Wildlife Disease Risk Analysis Working Group Report

Transcription

1 Wildlife Disease Risk Analysis Working Group Report Disease risks associated with the translocation of Tasmanian Devils to Maria Island Participants: Richard Jakob-Hoff (facilitator); Hans van Weerd; Sonja Luz, Judy Clarke, Eric Miller, Matt West, Bishan Singh Bonal PROBLEM DESCRIPTION (provided by Judy Clarke) Context and justification: Tasmanian devil populations have been severely impacted by DFTD (Devil Facial Tumour Disease) and one of the options to protect the species is to establish disease free meta-populations in a number of locations. Disease free populations have to date been established in a combination of captive institutions and free range enclosures (exclosures) in Tasmania and mainland Australia. A free-living population of healthy devils is planned to be established on Maria Island (MI) in November this year to expand the insurance population in a manner that will also maintain wild behaviours. The objective is to increase devil populations over the long term with the aim of re-establishing the species throughout its natural range once DFTD has burnt itself out. Other points of relevance to this DRA are: Devils have never previously been recorded on Maria Island (MI). An initial release of animals is scheduled for November 2012, with post-release monitoring planned. Further releases to occur over next 1-2 years; up to a total of 50 animals. The carrying capacity for devils on the island is estimated around animals. Animals for release will be selected based on their genetic, health, and behavioral suitability. Post-release monitoring planned for TD and other associated native fauna. Can monitor the animals post release-as they are relatively easy to trap. A subset of released animals will be radio collared. Supplementary feeding is initially planned. MI is approx 10km off the east coast of Tasmania and it is approx 15km long x 3km wide, with a range of habitat types. The island is managed as a National Park which people can visit freely. Visitors can camp on the island but there are no permanent residents except park rangers. Other previous animal introductions include other marsupials, (such as kangaroos, wombats) and birds. There is a large macropod population on MI that is managed by culling. It is possible that Tasmanian devils may help to control over-abundance of these macropods through predation. Feral cats are present but foxes do not occur on the island and no quolls are present. Wedge-tailed eagles and White-bellied sea eagles are potential competitors and predators of young devils. Tasmanian devils are a high profile species that has gained general public sympathy since discovery of DFTD. Consequently there will be strong public interest in this project with concerns for effects on the resident shorebirds, geese, wombats, penguins and shearwaters. There is also potential for devils to become a public nuisance at campsites but the likelihood is unknown. Due to this concern, a formal DRA has been requested by the Parks and Wildlife Department. However, as noted above, there is a compressed timeline. Financial support for the translocation is through Save the Tasmanian Devil program which is funded by both public and government. 1

2 Goals of the DRA: 1. To determine and assess the risk of Tasmanian devils exposing the native fauna on MI to infectious and non-infectious disease hazards. 2. To identify the potential contagious diseases that they could transmit. 3. To minimize/manage/mitigate the risk of disease from devils to the other fauna on the island. 4. To assess whether the translocation of devils onto MI poses any significant risk to human health. Scope: The DRA will specifically examine the likelihood of devils introducing infectious and non-infectious hazards and the consequence of these on the native fauna and people on Maria Island. Source population: Devils will be sourced from multiple captive breeding sites and exclosures in Tasmania and mainland Australia. These animals have potentially been exposed to wild birds and mammals that have entered their enclosures pre-translocation. Hazards of primary concern to stakeholders are Leptospira, Salmonella, and Pasteurella. The occurrence or prevalence of these organisms on MI is not known but there is some data about Salmonella and Pasteurella in devils. Focus: This DRA focuses on threats to native animals and people at the destination site of Maria Island. In addition to tourists visiting the island and resident rangers, specific native animals of concern are wallabies, wombats, Cape Barren geese, shore birds, sea-birds (penguins, shearwaters) the endemic and endangered forty-spotted pardalote. 2

3 DRA question(s): What is the disease risk to resident native bird and mammal populations and to public health, associated with the introduction of Tasmanian devils from multiple sources to Maria Island, and how can these risks be managed? Assumptions: 1. All translocated devils will be identifiable. 2. The hazards that could be introduced to MI with Tasmanian devils are not currently having adverse effects on wildlife or public health on the island. 3. The resident birds and mammals on MI are susceptible to some or all of the hazards the devils may introduce. 4. Tasmanian devils will prey on some birds and mammals resident on MI. 5. There is a potential public health hazard associated with devil translocation to MI. 6. All devils will have a thorough health screen prior to translocation. Limitations: 1. Knowledge of what infectious diseases may be transmitted is scant. 2. There is very little baseline data on prevalence of diseases currently in wildlife on MI. 3. Knowledge of susceptibility to and effects of infectious diseases on resident birds and mammals on MI is scant. 4. Diagnostic tests and interpretation of results have not been validated on native wildlife. 5. Funding for monitoring and testing post-release is limited. 6. The level of stress that may be induced in resident native fauna as a result of devil introduction to MI is unknown. Acceptable Risk Small risk of disease transmission to humans (directly attributable to TD) would be acceptable. Major decline in resident MI fauna, below sustainable levels, would be unacceptable. Decline in the currently over-abundant macropod population would be acceptable. Disease impact on resident MI fauna that does not cause concern to the Parks and Wildlife Service or the public is considered an acceptable level of risk.. 3

