INVESTIGATING DISEASES IN AUSTRALIAN FUR-SEALS

Diseases are increasingly recognised as an important factor in wildlife conservation and management.  Dr Michael Lynch, Veterinarian, Melbourne Zoo is leading a research project to investigate the disease status of Australian Fur-seals (Arctocephalus pusillus doriferus): the presence and prevalence of diseases, and how these diseases relate to ecological processes. The project is also investigating two specific health issues.

DISEASE STATUS

Aims

• Document the presence and prevalence of antibodies to significant bacterial and viral pathogens.
• Investigate the epidemiology of detected diseases and assess their significance to the health of Australian Fur-seals, live-stock and humans.
• Conduct disease surveillance by post-mortem examination of dead seals found along the Victorian coastline
• Establish a bank of sera and tissues collected from Australian Fur-seals to assist the investigation of disease outbreaks in this, or other, species.
• Build and maintain a collaborative network of investigators to increase Victoria's capacity to investigate emerging wildlife-related diseases.

Methods

Blood samples are collected annually from pup, juvenile and adult seals at Kanowna Island near Wilson's Promotory, Victoria. These samples are screened for significant diseases. An information network has also been set up to procure dead juvenile and adult seals from the Victorian coastline for full post mortem examinations and tissue storage.

Results

At Kanowna Island, a high proportion of adult seals had antibodies to Brucella sp. No animals had antibodies to Mycobacteria, Morbilliviruses, Influenza A viruses, Leptospira interogens serovars or Toxoplasma gondii.  Post mortem examinations have revealed a wide variety of causes of death in Fur-seals, including head trauma, salmonellosis and internal abscessation caused by sting ray barbs.

HEALTH INVESTIGATIONS

1) ABORTION

Aim: Investigate whether infectious diseases are causing the relatively high incidence of abortions in Australian Fur-seals (10-40% in the second half of gestation).

Methods: Brucella species are well recognised causes of abortion in terrestrial mammals. The significance of Brucella infection in seals is being established by post mortem examination of aborted foeti and dead neonates found during field activities.

Results: Aborted seal pups have been collected from all study sites. Initial analyses have not identified infectious disease as the cause of reproductive failure. 

2) ALOPECIA

Aim: Establish the prevalence, cause and significance of alopecia (partial hair loss) syndrome observed in Australian Fur-seals.

Methods: Alopecia has been noticed in seals on Lady Julia Percy Island, south-west of Port Fairy, Victoria, within the last 5 years. It appears to be increasing in prevalence, and to be more common on this island than the other main Victorian breeding colonies. The prevalence of the disease is estimated by repeatedly counting the proportion of affected animals over a number of days. The causes of the syndrome are being investigated using a case-control study which compares the potential risk factors for the disease in affected animals (cases) and non-affected animals (controls) by analysing hormones, trace elements, genetics, diet and body condition. A thermal camera used to asses the impact of the disease on heat loss.

Results: The prevalence of seals with alopecia on Lady Julia Percy Island varies seasonally: up to 25% of juveniles are affected in spring and summer. The condition also appears to largely affect female seals. The condition is far more common on Lady Julia Percy Island than Kanowna Island. Samples have been collected to establish causality but final analysis is not yet complete. Thermographic images have also been collected.

PROJECT PARTNERS

This is a collaborative research project with Deakin University, Phillip Island Nature Parks, the University of Melbourne, CSIRO Livestock Health and the Melbourne Veterinary Specialist Centre.  The work has been generously supported by the Department of Primary Industries, the Department of Agriculture, Fisheries & Forestry, the Royal Prince Alfred Hospital and the Winifred Violet Scott Trust.

FOR MORE INFORMATION

- on this research project - click here to email Dr Michael Lynch (Principal Investigator).

- on The Action Plan for Australian Seals - click here.

- on Fur-seals at Melbourne Zoo - click here.