Tuberculosis In Badgers Research Articles

Bovine tuberculosis in badgers

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Fertility control as a means of controlling bovine tuberculosis in badger (Meles meles) populations in south-west England: predictions from a spatial stochastic simulation model.

A spatial stochastic simulation model was used to assess the potential of fertility control, based on a yet-to-be-developed oral bait-delivered contraceptive directed at females, for the control of bovine tuberculosis in badger populations in south-west England. The contraceptive had a lifelong effect so that females rendered sterile in any particular year remained so for the rest of their lives. The efficacy of fertility control alone repeated annually for varying periods of time was compared with a single culling operation and integrated control involving an initial single cull followed by annually repeated fertility control. With fertility control alone, in no instance was the disease eradicated completely while a viable badger population (mean group size of at least one individual) was still maintained. Near eradication of the disease (less than 1% prevalence) combined with the survival of a minimum viable badger population was only achieved under a very limited set of conditions, either with high efficiency of control (95%) over a short time period (1-3 years) or a low efficiency of control (20%) over an intermediate time period (10-20 years). Under these conditions, it took more than 20 years for the disease to decline to such low levels. A single cull of 80% efficiency succeeded in near eradication of the disease (below 1% prevalence) after a period of 6-8 years, while still maintaining a viable badger population. Integrated strategies reduced disease prevalence more rapidly and to lower levels than culling alone, although the mean badger group size following the onset of control was smaller. Under certain integrated strategies, principally where a high initial cull (80%) was followed by fertility control over a short (1-3 year) time period, the disease could be completely eradicated while a viable badger population was maintained. However, even under the most favourable conditions of integrated control, it took on average more than 12 years following the onset of control for the disease to disappear completely from the badger population. These results show that whilst fertility control would not be a successful strategy for the control of bovine tuberculosis in badgers if used alone, it could be effective if used with culling as part of an integrated strategy. This type of integrated strategy is likely to be more effective in terms of disease eradication than a strategy employing culling alone. However, the high cost of developing a suitable fertility control agent, combined with the welfare and conservation implications, are significant factors which should be taken into account when considering its possible use as a means of controlling bovine tuberculosis in badger populations in the UK.

Modelling the Control of Bovine Tuberculosis in Badgers in England: Culling and the Release of Lactating Females

1. A simulation model was used to evaluate the effect of different levels of culling on six badger social groups in an attempt to reduce or eradicate TB infection from the population. Apart from fecundity, all model parameters were derived from a comprehensive study of a naturally-infected badger population in England. 2. Badger control was simulated using a trap-and-cull of 80% of all badgers in either two social groups (localized strategy) or all six social groups (wide area strategy). Lactating females were permitted to infect none or all of their young, to simulate the extremes of sow-to-cub (pseudo-vertical) transmission. Trapped lactating sows were either all released or all killed. 3. Simulations where all infected badgers can be correctly diagnosed were also run to determine the importance of an improved live test for TB. 4. In the absence of badger control, pseudo-vertical transmission increased the persistence and prevalence of TB in the simulated population. 5. A single control operation was capable of eradicating TB from the population only if all six badger social groups were subjected to culling. If only infected individuals were killed, disease eradication was possible without a marked increase in population extinction. If all individuals were killed, the increased level of disease eradication occurred as a result of an increase in population extinction. 6. Killing lactating sows had no effect on the medium-term prevalence (up to 20 years) of the disease and resulted only in a reduced persistence of TB when a wide area badger control strategy was used.

The Effects of Stochasticity and Seasonality on Model Dynamics: Bovine Tuberculosis in Badgers

Field measurement of bovine tuberculosis in badgers (Meles meles) suggests that disease prevalence varies between years in an apparently cyclic fashion. Here, the ability of the simple compartment model of the disease presented by Bentil & Murray (1993) to reproduce this behaviour is investigated. The model predicts that, for realistic parameter values, the disease prevalence will stabilize at a fixed equilibrium, although the transient motion towards this equilibrium may involve damped cycles. The model is extended to include the effects of seasonality and stochasticity, both of which have been shown to reduce stability in similar models parameterized for childhood diseases in humans. However, these changes are found not to sustain the transient cycles. It is argued that, by analogy with models of childhood diseases, the addition of age-structure to the model is unlikely to increase its propensity to exhibit cycles. Finally, it is suggested that one of the fundamental assumptions underlying compartment models makes them unsuitable for representing this problem, which must be addressed using spatially explicit models.

Badgers and bovine tuberculosis

The Ministry of Agriculture, Fisheries and Food (MAFF) has now published its 18th annual report on bovine tuberculosis in badgers. Previous reports in this series have, over the years, detailed the evidence that badgers can be involved in the maintenance and spread of the disease, and the actions that have been taken to deal with the problem.

Bovine tuberculosis in badger (Meles meles) populations in southwest England: the use of a spatial stochastic simulation model to understand the dynamics of the disease.

