Simulation model of within-herd transmission of bovine tuberculosis in Argentine dairy herds

Industry-led culling of badgers has occurred in England to reduce the incidence of bovine tuberculosis in cattle for a number of years. Badger vaccination is also possible, and a move away from culling was “highly desirable” in a recent report to the UK government. Here we used an established simulation model to examine badger control option in a post-cull environment in England. These options included no control, various intermittent culling, badger vaccination and use of a vaccine combined with fertility control. The initial simulated cull led to a dramatic reduction in the number of infected badgers present, which increased slowly if there was no further badger management. All three approaches led to a further reduction in the number of infected badgers, with little to choose between the strategies. We do note that of the management strategies only vaccination on its own leads to a recovery of the badger population, but also an increase in the number of badgers that need to be vaccinated. We conclude that vaccination post-cull, appears to be particularly effective, compared to vaccination when the host population is at carrying capacity.

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Bovine tuberculosis and udder health in Irish dairy herds

The Veterinary Journal ◽

10.1016/j.tvjl.2011.04.004 ◽

2012 ◽

Vol 192 (1) ◽

pp. 71-74

Author(s):

F. Boland ◽

G.E. Kelly ◽

M. Good ◽

S.J. More

Keyword(s):

Bovine Tuberculosis ◽

Dairy Herds ◽

Udder Health

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Minimization of bovine tuberculosis control costs in US dairy herds

Preventive Veterinary Medicine ◽

10.1016/j.prevetmed.2013.07.014 ◽

2013 ◽

Vol 112 (3-4) ◽

pp. 266-275 ◽

Cited By ~ 9

Author(s):

Rebecca L. Smith ◽

Loren W. Tauer ◽

Ynte H. Schukken ◽

Zhao Lu ◽

Yrjo T. Grohn

Keyword(s):

Bovine Tuberculosis ◽

Dairy Herds ◽

Tuberculosis Control

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Simulation model estimates of test accuracy and predictive values for the Danish Salmonella surveillance program in dairy herds

Preventive Veterinary Medicine ◽

10.1016/j.prevetmed.2006.08.001 ◽

2006 ◽

Vol 77 (3-4) ◽

pp. 284-303 ◽

Cited By ~ 27

Author(s):

L.D. Warnick ◽

L.R. Nielsen ◽

J. Nielsen ◽

M. Greiner

Keyword(s):

Simulation Model ◽

Surveillance Program ◽

Dairy Herds ◽

Test Accuracy ◽

Predictive Values

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Bovine tuberculosis in badger ( Meles meles ) populations in southwest England: the use of a spatial stochastic simulation model to understand the dynamics of the disease

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1995.0126 ◽

1995 ◽

Vol 349 (1330) ◽

pp. 391-413 ◽

Cited By ~ 40

Keyword(s):

Point Source ◽

Simulation Model ◽

Stochastic Simulation ◽

Group Size ◽

Bovine Tuberculosis ◽

Grid Cell ◽

Meles Meles ◽

Individual Level ◽

Stochastic Simulation Model ◽

Disease Free

A spatial stochastic simulation model was developed to describe the dynamics of bovine tuberculosis in badger populations in southwest England, based on data from the literature and from unpublished sources. As there are no data on intra- and intergroup infection probabilities, estimates of these were obtained through repeated simulations based on field observations of the spread and prevalence of the disease. The model works on a grid-cell basis, with each grid cell potentially occupied by one badger social group; immigration to and emigration from the main grid are incorporated. Population regulation is assumed to occur at the group level through density-dependent fecundity and cub mortality, and the model can be run for various disease-free equilibrium group sizes (which are determined by the carrying capacity of the environment). The model works on a quarterly (three-monthly) basts and processes are stochastic at the individual level. Three classes of individual (adults, yearlings and cubs) and three classes of infection (susceptible, infected-but-not-infectious and infectious) are recognized. Bovine tuberculosis was shown to persist in badger populations for long periods of time, even in populations with a disease-free equilibrium group size of only four adults and yearlings. However, with standard rates of intergroup infection and movement, the disease only became endemic in populations with a disease-free equilibrium group size greater than six adults and yearlings. In the endemic situation the prevalence of the disease ranged between 11- 22% depending on the combination of inter- and intragroup infection probabilities used. Endemic infection within the homogeneous environment of the grid was characterized by a high degree of heterogeneity. Patches of infection were spatio-temporally unstable, but shifted in location relatively slowly. Spread of the disease from a point source of infection with standard rates of intergroup movement and infection only occurred to any marked extent in populations with disease-free equilibrium group sizes of eight or more adults and yearlings. Increasing the intergroup infection probability had a significant effect on increasing the probability and rate of spread, and considerably lowered the threshold group size for spread from a point source to around four adults and yearlings. However, increasing the rates of intergroup movement reduced the probability of spread of the disease except at the largest group sizes. When both intergroup infection and movements were increased, the effects of increased infection in enhancing spread were offset to some degree by the increased movements. Perturbation to the badger population, as may be caused by control operations, could therefore increase the probability of persistence or spread of an infection.

