The effect of poisoned and notional vaccinated buffers on possum (Trichosurus vulpecula) movements: minimising the risk of bovine tuberculosis spread from forest to farmland

2010 ◽  
Vol 37 (4) ◽  
pp. 283 ◽  
Author(s):  
R. Pech ◽  
A. Byrom ◽  
D. Anderson ◽  
C. Thomson ◽  
M. Coleman
Keyword(s):  
Bovine Tuberculosis ◽  
Cost Effective ◽  
Acceptable Level ◽  
Disease Spread ◽  
Initial Population ◽  
Home Ranges ◽  
Trichosurus Vulpecula ◽  
Buffer Zones ◽  
Lethal Control ◽  
Forest Buffer

Context. Vaccination of brushtail possums (Trichosurus vulpecula) has been proposed as a cost-effective alternative to lethal control for preventing potentially bovine tuberculosis (Tb)-infected possums from crossing forested buffer zones that abut farmland. Aim. Evaluation of these two management option requires an estimation of the buffer width required to reduce the risk of disease spread to an acceptable level. Methods. The movements of two groups of adult and subadult possums were monitored for up to 12 months in the Kaimanawa Range, North Island of New Zealand, using GPS technology. One group was in untreated forest immediately adjacent to a recently poisoned forest buffer, and the second group was 2 km further into untreated forest, which mimicked a vaccinated buffer with no reduction in possum abundance. Key results. Close to the poisoned buffer, where the initial population density was 0.49–1.45 ha–1, adult possum home ranges averaged 10.2 ha in the summer immediately after control and 9.5 ha in the following winter. Two kilometres into the untreated forest, where the density was >3 ha–1, the corresponding values were only 3.5 ha and 2.8 ha. Over the first 6 months of monitoring, a ~350-m wide poisoned buffer would have contained 95% of movements by adult possums, as well as movements by most individuals, but a ~150-m wide vaccinated buffer would have been as effective. Equivalent results for the subsequent 6-month period were ~450 m and ~200 m for poisoned and vaccinated buffers, respectively. Movements by possums were not biased in the direction of the population ‘vacuum’ created by the poisoning operation. When subadult possums were included in the analysis, buffer widths of ~500–600 m for both poisoning and vaccination would be required to contain 95% of new den site locations. Conclusions and implications. Detailed data on possum movements provide a means for agencies managing Tb to specify the width of a buffer, subject to an acceptable level of risk that it could be breached by a potentially infected possum. As well as depending on the width of a treated buffer, the final cost-effectiveness of vaccination compared with poisoning will depend on the relative cost of applying the two control techniques, and the frequency of application required either to prevent Tb from establishing (in the case of vaccination) or to suppress possum density (in the case of lethal control).

Electric Fences and Poison Buffers as Barriers to Movements and Dispersal of Brushtail Possums (Trichosurus Vulpecula) on Farmland.

1993 ◽  
Vol 20 (5) ◽  
pp. 671 ◽  
Author(s):  
PE Cowan ◽  
DS Rhodes
Keyword(s):  
Bovine Tuberculosis ◽  
Average Distance ◽  
Buffer Zone ◽  
Control Site ◽  
Trichosurus Vulpecula ◽  
Buffer Zones ◽  
North West ◽  
North East ◽  
Live Trapping ◽  
Electric Fence

Limitation of the spread of bovine tuberculosis by brushtail possums (Trichosurus vulpecula) in New Zealand involves creating buffer zones 3-5km wide around areas where the disease is endemic in possum populations; low possum density is established by aerial and ground poisoning and maintained by repeated control. The effectiveness of a buffer zone was examined using live-trapping and radiotracking to study movements and dispersal of juvenile and adult possums in comparison with a nearby, undisturbed (control) site. At a third site, the effect of a 3-km long, 9-strand electric fence, erected from ridge to ridge across a valley catchment, for reducing possum dispersal was measured, as an alternative to a buffer zone. Adult possums were highly sedentary; only one permanent shift of more than 0.5km was detected during repeated live-trapping and radio-tracking, and most consecutive live captures were in traps less than 200m apart. None of the radio-tagged adults adjacent to the poison buffer zones moved permanently into the low-density areas. By contrast, about 20% of radio-tagged juveniles dispersed more than 0.5km, moving up to 11.6km from their natal areas, most in a generally west-north-west to east-north-east direction. About equal numbers dispersed upstream, downstream, or in other directions. Significantly more males dispersed than females, but their dispersal distances were similar. Some dispersing possums moved more than 2km overnight, and females, particularly, often made several moves before settling. Most juveniles dispersed before they were one year old, mainly in the three months immediately preceding the peak of births in autumn. Neither the poison buffer zone nor the electric fence appeared to influence the proportion of juveniles that dispersed more than 0.5km, or the average distance dispersed. The implications of these findings in preventing the spread of bovine tuberculosis are discussed.

scholarly journals Sheep scab spatial distribution: the roles of transmission pathways

