The incidence of Mycobacterium bovis, the causative agent of bovine tuberculosis, has been increasing in UK cattle herds resulting in substantial economic losses. The European badger (Meles meles) is implicated as a wildlife reservoir of infection. One likely route of transmission to cattle is through exposure to infected badger urine and faeces. The relative importance of the environment in transmission remains unknown, in part due to the lack of information on the distribution and magnitude of environmental reservoirs. Here we identify potential infection hotspots in the badger population and quantify the heterogeneity in bacterial load; with infected badgers shedding between 1 × 103 − 4 × 105 M. bovis cells g−1 of faeces, creating a substantial and seasonally variable environmental reservoir. Our findings highlight the potential importance of monitoring environmental reservoirs of M. bovis which may constitute a component of disease spread that is currently overlooked and yet may be responsible for a proportion of transmission amongst badgers and onwards to cattle.
eThe incidence of Mycobacterium bovis, the causative agent of bovine tuberculosis, in cattle herds in the United Kingdom is increasing, resulting in substantial economic losses. The European badger (Meles meles) is implicated as a wildlife reservoir and is the subject of control measures aimed at reducing the incidence of infection in cattle populations. Understanding the epidemiology of M. bovis in badger populations is essential for directing control interventions and understanding disease spread; however, accurate diagnosis in live animals is challenging and currently uses invasive methods. Here we present a noninvasive diagnostic procedure and sampling regimen using field sampling of latrines and detection of M. bovis with quantitative PCR tests, the results of which strongly correlate with the results of immunoassays in the field at the social group level. This method allows M. bovis infections in badger populations to be monitored without trapping and provides additional information on the quantities of bacterial DNA shed. Therefore, our approach may provide valuable insights into the epidemiology of bovine tuberculosis in badger populations and inform disease control interventions.M ycobacterium bovis infection in wildlife is an issue of growing importance worldwide, with infections found in a range of species, including buffalo in Africa (1), wild boar in Spain (2), brushtail possums in New Zealand (3), and European badgers in the United Kingdom (4) and the Republic of Ireland (5). In the United Kingdom and the Republic of Ireland, badgers are involved in the transmission of tuberculosis (TB) to cattle (6-8). The incidence of M. bovis in cattle herds in the United Kingdom has been increasing for over 30 years (9), resulting in substantial economic losses (10). Once infected, badgers may intermittently shed M. bovis cells in sputum, feces, and urine (4), creating an environmental source of potential infection for other badgers and cattle (11,12). M. bovis DNA has been shown to survive outside the host for up to 21 months, and 16S rRNA has been detected in badger setts and latrines (13). In addition, studies have found a 2.5% positivity rate when culturing from badger feces (14), and M. bovis has been cultured from cattle feces several months after excretion (15). Furthermore, M. bovis that had persisted in soil for over 12 months was able to colonize mice (16). This indicates that at least a proportion of M. bovis cells shed in badger feces can remain viable in the environment. Monitoring M. bovis infections in badger populations is important for understanding the location and spread of disease and directing control efforts. TB control interventions targeted at badgers are currently based on culling, vaccination, and farm biosecurity (17).Accurate diagnosis of M. bovis infections in live animals is challenging yet essential in order to understand the epidemiology of the disease and its onward spread. Currently, infections in live badgers can be monitored through trapping and diagnosis with immunoassays (g...
White-tailed deer (Odocoileus virginianus) in Kentucky represent an example of successful wildlife restoration. Eliminated from all but a few remnant areas by the early part of the twentieth century, the species is once again widely distributed and abundant as a result of intensive restocking efforts since the 1940s. Seven DNA microsatellite markers were used to survey the extent and pattern of genetic variation in 322 deer from multiple localities throughout the commonwealth. Six genetically homogeneous regions and 1 heterogeneous region were identified across Kentucky. High levels of allelic diversity were detected with no apparent reduction in heterozygosity, disproportionate loss of rare alleles, or shift in modal allele frequency class as might be expected if the severe historical population size reduction generated a concomitant genetic bottleneck. These results are consistent with predictions of founder-flush models: that rapid population growth may minimize the loss of genetic variability associated with a population bottleneck. Nevertheless, comparisons of our data to that derived from other imperiled taxa suggest that species demographics can also play an important role in determining the genetic consequences of population size reduction and subsequent recovery. Our data also illuminate the critical role of deer from Land Between the Lakes (LBL) as the initial source population from which all extant Kentucky deer are descended. While generally supporting current regional management perspectives, our results argue for recognition of the LBL herd as a distinct management island of genetic and historical value. JOURNAL OF WILDLIFE MANAGEMENT 69(1):345-355; 2005
Advances in the diagnosis of Mycobacterium bovis infection in wildlife hosts may benefit the development of sustainable approaches to the management of bovine tuberculosis in cattle. In the present study, three laboratories from two different countries participated in a validation trial to evaluate the reliability and reproducibility of a real time PCR assay in the detection and quantification of M. bovis from environmental samples. The sample panels consisted of negative badger faeces spiked with a dilution series of M. bovis BCG Pasteur and of field samples of faeces from badgers of unknown infection status taken from badger latrines in areas with high and low incidence of bovine TB (bTB) in cattle. Samples were tested with a previously optimised methodology. The experimental design involved rigorous testing which highlighted a number of potential pitfalls in the analysis of environmental samples using real time PCR. Despite minor variation between operators and laboratories, the validation study demonstrated good concordance between the three laboratories: on the spiked panels, the test showed high levels of agreement in terms of positive/negative detection, with high specificity (100%) and high sensitivity (97%) at levels of 105 cells g−1 and above. Quantitative analysis of the data revealed low variability in recovery of BCG cells between laboratories and operators. On the field samples, the test showed high reproducibility both in terms of positive/negative detection and in the number of cells detected, despite low numbers of samples identified as positive by any laboratory. Use of a parallel PCR inhibition control assay revealed negligible PCR-interfering chemicals co-extracted with the DNA. This is the first example of a multi-laboratory validation of a real time PCR assay for the detection of mycobacteria in environmental samples. Field studies are now required to determine how best to apply the assay for population-level bTB surveillance in wildlife.
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