OBJECTIVES:We present the results of a 2005 case-control study of bovine tuberculosis (bTB) breakdowns in English and Welsh herds. The herd management, farming practices, and environmental factors of 401 matched pairs of case and control herds were investigated to provide a picture of herd-level risk factors in areas of varying bTB incidence. METHODS:A global conditional logistic regression model, with region-specific variants, was used to compare case herds that had experienced a confirmed bTB breakdown to contemporaneous control herds matched on region, herd type, herd size, and parish testing interval. RESULTS:Contacts with cattle from contiguous herds and sourcing cattle from herds with a recent history of bTB were associated with an increased risk in both the global and regional analyses. Operating a farm over several premises, providing cattle feed inside the housing, and the presence of badgers were also identified as significantly associated with an increased bTB risk. CONCLUSIONS:Steps taken to minimize cattle contacts with neighboring herds and altering trading practices could have the potential to reduce the size of the bTB epidemic. In principle, limiting the interactions between cattle and wildlife may also be useful; however this study did not highlight any specific measures to implement.

Bovine tuberculosis (TB) is a zoonotic disease that can have serious consequences for cattle farming and, potentially, for public health. In Britain, failure to control bovine TB has been linked to persistent infection of European badger (Meles meles) populations. However, culling of badgers in the vicinity of recent TB outbreaks in cattle has failed to reduce the overall incidence of cattle TB. Using data from a large-scale study conducted in 1998-2005, we show that badgers collected on such localized culls had elevated prevalence of Mycobacterium bovis, the causative agent of bovine TB, suggesting that infections in cattle and badgers were indeed associated. Moreover, there was a high degree of similarity in the M. bovis strain types isolated from cattle and associated badgers. This similarity between strain types appeared to be unaffected by time lags between the detection of infection in cattle and culling of badgers, or by the presence of purchased cattle that might have acquired infection elsewhere. However, localized culling appeared to prompt an increase in the prevalence of M. bovis infection in badgers, probably by disrupting ranging and territorial behavior and hence increasing intraspecific transmission rates. This elevated prevalence among badgers could offset the benefits, for cattle, of reduced badger densities and may help to explain the failure of localized culling to reduce cattle T13 incidence.

1. In most social animals, the prevalence of directly transmitted pathogens increases in larger groups and at higher population densities. Such patterns are predicted by models of Mycobacterium bovis infection in European badgers (Meles meles). 2. We investigated the relationship between badger abundance and M. bovis prevalence, using data on 2696 adult badgers in 10 populations sampled at the start of the Randomized Badger Culling Trial. 3. M. bovis prevalence was consistently higher at low badger densities and in small social groups. M. bovis prevalence was also higher among badgers whose genetic profiles suggested that they had immigrated into their assigned social groups. 4. The association between high M. bovis prevalence and small badger group size appeared not to have been caused by previous small-scale culling in study areas, which had been suspended, on average, 5 years before the start of the current study. 5. The observed pattern of prevalence might occur through badgers in smaller groups interacting more frequently with members of neighbouring groups; detailed behavioural data are needed to test this hypothesis. Likewise, longitudinal data are needed to determine whether the size of infected groups might be suppressed by disease-related mortality. 6. Although M. bovis prevalence was lower at high population densities, the absolute number of infected badgers was higher. However, this does not necessarily mean that the risk of M. bovis transmission to cattle is highest at high badger densities, since transmission risk depends on badger behaviour as well as on badger density.