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Emily Joanne Nixon ◽  
Ellen Brooks-Pollock ◽  
Richard Wall
Keyword(s):  
Disease Transmission ◽  
Movement Control ◽  
Cost Effective ◽  
Infected Sheep ◽  
Disease Spread ◽  
Psoroptes Ovis ◽  
Long Distance ◽  
Sheep Scab ◽  
The Uk ◽  
The Impact

Abstract Background Ovine psoroptic mange (sheep scab) is a highly pathogenic contagious infection caused by the mite Psoroptes ovis. Following 21 years in which scab was eradicated in the UK, it was inadvertently reintroduced in 1972 and, despite the implementation of a range of control methods, its prevalence increased steadily thereafter. Recent reports of resistance to macrocyclic lactone treatments may further exacerbate control problems. A better understanding of the factors that facilitate its transmission are required to allow improved management of this disease. Transmission of infection occurs within and between contiguous sheep farms via infected sheep-to-sheep or sheep–environment contact and through long-distance movements of infected sheep, such as through markets. Methods A stochastic metapopulation model was used to investigate the impact of different transmission routes on the spatial pattern of outbreaks. A range of model scenarios were considered following the initial infection of a cluster of highly connected contiguous farms. Results Scab spreads between clusters of neighbouring contiguous farms after introduction but when long-distance movements are excluded, infection then self-limits spatially at boundaries where farm connectivity is low. Inclusion of long-distance movements is required to generate the national patterns of disease spread observed. Conclusions Preventing the movement of scab infested sheep through sales and markets is essential for any national management programme. If effective movement control can be implemented, regional control in geographic areas where farm densities are high would allow more focussed cost-effective scab management. Graphical Abstract

scholarly journals Contact chains of cattle farms in Great Britain

2019 ◽  
Vol 6 (2) ◽  
pp. 180719 ◽  
Author(s):  
Helen R. Fielding ◽  
Trevelyan J. McKinley ◽  
Matthew J. Silk ◽  
Richard J. Delahay ◽  
Robbie A. McDonald
Keyword(s):  
Great Britain ◽  
Bovine Tuberculosis ◽  
Bimodal Distribution ◽  
Disease Spread ◽  
Scale Free ◽  
Network Analyses ◽  
Directed Paths ◽  
System Data ◽  
Epidemiological Characteristics ◽  
Cattle Farms

Network analyses can assist in predicting the course of epidemics. Time-directed paths or ‘contact chains' provide a measure of host-connectedness across specified timeframes, and so represent potential pathways for spread of infections with different epidemiological characteristics. We analysed networks and contact chains of cattle farms in Great Britain using Cattle Tracing System data from 2001 to 2015. We focused on the potential for between-farm transmission of bovine tuberculosis, a chronic infection with potential for hidden spread through the network. Networks were characterized by scale-free type properties, where individual farms were found to be influential ‘hubs' in the network. We found a markedly bimodal distribution of farms with either small or very large ingoing and outgoing contact chains (ICCs and OCCs). As a result of their cattle purchases within 12-month periods, 47% of British farms were connected by ICCs to more than 1000 other farms and 16% were connected to more than 10 000 other farms. As a result of their cattle sales within 12-month periods, 66% of farms had OCCs that reached more than 1000 other farms and 15% reached more than 10 000 other farms. Over 19 000 farms had both ICCs and OCCs reaching more than 10 000 farms for two or more years. While farms with more contacts in their ICCs or OCCs might play an important role in disease spread, farms with extensive ICCs and OCCs might be particularly important by being at higher risk of both acquiring and disseminating infections.

Low wolverine (Gulo gulo) density in a national park complex of the Canadian Rocky Mountains

2020 ◽  
Vol 98 (5) ◽  
pp. 287-298
Author(s):  
M. Barrueto ◽  
M.A. Sawaya ◽  
A.P. Clevenger
Keyword(s):  
National Parks ◽  
Edge Effects ◽  
Rocky Mountains ◽  
Population Data ◽  
Home Ranges ◽  
Large Carnivores ◽  
Canadian Rocky Mountains ◽  
High Quality ◽  
Buffer Zones ◽  
Gulo Gulo

Large carnivores are sensitive to human-caused extirpation due to large home ranges, low population densities, and low reproductive rates. Protected areas help maintain populations by acting as sources, but human-caused mortality, habitat displacement, and edge effects occurring at protected area boundaries may reduce that function. The national parks Banff, Yoho, and Kootenay in the Canadian Rocky Mountains are refugia for large carnivores, including wolverines (Gulo gulo (Linnaeus, 1758)). Despite growing conservation concern, empirical baseline population data for wolverines remain scarce throughout their range, including most of Canada. We hypothesized (i) that in these national parks, wolverine density matched values expected for high-quality habitat, and (ii) that edge effects decreased density towards park boundaries. We conducted systematic non-invasive genetic sampling surveys covering >7000 km2 (2011 and 2013). Using spatial capture–recapture models, we estimated mean (±SE) female (1.5 ± 0.3 and 1.4 ± 0.3 wolverine/1000 km2), male (1.8 ± 0.4 and 1.5 ± 0.3 wolverine/1000 km2), and combined (3.3 ± 0.5 and 3.0 ± 0.4 wolverine/1000 km2) densities for 2011 and 2013, respectively. These estimates were lower than predictions based on density extrapolation from nearby high-quality habitat, and density decreased towards park boundaries. To benefit the population, we recommend creating buffer zones around parks that protect female habitat and prohibit harvest.

