Longevity of<i>Mycobacterium bovis</i>in brushtail possum (<i>Trichosurus vulpecula</i>) carcasses, and contact rates between possums and carcasses

Barron, M. C.; Pech, R.P.; Whitford, Jackie; Yockney, Ivor; Lisle, GW de; Nugent, Graham

doi:10.1080/00480169.2011.595905

Cited by 11 publications

(10 citation statements)

References 29 publications

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“…the percentage of carcasses consumed) are likely to be overestimates as (1) they do not try to estimate the probability of infection given scavenging (it is assumed to be 1.0), and (2) it is assumed that carcasses are contacted or scavenged within the period that M. bovis bacteria remain viable, as has been found for free-ranging possums encountering dead possums, and for free-ranging possums and ferrets visiting pig remains (Yockney and Nugent 2003 ; Barron et al . 2011 ).…”

Section: Methodsmentioning

confidence: 99%

The role of multiple wildlife hosts in the persistence and spread of bovine tuberculosis in New Zealand

Barron¹,

Tompkins²,

Ramsey³

et al. 2015

New Zealand Veterinary Journal

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AIM: To explore how the inclusion of multi-host dynamics affects the predicted prevalence of bovine tuberculosis (TB) in possums and other host species following the current best practice for control of TB in large difficult and remote areas, to identify which host species are responsible for changes in predicted prevalence, and whether TB can persist in possum-free host communities.METHODS: Multi-host TB models were constructed, comprising three host species with density-dependent population growth, density-dependent disease transmission and susceptible and infected classes. Models were parameterised for two case studies of current concern in New Zealand, namely chronic TB persistence in a possum-deer-pig complex in extensive forest, and in a possum-pig-ferret complex in unforested semi-arid shrub and grasslands. Persistence of TB in the face of best practice possum control was evaluated from model simulations, and the contribution of different hosts to persistence of TB was assessed by removing each host species in turn from the simulations. A sensitivity test explored how different parameter values affected modelled persistence of TB.RESULTS: The forest multi-host model-predicted amplification of TB prevalence due to the presence of pigs. The presence of pigs and/or deer did not jeopardise the success of best practice possum control in eradicating TB from the system, as pigs and deer are effectively end-hosts for TB. Sensitivity analyses indicated these interpretations were robust to uncertainty in model parameter values. The grassland system model predicted that the multi-host species complex could potentially lead to failure of eradication of TB under possum-only control, due to TB persisting in ferret and pig populations in the absence of possum hosts through reciprocal scavenging, resulting in spillback transmission to possums once their populations had started to recover from control.CONCLUSIONS: With respect to management of TB, for modelled forest habitats, 15 years of effective possum control was predicted to eradicate TB from the possum-deer-pig host community, indicating the current focus on possum-only control is appropriate for such areas. For grassland model systems, TB was predicted to persist in the ferret-pig host complex in the absence of possums, potentially jeopardising the effectiveness of possum-only control programmes. However this outcome depended on the occurrence and rate of pigs acquiring TB from ferrets, which is unknown. Thus some estimation of this transmission parameter is required to enable managers to assess if multi-host disease dynamics are important for their TB control programmes.

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Section: Methodsmentioning

confidence: 99%

The role of multiple wildlife hosts in the persistence and spread of bovine tuberculosis in New Zealand

Barron¹,

Tompkins²,

Ramsey³

et al. 2015

New Zealand Veterinary Journal

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“…Experimental studies demonstrate that M. bovis can be isolated >5 months after inoculation when mixed with faeces [176] and after one month in spiked possum carcasses [181]. Viable bacteria were recovered from hay at 7 days after inoculation and could still be isolated from samples of apples, corn and potatoes after 112 days [182].…”

