Risk of disease from wildlife reservoirs: Badgers, cattle, and bovine tuberculosis

Livestock face complex foraging options associated with optimizing nutrient intake while being able to avoid areas posing risk of parasites or disease. Areas of tall nutrient-rich swards around fecal deposits may be attractive for grazing, but might incur fitness costs from parasites. We use the example of dairy cattle and the risks of tuberculosis transmission posed to them by pastures contaminated with badger excreta to examine this trade-off. A risk may be posed either by aerosolized inhalation through investigation or by ingestion via grazing contaminated swards. We quantified the levels of investigation and grazing of 150 dairy cows at badger latrines (accumulations of feces and urine) and crossing points (urination-only sites). Grazing behavior was compared between strip-grazed and rotation-grazed fields. Strip grazing had fields subdivided for grazing periods of

Public values for badgers, bovine TB reduction and management strategies

This paper applies an attribute-based stated choice experiment approach to estimate the value that society places on changes to the size of the badger population in England and Wales. The study was undertaken in the context of a rising incidence of bovine tuberculosis (bTB) in cattle and the government's review of current bTB control policy. This review includes consideration of culling badgers to reduce bTB in cattle, since badgers are thought to be an important wildlife reservoir for the disease. The design of the CE involved four attributes (size of badger population, cattle slaughtered due to bTB, badger management strategy and household tax) at four levels with eight choice sets of two alternatives presented to respondents. Telephone interviews were undertaken with over 400 respondents, which elicited their attitudes and preferences concerning badgers, bTB in cattle and badger management strategies. The study estimated a willingness to pay of 0.10 pound per household per year per 100,000 badgers and 1.52 pound per household per year per 10,000 cattle slaughtered due to bTB which aggregated to 22 per badger and 3298 pound per bTB slaughtered animal for all households in England and Wales. Management strategy toward badgers had a very high valuation, highlighting the emotive issue of badger culling for respondents and the importance of government policy towards badgers.

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. (c) 2005 Elsevier Ltd. All rights reserved.

Estimating the extent of spatial association of Mycobacterium bovis infection in badgers in Ireland

Mycobacterium bovis infects the wildlife species badgers Meles meles who are linked with the spread of the associated disease tuberculosis (TB) in cattle. Control of livestock infections depends in part on the spatial and social structure of the wildlife host. Here we describe spatial association of M. bovis infection in a badger population using data from the first year of the Four Area Project in Ireland. Using second-order intensity functions, we show there is strong evidence of clustering of TB cases in each the four areas, i.e. a global tendency for infected cases to occur near other infected cases. Using estimated intensity functions, we identify locations where particular strains of TB cluster. Generalized linear geostatistical models are used to assess the practical range at which spatial correlation occurs and is found to exceed 6 in all areas. The study is of relevance concerning the scale of localized badger culling in the control of the disease in cattle.

Risk of Disease from Wildlife Reservoirs: Badgers, Cattle, and Bovine Tuberculosis

Livestock face complex foraging options associated with optimizing nutrient intake while being able to avoid areas posing risk of parasites or disease. Areas of tall nutrient-rich swards around fecal deposits may be attractive for grazing, but might incur fitness costs from parasites. We use the example of dairy cattle and the risks of tuberculosis transmission posed to them by pastures contaminated with badger excreta to examine this trade-off. A risk may be posed either by aerosolized inhalation through investigation or by ingestion via grazing contaminated swards. We quantified the levels of investigation and grazing of 150 dairy cows at badger latrines (accumulations of feces and urine) and crossing points (urination-only sites). Grazing behavior was compared between strip-grazed and rotation-grazed fields. Strip grazing had fields subdivided for grazing periods of <24 h, whereas rotational grazing involved access to whole fields for 1 to 7 d each. A higher proportion of the herd investigated badger latrines than crossing points or controls. Cattle initially avoided swards around badger latrines but not around crossing points. Avoidance periods were shorter in strip- compared with rotation-grazing systems. In rotation-grazing management, latrines were avoided for longer times, but there were more investigative contacts than with strip-grazing management. If investigation is a major route of tuberculosis transmission, the risk to cattle is greatest in extensive rotation-grazing systems. However, if ingestion of fresh urine is the primary method of transmission, strip-grazing management may pose a greater threat. Farming systems affect the level and type of contact between livestock and wildlife excreta and thus the risks of disease.

BADGERS (Taxidea taxus) AS OCCASIONAL PESTS IN AGRICULTURE

The badger (Taxidea taxus). because of its strong propensity for digging, is considered North America's fossorial carnivore, feeding mostly on ground squirrels, pocket gophers, and mice throughout much of the western and midwestern continent. Badger excavations, primarily in search of food, produce mounds and deep holes which can damage alfalfa and other crops and damage farm equipment and water systems. Depredations include poultry, waterfowl, and eggs. Overall, the badger is considered a relatively minor vertebrate pest. As a furbearer it is considered a renewable natural resource. Most local pest problems are currently reduced through leghold trapping and shooting. Habitat modification through continuous rodent control is effective and a long-lasting badger control method.

