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.

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.

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.

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 cattle1. 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 trial3,4,5 that indicate that localized badger culling not only fails to control but also seems to increase TB incidence in cattle.

The Independent Scientific Group on Cattle TB was appointed by the Government in 1998 to implement and develop the research recommendations of the 1997 Krebs report on bovine tuberculosis in cattle and badgers. In this article, members of the group discuss the approach they are adopting in attempting to ensure that future control strategies are scientifically based. In a second article, to be published in next week's Veterinary Record, the group will consider the extent to which efforts to control the disease in cattle may be constrained by limitations in current testing procedures.

The incidence of bovine TB, a potential threat to human health and the livelihood of farmers, is rising in parts of Britain. The disease is thought to be transmitted to cattle by badgers, a protected wildlife species. A recently published review suggests that the British Government should adopt a more scientific approach tan in the past to evaluating control strategies.

The spread of bovine virus diarrhoea virus (BVDV) in a closed dairy herd maintained under typical management conditions is studied using two approaches. In the first instance a stochastic computer model is used to simulate the month-to-month changes in the infection status of each animal. These results are contrasted with the results of a mass-action model which uses three differential equations. A comparison of the two approaches indicates that the results are in broad agreement. The stochastic approach has the benefit of providing an estimate of the probability of the infection becoming extinct and the herd becoming BVDV-free for different herd sizes.

This paper describes a computer model that mimics the spread of bovine viral diarrhoea virus (BVDV) infection through a closed herd. The model is able to simulate the spread of infection when a persistently infected (PI) animal is introduced into an infection-free herd, and it is used to investigate the role of persistently infected animals, seroconverting animals, loss of PI calves and duration of immunity on the level of infection within the herd. Under typical management conditions one persistently infected animal poses a real threat to a herd, and the prospect of the herd becoming infection free in a 10-year period without intervention is remote. Seroconverting animals are found to be an important source of infection in herds with few immune animals. The increased loss of PI calves is likely to restrict the numbers of PI animals in a herd, and loss of immunity is important since it increases the possibility of a PI calf being born.

Cloned bovine lymphoblastoid cell lines, transformed by the protozoan parasite Theileria parva were infected with cell culture-attenuated rinderpest virus vaccine. The virus grew readily in lymphoid B cells, CD4+ and CD8+ alpha/beta T cells and gamma/delta T cells producing new infectivity, viral antigens, c.p.e. and total cell death. There did not appear to be a predilection for any particular phenotype of lymphoblast. The results imply that if the vaccine causes immunosuppression, it could do so through a variety of mechanisms.

Equine Veterinary JournalVolume 23, Issue S12 p. 6-9 Toward an understanding of the immune responses that control infectious diseases W. I. Morrison, W. I. Morrison AFRC Institute for Animal Health, Compton, Nr Newbury, Berkshire RG16 ONN, UK.Search for more papers by this author W. I. Morrison, W. I. Morrison AFRC Institute for Animal Health, Compton, Nr Newbury, Berkshire RG16 ONN, UK.Search for more papers by this author First published: September 1991 https://doi.org/10.1111/j.2042-3306.1991.tb04750.xAboutPDF 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 onFacebookTwitterLinkedInRedditWechat Volume23, IssueS12September 1991Pages 6-9 RelatedInformation