Summary Bovine tuberculosis (TB), caused by Mycobacterium bovis, has serious consequences for Britain's cattle industry. European badgers (Meles meles) can transmit infection to cattle, and for many years the British government culled badgers in a series of attempts to reduce cattle infections. We investigated the impact of badger culling on the spatial distribution of M. bovis infection in badger and cattle populations in replicated areas in England. M. bovis infection was significantly clustered within badger populations, but clustering was reduced when culls were repeated across wide areas. A significant spatial association between M. bovis infections in badgers and cattle herds likewise declined across successive culls. These patterns are consistent with evidence that badgers are less territorial and range more widely in culled areas, allowing transmission to occur over greater distances. Prior to culling, M. bovis infections were clustered within cattle populations. Where badger culling was localised, and in unculled areas just outside widespread culling areas, cattle infections became less spatially clustered as badger culling was repeated. This is consistent with expanded badger ranging observed in these areas. In contrast, clustering of infection in cattle persisted over time on lands where badgers were repeatedly culled over wide areas. While this lack of a temporal trend must be interpreted with caution, it might reflect persistent infection within, and continued transmission between, cattle herds in areas where transmission from badgers to cattle had been reduced by badger culling. Continued spatial association of infections in cattle and badgers in such areas might partly reflect transmission from cattle. Synthesis and applications: Our findings confirm that badger culling can prompt spatial spread of M. bovis infection, a phenomenon likely to undermine the utility of this approach as a disease control measure. Possible evidence of transmission from cattle, both to other cattle and to badgers, suggests that improved cattle controls might yield multiple benefits for TB management.

Veterinary RecordVolume 161, Issue 18 p. 633-635 Letter TB policy and the ISG's findings F. J. Bourne, F. J. Bourne Former members Independent Scientific Group on Cattle TBSearch for more papers by this authorC. A. Donnelly, C. A. Donnelly Independent Scientific Group on Cattle TBSearch for more papers by this authorD. R. Cox, D. R. Cox Independent Scientific Group on Cattle TBSearch for more papers by this authorG. Gettinby, G. Gettinby Independent Scientific Group on Cattle TBSearch for more papers by this authorJ. P. McInerney, J. P. McInerney Independent Scientific Group on Cattle TBSearch for more papers by this authorW. I. Morrison, W. I. Morrison Independent Scientific Group on Cattle TBSearch for more papers by this authorR. Woodroffe, R. Woodroffe Independent Scientific Group on Cattle TBSearch for more papers by this author F. J. Bourne, F. J. Bourne Former members Independent Scientific Group on Cattle TBSearch for more papers by this authorC. A. Donnelly, C. A. Donnelly Independent Scientific Group on Cattle TBSearch for more papers by this authorD. R. Cox, D. R. Cox Independent Scientific Group on Cattle TBSearch for more papers by this authorG. Gettinby, G. Gettinby Independent Scientific Group on Cattle TBSearch for more papers by this authorJ. P. McInerney, J. P. McInerney Independent Scientific Group on Cattle TBSearch for more papers by this authorW. I. Morrison, W. I. Morrison Independent Scientific Group on Cattle TBSearch for more papers by this authorR. Woodroffe, R. Woodroffe Independent Scientific Group on Cattle TBSearch for more papers by this author First published: 03 November 2007 https://doi.org/10.1136/vr.161.18.633-bRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume161, Issue18November 2007Pages 633-635 RelatedInformation

SUMMARYThe Randomized Badger Culling Trial (RBCT) began in 1998 to determine the impact of badger culling in controlling bovine tuberculosis in cattle. A total of 1166 badgers (14% of total) proactively culled during the RBCT were found to be tuberculous, offering a unique opportunity to study the pathology caused byMycobacterium bovisin a large sample of badgers. Of these, 39% of adults (~6% of all adults culled) had visible lesions (detectable at necropsy) of bovine tuberculosis; cubs had a lower prevalence of infection (9%) but a higher percentage of tuberculous cubs (55·5%) had visible lesions. Only ~1% of adult badgers had extensive, severe pathology. Tuberculous badgers with recorded bite wounds (~5%) had a higher prevalence of visible lesions and a different distribution of lesions, suggesting transmission via bite wounds. However, the predominance of lesions in the respiratory tract indicates that most transmission occurs by the respiratory route.

