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Badger Vaccination and related science

Summary of my considered opinion on the effectiveness of Badger Vaccination

Clearly it is possible to trap and vaccinate badgers with intramuscular BCG vaccine; I have done it in Bucks, Oxfordshire, Shropshire and Worcestershire.  It seems like a good thing to do, but there is no evidence that it makes badgers healthier, eliminates bTB from a badger population, or reduces bTB prevalence in cattle.

From the very limited scientific studies that have been done that, as I write this (February 2019), there is no complete bTB strategy in the UK or Ireland that is capable of reducing infection levels in badgers and cattle to a point where the bTB prevalence can be eliminated.

Without such a strategy, potential short term gains in reducing bTB (if they occur at all)  by vaccinating badgers are unfortunately a waste of time and effort, and give false hope.  The same is true of culling badgers which is also a cruel waste of wildlife.
Whether it works as a desperate strategy to prevent/postpone culling is debatable.

Bob Simpson (Chairman) Feb 2018

In the sections below I have tried to highlight key points from the literature, with references.  Bovine TB is a very complicated disease and is hard to summarize.  I am continually working on this page to improve understanding of the issues.  Comments welcome.

Conclusions from literature relating to effectiveness of Badger Vaccination

In a single year, if you trap and vaccinate 100 badgers, on average

20 will already have bTB
44 will be trapped and vaccinated (80 * 55%)
26 will be protected from bTB (44 * 59%)

After the usual 4 years of annual vaccination, of the 100 badger population, on average

15 will still have bTB (modelled with re-infection and population turnover)
50 will be protected from bTB (modelled)

bTB transmission occurs almost entirely by indirect routes between badgers and cattle.  M. bovis survives long enough to be transferred between the two species although the exact route is not known.  Probably via pasture and latrines.

Analysis done on the ‘intensive action area’ (IAA) and the ‘badger vaccine deployment area’ (BVDP) which were large scale badger vaccine trials, both concluded that no reduction in cattle bTB prevalence could be attributed to the badger vaccination

Further, the extensive areas of badger culling which must significantly reduce the prevalence of bTB infected badgers, have also shown no effect on cattle TB.  I would expect badger vaccination to have a smaller effect on badger TB than culling.

Numerous sources make the point that science is severely lacking on all aspects of bTB infection in the two host system of cattle and badgers.  In particular,  the transmission routes for badger to cattle and cattle to badger bTB infection, and the effectiveness of badger vaccination or widespread culling in reducing bTB in cattle, need urgent scientific study.

Key Points from the Bovine TB literature;
from scientific papers and reputable sources [with references]

  • Managing cattle-to-cattle transmission is likely to contribute far more to TB control and eradication than managing badger-to-cattle transmission” [1.1]
  • “infected and infectious badgers often live with the disease asymptomatically throughout their natural lives” [1.2]
  • At the moment there is limited information about the relative effectiveness of vaccination and culling [badgers] on incidence of the disease in cattle ” [1.4]
  • There is not a consensus amongst epidemiologists about whether R0 within badger populations is above or below [1]. i.e. bTB in badgers may or may not be self-sustaining in the absence of infection from cattle [1.4]
  • During Foot and Mouth outbreak, ” delayed removal of TB-affected cattle, was associated with a widespread increase in the prevalence of M. bovis infection in badgers [1.5]

  • Vaccine efficacy in badgers 59% i.e only 59% of vaccinated badgers protected. Note: non-standard vaccination method but immune response verified [2.1]
  • 55 out of 239 (23%) non-vaccinated badgers infected during study, cf. 40 of 201 (19.9%) vaccinated badgers [2.1]
  • In BVDP study, vaccine efficacy in badgers 52% (using triple bTB analysis) i.e 52% only of vaccinated badgers protected [2.2]
  • During IAA badger vaccination trapping coverage 55% per year, 70-85% over 4years [2.3]

  • Badger cull first 2 years analysis “it would be unwise to use these findings to develop generalizable inferences about the effectiveness of the policy at present” [3.2]

