A comparison of badger activity in two areas of high and low bovine tuberculosis incidence of Northern Ireland

During 2005, a field survey of badger activity was carried out to evaluate differences between two areas with different levels of bovine tuberculosis (annual herd incidences of 16% and 4%) and to assess the awareness of herd keepers in relation to badgers. A random selection of herd keepers was interviewed and their farm land surveyed for the presence of badgers. The survey end point for each farm was the discovery of an active badger sett. Participation was very high in both areas (>80%). Evidence of badger activity was recorded on a higher proportion of farms in the area with a high tuberculosis herd incidence. However, when the difference in quality of agricultural land within each area was taken into account, a statistically significant association was not demonstrated. This suggests that the quality of agricultural land is a major determinant in the location of active badger setts. Nevertheless, the study did demonstrate the potential for increased exposure of cattle to badgers in the high incidence area. Herd keepers accurately identified the presence of badger setts on their land (positive predictive value=97%) but herd keepers reporting the absence of badger setts/activities on their land were found to be less accurate. Overall, the conclusions from this study tend to reflect the findings observed in other studies.     

Effects of farm management practices on cattle grazing behaviour and the potential for transmission of bovine tuberculosis from badgers to cattle

Despite the large body of circumstantial evidence to suggest a link, the means by which bovine tuberculosis is passed from badgers to cattle remains unclear; pasture contamination with the urine, faeces and/or sputum of infectious badgers is believed to be the main route of transmission. Therefore the behaviour of grazing cattle was studied to determine whether they avoided investigating and/or grazing pasture contaminated with badger excreta, and whether different farm management practices enhanced the potential for disease transmission. Active latrines were avoided by most cattle until the sward length in the rest of the field was reduced, after which there was an increasing likelihood that active badger latrines would be grazed. Most of the cattle grazed active badger latrines, but cattle of low rank within the herd grazed latrines more heavily. Farm management practices that reduced the availability of long swards shortened the period of investigative behaviour and greatly enhanced the risk that cattle would graze active badger latrines. Cattle were more likely to graze pasture away from latrines that was contaminated either with badger urine or single faeces. Because bacilli remain viable in the soil for up to 2 years, there is the potential for bacilli to accumulate at active badger latrines, and these could pose a significant risk to cattle, even when the latrine is no longer being used by badgers. Cattle readily grazed the lush sward at disused latrines, during which they could ingest contaminated soil; the amount of soil ingested increases as sward length decreases.     

Advances and prospects for management of TB transmission between badgers and cattle

Bovine tuberculosis (bTB) is the most serious endemic disease facing the livestock industry in the United Kingdom (UK) and Republic of Ireland (RoI), where its management has been confounded by the presence of persistent infection in the Eurasian badger (Meles meles). Field evidence suggests that the social structure of badger populations can have an important influence on disease dynamics, and on the outcome of management interventions. Recent, large-scale badger culling experiments in the UK and RoI had complex epidemiological outcomes. In the UK, proactive culling led to reduced bTB incidence in cattle herds inside culled areas, but a temporary increase in adjacent areas. Reactive culling in response to herd breakdowns was associated with an increase in the incidence of bTB in cattle. In contrast, badger culling in RoI was reported to have only beneficial effects on bTB incidence in cattle. The reasons for these differences are not clear. The complexity of the evidence base for culling is highlighted by the different management approaches currently being adopted by the different authorities of the UK and RoI. It is generally accepted that a holistic approach to bTB management, which targets both cattle and wildlife, is necessary. Consequently recent research activities have also focussed on cattle and badger vaccines, and biosecurity on farms. This paper describes recent advances in our understanding of the epidemiology of bTB in badgers and the consequences of culling, and current research to develop approaches for the vaccination of badgers, and methods of managing the risks of contact between badgers and cattle in farm buildings.     

