The spatio-temporal distribution of Mycobacterium bovis (bovine tuberculosis) infection in a high-density badger population (original) (raw)
Related papers
Journal of Animal Ecology, 2007
1. The culling of European badgers Meles meles has been a central part of attempts to control bovine tuberculosis (TB) in British cattle for many years. Recent results, however, indicate that this approach could in practice enhance disease spread. 2. This paper looks at the relationship between TB incidence and badger ecology in a high-density population in southwest England, which has been the subject of a longterm intensive study. The principal aims were to relate the probability of TB incidence, as detected by culture of clinical samples (i.e. excretion of bacilli), at the level of the individual and of the social group to demographic processes, movement, social organization and disease dynamics. 3. The probability of an individual being an incident case was greater in groups where TB was already present, although this was less influential in groups that were subject to some instability in numbers. Both individuals and groups were more likely to be incident cases where the social group was diminishing in size, although no relationship was observed with group size itself. This suggests that the process of group size reduction rather than group size per se has most influence on disease dynamics. The likelihood that either an individual or a group was an incident case was positively correlated with both individual and group-level movement. When the proportion of females in a social group was high, the positive association between movement and incidence was found to be more pronounced and there was a significantly higher probability of incident cases among males. 4. These relationships highlight the importance of social structure in driving TB transmission dynamics in this stable, high-density badger population. The results support the idea that a stable social structure mitigates against new incident cases of disease, and are consistent with the contention that badger culling may create the social circumstances for enhanced transmission of TB.
Evaluating evidence of association of bovine tuberculosis in cattle and badgers
Journal of Applied Ecology, 2008
Bovine tuberculosis (TB) occurs in cattle and badgers in the UK and control efforts are undertaken to reduce the spread of the disease. 2. This study evaluates relationships predicted by nine epidemiological two-host models of disease spread generated by various combinations of density-dependent, frequency-dependent and environmental pathogen transmission. The relationships of interest are between measures of TB in cattle and in badgers from 10 sites which were randomly selected to be proactive badger culling sites in the UK Randomized Badger Culling Trial. The data are from the initial badger cull only.
Bovine tuberculosis in cattle and badgers in localized culling areas
2009
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 TB incidence.
Is There an Association between Levels of Bovine Tuberculosis in Cattle Herds and Badgers?
Statistical Communications in Infectious …, 2010
Wildlife diseases can have undesirable effects on wildlife, on livestock and people. Bovine tuberculosis (TB) is such a disease. This study derives and then evaluates relationships between the proportion of cattle herds with newly detected TB infection in a year and data on badgers, in parts of Britain. The relationships are examined using data from 10 sites which were randomly selected to be proactive culling sites in the UK Randomized Badger Culling Trial. The badger data are from the initial cull only and the cattle incidence data pre-date the initial badger cull. The analysis of the proportion of cattle herds with newly detected TB infection in a year, showed strong support for the model including significant frequency-dependent transmission between cattle herds and significant badger-to-herd transmission proportional to the proportion of M. bovisinfected badgers. Based on the model best fitting all the data, 3.4% of herds (95% CI: 0-6.7%) would be expected to have TB infection newly detected (i.e. to experience a TB herd breakdown) in a year, in the absence of transmission from badgers. Thus, the null hypothesis that at equilibrium herd-to-herd transmission is not sufficient to sustain TB in the cattle population, in the absence of transmission from badgers cannot be rejected (p=0.18). Omitting data from three sites in which badger carcase storage may have affected data quality; the estimate dropped to 1.3% of herds (95% CI: 0-6.5%) with p=0.76. The results demonstrate close positive relationships between bovine TB in cattle herds and badgers infectious with M. bovis. The results indicate that TB in cattle herds could be substantially * The Randomized Badger Culling Trial (RBCT) in Britain was designed, overseen and analysed by the Independent Scientific Group on Cattle TB
Scientific Reports, 2015
Bovine TB (bTB) is endemic in Irish cattle and has eluded eradication despite considerable expenditure, amid debate over the relative roles of badgers and cattle in disease transmission. Using a comprehensive dataset from Northern Ireland (>10,000 km 2 ; 29,513 cattle herds), we investigated interactions between host populations in one of the first large-scale risk factor analyses for new herd breakdowns to combine data on both species. Cattle risk factors (movements, international imports, bTB history, neighbours with bTB) were more strongly associated with herd risk than arealevel measures of badger social group density, habitat suitability or persecution (sett disturbance). Highest risks were in areas of high badger social group density and high rates of persecution, potentially representing both responsive persecution of badgers in high cattle risk areas and effects of persecution on cattle bTB risk through badger social group disruption. Average badger persecution was associated with reduced cattle bTB risk (compared with high persecution areas), so persecution may contribute towards sustaining bTB hotspots; findings with important implications for existing and planned disease control programmes.