Culling is often considered as a tool for controlling wildlife diseases that can also infect people or livestock. Culling European badgers Meles meles can cause both positive and negative effects on the incidence of bovine tuberculosis (TB) in cattle. One factor likely to influence the outcome of different badger-culling strategies for cattle TB is the reduction in badger population density achieved. However, this reduction is difficult to measure because badgers, being nocturnal and fossorial, are difficult to count. Here, we use indices of badger abundance to measure the population impacts of two culling strategies tested in Britain. The densities of badger setts and latrines recorded before culling were correlated with the densities of badgers captured on initial culls, suggesting that both were indices of actual badger abundance. Widespread ‘proactive’ culling was associated with a 73% reduction in the density of badger latrines, a 69% reduction in the density of active burrows and a 73% reduction in the density of road-killed badgers. This population reduction was achieved by a coordinated effort entailing widespread and repeated trapping over several years. However, this strategy caused only modest reductions in cattle TB incidence in culled areas and elevated incidence in neighbouring unculled areas. Localized ‘reactive’ culling caused a 26% reduction in latrine density, a 32% reduction in active burrow density and a 10% reduction in the density of road-killed badgers, but apparently increased the incidence of cattle TB. These results indicate that the relationship between badger population reduction and TB transmission to cattle is strongly non-linear, probably because culling prompts changes in badger behaviour that influence transmission rates. These findings raise serious questions about the capacity of badger culling to contribute to the control of cattle TB in Britain.

Background: Bovine tuberculosis (TB) has re-emerged as a major problem for British cattle farmers. Failure to control the infection has been linked to transmission from European badgers; badger cutting has therefore formed a component of British TB control policy since 1973.Objectives and design: To investigate the impact of repeated widespread badger cutting on cattle TB, the Randomised Badger Cutting Trial compared TB incidence in cattle herds in and around ten cutting areas (each 100 km(2)) with those in and around ten matched unculled areas.Results: Overall, cattle TB incidence was 23.2% tower (95% confidence interval (Cl) 12.4-32.7% tower) inside culled areas, but 24.5% (95% Cl 0.6% lower-56.0% higher) higher on land <= 2 km outside, relative to matched unculled areas. Inside the cutting area boundary the beneficial effect of cutting tended to increase with distance from the boundary (p = 0.085) and to increase on successive annual cults (p = 0.064). In adjoining areas, the detrimental effect tended to diminish on successive annual cults (p = 0.17). On the basis of such linear trends, the estimated net effect per annum for cutting areas similar to those in the trial was detrimental between the first and second cults, but beneficial after the fourth and later cults, for the range of analyses performed.Conclusions: Careful consideration is needed to determine in what settings systematic repeated cutting might be reliably predicted to be beneficial, and in these cases whether the benefits of such cutting warrant the costs involved. (C) 2007 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Human and livestock diseases can be difficult to control where infection persists in wildlife populations. For three decades, European badgers (Meles meles) have been culled by the British government in a series of attempts to limit the spread of Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), to cattle1. Despite these efforts, the incidence of TB in cattle has risen consistently, re-emerging as a primary concern for Britain's cattle industry. Recently, badger culling has attracted controversy because experimental studies have reached contrasting conclusions (albeit using different protocols), with culled areas showing either markedly reduced2,3 or increased4,5 incidence of TB in cattle. This has confused attempts to develop a science-based management policy. Here we use data from a large-scale, randomized field experiment to help resolve these apparent differences. We show that, as carried out in this experiment, culling reduces cattle TB incidence in the areas that are culled, but increases incidence in adjoining areas. These findings are biologically consistent with previous studies2,3,4,5 but will present challenges for policy development.

Summary The incidence of bovine tuberculosis (TB) in British cattle has risen markedly over the last two decades. Failure to control the disease in cattle has been linked to the persistence of a reservoir of infection in European badgers Meles meles, a nationally protected species. Although badger culling has formed a component of British TB control policy for many years, a recent large‐scale randomized field experiment found that TB incidence in cattle was no lower in areas subject to localized badger culling than in nearby areas where no experimental culls occurred. Indeed, analyses indicated that cattle incidence was higher in culled areas. One hypothesis advanced to explain this pattern is that localized culling disrupted badgers’ territorial behaviour, potentially increasing the rate of contact between cattle and infected badgers. This study evaluated this hypothesis by investigating badger activity and spatial organization in 13 study areas subjected to different levels of culling. Badger home ranges were mapped by feeding colour‐marked baits at badger dens and measuring the geographical area in which colour‐marked faeces were retrieved. Badger home ranges were consistently larger in culling areas. Moreover, in areas not subjected to culling, home range sizes increased with proximity to the culling area boundary. Patterns of overlap between home ranges were also influenced by culling. Synthesis and applications. This study demonstrates that culling badgers profoundly alters their spatial organization as well as their population density. These changes have the potential to influence contact rates between cattle and badgers, both where culls occur and on adjoining land. These results may help to explain why localized badger culling appears to have failed to control cattle TB, and should be taken into account in determining what role, if any, badger culling should play in future control strategies.