Spatial relationship between Mycobacterium bovis strains in cattle and badgers in four areas in Ireland

We investigated whether strains (restriction fragment length polymorphism, RFLP-types) of Mycobacterium bovis isolated from badgers and from cattle clustered among and within four areas in Ireland. The spatial scan test and nearest-neighbor analysis were used as the spatial cluster-detection techniques. In addition, for each of the major strains, associations between the distance to badger setts and the "centroid" of the cattle farm were assessed in a logistic model. Overall, between September 1997 and May 2000, 316 and 287 M. bovis samples, from badgers and cattle, respectively, were strain-typed. The distribution of strains in badgers, and separately in cattle, differed among areas. Within each of the four large areas, badgers and cattle tended to have similar strains; this is consistent with the sharing of M. bovis strains within an area. In more detailed within-area analyses, some spatial clusters of M. bovis strains were detected, separately, in both cattle and badgers. Almost half of the infected badger setts with a specific strain were located outside of the "detected" clusters. There was no association between the number of infected badgers with a specific M. bovis strain within 2 or 5 km distances to cattle herds, and the risk of the same strain in cattle. We speculate about the dynamic nature of badger movements, as an explanation for the absence of more clusters of most of the strains of M. bovis isolated from badgers, and its impact on trying to study transmission of M. bovis between cattle and badger.     

Husbandry practices, badger sett density and habitat composition as risk factors for transient and persistent bovine tuberculosis on UK cattle farms

Bovine tuberculosis (bTB) is a persistent problem in cattle herds in Great Britain and Ireland. Farm management and cattle husbandry practices can influence the risk of transmission of bTB and hence the likelihood of bTB breakdown (>or=1 reactor to the tuberculin skin test). Biological differences are expected in the transmission dynamics, and hence risk factors for bTB breakdown, on farms where infection persists in the herd compared to farms where infection is more sporadic or short-lived. Comparative case-control studies were performed to test farm management practices as potential risk factors for transient (under breakdown restrictions for 6 months) bTB breakdown over 5 years (1995-1999) on 179 and 171 UK cattle farms, respectively. Farms were characterised for badger sett density and farm habitat composition by ground survey, farmers were questioned retrospectively on management practices, and cases and controls were identified from national tuberculin test records. Controlling for routine tuberculin testing interval, log-transformed herd size, regional location, badger sett density and farm habitat complexity, multivariable logistic regression identified increased odds of both transient and persistent breakdown on farms that bought-in cows (odds ratio (OR)>or=4.9; 95% confidence interval (CI)>or=1.1;22.8). In addition, the purchase of >50 head of cattle (OR=4.0, 95% CI=1.0;16.0) and the storage of manure for >or/=6 months (OR=4.4; 95% CI=1.3;15.4) were risk factors for transient breakdown, whereas the use of silage clamps (OR=9.1; 95% CI=2.0;40.8) increased the risk of persistent breakdown. Decreased odds of both transient and persistent breakdown were associated with higher stocking densities (>3cattle/ha) (OR相似文献   

Quantifying badger exposure and the risk of bovine tuberculosis for cattle herds in county Kilkenny, Ireland

The objectives of the study were to quantify the levels of badger exposure for cattle and to test the hypothesis that increased badger exposure does not increase the risk of bovine tuberculosis (BTB) in a herd. Information that became available from the targeted removal of badgers over the study period, and from a badger-removal project in county Kilkenny, during 1996-1999 was used. The specific location of cattle within each farm, and the length of time that cattle spent in each farm field during the grazing season, and in the barnyard during winter, was used to build an exposure coefficient to quantify the amount of badger exposure that cattle encountered either on pasture or in the barn. The study design was a matched case-control study in which the control herds were selected using incidence density sampling. During the 4-year study period, 543 badgers were removed and of these 96 badgers were classified as tuberculosis positive; 96 BTB herd breakdowns occurred. There was a significant association between case herds and having a higher badger sett exposure coefficient during 1996-1998. No significant association between case herds and having a higher exposure coefficient based on the number of badgers, or the number of tuberculous badgers, during September 1997-December 1999 was found.     