A spatial stochastic simulation model was developed to describe the dynamics of bovine tuberculosis in badger populations in southwest England, based on data from the literature and from unpublished sources. As there are no data on intra- and intergroup infection probabilities, estimates of these were obtained through repeated simulations based on field observations of the spread and prevalence of the disease. The model works on a grid-cell basis, with each grid cell potentially occupied by one badger social group; immigration to and emigration from the main grid are incorporated. Population regulation is assumed to occur at the group level through density-dependent fecundity and cub mortality, and the model can be run for various disease-free equilibrium group sizes (which are determined by the carrying capacity of the environment). The model works on a quarterly (three-monthly) basis and processes are stochastic at the individual level. Three classes of individual (adults, yearlings and cubs) and three classes of infection (susceptible, infected-but-not-infectious and infectious) are recognized. Bovine tuberculosis wa shown to persist in badger populations for long periods of time, even in populations with a disease-free equilibrium group size of only four adults and yearlings. However, with standard rates of intergroup infection and movement, the disease only became endemic in populations with a disease-free equilibrium group size greater than six adults and yearlings. In the endemic situation, the prevalence of the disease ranged between 11-22 degrees depending on the combination of inter- and intragroup infection probabilities used. Endemic infection within the homogeneous environment of the grid was characterized by a high degree of heterogeneity. Patches of infection were spatio-temporally unstable, but shifted in location relatively slowly. Spread of the disease from a point source of infection with standard rates of intergroup movement and infection only occurred to any marked extent in populations with disease-free equilibrium group sizes of eight or more adults and yearlings. Increasing the intergroup infection probability had a significant effect on increasing the probability and rate of spread, and considerably lowered the threshold group size for spread from a point source to around four adults and yearlings. However, increasing the rates of intergroup movement reduced the probability of spread of the disease except at the largest groups sizes. When both intergroup infection and movements were increased, the effects of increased infection in enhancing spread were offset to some degree by the increased movements. Perturbation to the badger population, as may be caused by control operations, could therefore increase the probability of persistence or spread of an infection.

Bovine tuberculosis in badger (Meles meles) populations in southwest England: an assessment of past, present and possible future control strategies using simulation modelling.

A spatial stochastic simulation model was used to compare the efficacy of different badger control policies and to determine the theoretical requirements for the control of endemic bovine tuberculosis in badger populations in southwest England. Culling-based strategies for controlling endemic disease were compared with strategies employing a yet-to-be-developed oral vaccine which would provide uninfected badgers with immunity to the infection. A comparative assessment was made of the efficacy of previous and proposed culling-based strategies employed by the Ministry of Agriculture, Fisheries and Food for the control of localized disease, and the potential for an oral vaccine-based strategy for the control of localized disease was examined. For endemic bovine tuberculosis, to achieve a reasonable probability (p > 0.70) of successful control with a strategy involving a single culling operation, a very high proportion of the badger population (> 90%) must be culled. Single vaccination would not be successful in combating endemic disease. However, strategies involving repeated annual vaccination would have a very high probability of eradicating endemic disease, even with a relatively low (40-50%) annual vaccination efficiency. The most successful culling-based strategies for the control of localized disease were the gassing and clean ring strategies. Compared with no control at all, the interim strategy only offered benefits of a lower probability of disease spread and persistence in populations with low disease-free equilibrium group sizes or low initial prevalences of infection. In all other instances the benefits were negligible. The live test strategy will offer an improvement over the interim strategy, but will not be as effective as either the gassing or clean-ring strategies. In addition, it is likely to necessitate the culling of approximately four times as many badgers each year as the interim strategy, and the proportion of those killed that are infected will be approximately half that under the interim strategy. The efficacy of a strategy involving annually repeated oral vaccination of the badgers within a similar area to that covered by the live test depended on the efficiency of vaccination. A vaccination efficiency of 20-60% represented an overall improvement in efficacy over the interim strategy, being equivalent to the live test strategy. However, only vaccination efficiencies of 60-80% or greater achieved similar results to the gassing strategy, and none were so successful as the clean-ring strategy. Recommendations for future management are provided. Reactive strategies based on culling or vaccination will not solve the problem of bovine tuberculosis in badgers. Proactive strategies directed in those areas with a recent history of bovine tuberculosis in badgers should be considered as an alternative short-term control measure. The only strategy likely to eradicate bovine tuberculosis from badger populations in the long term is the use of repeated vaccination in proactive control operations in areas with a history of bovine tuberculosis in the badger population. Analyses should be conducted to evaluate whether the economic benefits of the live-test strategy are likely to outweigh its economic and ecological costs and whether continued research into the development of a vaccine for badgers is likely to offer any significant long-term economic benefits.

Bovine tuberculosis in badgers

The seventeenth report of a series on bovine tuberculosis in badgers has been published by MAFF. It was prepared by the Consultative Panel on Badgers and Bovine Tuberculosis which was set up by the Ministry with the remit of: i) keeping under review the evidence relating to bovine tuberculosis in badgers, including its distribution, its prevalence and its relationship to bovine tuberculosis in cattle;ii) advising on the operations to be undertaken by the Ministry in order to limit the transmission of tuberculosis from badgers to cattle;iii) recommending research appropriate to the problem of badgers and bovine tuberculosis.