The lyon, the legend, and the badgers; a fable ...

Mode of access: Internet.

The community of medium-sized carnivores: the interactions between species, habitats and rabies

The composition of the carnivore community influences the different forms of inter-specific interactions. Furthermore, inter-specific interactions of carnivores have important implications for intra-guild competition, epidemiology and strategies of species-specific population management. Zoonooses, such as rabies, are diseases that can be transmitted from wildlife to people. Knowing the ecological characteristics of the species helps us to choose the right preventive actions and to time them accurately. In this thesis, I have studied how raccoon dogs Nyctereutes procyonoides, European badgers Meles meles, red foxes Vulpes vulpes and domestic cats Felis silvestris catus act as members of carnivore community, and how these interactions relate to the transmission risk of rabies. In the study area, these species form a community of medium-sized and rather generalist predators. They live in the same areas, in spatially and temporally overlapping home ranges and use the same habitats and dens and even have similar diets. However, there is no direct evidence of competition. Shared dens point to good tolerance of other species. Numerous observations of animals moving in each other’s proximity give similar clues. However, overlapping home ranges and similar habitat preferences lead to frequent inter-specific contacts, which increase the risk of possible rabies transmission. Also, the new insight of habitat use gained by this study illustrates the similar favouring of deciduous forests and fields by these sympatric medium-sized carnivores, creating a basis for contact zones, i.e. risky habitats for rabies transmission and spread. This study is so far the only simultaneous radio tracking study of raccoon dogs, badgers, foxes and cats. These results give new insight of the interactions in the carnivore community, as well as of the behaviour of each individual species. Also, these results have significant implications for the planning of rabies control. In order to reach viable management decisions, not only one or two species should be taken into consideration, but the whole community. In particular, this changes the perspective to inter-specific contacts, animal densities, densities of individuals susceptible to diseases and the magnitude of preventive actions. Rabies should be considered as a multi-vector disease, at least in Finland and the Baltic states. It is of interest for disease management to be able to model an epizootic with local parameters to reflect the real situation and also to suite best the local management needs.

The ecology of the European hedgehog (Erinaceus europaeus) in rural Ireland

This study on the ecology of Irish hedgehogs (Erinaceus europaeus) has provided information on detection techniques, home range, habitat selection, hedgehog prey, nesting, courtship, genetics, road mortality, parasites, ageing and morphology of this species. Data were obtained from a focal study area in rural Cork, in which 24 radio tagged hedgehogs were monitored from June 2008 to June 2010. Further data were obtained through road kill surveys and the collection of hedgehog carcasses from around Ireland. Hedgehogs of both sexes were found to display philopatry. Habitat was not used in proportion to its availability, but certain habitats were selected and a similar pattern of habitat selection was evident in successive years. Hedgehogs preferred arable land in September and October and, unlike studies elsewhere, were observed to forage in the centre of fields. Badgers were regularly seen at the study site and did not appear to negatively affect hedgehogs’ use of the area. Instead the intra- and inter-habitat distribution of hedgehogs was closely correlated with that of their potential prey. Male hedgehogs had a mean annual home range of 56 ha and females 16.5 ha, although monthly home ranges were much more conservative. Male home range peaked during the breeding season (April-July) and a peak in road deaths was observed during these months. The majority of road kill (54%) were individuals of one year old or less, however, individuals were found up to eight and nine years of age. Genetic analysis showed a distinct lack of genetic variation amongst Irish hedgehogs and suggests colonisation by a small number of individuals. The ectoparasites, Archaeopsylla erinacei, Ixodes hexagonus and Ixodes canisuga were recorded in addition to the endoparasites Crenosoma striatum and Capillaria erinacei. In light of the reported decline in many areas of the hedgehogs’ range, it is a species of conservation concern, and this is the first study examining the ecology of the hedgehog in Ireland.

Studies relating to the population dynamics of the European badger (Meles meles) in Ireland

European badgers (Meles meles) are an important part of the Irish ecosystem; they are a component of Ireland’s native fauna and are afforded protection by national and international laws. The species is also a reservoir host for bovine tuberculosis (bTB) and implicated in the epidemiology of bTB in cattle. Due to this latter point, badgers have been culled in the Republic of Ireland (ROI) in areas where persistent cattle bTB outbreaks exist. The population dynamics of badgers are therefore of great pure and applied interest. The studies within this thesis used large datasets and a number of analytical approaches to uncover essential elements of badger populations in the ROI. Furthermore, a review and meta-analysis of all available data on Irish badgers was completed to give a framework from which key knowledge gaps and future directions could be identified (Chapter 1). One main finding suggested that badger densities are significantly reduced in areas of repeated culling, as revealed through declining trends in signs of activity (Chapter 2) and capture numbers (Chapter 2 and Chapter 3). Despite this, the trappability of badgers was shown to be lower than previously thought. This indicates that management programmes would require repeated long-term efforts to be effective (Chapter 4). Mark-recapture modelling of a population (sample area: 755km2) suggested that mean badger density was typical of continental European populations, but substantially lower than British populations (Chapter 4). Badger movement patterns indicated that most of the population exhibited site fidelity. Long-distance movements were also recorded, the longest of which (20.1km) was the greatest displacement of an Irish badger currently known (Chapter 5). The studies presented in this thesis allows for the development of more robust models of the badger population at national scales (see Future Directions). Through the use of large-scale datasets future models will facilitate informed sustainable planning for disease control.