Tuberculosis in cattle herds are sentinels for Mycobacterium bovis infection in European badgers (Meles meles): the Irish Greenfield Study

In Ireland badgers are removed in response to tuberculosis (TB) breakdowns in cattle herds (focal culling). Prevalence studies, conducted using a detailed post mortem and bacteriological examination, showed that 36-50% of badgers were infected with Mycobacterium bovis. Focal culling forms part of the medium term national strategy for the control of bovine TB in cattle and is based on the premise that badgers in areas with herd breakdowns have a higher prevalence of infection than the badger population at large. However, the hypothesis that cattle can be used as sentinels for infection in the badger population has never been formally tested. In this study we tested the hypothesis by determining the infection prevalence in badgers in areas where there had been historically, a consistently low prevalence of infection in cattle. Low cattle TB prevalence areas were defined as those herds with ≤ 2 standard reactors in the annual round of skin testing over the preceding 5 years (Greenfield sites). Using GIS, and adjusting for variation in land use, previous culling and cattle density, 198 Greenfield sites were identified and surveyed, and 138 areas with badger setts or signs of badger activity were identified. A single badger was removed from 87 sites and all were examined using detailed post mortem and bacteriological procedures. A prevalence of M. bovis infection of 14.9% was found in the Greenfield site badgers. This prevalence was significantly lower (P<0.001) than in badgers removed during focal culling (36.6%). The results validate the use of cattle as sentinels for TB in badgers and support the medium term national strategy for the control of bovine TB. The geographic variation in M. bovis infection prevalence in the Irish badger populations will be used when devising strategies for the incorporation of badger vaccination into the long term bovine TB control programme.     

Geographical association between the genotype of bovine tuberculosis in found dead badgers and in cattle herds

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.     

Detection of Mycobacterium bovis infection and production of interleukin-2 by in vitro stimulation of badger lymphocytes

The Eurasian badger (Meles meles) is considered to be an important wildlife reservoir for Mycobacterium bovis infection of cattle in Ireland and in GB. However, rapid diagnosis of tuberculosis in live badgers has been constrained through a lack of suitable immuno-diagnostic reagents for detection of M. bovis-infected animals. To date, there have been no reports of cytokine activity in badgers that might be associated with specific immune responses to M. bovis infection. In this study, nine badgers were removed from an area with a persistent tuberculosis problem in cattle herds and tuberculosis was confirmed in four of the animals by "post-mortem" examination and M. bovis culture. In preliminary investigations of interleukin-2 (IL-2) activity, we were able to demonstrate that lymphoblasts prepared from badger peripheral blood mononuclear cells (PBMCs) proliferated when cultured in the presence of human recombinant IL-2 (HrIL-2). Supernatants derived from purified protein derivative of tuberculin (PPD-bovine) stimulated PBMC cultures also induced blastogenesis of badger-derived lymphoblasts. The results demonstrate that badger lymphocytes are responsive to HrIL-2 and that PPD-bovine stimulation of badger PBMC results in production of bio-active IL-2.     

Multi-species visit rates to farmyards: Implications for biosecurity

Disease transmission dynamics between wildlife and livestock are likely to be affected by contacts between the two populations. In this study, rates of visitation of rodents, badgers, red foxes and cats to 11 farmyards were quantified from July 2012 to August 2013. There was variation in rates of visitation between different species and between farmyards. Rates of visitation were 60.3% (n = 2374) for cats, 19.1% (n = 751) for rodents, 16.7% (n = 657) for red foxes and 3.9% (n = 153) for badgers. Multi-species visits are relevant to disease transmission, highlighting the need for increased biosecurity on farms.     

Responses of dairy cows to badger urine and faeces on pasture with reference to bovine tuberculosis transmission.

