The Australian fur seal is still recovering from the past exploitation of the commercial sealing era (18th and 19th centuries) and its numbers are presently <40% of the estimated pre-sealing levels.  In addition, it has one of the most restricted breeding distributions of any otariid (fur seal and sea lion) species, with colonies on only 10 islands in Bass Strait. A critical knowledge gap identified in Environment Australia’s Action Plan to guide the conservation of Australian seals (Shaughnessy 1999) was the disease status of these animals. Investigations are needed that establish what diseases are present in Australian seals and assess their significance.

Diseases in wildlife can impact on individuals and populations. Impacts may be sudden and catastrophic such as occurs following introduction of pathogens into naïve populations, or insidious and difficult to detect. A disease may also be significant because it is capable of infecting a range of species such as other wild animals, domestic animals or humans. Through systematic collection and analysis of blood and tissue samples, this project aims to detect, quantify and document the presence and prevalence of diseases that may impact on the conservation status of Australian fur seals. It will also enable a serum and tissue bank to be established which would be invaluable in the case of future infectious disease outbreaks in seals.

Melbourne Zoo’s veterinary department has secured funds both from within the zoo and external sources to investigate the disease status of free-ranging Australian fur seals. The project is been lead by Dr Michael Lynch and commenced in June 2007 Since then fieldwork has been conducted on Victoria’s four main Australian fur seal breeding colonies, Lady Julia Percy Island, Seal Rocks, Kanowna Island and The Skerries. In order to conduct an initial survey of diseases present in the population approximately 100 animals were captured at Kanowna Island, which is located south of Wilson’s Promontory. Blood samples from these animals have been analysed for antibodies that would indicate exposure to diseases reported to be of significance to seal populations elsewhere. Preliminary results indicate the seals have a high prevalence of antibodies to Brucella sp, a bacterial group that is an important as a cause of disease in livestock. The significance of infection in seals is unknown and is the focus of ongoing investigations.

This project is also investigating two potential health issues that have been observed in Australian Fur Seals. The first is directed at the relatively high incidence of gestational failure (abortion) seen in Australian Fur Seals in the second half of their gestation. The investigation aims to establish whether this is being caused by infectious disease within seal populations. A total of 14 freshly aborted foetuses were collected between July and October 2007 but initial analysis of these samples did not identify infectious disease as the cause of reproductive failure. However, the finding that a high proportion of adult seals have antibodies to Brucella sp. has prompted further investigation of these samples specifically looking for this bacterium. Results are pending on this analysis.

The second health investigation is examining a syndrome of partial hair loss (alopecia) that was first noticed in animals on Lady Julia Percy Island, located south of Port Fairy, within the last 5 years. It appears to be increasing in its prevalence. This syndrome would be expected to be significant in the individuals if effects as hair loss is likely to significantly compromise thermoregulatory capabilities and, hence, energy conservation. To date 18 animals (7 cases and 11 unaffected control animals) have been anaesthetised and sampled to try and establish the cause of this condition. It appears that infectious and parasitic pathogens are not involved in the alopecia syndrome. It appears likely that the nutritional status of animals is influencing whether they show this syndrome and investigations are continuing to further elucidate this process.

Michael Lynch
February 26, 2008