FP7-KBBE-2007-212414
Strategies for the eradication
of bovine tuberculosis
Publications | Epidemiology and risk assessment
TB-STEP
THEMATIC AREA 5
Epidemiology and risk assessment
- Contact networks in a wildlife-livestock host community: identifying high risk individuals in the transmission of bovine TB among badgers and cattle
- The effect of grazing management on livestock exposure to infection via the faecal-oral route
- Livestock grazing behavior and inter- versus intra-specific disease risk via the fecal-oral route
- Inter- and intra-specific exposure to parasites and pathogens via the faecal-oral route: a consequence of behaviour in a patchy environment
- Control of bovine tuberculosis in British livestock: there is no silver bullet
- High spoligotype diversity within a Mycobacterium bovis population: Clues to understanding the demography of the pathogen in Europe
- Tuberculosis in alpacas (Lama pacos) caused by Mycobacterium bovis
- Epidemiological significance of the domestic black pig (Sus scrofa) in maintenance of bovine tuberculosis in Sicily
Contact networks in a wildlife-livestock host community: identifying high risk individuals in the transmission of bovine TB among badgers and cattleBackground: Awareness of bovine tuberculosis (BTB) by cattle owners is of extreme importance to policy makers when considering mitigation. However, to our knowledge, little is known on cattle owners' awareness of BTB in Zambia. Similarly, such knowledge is uncommon within and outside Africa. The current study investigates the epidemiological characteristics of BTB in Zambian cattle in relation to awareness by cattle owners in high and low cattle BTB prevalence settings. A cross sectional study was designed and data was gathered based on 106 cattle owners and cattle herds; subjected to an interviewer-administered questionnaire and comparative intradermal tuberculin test using a cut-off for positivity of 4 mm, respectively.
Results: Reported levels of cattle and wildlife contact by respondents was at 40%, 58.2% and 1.8%, were relatively proportional to herd level prevalence of cattle BTB at 64.8%, 58.1% and 5.9% in Blue lagoon, Lochinvar and Kazungula respectively. Although 42/106 (39.6%) of cattle owners had heard of BTB, only 3 (7%) had an idea on how the disease was spread. Cattle contact with wildlife was associated with high levels of awareness by cattle owners (χ2 = 43.5, df = 2, P < 0.001). Awareness of BTB in low prevalence settings was lower compared to high prevalence settings. Conclusions: Our study has revealed low levels of awareness among cattle owners on BTB. These results could be useful for policy makers when planning mitigation measures to consider awareness levels by cattle owners for effective implementation. Such information is useful for determining sensitisation programs for cattle owners before mitigation. These results further provide useful insights that disease control is a multi-factorial process with cattle owners as an integral part that can support policy implementationThe effect of grazing management on livestock exposure to infection via the faecal-oral route In grazing systems, heterogeneous distributions of forage resources and faeces result in localised accumulations of nutrients and parasites (both macroparasites and microparasites), creating trade-offs between the costs of exposure to infestation or infection and the benefits of nutrient intake. Each contact between livestock and faeces in the environment is a potential parasite/pathogen transmission event. Thus, herbivores must make foraging decisions in complex environments which will affect their intake of both nutrients and parasites. However, the pattern of forage and faecal resources in agricultural environments will also be affected by the grazing management system in place. The aim of this study was to investigate the effect of grazing management on the risk of infection/infestation to livestock. We used a spatially explicit individual based stochastic foraging model to simulate livestock contact (both grazing and investigative) with faeces in the environment. The model was parameterised to simulate cattle grazing under three types of grazing management: set stock (i.e. where sward growth and cattle intake are in equilibrium in a single field); a two pasture rotation grazing system with increasing number of rotations; and a rotational grazing system with two rotations and increasing subdivisions of the pasture. Overall the amount of cattle contact with faecal-contaminated patches was similar in both set stocking and rotational grazing scenarios, suggesting no difference in the risk of infection or infestation between the different systems. However, the timing and absolute amounts of peak contact varied greatly indicating that different grazing management systems expose livestock to risks of different types of parasites at different times of the grazing season. Intensive rotational systems with small pasture blocks (especially the first grazing period) maximised livestock contact with fresh faeces, and thus exposure to microparasites (e.g. bacterial pathogens). Livestock re-entering pasture blocks in rotational systems and set stocked livestock had the highest contact with old faeces and thus have a greater risk of macroparasite transmission (gastrointestinal nematodes). This study highlights how livestock management affects the highly dynamic interaction between livestock and distributions of parasites in the environment and thus the levels of livestock exposure to parasites and pathogens via the faecal-oral route
Livestock grazing behavior and inter- versus intra-specific disease risk via the fecal-oral route Livestock herbivores are at risk of parasite/pathogen exposure from livestock and wild mammal feces during grazing. Livestock exposure to parasites/pathogens will be dependent on the behavioral contact processes between grazing livestock and host animal (both livestock and wild mammal) feces at the bite scale. Here we use 2 grazing experiments to determine the affect of feces from different species and in different defecation patterns on the grazing response of cattle. In experiment 1, there were 4 plots, each with 4 replicates of 5 patch treatments of different fecal contamination (240 g/m-super-2 of Eurasian badger feces, cattle feces, fallow deer feces, Eurasian rabbit feces, and noncontaminated control patches). In experiment 2, there were 3 treatment patterns of badger fecal contamination (one 1-m-super-2 circular patch contaminated with 960 g of badger feces; two 1-m-super-2 circular patches each contaminated with 480 g of badger feces; and four 1-m-super-2 circular patches each contaminated with 240 g of badger feces), divided into 2 plots per treatment. The cattle's grazing response was determined by measuring sward depletion at each of the treatment patches. In experiment 1, cattle-grazed control and rabbit fecal--contaminated patches the most, whereas badger-contaminated patches were grazed the least. In experiment 2, cattle grazed the treatment with the greatest number of fecal-contaminated patches the most. We conclude that cattle vary their grazing response to feces from different host species and to feces in different spatial patterns. Quantifying these behavioral responses to feces is a key step toward quantifying infection risk to herbivores via the fecal--oral route in grazing systems