Grazing cattle were observed when they encountered badger urine or faeces which, in all but the first study, came only from badgers which were not infected with bovine tuberculosis. The faeces were very strongly avoided and there was generally a strong avoidance of ingestion of badger urine. There was no evidence that cattle were attracted to badger latrines in an area where some infected badgers were present and cows actively avoided faeces up to 28 days old which was placed on grass turves or on pasture. 99.3% of cows took no bites from small grass plots contaminated with faeces and 88.7% of cows took no bites from urine-treated plots. There was generally avoidance of pasture treated with badger urine up to 14 days old. However, two cows out of 240 were willing to graze close to faeces and seven out of 240 were willing to graze near urine. Contaminated herbage was eaten most when attractive herbage became scarce. Wet weather did not reduce the strength of avoidance of urine. Some cows responded to badger urine, and to a lesser extent to faeces, by more sniffing, particularly when herbage was scarce. The odour of faeces, and sometimes that of urine, often resulted in the ejection of mouth contents. As a consequence of their avoidance of badger faeces and urine, the vast majority of cows are unlikely to contract tuberculosis from infected badgers by ingestion. Most cows totally avoid badger products so they are unlikely to be infected via inhalation. However, the small minority of unselective cows must be more at risk and this finding warrants further investigation.     

Trial design to estimate the effect of vaccination on tuberculosis incidence in badgers

The principal wildlife reservoir of Mycobacterium bovis in Ireland is the European badger. Studies in the Republic of Ireland (RoI) have shown that badgers culled in association with cattle herd tuberculosis breakdowns (focal culling) have a higher prevalence of infection than the badger population at large. This observation is one rationale for the medium term national strategy of focal badger culling. A vaccination strategy for the control of bovine tuberculosis (bTB) in badgers is a preferred long-term option. The Bacillus Calmette-Guérin (BCG) vaccine has been shown to decrease disease severity in captive badgers under controlled conditions. As the vaccine has been tested in a controlled environment with precise information on infection pressure, it cannot be assumed a priori that the effects of vaccination are similar in the wild, where other environmental and/or ecological factors prevail. For this reason we have designed a vaccine field trial to assess the impact of vaccination on the incidence of TB infection in a wild badger population. The selected study area for the vaccine trial (approximately 755 square kilometers) is divided into three zones each of which has similar characteristics in terms of size, number of main badger setts, cattle herds, cattle and land classification type. Three vaccination levels (100%, 50% and 0%) will be allocated to the three zones in a way that a gradient of vaccination coverage North to South is achieved. The middle zone (zone B) will be vaccinated at a 50% coverage but zone A and C will be randomly allocated with 100% or 0% vaccination coverage. Vaccination within zone B will be done randomly at individual badger level. The objective of this paper is to describe the design of a field tuberculosis vaccination trial for badgers, the epidemiological methods that were used to design the trial and the subsequent data analysis. The analysis will enable us to quantify the magnitude of the observed vaccination effect on M. bovis transmission in badgers under field conditions and to improve our knowledge of the biological effects of vaccination on susceptibility and infectiousness.     

Evaluation of farm management practices as risk factors for clinical listeriosis and fecal shedding of Listeria monocytogenes in ruminants

OBJECTIVE: To assess seasonal variation in prevalence of Listeria monocytogenes on ruminant farms and identify management practices associated with ruminant listeriosis and fecal shedding of L. monocytogenes. STUDY DESIGN: Case-control study. SAMPLE POPULATION: 2056 samples of feces, feed, soil, and water from 24 case farms with listeriosis and 28 control farms without listeriosis. PROCEDURE: Samples were collected and evaluated via bacterial culture for L. monocytogenes. Univariate associations between farm management practices and listeriosis and fecal shedding of L. monocytogenes were assessed. Multivariate models were developed to identify farm management practices associated with listeriosis and fecal shedding of L. monocytogenes. RESULTS: The prevalence of L. monocytogenes on cattle, goat, and sheep farms was seasonal, especially in fecal samples, with peak prevalence in winter. Although the prevalence of L. monocytogenes in feedstuffs from small-ruminant farms also peaked during winter, the bacterium was detected at a constant rate in cattle farm feedstuffs throughout the year. Farm management practices, animal health and hygiene, and feedstuff quality and storage were associated with ruminant listeriosis and fecal shedding of L. monocytogenes. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the prevalence of L. monocytogenes on ruminant farms is seasonal, management practices are associated with ruminant listeriosis and fecal shedding of L. monocytogenes, and the epidemiologic features of listeriosis differ in cattle versus small ruminants. Awareness of risk factors may be used to develop control measures to reduce animal disease and introduction of L. monocytogenes into the human food chain.     