4 RISK COMMUNICATION Group role Stakeholder Expert Information needs Communication method(s) When / Frequency Who Operational Parks and Wildlife Service MI Parks Rangers - Grant Hall - DPIWE Animal Ethics Committee TEMPLATE DEVELOPED AT WORKSHOP TO BE COMPLETED Tasmanian Devil program Birds Australia Captive management people -Judy Clarke Ecologists - Phil Weiss Veterinarian - Sarah Peck - Collette Hansen Operational & Advisors Government Laboratories Bruce Jackson Advisor Scientific Advisory Committee Ex-devil people ZAA ASMP 4

5 Group role Stakeholder Expert Information needs Communication method(s) When / Frequency Who Advisor Steering committee TO BE COMPLETED Australian Wildlife health Network (AWHN) Rupert Woods Governance Funding Agencies Save the Devil Tasmanian Government Politicians Indigenous Representatives Environment Minister Public/Media Ferry Operators Tour operators Media Private MI Guided Walk operator 5

6 HAZARD IDENTIFICATION Sources of information: Veterinary pathology services Publications: - Vogelnest and Woods (2008) Medicine of Australian Mammals - Ladd (2009) Pathology of Australian Native Wildlife - Others to be identified through literature search Databases: - Australian Wildlife Health Network - Australian Wildlife Pathology Registry - Experts unpublished information Associations - Wildlife Disease Association Australasia - AMA (Australian medical association) for public health data on zoonoses - Others Infectious hazards (in initial descending priority order based on discussion): Hazard 1.Toxoplamosis 2.Salmonella 3.Leptospirosis Explanation of priority Transmission to wallabies, but already on MI Public health concern Public health concern 4.Pasteurella 5.Chytrid fungus 6.Sarcoptic mange Non-infectious hazards (in initial priority order): Hazard Explanation of priority 1. Stress leading to susceptibility to other disease Unknown impact of major predator being introduced to a new range for the species 2. Predation of native resident fauna Primarily the risk to pardalotes Paired ranking of hazards Based on the potential impact of infectious organisms on the destination site wallabies, the following paired ranking exercise was performed by the group by considering the relative risk of each hazard with each other hazard. 6

7 Hazard 1 vs 2 1 vs 3 2 vs 3 1. Salmonella 2. Toxoplasma X X 3. Leptospira X Adding up the X s the ranking is: 1. Toxoplasma 2. Leptospira 3. Salmonella When the non-infectious hazard of stress was added to this list it ranked equally with Toxoplasma and Leptospira. Note that this ranking is based on the expertise in the room and could change with additional information. When discussed further, toxoplasmosis was considered less of a hazard to the island fauna then leptospirosis because feral cats (the only species able to disperse Toxoplasma in the environment) are already present on the island whereas there is no data on leptospirosis on the island. Leptospira have been recorded in devils on the Tasmanian mainland and have potential to be hazardous to people and other animals. For the purposes of this training exercise the group decided to focus on further evaluation of this potential hazard. Disease summary Leptospirosis - Caused by a spirochaete bacterium of the genus Leptospira... - Several serotypes are known some of which are pathogenic and others not - The serotype of most public health concern is Hardjo and this has been identified in some Australian wildlife (for example wombats) - Transmitted in urine, semen, and via contaminated water, soil and food - Vectors of disease include rodent species including rats found on Maria Island - Leptospirosis is known to cause disease in mammals including people - Infected individuals can be asymptomatic carriers - Clinical signs relate to kidney and/or liver disease and abortion may also occur - Diagnosis is via cultures and serology - The disease is treatable with antibiotics - Vaccination is available for some species It was considered by the group that the most likely mechanism of spread to resident native animals would be indirectly via rodents and contaminated water and (to a lesser extent) food sources. The group made a simple model or scenario tree to clarify the potential sources and routes of transmission of leptospira in the geographic areas and among the species of concern. 7

8 Scenario tree: Site 1 Site 2 Site 3 Captive facilities Rats Rats Rats Exclosure A Exclosure B Wallaby Wallaby Wombats Exclosures Rats Rats Devils Devils Maria Island Wombats DEVILS People WATER Wallabies Cats CCP 1 CCP2 CCP3 Rodents This scenario tree was subsequently used to identify and discuss the location of critical control points (CCP) at which risk mitigation actions could be introduced (see Risk Management below). Note that, in the scenario tree, water contamination following introduction of Leptospira onto the island by devils would subsequently be the major reservoir for transmission to susceptible species. 8