scholarly journals A comparison of fertility control and lethal control of bovine tuberculosis in badgers: the impact of perturbation induced transmission

1997 ◽  
Vol 352 (1353) ◽  
pp. 619-631 ◽  
Author(s):  
J. Swinton ◽  
F. Tuyttens ◽  
D. Macdonald ◽  
D. J. Nokes ◽  
C. L. Cheeseman ◽  
...  
Keyword(s):  
Bovine Tuberculosis ◽  
Fertility Control ◽  
Transmission Model ◽  
Infection Prevalence ◽  
Lethal Control ◽  
Advantages And Disadvantages ◽  
Contact Rates ◽  
Age Cohort ◽  
The Impact

In this paper we use mathematical modelling to consider the broad advantages and disadvantages of fertility control over lethal control for bovine tuberculosis in badger populations. We use a deliberately simple model, attempting to capture only the key transmission processes. The model is parametrized with reference to the long–term Woodchester Park study. Estimates of mortality rate from this study suggest no significant extra mortality risk for animals with evidence of infection as indicated by the presence of anti- Mycobacterium bovis antibodies or M. bovis isolation. We find that large reductions in prevalence are sometimes the consequence of only moderate reductions in population numbers. If we assume that the act of control does not in itself affect transmission rates, then as far as eradication is concerned, both fertility control and mortality control operate through the same epidemiological mechanism, the removal of susceptibles: if one is in principle capable of keeping a population low enough to be infection free then so is the other. It is necessary to continue either form of control at regular intervals to maintain a constant level of infection in the long term. If control were to be stopped, return to precontrol levels of badger population and infection prevalence would be expected within a few years. Fertility control is less effective in reducing population density than lethal control since it can only act, at maximum, to remove one age cohort per year. It is also less effective in reducing transmission as it can only ever remove susceptibles, while lethal control also removes infectious badgers. However, if the social disturbance caused by lethal control does in fact increase contact rates for the remaining infectious badgers, the relative efficacies of the two strategies become a great deal less clear. While we have no quantitative data on the extent to which social perturbation does act to promote transmission, model simulations show that it is possible to develop plausible scenarios in which the lethal control may actually act to increase the absolute numbers of animals infected, while reducing the number of uninfected animals to very low numbers.

scholarly journals Assessing Movements of Brushtail Possums (Trichosurus vulpecula) in Relation to Depopulated Buffer Zones for the Management of Wildlife Tuberculosis in New Zealand

PLoS ONE ◽  
2015 ◽  
Vol 10 (12) ◽  
pp. e0145636 ◽  
Author(s):  
Andrea E. Byrom ◽  
Dean P. Anderson ◽  
Morgan Coleman ◽  
Caroline Thomson ◽  
Martin L. Cross ◽  
...  
Keyword(s):  
New Zealand ◽  
Trichosurus Vulpecula ◽  
Buffer Zones

Distribution, Prevalence, and Epidemiology of Bovine Tuberculosis in Brushtail Possums, Trichosurus-Vulpecula, in the Hohonu Range, New-Zealand

1988 ◽  
Vol 15 (6) ◽  
pp. 651 ◽  
Author(s):  
JD Coleman
Keyword(s):  
Body Weight ◽  
Lymph Node ◽  
New Zealand ◽  
Disease Transmission ◽  
Bovine Tuberculosis ◽  
Infected Animal ◽  
Disease Prevalence ◽  
Trichosurus Vulpecula ◽  
Wide Range ◽  
Autumn And Winter

Over a 12-month period, 1467 brushtail possums were trapped and then killed or were poisoned along sampling lines on pasture-forest margins and in nearby forest. An additional 334 possums were shot on adjacent farm land. All possums were necropsied, and 141 had macroscopic lesions typical of bovine tuberculosis. Infected possums occurred most commonly in small foci of 2-5 individuals along pasture-forest margins; the furthest from pasture that an infected animal was taken was 4050 m. Lesions occurred in possums of all ages in both sexes, but disease prevalence was highest in immature males and during autumn and winter. Infected possums bred as successfully as non-infected individuals, but were of lighter body weight. Macroscopic lesions occurred in a wide range of visceral and lymph node sites. Lesions were most common in the lungs and axillary nodes, and occasionally formed open sinuses from which infected possums could shed M. bovis readily, and thus were likely to be highly infective. Evidence suggested that disease transmission occurs most frequently on pasture-forest margins, where possum numbers are greatest and possum and cattle mix most freely.

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