Peer Review #2 of "Bovine tuberculosis breakdown duration in cattle herds: an investigation of herd, host, pathogen and wildlife risk factors (v0.1)"

SUMMARYWe analysed the incidence of cattle herd breakdowns due to bovine tuberculosis (Mycobacterium bovis) in relation to experimental badger culling, badger populations and farm characteristics during the Randomized Badger Culling Trial (RBCT). Mixed modelling and event history analysis were used to examine the individual risk factors. The interdependencies of covariates were examined using structural equation modelling. There were consistent findings among the different analyses demonstrating that during a badger culling programme farms experiencing: reactive culling, larger herd sizes, larger holdings and holdings with multiple parcels of land were all at greater risk of a herd breakdown. Proactive culling reduced risks within the culling area, but we did not assess any potential effects in the periphery of the treatment area. Badger-related variables measured prior to the start of culling (number of social groups and length of badger territorial boundaries) did not consistently point to an increase in risk, when set against a background of ongoing badger culling. This could be because (1) the collected variables were not important to risk in cattle, or (2) there were insufficient data to demonstrate their importance. Our findings highlight the difficulty in identifying simple predictors of spatial variation in transmission risks from badger populations and the consequent challenge of tailoring management actions to any such field data.

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Clustering and spatial heterogeneity of bovine tuberculosis at the livestock/wildlife interface areas in Namwala District of Zambia

Veterinary World ◽

10.14202/vetworld.2020.478-488 ◽

2020 ◽

Vol 13 (3) ◽

pp. 478-488

Author(s):

Novan Fully Proud Tembo ◽

John Bwalya Muma ◽

Bernard Hang'ombe ◽

Musso Munyeme

Keyword(s):

Risk Factors ◽

Spatial Distribution ◽

Bovine Tuberculosis ◽

Significant Risk ◽

Interface Area ◽

Southern Province ◽

Trace Back ◽

Kafue Lechwe ◽

Cattle Herds ◽

Reservoir Hosts

Background and Aim: Bovine tuberculosis (bTB) remains a major public health issue in Zambia and has been exacerbated by human immunodeficiency virus prevalence and consumption of unpasteurized milk in the Southern Province of the country. The prevalence of bTB has been established to be linked to Kafue Lechwe, which act as reservoir hosts and share grazing fields with domestic cattle. No studies have so far used geographic information system (GIS) to investigate the relationship between the reservoir hosts (Kafue Lechwe) and domestic animals. This study, therefore, aimed to apply GIS to investigate the spatial distribution of bTB in Namwala District of the Southern Province of the country. Materials and Methods: To investigate the spatial distribution of bTB, geographical positioning system (GPS) coordinates representing 96 cattle herds across 20 independent villages were captured alongside risk factor data. The 96 herds were based on abattoir reports of condemned carcasses and a trace back. Positive herds were confirmed by cross-reference to purified protein derivative tests conducted by the District Veterinary Office. The GPS coordinates were transferred into ArcView 3.2 and laid on the map of Namwala District alongside physical features, including national parks, game management areas, and flood plains. Questionnaires were administered across 96 independent households to assess risk factors of bTB transmission. Results: The results revealed a "clustered" spatial distribution of the disease in cattle in Namwala District of Zambia, particularly significant in the eastern interface areas of the district (p=0.006 using Moran's I). Abattoir to production area trace back revealed a herd-level prevalence of 36.4% (95% CI=26.7-46.3%) among cattle herds in Namwala District, whereas individual animal prevalence ranged from 0% to 14% (95% CI=2.4-26.2%). Further, GPS data indicated that the majority of the positive herds were located at the livestock/wildlife interface area. Contacts with wildlife, coupled with sharing grazing, and watering points were found to be significant risk factors for bTB transmission. Conclusion: This study demonstrated the presence of bTB in cattle and associated spatial risk factors. In particular, bTB was observed to be a function of animal location within the livestock/wildlife interface area. GIS is thus an applicable and important tool in studying disease distribution.

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Herd-Level Risk Factors for Bovine Tuberculosis: A Literature Review

Veterinary Medicine International ◽

10.1155/2012/621210 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 65

Author(s):

Robin A. Skuce ◽

Adrian R. Allen ◽

Stanley W. J. McDowell

Keyword(s):

Risk Factors ◽

Bovine Tuberculosis ◽

Management Practices ◽

Scientific Evidence ◽

Epidemiological Studies ◽

Herd Size ◽

Herd Level ◽

Endemic Diseases ◽

Veterinary Profession ◽

Cattle Herds

Bovine tuberculosis (TB), caused byMycobacterium bovis, is one of the most challenging endemic diseases currently facing government, the veterinary profession, and the farming industry in the United Kingdom and Ireland and in several other countries. The disease has a notoriously complex epidemiology; the scientific evidence supports both cattle-cattle and wildlife-cattle transmission routes. To produce more effective ways of reducing such transmission, it is important to understand those risk factors which influence the presence or absence of bovine TB in cattle herds. Here we review the literature on herd-level risk factor studies. Whilst risk factors operate at different scales and may vary across regions, epidemiological studies have identified a number of risk factors associated with bovine TB herd breakdowns, including the purchase of cattle, the occurrence of bovine TB in contiguous herds, and/or the surrounding area as well as herd size. Other factors identified in some studies include farm and herd management practices, such as, the spreading of slurry, the use of certain housing types, farms having multiple premises, and the use of silage clamps. In general, the most consistently identified risk factors are biologically plausible and consistent with known transmission routes involving cattle-cattle and wildlife-cattle pathways.

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A simulation model for the spread of bovine tuberculosis within New Zealand cattle herds

Preventive Veterinary Medicine ◽

10.1016/s0167-5877(97)00002-0 ◽

1997 ◽

Vol 32 (1-2) ◽

pp. 57-75 ◽

Cited By ~ 66

Author(s):

N.D. Barlow ◽

J.M. Kean ◽

G. Hickling ◽

P.G. Livingstone ◽

A.B. Robson

Keyword(s):

New Zealand ◽

Simulation Model ◽

Bovine Tuberculosis ◽

Cattle Herds

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Evaluating the Bovine Tuberculosis Eradication Mechanism and Its Risk Factors in England’s Cattle Farms

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18073451 ◽

2021 ◽

Vol 18 (7) ◽

pp. 3451

Author(s):

Tabassom Sedighi ◽

Liz Varga

Keyword(s):

Risk Factors ◽

Bovine Tuberculosis ◽

Animal Health ◽

Dynamic Bayesian Network ◽

Policy Makers ◽

Domain Experts ◽

Actual Experience ◽

Complex Evaluation ◽

Risk Areas ◽

Cattle Farms

Controlling bovine tuberculosis (bTB) disease in cattle farms in England is seen as a challenge for farmers, animal health, environment and policy-makers. The difficulty in diagnosis and controlling bTB comes from a variety of factors: the lack of an accurate diagnostic test which is higher in specificity than the currently available skin test; isolation periods for purchased cattle; and the density of active badgers, especially in high-risk areas. In this paper, to enable the complex evaluation of bTB disease, a dynamic Bayesian network (DBN) is designed with the help of domain experts and available historical data. A significant advantage of this approach is that it represents bTB as a dynamic process that evolves periodically, capturing the actual experience of testing and infection over time. Moreover, the model demonstrates the influence of particular risk factors upon the risk of bTB breakdown in cattle farms.

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