Section: Landscape Climate and Other Environmental Risk Factorsmentioning

confidence: 99%

A review of risk factors for bovine tuberculosis infection in cattle in the UK and Ireland

et al. 2016

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Bovine tuberculosis (bTB) is an important disease of cattle caused by infection with Mycobacterium bovis, a pathogen that may be extremely difficult to eradicate in the presence of a true wildlife reservoir. Our objective was to identify and review relevant literature and provide a succinct summary of current knowledge of risk factors for transmission of infection of cattle. Search strings were developed to identify publications from electronic databases to February 2015. Abstracts of 4255 papers identified were reviewed by three reviewers to determine whether the entire article was likely to contain relevant information. Risk factors could be broadly grouped as follows: animal (including nutrition and genetics), herd (including bTB and testing history), environment, wildlife and social factors. Many risk factors are inter-related and study designs often do not enable differentiation between cause and consequence of infection. Despite differences in study design and location, some risk factors are consistently identified, e.g. herd size, bTB history, presence of infected wildlife, whereas the evidence for others is less consistent and coherent, e.g. nutrition, local cattle movements. We have identified knowledge gaps where further research may result in an improved understanding of bTB transmission dynamics. The application of targeted, multifactorial disease control regimens that address a range of risk factors simultaneously is likely to be a key to effective, evidence-informed control strategies.

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“…( 2013 ) demonstrated that, for wild possums artificially infected with M. bovis , 61% of the animals had died within 4 months, while Barron et al . ( 2011 ) demonstrated that M. bovis bacilli can remain viable in possum carcasses for only a matter of weeks, even under favourable environmental conditions. A previous study also referred to the survival time of possums following first detection of clinical signs of TB, indicating that this is usually <4 months (Norton et al .…”

Section: Methods For Estimating Possum Populations Following Populatimentioning

confidence: 99%

Development of integrated surveillance systems for the management of tuberculosis in New Zealand wildlife

Anderson

Ramsey

Lisle

et al. 2015

New Zealand Veterinary Journal

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Disease surveillance for the management of bovine tuberculosis (TB) in New Zealand has focussed, to a large extent, on the development of tools specific for monitoring Mycobacterium bovis infection in wildlife. Diagnostic techniques have been modified progressively over 30 years of surveillance of TB in wildlife, from initial characterisation of gross TB lesions in a variety of wildlife, through development of sensitive culture techniques to identify viable mycobacteria, to molecular identification of individual M. bovis strains. Of key importance in disease surveillance has been the elucidation of the roles that different wildlife species play in the transmission of infection, specifically defining brushtail possums (Trichosurus vulpecula) as true maintenance hosts compared to those that are predominantly spillover hosts, but which may serve as useful sentinel species to indicate TB persistence. Epidemiological modelling has played a major role in TB surveillance, initially providing the theoretical support for large-scale possum population control and setting targets at which control effort should be deployed to ensure disease eradication. As TB prevalence in livestock and wildlife declined throughout the 2000s, more varied field tools were developed to gather surveillance data from the diminishing possum populations, and to provide information on changing TB prevalence. Accordingly, ever more precise (but disparate) surveillance information began to be integrated into multi-faceted decision-assist models to support TB management decisions, particularly to provide informed parameters at which control effort could be halted, culminating in the Proof of Freedom modelling framework that now allows an area to be declared TB-free within chosen confidence limits. As New Zealand moves from large-scale TB control to regional eradication of disease in the coming years, further integrative models will need to be developed to support management decisions, based on combined field data of possum and TB prevalence, sentinel information, risk assessment in relation to financial benefits, and changing political and environmental needs.

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Longevity ofMycobacterium bovisin brushtail possum (Trichosurus vulpecula) carcasses, and contact rates between possums and carcasses

Cited by 11 publications

References 29 publications

The role of multiple wildlife hosts in the persistence and spread of bovine tuberculosis in New Zealand

The role of multiple wildlife hosts in the persistence and spread of bovine tuberculosis in New Zealand

A review of risk factors for bovine tuberculosis infection in cattle in the UK and Ireland

Development of integrated surveillance systems for the management of tuberculosis in New Zealand wildlife

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