Culling and cattle controls influence tuberculosis risk for badgers
Proceedings of the National Academy of Sciences, 2006
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.
Modelling bovine tuberculosis in badgers in England: preliminary results
Mammalia, 1995
Bovine tuberculosis (TB) appears to be endemic within the badger population of southwest England. The total number of cattle herds with confirmed tuberculosis has increased from 197 in 1992 to 320 in 1993, and the badger is believed to be responsible for many of these breakdowns. Data on a high density badger population naturally infected with tuberculosis have been collected since the late 1970s. This paper presents some of the results of this epidemiological study and shows how localised the disease has been over a number of years. We also describe a number of models that have been used to help understand the progression of the disease within the population. These are simple, within-group infection models used primarily to help to understand the disease dynamics. The option to add vaccination, or restructure the model for other species, such as possums is always available. The results suggest that TB would only be sustained for long periods in social groups with about eight or more members, and that disease spread does not correspond to classical epidemiological models. Resume.-La tuberculose bovine (TB) apparait etre endemique chez les blaireaux du sudouest de l'Angleterre. Le nombre total de troupeaux de betail avec une tuberculose confirmee s'est accru de 197 en 1992 ä 320 en 1993, et le blaireau est considere comme responsable de beaucoup de ces cas. Des donnees concernant une population ä haute densite de blaireaux naturellement infectes par la tuberculose ont etc collectees depuis les annees 1970. Cette note presente certains des resultats de cette etude epidemiologique et montre combien la maladie a etc localisee pendant un certain nombre d'annees. Nous decrivons aussi un certain nombre de modeles qui ont etc utilises pour aider a la comprehension de la progression de la maladie dans la population. Ceux-ci sont des modeles simples d'infection intra-groupe, utilises pour aider ä la comprehension de la dynamique de la maladie. L'option d'ajouter la vaccination, ou de restructurer le modele pour d'autres especes, comme les opossums, est possible. Les resultats suggerent que la tuberculose se maintiendrait longtemps dans des groupes sociaux d'environ huit membres, et que la dispersion de la maladie ne correspond pas a des modeles epidemiologiques classiques.
Effects of culling on spatial associations of Mycobacterium bovis infections in badgers and cattle
Journal of Applied Ecology, 2007
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. 2. 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. 3. 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. 4. 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. 5. 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. 6. 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 Record, 2012
Veterinary Record 170: 259 (2012). doi: 10.1136/vr.100193 In a survey, 457 badgers that had been found dead in Wales were postmortem-examined, and samples were examined by histology and by extended culture (for up to 12 weeks). Mycobacterium bovis was cultured from 55 badgers (12.0 per cent), and the histology typical of M bovis infection was seen in a further six (1.3 per cent). The prevalence in badgers in each of 10 geographical areas varied between 0 and 26 per cent (P<0.001), and was associated with the incidence of confirmed M bovis infection in cattle herds in the same areas (P<0.01). In northern Wales, bTB was rare in both hosts. An infected badger was 12.3 times more likely to be within 5 km of a confirmed cattle bTB breakdown than an uninfected badger. The M bovis isolates from badgers belonged to one of four genotypes defined by spoligotype and variable number tandem repeat type. These genotypes were also found in 290 concurrent confirmed herd breakdowns, and tended to be similar to the genotypes in badgers in the same geographical areas. When badgers and cattle no more than 30 km apart were compared, the genotype diversity was greater in cattle than in badgers (P=0.016), suggesting that the movement of cattle plays a greater part in the spatial distribution of M bovis than the movement of badgers.
Spatial association of Mycobacterium bovis infection in cattle and badgers Meles meles
Journal of Applied Ecology, 2005
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-tobadger 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.