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Bovine tuberculosis in badger (Meles Meles ) populations in southwest England: an assessment of past, present and possible future control strategies using simulation modelling

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1995.0127 ◽

1995 ◽

Vol 349 (1330) ◽

pp. 415-432 ◽

Cited By ~ 36

Keyword(s):

Simulation Model ◽

Stochastic Simulation ◽

Bovine Tuberculosis ◽

Control Strategies ◽

Oral Vaccine ◽

Simulation Modelling ◽

Meles Meles ◽

Comparative Assessment ◽

Localized Disease ◽

Stochastic Simulation Model

A spatial stochastic simulation model was used to compare the efficacy of different badger control policies and to determine the theoretical requirements for the control of endemic bovine tuberculosis in badger populations in southwest England. Culling-based strategies for controlling endemic disease were compared with strategies employing a yet-to-be-developed oral vaccine which would provide uninfected badgers with immunity to the infection. A comparative assessment was made of the efficacy of previous and proposed culling-based strategies employed by the Ministry of Agriculture, Fisheries and Food for the control of localized disease, and the potential for an oral vaccine-based strategy for the control of localized disease was examined.

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The variable prevalence of bovine tuberculosis among dairy herds in Central Ethiopia provides opportunities for targeted intervention

PLoS ONE ◽

10.1371/journal.pone.0254091 ◽

2021 ◽

Vol 16 (7) ◽

pp. e0254091

Author(s):

Gizat Almaw ◽

Andrew J. K. Conlan ◽

Gobena Ameni ◽

Balako Gumi ◽

Alemseged Alemu ◽

...

Keyword(s):

Risk Factors ◽

Bovine Tuberculosis ◽

Significant Risk ◽

Dairy Farms ◽

Herd Size ◽

P Value ◽

Dairy Herds ◽

Individual Animal ◽

Central Ethiopia ◽

High Prevalence

Bovine tuberculosis (bTB) is an important disease for dairy productivity, as well as having the potential for zoonotic transmission. Previous prevalence studies of bTB in the dairy sector in central Ethiopia have suggested high prevalence, however, they have been limited to relatively small scale surveys, raising concerns about their representativeness. Here we carried out a cross sectional one-stage cluster sampling survey taking the dairy herd as a cluster to estimate the prevalence of bTB in dairy farms in six areas of central Ethiopia. The survey, which to date is by far the largest in the area in terms of the number of dairy farms, study areas and risk factors explored, took place from March 2016 to May 2017. This study combined tuberculin skin testing and the collection of additional herd and animal level data by questionnaire to identify potential risk factors contributing to bTB transmission. We applied the single intradermal cervical comparative tuberculin (SICCT) test using >4mm cut-off for considering an individual animal as positive for bTB; at least one reactor animal was required for a herd to be considered bTB positive. Two hundred ninety-nine dairy herds in the six study areas were randomly selected, from which 5,675 cattle were tested. The overall prevalence of bTB after standardisation for herd-size in the population was 54.4% (95% CI 48.7–60%) at the herd level, and it was 24.5% (95% CI 23.3–25.8) at the individual animal level. A Generalized Linear Mixed Model (GLMM) with herd and area as random effect was used to explore risk factors association with bTB status. We found that herd size, age, bTB history at farm, and breed were significant risk factors for animals to be SICCT positive. Animals from large herds had 8.3 times the odds of being tuberculin reactor (OR: 8.3, p-value:0.008) as compared to animals from small herds. The effect of age was strongest for animals 8–10 years of age (the oldest category) having 8.9 times the odds of being tuberculin reactors (OR: 8.9, p-value:<0.001) compared to the youngest category. The other identified significant risk factors were bTB history at farm (OR: 5.2, p-value:0.003) and cattle breed (OR: 2.5, p-value: 0.032). Our study demonstrates a high prevalence of bTB in central Ethiopia but with a large variation in within-herd prevalence between herds, findings that lays an important foundation for the future development of control strategies.

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