Human and livestock diseases can be difficult to control where infection persists in wildlife populations. In Britain, European badgers (Meles meles) are implicated in transmitting Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), to cattle. Badger culling has therefore been a component of British TB control policy for many years. However, large-scale field trials have recently shown that badger culling has the capacity to cause both increases and decreases in cattle TB incidence. Here, we show that repeated badger culling in the same area is associated with increasing prevalence of M. bovis infection in badgers, especially where landscape features allow badgers from neighboring land to recolonize culled areas. This impact on prevalence in badgers might reduce the beneficial effects of culling on cattle TB incidence, and could contribute to the detrimental effects that have been observed. Additionally, we show that suspension of cattle TB controls during a nationwide epidemic of foot and mouth disease, which substantially delayed removal of TB-affected cattle, was associated with a widespread increase in the prevalence of M. bovis infection in badgers. This pattern suggests that infection may be transmitted from cattle to badgers, as well as vice versa. Clearly, disease control measures aimed at either host species may have unintended consequences for transmission, both within and between species. Our findings highlight the need for policymakers to consider multiple transmission routes when managing multihost pathogens.

SIR, – We wish to respond to the letter of Gallagher and others ( VR , March 4, 2006, vol 158, pp 310-311), in which a number of issues were raised with respect to the contribution that culling badgers might make to the control of cattle tuberculosis (TB). The Government has made it clear that

As an aid to the study of bovine tuberculosis (TB), a simple model has been developed of an epidemic involving two species, cattle and badgers. Each species may infect the other. The proportion of animals affected is assumed relatively small so that the usual nonlinear aspects of epidemic theory are avoided. The model is used to study the long-run and transient effect on cattle of culling badgers and the effect of a period without routine testing for TB, such as occurred during the 2001 epidemic of foot-and-mouth disease in Great Britain. Finally, by examining the changes in cattle TB over the last 15 years, and with some other working assumptions, it is estimated that the net reproduction number of the epidemic is approximately 1.1. The implications for controlling the disease are discussed.

Journal of Agricultural EconomicsVolume 56, Issue 3 p. 459-461 Professor Watkin James Thomas, 1919–2005 Professor (Emeritus) David Colman, Professor (Emeritus) David Colman University of ManchesterSearch for more papers by this authorProfessor (Emeritus) John P. McInerney, Professor (Emeritus) John P. McInerney Exeter UniversitySearch for more papers by this author Professor (Emeritus) David Colman, Professor (Emeritus) David Colman University of ManchesterSearch for more papers by this authorProfessor (Emeritus) John P. McInerney, Professor (Emeritus) John P. McInerney Exeter UniversitySearch for more papers by this author First published: 20 December 2005 https://doi.org/10.1111/j.1477-9552.2005.00025.xRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Volume56, Issue3December 2005Pages 459-461 RelatedInformation

A case–control study of the factors associated with the risk of a bovine tuberculosis (TB) breakdown in cattle herds was undertaken within the randomized badger culling trial (RBCT). TB breakdowns occurring prior to the 2001 foot-and-mouth disease epidemic in three RBCT triplets were eligible to be cases; controls were selected from the same RBCT area. Data from 151 case farms and 117 control farms were analysed using logistic regression. The strongest factors associated with an increased TB risk were movement of cattle onto the farm from markets or farm sales, operating a farm over multiple premises and the use of either covered yard or ‘other’ housing types. Spreading artificial fertilizers or farmyard manure on grazing land were both associated with decreased risk. These first case–control results from the RBCT will be followed by similar analyses as more data become available.

