Impact of bovine tuberculosis on a population of brushtail possums (Trichosurus vulpecula Kerr) in the Orongorongo Valley, New Zealand

2004 ◽  
Vol 31 (4) ◽  
pp. 389 ◽  
Author(s):  
A. Arthur ◽  
D. Ramsey ◽  
M. Efford
Keyword(s):  
Overall Survival ◽  
New Zealand ◽  
Population Density ◽  
Bovine Tuberculosis ◽  
Local Population ◽  
Trichosurus Vulpecula ◽  
Considerable Uncertainty ◽  
Highly Sensitive ◽  
Competing Models ◽  
The Impact

Brushtail possums are the main wildlife vectors of bovine tuberculosis (Tb) in New Zealand. Possum–Tb models form the basis of possum control aimed at eradicating the disease, and yet competing models show different behaviour, and are highly sensitive to parameters about which there is considerable uncertainty. One area of great uncertainty is the impact of the disease on possum populations. We investigated the impact of Tb on a local population of brushtail possums in the Orongorongo Valley, Wellington. Bovine Tb was first detected in 1997 at one site within an intensively studied population, but has not been detected in another intensively studied population 3 km away since the early 1980s. Using a Before-After-Control-Impact (BACI) analysis, detection of Tb coincided with a 42% (95% CI = 23–56%) reduction in the odds of apparent yearly survival of a possum >17 months of age, i.e. a decrease in yearly survival from 0.85 to 0.77 in 'good' years, and a decrease from 0.71 to 0.60 in 'bad' years. This suggests that Tb had a significant impact on overall survival. However, there was no impact on local population density in September each year due to compensatory recruitment.

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.

scholarly journals Geographic distribution of restriction types ofMycobacterium bovisisolates from brush-tailed possums (Trichosurus vulpecula) in New Zealand

1986 ◽  
Vol 96 (3) ◽  
pp. 431-438 ◽  
Author(s):  
D. M. Collins ◽  
G. W. De Lisle ◽  
D. M. Gabric
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Mycobacterium Bovis ◽  
Bovine Tuberculosis ◽  
Restriction Enzymes ◽  
Restriction Endonuclease Analysis ◽  
Trichosurus Vulpecula ◽  
Typing System ◽  
Dna Restriction ◽  
Endonuclease Analysis

SUMMARYDNA restriction endonuclease analysis was used for intra-specific typing ofMycobacterium bovisisolates from 83 brush-tailed possums (Trichosurus vulpecula) obtained between 1982 and 1984 from the three major regions in New Zealand with endemic bovine tuberculosis. All the isolates were found to be genetically very similar. Differentiation of the isolates into 33 restriction types was achieved by using high-resolution electrophoresis and the combined results from separate digestions with the restriction enzymesBstEII,PvuII andBclI. The typing system was entirely reproducible. Isolates of the same type were usually found in adjacent localities and were always limited to one of the three major regions. In some cases, isolates of the same type were found in both 1982 and 1984. The phenotypic significance of the small genetic differences identified between different isolates is unknown. The typing system will be useful for monitoring the transmission ofM. bovisto other species and the future spread of differentM. bovistypes through possum populations.

scholarly journals The relation of environmental and climatic changes and migration situation in Oceania

2019 ◽  
Vol 27 (2) ◽  
pp. 313-325
Author(s):  
Galina N Ochirova ◽  
Evgeniya M Moiseeva ◽  
Anastasiya S Maksimova
Keyword(s):  
Climate Change ◽  
New Zealand ◽  
Local Population ◽  
Climatic Changes ◽  
Natural Phenomena ◽  
Island States ◽  
The Usa ◽  
Employment Education ◽  
And Migration ◽  
The Impact

The article presents overview of environmental and climatic, economic and migration situations in the countries of Oceania. In order to determine the relation of environmental and climatic changes and migration processes in the island states and territories of Oceania, New Zealand and Australia, analytical reports and censuses of the population of the states, estimates and statistics of international organizations are studied. The article analyses the state policy of island states and territories in the field of sustainable development and migration, as well as immigration policies of the main host countries such as Australia, New Zealand and the USA. It was found that internal and external migration in Oceania is mainly driven by socio-economic factors (problems with employment, education and medical services), while internal migration is usually directed to urban area, and external - from the city to foreign countries. Exploring the peculiarities of climate change and natural phenomena and their impact on the livelihoods of people in the region of Oceania, we can conclude that natural and climatic influences directly and indirectly affect different spheres of life of the local population. Nevertheless, the impact of climate change and natural phenomena on the migration of the population of Oceania at the moment is insignificant (no more than 10-12% of international flows), however, in the case of an increase in the intensity and frequency of na- tural disasters, and also due to an increase in the number and density of population (71 million people will live in the region to 2100) an increase in the flow of environmental migrants is inevitable.