  • IAA Summary conclusion: “Notable differences in indicators of TB Incidence have not yet been seen” [4.2]
  • Cheshire roadkill based study. 20 out of 94 carcases bTB infected Feb 2014/15 [4.3]
  • Spoligotypes (particular strain of M. bovis) SB0129 and others in badgers frequently matched those of cattle moved into area [4.3]
  • Cattle and badgers had same spoligotypes and implies that spread is quick between species [4.3]

  • Large impacts on disease in wildlife will be required to avoid each individual transmission event to cattle.”  [5.1]
  • By modelling RBCT data, eliminating badger-to-badger transmission only reduces time to TB free cattle from 92 to 64 years! [5.2]
  • “Reducing cattle-to-cattle transmission is essential” but model suggests bTB is close to being controlled [5.2]
  • Cattle pasture was badgers’ most preferred habitat ” [5.3]
  • Specific cattle and/or badgers can have high contact rates with the other species [5.4]

  • M. bovis in the environment is prevalent on a large proportion of endemic cattle farms in Britain [6.1]
  • M. bovis can survive in the environment for many months, especially in cool conditions with minimal sunlight [6.2] [6.3]
  • Evidence presented for indirect transmission of M. Bovis via common feeding areas / food sources [6.3]

Bovine TB literature references

1. TB Reviews
1.1 Eradicating TB from cattle and badgers – a review of evidence   ZSL 2018
1.2 Badgers and Bovine TB   RSB on-line article 2014
1.3 The role of badgers in the epidemiology of Mycobacterium bovis infection (tuberculosis) in cattle in the United Kingdom and the Republic of Ireland: current perspectives on control strategies  Bhuachalla et al. 2015
1.4 Bovine TB strategy review (Uk Gov)  Godfray 2018
1.5 Culling and cattle controls influence tuberculosis risk for badgers  Woodroffe et al. 2006

2 Badger Vaccination
2.1 Quantification of Mycobacterium bovis transmission in a badger vaccine field trial   Aznar et al. 2017
2.2 BCG Vaccination Reduces Risk of Tuberculosis Infection in Vaccinated Badgers and Unvaccinated Badger Cubs   Carter et al. 2012
2.3 Estimating wildlife vaccination coverage using genetic methods   APHA and others 2017
2.4 Bacillus Calmette-Guerin vaccination reduces the severity and progression of tuberculosis in badgers   Chambers et al. 2010

3 Badger Culling
3.1 Bovine TB in cattle: badger control areas monitoring report For the period 2013 – 2017   APHA web 2018
3.2 Assessing the effects of the first 2 years of industry-led badger culling in England on the incidence of bovine tuberculosis in cattle in 2013–2015   Brunton et al. 2017

4 Scientific Field Trials / studies
4.1 A descriptive analysis of the effect of badger vaccination on the incidence of bovine tuberculosis in cattle within the Badger Vaccine Deployment Project area, using observational data   Woodroffe et al. 2006
4.2 Differences between bovine TB indicators in the IAA and the Comparison Area:First six years, 1st May 2010 to 30th April 2016
O’Connor et al. 2016
4.3 A study of tuberculosis in road traffic-killed badgers on the edge of the British bovine TB epidemic area   Barron et al. 2018

5 TB Transmission Models and pathways
5.1 A new bovine tuberculosis model for England and Wales (BoTMEW) to simulate epidemiology, surveillance and control   Birch et al. 2018
5.2 Eliminating bovine tuberculosis in cattle and badgers: insight from a dynamic model   Brooks-Pollock et al. 2015
5.3 Badgers prefer cattle pasture but avoid cattle: implications for bovine tuberculosis control   Woodroffe et al. 2016
5.4 Contact Networks in a Wildlife-Livestock Host Community: Identifying High-Risk Individuals in the Transmission of Bovine TB among Badgers and Cattle Bohm et al. 2009

6 Mycobacterium Bovis survival in the environment
6.1 Is Mycobacterium bovis in the environment important for the persistence of bovine tuberculosis?  Courtenay et al. 2006
6.2 Impact of temperature and soil type on Mycobacterium bovis survival in the environment  Barbier et al. 2017
6.3 A Study of the Persistence of Mycobacterium bovis in the Environment under Natural Weather Conditions in Michigan, USA  Fine et al. 2011