Farmers' confidence in vaccinating badgers against bovine tuberculosis

This paper examines UK farmers' levels of confidence in vaccinating badgers against bovine tuberculosis (bTB) and their trust in the Government's ability to deal with bTB. In 2010, a badger vaccine based on the BCG vaccine was licensed following field trials and used as part of the UK Government's Badger Vaccination Deployment Project. A stratified random sample of cattle farmers in five different locations of England was surveyed using a telephone survey to elicit their views of badger vaccination. The survey provided a total of 341 responses with a response rate of 80 per cent. Results suggest that the farmers are cautious about badger vaccination, appearing to be neither overly confident nor unconfident in it. However, the farmers did not reveal high levels of trust in the Government to manage bTB policy or badger vaccination. There were no differences in the levels of confidence or trust between farms that were under bTB restrictions at the time of the survey and those that were not or between farms with historically high levels of bTB. Analysis of principal components suggests that 33 per cent of the farmers accepted badger vaccination, but that acceptance is dependent on the wider social and political environment.     

Mycobacterium bovis infection in badger cubs: Re-assessing the evidence for maternally derived immunological protection from advanced disease

The Eurasian badger (Meles meles) is a significant source of bovine tuberculosis in cattle in the UK and Ireland. Protection from infectious diseases, arising from maternal antibody transfer, is a well-established immunological phenomenon in mammals. In a previous study of wild badgers, transient serological responses in cubs were taken as evidence of maternal antibody transfer, and it was speculated this conferred protection from subsequent mycobacterial excretion following acquisition of tuberculosis. However successful defence against mycobacterial infections is likely to be dominated by a cell-mediated response. Using a substantially larger dataset from the same badger population, we revisited the hypothesis of maternally derived protection. Whilst we found a significant association between transient serological responses and absence of subsequent Mycobacterium bovis excretion, the likelihood of detection of such responses was not significantly associated either with badger age, or with infection in the breeding females within a cub's natal group. We concluded that although maternal antibody transfer in badgers almost certainly occurs, transient serological responses represent an invalid proxy, and the reduced likelihood of M. bovis excretion associated with transient responses was more likely to be due to the lower sensitivity of the Brock ELISA test in detecting badgers with less advanced disease.     

A cost-benefit analysis of culling badgers to control bovine tuberculosis

Bovine tuberculosis (TB) is an important economic problem. The incidence of TB in cattle herds has steadily risen in the UK, and badgers are strongly implicated in spreading disease. Since the mid-1970s the UK government has adopted a number of badger culling strategies to attempt to reduce infection in cattle. In this report, an established model has been used to simulate TB in badgers, transmission to cattle, and control by badger culling. Costs were supplied by the UK Government's Department for Environment Food and Rural Affairs (Defra) for badger trapping and gassing. Regardless of culling intensity or area simulated, an overall reduction in the herd breakdown rate was seen. With a high culling efficacy and no social perturbation, the mean Net Present Value of a few simulated culling strategies in an "ideal world" was positive, meaning the economic benefits outweighed the costs. Further work is required before these results could be considered definitive, as it is necessary to evaluate uncertainties and simulate less than perfect conditions.     