Restricting the movements of brushtail possums (Trichosurus vulpecula) on farmland with electric fencing

1992 ◽  
Vol 19 (1) ◽  
pp. 47 ◽  
Author(s):  
PE Cown ◽  
DS Rhodes
Keyword(s):  
New Zealand ◽  
Bovine Tuberculosis ◽  
Trichosurus Vulpecula ◽  
Electric Fence ◽  
Electric Fencing

A trial was conducted to test whether an electric fence would limit local movements of brushtail possums (Trichosurus vulpecula) on farmland in the central North I. of New Zealand. If effective, such a system could be used to reduce possum and cattle interactions and the spread of bovine tuberculosis. A 3-km-long, 9-strand electric fence was erected from ridge to ridge across a valley catchment of about 160 ha. Possums were live-trapped and released at bush patches within the study area and in open areas immediately adjacent to the electric fence. Only about 30% of possums caught at local bush patches were ever retrapped at the fence, and most were caught only once at the fence. About a third of possums caught at the fence were trapped at least once on both sides of the fence. The electric fence reduced possum movements through the fenced area by about 60-80%. Most possums trapped at the fence had come from bush patches within 200 m of the fence. When the fence was switched off, possum captures on the outside increased rapidly. The effectiveness of the fence was reduced because of frequent voltage reduction by earthing from a wide variety of causes, and because possums learned to move around the ends of the fence and the fences along the farm roads. Improvements to fence design are discussed.

A new trap-catch index of patchiness in animal distribution

2004 ◽  
Vol 31 (4) ◽  
pp. 433 ◽  
Author(s):  
J. A. Brown ◽  
R. J. McAuliffe ◽  
G. J. Hickling
Keyword(s):  
New Zealand ◽  
Species Distribution ◽  
Bovine Tuberculosis ◽  
Trichosurus Vulpecula ◽  
Trap Catch ◽  
Animal Distribution ◽  
Wildlife Species ◽  
Wildlife Populations ◽  
Catch Rates ◽  
Index Of Abundance

Researchers and managers commonly use catch rates on trap-transects as an index of abundance for trappable wildlife species. We describe a method whereby the data collected from such surveys can be further analysed to obtain information on the patchiness of the trapped species' distribution on those transects. For certain applications, such as the management of wildlife disease, the index is likely to have significant advantages over traditional indices of spatial aggregation. One such situation is the management of brushtail possums (Trichosurus vulpecula) in New Zealand to inhibit the spread of bovine tuberculosis within their populations. Trap-catch data from a possum survey are used to illustrate the proposed method, and the potential for application of such monitoring to wildlife populations is discussed.

The effect of manipulating population density on the probability of den-sharing among common brushtail possums, and the implications for transmission of bovine tuberculosis

1998 ◽  
Vol 25 (4) ◽  
pp. 383 ◽  
Author(s):  
P. Caley ◽  
N. J. Spencer ◽  
R. A. Cole ◽  
M. G. Efford
Keyword(s):  
New Zealand ◽  
Population Density ◽  
Bovine Tuberculosis ◽  
Brushtail Possum ◽  
Contact Rate ◽  
Animal Disease ◽  
Per Capita ◽  
A Site ◽  
And Control ◽  
The Relationship

Common brushtail possums (Trichosurus vulpecula) act as a reservoir of bovine tuberculosis (Mycobacterium bovis) in New Zealand and the simultaneous sharing of dens may result in the transmission of Tb between possums. The effect of manipulating population density on the per capita probability of simultaneous den-sharing among possums was investigated at a site near Dunedin, New Zealand. Den characteristics that could affect the probability of simultaneous sharing were also investigated, though none were found to be significant. The daily probability of a possum sharing a den was estimated to be 0.07 for possums denning within uncontrolled areas of the study area. Den-sharing was most common between female pairs, though sharing was also recorded between male–female and male–male pairs. The highest number of possums recorded sharing a single den was four. Reducing population density significantly lowered the probability of possums simultaneously sharing dens within the study area, with greater than 60% reductions estimated to eliminate simultaneous den-sharing altogether. The relationship between the contact rate arising from den-sharing and population density was convex-down, rather than convex-up, as often hypothesised for animal–animal disease contact processes. The implications of simultaneous den-sharing for the transmission and control of bovine tuberculosis in brushtail possum populations are discussed.

Ethnic political exclusion and terrorism: Analyzing the local conditions for violence

2018 ◽  
Vol 37 (3) ◽  
pp. 280-300 ◽  
Author(s):  
Holley E. Hansen ◽  
Stephen C. Nemeth ◽  
Jacob A. Mauslein
Keyword(s):  
Population Density ◽  
Ethnic Group ◽  
Local Population ◽  
Ethnic Violence ◽  
Regime Type ◽  
Local Conditions ◽  
Intergroup Competition ◽  
Political Exclusion ◽  
The Impact ◽  
Terrorist Violence

Previous work finds that countries that contain an excluded group are at higher risk of terrorism. However, there are good reasons to think that the impact of exclusion may be more likely to motivate ethnic violence when this exclusion is paired with local conditions that increase awareness of intergroup competition. In this study, we examine sub-national terrorist violence and find that areas that contain an excluded ethnic group are at higher risk of violence. Moreover, this risk is heightened by local population density, wealth, and country regime type.

