) equivalent to that seen in pilot whales (Globicephala melas) in New Zealand, the North Atlantic and Mediterranean where infection is thought to be endemic.2,4,5,6 The spring of 2009 also saw the first clinical cases of morbillivirus-associated mortality in T. aduncus from the Swan River near Perth. Two dolphins that died from systemic aspergillosis were later found to have morbillivirus detectable in tissues by PCR and immunohistochemistry.7 Much still remains to be learned about the epidemiology of morbilliviruses in marine mammals of this region.
The most significant pinniped disease to emerge over the review period were consecutive epidemics of Klebsiella pneumoniae septicaemia in New Zealand sea lions (Phocarctos hookeri) pups in the breeding seasons between 2001–02 and 2002–03.8 In each of these seasons, the epidemics increased the mean mortality rate at the main Auckland Island colonies three fold and had a measurable impact on recruitment for this endangered species.9 Across the water, along the Bass Straits between Victoria and Tasmania, another threatened otariid, the Australian fur seal (Arctocephalus pusillus doriferus) was the subject of an intensive multi-year health surveillance program.10 High abortion and still birth rates (37%) were reported at some breeding sites and serology detected antibodies against Brucella sp. in 57% of breeding age females.11,12 However, attempts to isolate the causative organism in culture or by PCR were unsuccessful. The study also investigated another unusual clinical presentation first noted in 1989 in Australian fur seals. The condition is characterized by symmetrical alopecia mainly affecting juvenile females that occurs seasonally at the largest breeding colony in NW Bass Strait. Although the epidemiology has now been described, the etiology remains obscure.13 Continuing with the theme of unresolved skin disease, a particularly severe fulminating pustular and ulcerative dermatitis has been observed at least in two separate outbreaks affecting in-shore Tursiops sp. The first occurred in the Gippsland lakes of eastern Victoria in Oct–Nov 2009 while the second occurred in the Swan River, WA, Oct–Nov 2009.7 Adult dolphins were affected and pathology was identical in both events. Although the investigations into etiology are not fully resolved, there are intriguing associations with water quality at both sites.
Literature Cited
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13. Lynch M, Kirkwood R, Mitchell A, Duignan P, Arnould JPY. 2011. Prevalence and significance of an alopecia syndrome in Australian fur seals (Arctocephalus pusillus doriferus). J. Mammalogy 9: 342–351.