Changes in the prevalence of badger persecution in Northern Ireland.

Animal populations generally increase after release from hunting pressure and/or cessation of illegal persecution. Implementation of full legislative protection of the Eurasian badger Meles meles in Great Britain is thought to have led to increases in badger abundance due to reduced levels of persecution. Conversely, prevalence of badger persecution in Northern Ireland was historically much higher than in Great Britain, and badger abundance remained stable over time despite similar legislative protection. We examined temporal changes in the prevalence of badger sett disturbance in Northern Ireland from 1990/1993 to 2007/2008 in relation to population status. A total of 56 (12.6%) of 445 setts surveyed during 1990/1993 had been disturbed compared to 29 (4.4%) of 653 setts during 2007/2008. This was a significant decline (-65%) in the incidence of sett disturbance over the 14–18-year period. Most notably, the incidence of digging at badger setts, indicative of local badger baiting activity, declined from 50% to 3.5% of disturbed setts. Signs of recent disturbance were significantly more frequent at disused setts suggesting that once disturbed, badgers may vacate a sett. The number of badger social groups in Northern Ireland did not differ between the two study periods, suggesting that previously high levels of badger persecution did not limit the number of badger social groups. The stability of the badger population in Northern Ireland compared to the growing population in Great Britain cannot be attributed to changes in the prevalence of persecution. Differences in the trajectories of both populations could be due to a range of factors including climate, habitat composition and structure, farming practices or food availability. More work is needed to determine how such factors influence badger population dynamics.

Monitoring and population estimation of the European badger (Meles meles) in Northern Ireland

The estimation of animal abundance has a central role in wildlife management and research, including the role of badgers Meles meles in bovine tuberculosis transmission to cattle. This is the first study to examine temporal change in the badger population of Northern Ireland over amedium- to long-term time frame of 14-18 years by repeating a national survey first conducted during 1990-1993. A total of 212 1-km2 squares were surveyed during 2007-2008 and the number, type and activity of setts therein recorded. Badgers were widespread with 75% of squares containing at least one sett. The mean density of activemain setts,which was equivalent to badger social group density, was 0.56 (95%CI: 0.46-0.67) active main setts per km2 during 2007-2008. Social group density varied significantly among landclass groups and counties. The total number of social groups was estimated at 7,600 (95%CI: 6,200-9,000) and, not withstanding probable sources of error in estimating social group size, the total abundance of badgers was estimated to be 34,100 (95% CI: 26,200-42,000). There was no significant change in the badger population from that recorded during 1990-1993. A resource selection model provided a relative probability of sett construction at a spatial scale of 25m. Sett locations were negatively associated with elevation and positively associated with slope, aspect, soil sand content, the presence of cover, and the area of improved grassland and arable agriculture within 300 m.

Evaluation of the diagnostic potential of a novel field immunomagnetic separation-immunochromatographic lateral flow assay to detect Mycobacterium bovis cells in European badger (Meles meles) faeces

The European badger (Meles meles) is a natural reservoir for Mycobacterium bovis, the causative agent of Bovine Tuberculosis, and has consequently been implicated in transmission of the disease to cattle. This study describes application of a novel M. bovis-specific immunochromatographic (lateral flow) assay in combination with immunomagnetic separation (IMS-LFD), to test badger faeces samples. In total, 441 faeces samples from badgers of unknown disease status collected from latrines at 110 badger setts throughout Northern Ireland (NI) and 100 faeces samples from badgers of known infection status from Great Britain (GB) were tested. Faeces (approx. 1g) was homogenised in 9 ml phosphate buffered saline, filtered (70 µm), and then 6-8 ml subjected to the IMS-LFD test. Residual clarified faecal homogenates were subjected to automated IMS followed by MGIT™ liquid culture (AIMS-MGIT™ culture) and qPCR (AIMS-qPCR). Evidence for the presence of M. bovis was obtained for 78 (18%), 61 (14%) and 140 (32%) of 441 NI badger faeces samples, and 10 (10%), 41 (41%) and 56 (56%) of 100 GB badger faeces samples, by IMS-LFD, AIMS-MGIT culture and AIMS-qPCR tests, respectively. The IMS-LFD test was less sensitive than AIMS-qPCR for detection of M. bovis and was, therefore, detecting badgers shedding high numbers of M. bovis in their faeces only. However, these ‘super shedders’ may be primarily responsible for the spread of Bovine Tuberculosis so are, therefore, an important target. This non-invasive test could form the basis of a field surveillance tool to indicate infected badger groups which are actively spreading M. bovis.

Herd-level bovine tuberculosis risk factors: assessing the role of low-level badger population disturbance

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 km²; 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 area-level 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.