Investigating brushtail possum (Trichosurus vulpecula) home-range size determinants in a New Zealand native forest

2017 ◽  
Vol 44 (4) ◽  
pp. 316 ◽  
Author(s):  
K. S. Richardson ◽  
C. Rouco ◽  
C. Jewell ◽  
N. P. French ◽  
B. M. Buddle ◽  
...  
Keyword(s):  
New Zealand ◽  
Population Density ◽  
Home Range ◽  
Disease Transmission ◽  
Home Range Size ◽  
Range Size ◽  
Home Ranges ◽  
Native Forest ◽  
Trichosurus Vulpecula ◽  
Age And Sex

Context The Australian brushtail possums (Trichosurus vulpecula) introduction to New Zealand has exacted a heavy toll on native biodiversity and presented the country with its greatest wildlife reservoir host for bovine tuberculosis (TB). Management efforts to control both possums and TB have been ongoing for decades, and the biology of possums has been studied extensively in Australia and New Zealand over the past 50 years; however, we still do not have a clear understanding of its home-range dynamics. Aims To investigate determinants of home range size by using a uniquely large dataset in the Orongorongo Valley, a highly monitored research area in New Zealand and compare our findings with those of other studies. Methods Possum density was estimated, for subpopulations on four 13-ha cage-trap grids, by the spatially explicit capture–mark–recapture analysis of trapping data from 10 consecutive months. Home ranges were estimated from trap locations using a 100% minimum convex polygon (MCP) method for 348 individuals and analysed with respect to grid, age and sex. Key results Mean (standard error) possum density, estimated as 4.87 (0.19), 6.92 (0.29), 4.08 (0.21) and 4.20 (0.19) ha–1 for the four grids, was significantly negatively correlated with mean MCP home-range size. Grid, age, and the interaction of age and sex were significantly related to home-range size. Older possums had larger home ranges than did younger possums. When ‘juvenile cohort’ and ‘adult cohort’ data were analysed separately, to investigate the significant interaction, males in the ‘adult cohort’ had significantly larger home ranges than did females, with the grid effect still being apparent, whereas neither sex nor grid effects were significant for the ‘juvenile cohort’. Conclusions Our findings indicate that, in addition to density, age and sex are likely to be consistent determinants of possum home-range size, but their influences may be masked in some studies by the complexity of wild-population dynamics. Implications Our findings have strong implications regarding both disease transmission among possums and possum management. The fact that adult males occupy larger home ranges and the understanding that possum home range increases as population density decreases are an indication that males may be the primary drivers of disease transmission in possum populations. The understanding that possum home range increases as population density decreases could be a direct reflection of the ability of TB to persist in the wild that counteracts current management procedures. If individuals, and particularly males, infected with TB can withstand control measures, their ensuing home-range expansion will result in possible bacteria spread in both the expanded area of habitation and new individuals becoming subjected to infection (both immigrant possums and other control survivors). Therefore, managers should consider potential approaches for luring possum males in control operations.

Modelling immunocontraception in disseminating systems

1997 ◽  
Vol 9 (1) ◽  
pp. 51 ◽  
Author(s):  
N. D. Barlow
Keyword(s):  
New Zealand ◽  
Population Density ◽  
Related Species ◽  
Breeding Population ◽  
Trichosurus Vulpecula ◽  
Wild Type ◽  
Target Species ◽  
Closely Related Species ◽  
Novel Technology ◽  
High Prevalence

Vectored immunocontraception is a novel technology and simple models are described to help predict whether, and how, it might work. That is, given that an effective immunocontraceptive agent can be produced, and given that it can be inserted into a microparasitic or macroparasitic infective vector, would the vector persist and reach a high prevalence in the host and, if so, would it sterilize a sufficient proportion of the host breeding population to significantly reduce its density? Both conditions are necessary for success. The first question is an epidemiological one, relating solely to disseminating systems and differing according to whether the vector itself is newly introduced or pre-existing. If it is newly introduced, the assumption is that it is present in some other geographical areas occupied by the same target species, or is found in closely-related species. If the vector already exists in the population, the issue is one of competition between the engineered and wild-type vectors. The second question is an ecological one, common to both non-disseminating and disseminating systems. Whatever level of sterilization the immunocontraception provides must translate into a significant reduction in population density, having regard to the nature and extent of compensatory, density-dependence mechanisms in the population. These two questions, together with other more minor issues, are addressed in turn with particular reference to models for immunocontraception of brushtail possums (Trichosurus vulpecula)in New Zealand.

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