Inter- and intra-specific exposure to parasites and pathogens via the faecal-oral route: a consequence of behaviour in a patchy environment Livestock herbivores are at risk of inter- and intra-specific exposure to parasites/pathogens via the faecal–oral route during grazing. Each contact between livestock and faeces in the environment is a potential parasite/pathogen transmission event. Cattle grazing contact with faeces varies in relation to the species depositing the faeces and the distribution of the faeces. We used a foraging model to simulate the grazing behaviour of beef cattle in two grazing systems to compare the relative inter-specific and intra-specific exposure risks to parasites/pathogens. Overall, there is a greater level of intra- vs. inter-specific risk via the faecal–oral route. However, under certain conditions, particularly for microparasite infections, e.g. paratuberculosis in rabbits and bovine tuberculosis in badgers, wildlife may pose a significant exposure risk to parasites/pathogens. These risks can be enhanced when cattle are first turned out onto pasture and in situations where intra-specific variations in wildlife behaviour result in more dispersed defecation patterns
Control of bovine tuberculosis in British livestock: there is no silver bullet Bovine tuberculosis (bTB; Mycobacterium bovis) is a bacterial infection of cattle that also affects certain wildlife species. Culling badgers (Meles meles), the principal wildlife host, results in perturbation of the badger population and an increased level of disease in cattle. Therefore, the priority for future management must be to minimize the risk of disease transmission by finding new ways to reduce the contact rate among the host community. At the farm level, targeting those individuals that represent an elevated risk of transmission might prove to be effective. At the landscape level, risk mapping can provide the basis for targeted surveillance of the host community. Here, we review the current evidence for bTB persistence in Britain and make recommendations for future management and research
High spoligotype diversity within a Mycobacterium bovis population: Clues to understanding the demography of the pathogen in Europe Mycobacterium bovis is the main causative agent of bovine tuberculosis. This zoonotic disease produces important economic losses and must be considered a threat to endangered animal species and public health. This study was performed (1) to assess the degree of diversity of the Spanish M. bovis isolates and its effect on the epidemiology of the infection, and (2) to understand the connection of M. bovis populations within a European context. In this report we resume the DVR-spoligotyping results of 6215 M. bovis isolates collected between 1992 and 2007 from different hosts. The isolates clustered into 252 spoligotypes which varied largely in frequency, geographical distribution and appearance in different animal species. In general, the most frequent spoligotypes were found all over the country and in different animal species, though some were restricted to a geographical area. Among our most often isolated spoligotypes, SB0121 and SB0120 (BCG-like) are a common feature between mainland European countries, however, the spoligotypes differ with those found in the UK, the Republic of Ireland and abroad. A comparison of spoligotypes reported from other countries reveals hints for the M. bovis demography in Europe and suggests a common ancestor strain. This study gives insight into the usefulness of the standardized DVR-spoligotyping technique for epidemiological studies in a country with a high degree of strain diversity.
Tuberculosis in alpacas (Lama pacos) caused by Mycobacterium bovis We report three cases of tuberculosis in alpacas from Spain caused by Mycobacterium bovis. The animals revealed two different lesional patterns. Mycobacterial culture and PCR assay yielded positive results for M. bovis. Molecular typing of the isolates identified spoligotype SB0295 and identical variable number tandem repeat (VNTR)allele sizes
Epidemiological significance of the domestic black pig (Sus scrofa) in maintenance of bovine tuberculosis in SicilyBovine tuberculosis (bTB) is an emerging disease among wild animals in many parts of the world. Wildlife reservoir hosts may thus represent a potential source of infection for livestock and humans. We investigated the role played by the Sicilian black pig, an autochthonous free- or semi-free-ranging domestic pig breed, as a potential source of bTB infection in an area where bTB prevalence in cattle is high. We initially performed a preliminary field study to assess the occurrence of bTB in such animals. We sampled 119 pigs at abattoir and found 6.7% and 3.4% of them to be affected by gross tuberculous-like lesions (TBL) and Mycobacterium bovis culture positive, respectively. We then proceeded to investigate the dissemination and characteristics of lesions in a second field study performed on 100 animals sampled from infected herds. Here, tissues collected at the abattoir were examined macroscopically, microscopically, and by culture tests. Most pigs with TBL showed generalized lesions in both gross and histological examinations (53% and 65.5%, respectively). Head lymph nodes were the most frequently affected in both localized and generalized TB cases observed macroscopically and microscopically. M. bovis was the most frequently isolated etiologic agent. The molecular characterization of isolates from both field studies by spoligotyping and analysis of 12 mycobacterial interspersed repetitive-unit–variable number tandem repeat (MIRU-VNTR) loci, followed by their comparison to isolates of cattle origin, suggested a potential transmission of mycobacteria from domestic animals to black pigs and vice versa. Our findings, along with ethological, ecological, and management considerations, suggest that the black pig might act as a bTB reservoir in the ecosystem under study. However, additional studies will be necessary to establish the true epidemiological significance of the Sicilian black pig.
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