9 RISK ASSESSMENT (Rough Assessment Sheet) Due to limitations of time and information during the workshop, the group was restricted to a qualitative analysis of the risk of leptospirosis transmission from rodents to other species of concern only. Other identified high priority hazards would normally be added to this table to enable a relative priority ranking. The relative risk to species of concern was derived by adding the scores for likelihood and multiplying this with the score for the consequences (severity) for the species of concern. Hazard Likelihood of susceptibility of the Rodents Likelihood of exposure of the Rodents Likelihood of rodents becoming infected if exposed Likelihood of transmission by rodents to others species of concern* Severity for the population of species of concern Relative risk to species of concern* Leptospirosis wallaby & wombat = 1 People = 2 11 wallaby & wombat 22 - people *Species of concern identified by the group were: wallabies, wombats and people 1 = low likelihood/consequence 3 = high likelihood/consequence Reasons for determining the rank for each hazard against the criteria in the table: Transparency is a very important part of the wildlife DRA process. Therefore the following explanations are given for the thinking behind each of the scores in the above table. Hazard synopsis: Leptospirosis transmission via rodents to other species of concern; an assumption is made that Leptospira are currently not present on Maria Island. Likelihood of susceptibility of rodents (3) Rodents are known to be a common reservoir. Likelihood of exposure of rodents (2) This is dependent on the density of the rodent population and the number of infected devils that are introduced. This is largely unknown, as the density of rodents and prevalence of the organism on MI is unknown. Likelihood of rodents becoming infected if exposed (3) This is dependent on the density of the rodent population and the number of infected devils that are introduced. Likelihood of rodents transmitting the organism to other species of concern (3) As rodents rarely show symptoms or suffer from disease they are very likely to shed the bacterium throughout their entire life. 9

10 The organism is likely to spread rapidly throughout rodent populations due to their highly social behaviour, high reproductive rates and transmission of the organism via urine and in utero. Severity for the populations of concern (wallabies & wombats = 1; humans = 2) Wallabies and wombat are relatively resistant to the disease whereas people are more susceptible to disease if infected. Estimated Significance to the Program (wallabies & wombats += 11; people = 22) Wallabies and wombats are relatively resistant to the disease whereas people are more susceptible to disease if infected. 10

11 RISK MANAGEMENT Risk evaluation: Is the risk sufficient to require risk management action? YES/NO; If YES: explain why: The primary concern with leptospirosis is the potential threat to public health. Option Evaluation Critical Control Point Risk Management Option(s) in priority order Explanation for priority ranking Likely effectiveness Likely feasibility 1: Preventing infection of captive Tasmanian Devils by rodents Pest control Stops infection at source population Very effective if it can be achieved Control needs ongoing effort Zero risk is not feasible Monitor rodents and devils for lepto - ongoing Informs control effectiveness and level of risk Provides evaluation for effectiveness Costly, but feasible Vaccination of devils against lepto Unknown feasibility unknown Needs research Unlikely in time available 2:Prevent entry of disease through translocation Testing of devils prior to shipment in quarantine Informs on status and necessity of other management decisions Sensitivity and specificity of the serological test is unknown Cost, feasible Culture needed to confirm infection Need to test for all infectious serotypes 11

12 Exclude or treat animals that have tested positive to culture test Exclusion very effective Effectiveness of treatment is unknown, but it could be effective Exclusion - High cost Treatment -Low cost 12

13 IMPLEMENTATION AND REVIEW Goal Objective Actions Responsibility Collaborators Timeline Cost Evaluation Obstacles Pest Control Prevent contact between rodents and devils Rodent proof enclosures and trap/bait rodents, hygiene, limit food available for rodent Site manager Site staff immediate variable Ongoing monitoring for rodents Cost, Compliance, Time Reinvasion Monitoring for Leptospirosis Disease detection Serology, Necropsy and pathology dead devils and of dead rats Site manager and Veterinary Staff Lab technicians And site staff Immediate and at twice yearly intervals Initially high depending on numbers of animals tested and degree of confidence required Was it done effectively Cost Compliance Time Vaccination of Devils Prevent infection Research on significance of disease and use of antibiotics in devils Program managers Vet staff Researchers Long-term commitment unknown Testing and challenge Cost Ethics Expertise Politics Feasibility study 13

14 Goal Objective Actions Responsibility Collaborators Timeline Cost Evaluation Obstacles Prevent disease entering through translocation Prevent disease entering through translocation Establish rat fee quarantine, transfer devils, Site Manager Veterinary Staff Site Manager Veterinary Staff Site staff Site staff Commence immediately Immediately following establishment of quarantine high low Are rats present? Were they transferred? Cost, Compliance, Time Cost, Compliance, Time determine labs that can perform testing Site Manager Veterinary Staff Lab technicians 30 day minimum quarantine low Lab identified? Availability Capacity Time test devils using serology and bacterial culture Veterinary Staff Site staff Lab technicians Immediately following transfer of devils to quarantine moderate Were they tested? Cost, Compliance, Time undertake decision analysis to exclude or include animals in release Steering committee Site Manager Veterinary Staff Immediately low Decision framework created? Time Agreement 14

15 RESEARCH PRIORITIES IDENTIFIED IN THIS ANALYSIS: Results of the following research would provide that would enhance the rigor of this risk analysis Surveillance for leptospirosis on MI (wildlife) Surveillance for leptospirosis in captive institutions (rats and devils) Research into the effects of leptospirosis on devils and the use of suitable antibiotics in devils Vaccine development and testing Effects of Leptospirosis on native wildlife 15