Risk factors for BSE-infections in Lower Saxony, Germany

In order to generate data on the cattle population and farm management in the state of Lower Saxony, Germany, a basic demographic survey was conducted. Afterwards these BSE-free farms as a reference population were compared with the population on BSE farms to identify risk factors for BSE infections. A variety of risk factors for BSE were reviewed, including the import of cattle from the United Kingdom, commercial foodstuff, dairy farming, herd size and cross-contamination with foodstuff for other farm animals. For the basic demographic survey of the reference, a questionnaire was mailed to a representative sample of cattle farms in Lower Saxony where BSE cattle had not occurred before the sample was taken. Distribution of risk factors within this reference population (n=731) and the BSE population (n=49) were compared following the concept of indirect standardisation in stratified populations. The size of farms was used as the stratification variable, with three strata. Under the same rate as in the reference population, the portion of Red Holstein cattle breed was four fold higher than in the BSE population (SER=4.03; p=0.0003). Milk replacer was fed 1.41 times more often on BSE farms (p=0.0478). However, the use of concentrated foodstuff for pigs (SER=0.21) was significantly less frequent in the BSE population than expected (p=0.0001), whereas the husbandry of sheep, goats or game animals seemed to increase the risk of BSE 2.85 times (p=0.0413). There were no significant differences between the two populations concerning the purchase of cattle (p=0.1514) and the use of concentrated feed for calves during the 1990s (p=0.6212). This is an epidemiological indication of increased susceptibility of Red Holstein cattle to BSE. However, this study did not confirm the assumption that the use of commercial foodstuff other than milk replacer or the purchase of cattle increases the risk of BSE infection. It nevertheless remains likely that commercial foodstuffs such as concentrated feed for calves were risk factors in Germany as well.     

Value of existing serological tests for identifying badgers that shed Mycobacterium bovis

In the UK there has been a sharp rise in the incidence of bovine tuberculosis since the early 1990s and the badger has been identified as an important wildlife reservoir for this infection. Infected badgers can excrete Mycobacterium bovis, putting other badgers and cattle at risk of becoming infected. Vaccination has been proposed as an approach to reducing the excretion of M. bovis by tuberculous badgers. In order to evaluate the efficacy of a badger vaccine it will be necessary to accurately determine the number of badgers excreting M. bovis without removing them for post-mortem evaluation. The existing live tests for tuberculosis in the badger (culture, indirect ELISA, Western blot) have not been assessed for their ability to detect badgers excreting M. bovis. Over the past 18 years, badgers from 31 social groups have been trapped and sampled in a study area of the Cotswold escarpment. We have examined the serological responses of 128 badgers trapped between 1985 and 1998 from social groups where M. bovis infection was endemic. These responses were compared with culture from faeces, urine, tracheal aspirates and bite wound swabs taken from these animals while alive. ELISA was found to be more sensitive than Western blot in detecting badgers excreting M. bovis. The majority of culture-positive badgers excreted M. bovis intermittently over the period of study. As a result, there was only a 27.5% chance of sampling a badger for culture when it was excreting M. bovis. In contrast, a positive ELISA result correctly predicted 68.2% of badgers with a history of excreting M. bovis. In the absence of alternative live tests for the badger, the Brock Test indirect ELISA appears to be more valuable than culture for measuring the effect of vaccination on reducing the number of badgers at risk of transmitting tuberculosis.     

Environmental and farm management factors associated with tuberculosis on cattle farms in northeastern Michigan

OBJECTIVE: To identify major environmental and farm management factors associated with the occurrence of tuberculosis (TB) on cattle farms in northeastern Michigan. DESIGN: Case-control study. SAMPLE POPULATION: 17 cattle farms with infected cattle and 51 control farms. PROCEDURE: Each case farm (laboratory confirmed diagnosis of Mycobacterium bovis infection) was matched with 2 to 4 control farms (negative whole-herd test results within previous 12 months) on the basis of type of farm (dairy or beef) and location. Cattle farm data were collected from in-person interviews and mailed questionnaires. Wildlife TB data were gathered through state wildlife surveillance. Environmental data were gathered from a satellite image-based geographic information system. Multivariable conditional logistic regression for matched analysis was performed. RESULTS: Major factors associated with increased farm risk of TB were higher TB prevalence among wild deer and cattle farms in the area, herd size, and ponds or creeks in cattle housing areas. Factors associated with reduced farm risk of TB were greater amounts of natural open lands in the surrounding area and reducing deer access to cattle housing areas by housing cattle in barns, barnyards, or feedlots and use of electrified wire or barbed wire for livestock fencing. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that certain environmental and management factors may be associated with risk of TB on cattle farms.