Tuberculosis in badgers ( Meles meles)

This review examines the incidence of tuberculosis in badgers, the pathogenesis and diagnosis of the disease in the badger, and the control prospects related to spread of tuberculosis from badgers to cattle.

Modelling Bovine Tuberculosis in Badgers

We use deterministic models to study the spread of bovine tuberculosis (Mycobacterium bovis) infection within badger Meles meles subpopulations. We obtain analytical results for the models and adopt an easy-to-use approach―the Logical Parameter Search (LPS) Method―to generate appropriate parameter values for the model equations. We compare our computer-generated model parameter values with those obtained from the literature and present numerical simulations for the model system, some of which mimic the observed cyclic trend in disease incidence and prevalence as suggested, for example, by Cheeseman et al. (1989)

Epidemiological methods for investigating wild animals reservoirs of animal disease

The epidemiological and ecological methodologies used to investigate tuberculosis in badgers (Meles meles) in Great Britain are reviewed. The objectives of these studies have been, on the one hand, to investigate the causal association between Mycobacterium bovis infection in badgers and the occurrence of tuberculosis in cattle and, on the other, to acquire knowledge of the population biology of badgers and the dynamics of infection in order to identify, formulate and assess potential strategies. The studies provide examples of the possible approaches and the practical difficulties that investigations of wild animal populations present; the importance of a multi-disciplinary team which can be maintained for the protracted periods necessary for prospective studies is also highlighted. The most successful components of the research programme have been specific prospective studies of populations, as they provide the only means of understanding the dynamic aspects of the population biology and the epidemiology of infection and disease. Expedient, cross-sectional studies have, however, proved valuable in supplementing the main long-term studies.

Tuberculosis in badgers: a review.

Tuberculosis in badgers: a review.

Development of diagnostic tests for, and vaccination against, tuberculosis in Badgers

Development of diagnostic tests for, and vaccination against, tuberculosis in Badgers

Population ecology and prevalence of tuberculosis in Badgers in an area of Staffordshire

ABSTRACTForty‐five badgers representing five social groups were removed from an area in Staffordshire where tuberculosis had occurred in cattle. Prior to removal, the tuberculosis status of the badger population was investigated by screening faeces samples, collected at fortnightly intervals, and badger social‐group territories were determined by bait‐marking. Samples for cultural and biological examination were taken from the live badgers before euthanasia and detailed post‐mortem examination. The adult badger population density was 6‐2/km2 and Mycobacterium bovis was isolated from samples taken post mortem from eight (17‐8%) badgers. The results are reviewed in relation to previous findings.

Badger tuberculosis: Bring in your dead

Badger tuberculosis: Bring in your dead

Bovine tuberculosis in badgers

Bovine tuberculosis in badgers

Aspects of the epidemiology of bovine tuberculosis in badgers and cattle. II. The development and use of a typing system for Mycobacterium bovis.

A relatively simple method for the detection of intra-specific variation of Mycobacterium bovis is described, based on the ability of strains to utilize or remove amino acids from solution. Using the method, 31 strains of M. bovis, isolated badgers and cattle, have been divided in to four major groups with some additional sub-groups and intermediate strains. Preliminary results suggest that the biotypes observed are relatively stable. The method was used in the investigation of an outbreak of bovine tuberculosis in cattle in Gloucestershire where badgers were implicated as a source of infection. The results suggested that transmission of infection had occurred on at least two or three separate occasions. It is suggested that the method could be used in studying the epidemiology of bovine tuberculosis in wild animals, cattle and man.

Aspects of the epidemiology of bovine tuberculosis in badgers and cattle. I. The prevalence of infection in two wild animal populations in south-west England.

The prevalence of infections caused by Mycobacterium bovis was estimated in two populations of wild animals in the south west of England. A variety of mammalian species was trapped on farm land where incidents of infection with tuberculosis had occurred in cattle. Bacteriological analysis of lymph node samples and lesions showed that the only animals acting as a reservoir for M. bovis were badgers. Examination of arthropod ectoparasites of infected badgers proved negative for M. bovis and suggests that these are unlikely to act as vectors in transmission of the disease.

A pilot study to assess the usefulness of ELISA in detecting tuberculosis in badgers

A pilot study to assess the usefulness of ELISA in detecting tuberculosis in badgers

Tuberculosis in wild badgers (Meles meles) in Gloucestershire: pathology.

The gross and histological appearances of the lesions of tuberculosis in 36 wild badgers found to be infected with Mycobacterium bovis are described. These badgers were examined over a period of two years during an investigation into the possible epidemiological association of tuberculosis in badgers and cattle. The possible significance of the lesions in transmission of M bovis to cattle and other badgers is discussed. The histological appearance of the lesions was considered to be indicative of a lesser hypersensitivity reaction than is seen in the bovine.