For the past 25 years, European badgers (Meles meles) have been subject to culling in Britain in attempts to limit the spread of tuberculosis (TB) to cattle. As part of a far-reaching evaluation of the effectiveness and acceptability of badger culling as a TB control measure, this paper assesses one aspect of the welfare of badger populations subjected to culling: the killing of breeding females, which risks leaving their unweaned cubs to starve in the den. To avoid this possibility, a three-month closed season was adopted, running from 1st February to 30th April, based on the best available estimates of the timing of birth and weaning in British badgers. During May 1999–2003, when a total of 4705 adult badgers were culled, field teams failed to capture 12 unweaned litters when their mothers were despatched. In 31 other cases, lactating females were culled but litters of almost-weaned cubs were also caught and despatched at the same dens, usually within a day of capture of the mother. The number of unweaned cubs missed by culling teams — estimated at approximately nine per year on average — was dramatically lower than that projected by a badger welfare lobby group. Our data suggest that the closed season is effective in reducing the suffering of unweaned cubs in badger populations subject to culling, and we recommend that this measure be maintained should badger culling form a component of any future TB control policy.

For over 25 years, European badgers ( Meles meles ) have been subject to culling in Britain in attempts to limit the spread of tuberculosis (TB) to cattle. As part of a far-reaching evaluation of the effectiveness and acceptability of badger culling as a TB control measure, this paper assesses one aspect of the welfare of badger populations subjected to culling: the risk of badgers confined to cage traps prior to despatch becoming injured as a result of rubbing or biting on the cage. In a large-scale field trial, 88% of badgers received no detectable injuries as a result of being confined in the trap. Of those that were injured, 72% received only minor skin abrasions. A minority (1.8% of the total) acquired damage to the teeth or jaws that may have caused serious pain. Although trap rounds were commenced in the early morning, badgers were no more likely to sustain injuries when they remained in traps until later in the day. Coating of cage traps, intended to give the wire mesh a smoother surface, was associated with a reduction in the incidence of minor skin abrasions, although it may have slightly increased the frequency of less common but more serious abrasions. Modification of the door design reduced tooth damage. Traps will be further modified if appropriate. However, all aspects of the conduct of trapping operations must balance badger welfare with concerns for the health and safety of field staff.

In order that future TB control policies can be science based, Defra on ISG advice has put in place a comprehensive programme of research to better understand the epidemiology of TB in both cattle and badgers.1,2,3 This research is now providing a flow of valuable data on a range of topics, extending beyond the trial on culling badgers that was originally proposed in the Krebs report.4 Emerging data, as yet incomplete, will allow secure scientific conclusions to be drawn.5

1. Control of zoonotic disease is difficult to achieve when populations of multiple hosts, particularly wildlife, become persistently infected. Bovine tuberculosis (TB) is one such disease: its causative agent, Mycobacterium bovis, infects cattle, humans and multiple wildlife species including European badgers Meles meles.2. In Britain, from 1974 to 1998 various strategies for the control of cattle TB involved culling badgers in the immediate vicinity of TB-affected herds. However, patterns of association between cattle and badgers had not been investigated at a local scale.3. Using data from the Randomized Badger Culling Trial, an ongoing large-scale study of TB dynamics and control, we investigated local geographical associations between M. bovis infection in badgers and cattle.4. Mycobacterium bovis infections were locally clustered within both badger and cattle populations.5. We show, for the first time, that M. bovis infections in badgers and cattle are spatially associated at a scale of 1-2 km. Badgers and cattle infected with the same strain type of M. bovis are particularly closely correlated. These observational data support the hypothesis that transmission occurs between the two host species; however, they cannot be used to evaluate the relative importance of badger-to-cattle and cattle-to-badger transmission.6. Synthesis and applications. The close associations between M. bovis infections in cattle and badgers suggest that localized badger culling could reasonably be expected to reduce the risks of cattle TB infection; however, experimental culls have found no such beneficial effects over the time-scale on which they were tested. This demonstrates the difficulty of predicting the outcome of management interventions, and reinforces the need for well-designed empirical assessments of future control strategies.