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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.

Human and livestock diseases can be difficult to control where infection persists in wildlife populations. In Britain, European badgers (Meles meles) are implicated in transmittingMycobacterium 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 ofM. bovisinfection 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 ofM. bovisinfection 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 have read with interest the criticisms of the randomised badger culling trial (rbct) made by [Gallagher and others (2007)][1]; we consider them to have no scientific basis. While the authors contrast the rbct findings with the results of ‘previous trials in this country’, in fact no

Summary 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.

Economic studies on disease in farm livestock have focused largely on cost/benefit analyses of control programs or gross estimates of the costs due to particular diseases. Neither offers an adequate basis to guide economic decisions. This paper develops a framework with a more rigorous underpinning in economic concepts and principles. First, the total economic cost of a disease is explained in terms of two distinct components: (i) output losses following disease occurrence; (ii) expenditures made to treat disease or prevent its occurrence. We then develop the general relationship between these two components, calling it the ‘loss-expenditure frontier’, and use it to define the economically optimal level of disease costs. This shows that the relevant measures of the economic cost of disease are not the total cost figures usually estimated. The paper explains how, in principle, the loss-expenditure frontier can provide the appropriate information for decisions on disease control, and demonstrates this using survey data on subclinical mastitis in the UK dairy national herd.

Animal welfare concerns have gained greater prominence over recent decades as livestock production techniques have become more intensive. Welfare issues are now considered among the principal problems that agriculture must confront in the future. The central theme of this paper is that, notwithstanding the objective assessments of the animal scientist, animal welfare is primarily a subjective matter of human perceptions; further, because people's preferences determine action, in practice it will be treated as a subset of human welfare. The inherent conflict between animal and human interest is captured in the relationship between welfare and livestock productivity, highlighting the fact that higher welfare standards in modern farming would inevitably raise the price of food. In the light of this, the paper considers both the legal imposition of welfare codes and an approach which allows food consumers to determine the ‘socially appropriate’ standards via conventional market processes. In the last analysis neither animal science nor economics can do more than cast light on what is fundamentally a socio-political issue.

Pathogens that are transmitted between wildlife, livestock and humans present major challenges for the protection of human and animal health, the economic sustainability of agriculture, and the conservation of wildlife. Mycobacterium bovis, the aetiological agent of bovine tuberculosis (TB), is one such pathogen. The incidence of TB in cattle has increased substantially in parts of Great Britain in the past two decades, adversely affecting the livelihoods of cattle farmers and potentially increasing the risks of human exposure. The control of bovine TB in Great Britain is complicated by the involvement of wildlife, particularly badgers (Meles meles), which appear to sustain endemic infection and can transmit TB to cattle. Between 1975 and 1997 over 20,000 badgers were culled as part of British TB control policy, generating conflict between conservation and farming interest groups2. Here we present results from a large-scale field trial3–5 that indicate that localized badger culling not only fails to control but also seems to increase TB incidence in cattle.

The present paper presents a non-technical overview of contemporary developments in food supply, as seen from the standpoint of economic adjustment. The historical concerns over availability and price of food have now passed in the UK, and agriculture is no longer dominantly driven by the supply-side forces of new farming technology and the stimulus of support policies. As a now demand-driven sector of the economy, it is the developing diversity of consumer food preferences that will increasingly determine the adjustment path of agricultural production. Those demands seek distinctive elements of food value, many of which are entirely created and delivered by industries beyond the farm gate. However, many of the quality characteristics of food that consumers increasingly seek are associated explicitly with what takes place on farms and how crop and livestock husbandry is conducted. In responding to these demand preferences many farmers will shift from being merely raw material producers to becoming genuine producers of food, or capturing more of the final value of the products consumed. As a result a dual structure within farming will develop, with a ‘quality agriculture’ becoming increasingly differentiated from a ‘commodity agriculture’ as two distinct strategies for farm business survival.

The introduction of new technology into agriculture is a central feature of development schemes, but is regularly criticised because of its distributive effects. Technology change is unavoidably biased, however, and cannot easily be used to serve specific distribution objectives. Ex post studies do not necessarily guide the appropriate choice of technology as they rarely offer causal explanations. Predicting the consequences of innovation is hampered by the narrowness of established economic models and the conceptual indefiniteness of technology as a variable in those models. In the absence of a wider system framework, technology for development is selected according to more general guides. These emphasise either the primacy of output objectives or advocate technology forms presumed appropriate to distribution objectives. Neither adequately substitutes for a broad framework to guide the choice of technology as an instrument in development.