One of the primary factors reducing the effectiveness ofculling in preventing the spread of Bovine Tuberculosis is the socialperturbation this induces in Eurasian badgers. A study published in the Journal of applied ecology 20061was conducted over thirty assigned trial areas, each covering one hundredsquare kilometres. These areas were grouped into triplets, containing one areaof proactive culling (which aimed to reduce populations within the area to avery low level), one are of reactive culling (which sought to remove onlybadgers whose ranges overlapped with farms currently experiencing bTB outbreaks),and one non-culling, ‘survey only’ area. The spatial organisation of badgerpopulations was recorded using bait marking, where bait containing colouredbeads was paced at the sett and areas were the beads were found in badgerstools used to indicate the territories of these setts. Wider ranging stoolrecordings as well as those occurring close to stool returns from other badgersetts indicated disruption of the population or overlapping badger territories,which could present increased opportunity for disease transmission. From this experiment, it was demonstratedthat culling of badgers significantly impacted the movement of the remainingpopulations, resulting in increased overlapping of ranges as badgers moved intothe newly available territory. The journal suggests in its concluding notesthat this may result in increased opportunity for transition of bTB in alocalised culling model, as disrupted groups became more likely to come intocontact with one another. This is reflected in the increased occurrence ofoverlapping ranges in the bait marking experiment within the culled zones andthe surrounding area.
Therefore, while the overall population density ofbadgers within the cull zone decreased, the badgers in the surrounding area hadan increased likelihood of exposure to potential carriers of bTB. In addition,this experiment demonstrated that the disruption not only resulted in increasedcontact between different badger groups, but in wider territorial ranges, shown by the wider spread of baitmarked faecal matter in cull zones and the surrounding area. This increasedterritory size could lead to increased contact with cattle, as well as transmissionbetween infected and clean herds as larger territories may expand between several farm’s land, carrying infectionbetween herds. The findings of this study are supported in ‘Culling-induced social perturbation in Eurasian badgers Meles melesand the management of TB in cattle: an analysis of a critical problem inapplied ecology’2,where it is suggested that the impacts of culling may remain evident for aslong as eight years after the cull takes place. The long term impacts ofculling have led some people to speak out against culling, arguing that itultimately may cause an increase in the spread of Bovine Tuberculosis ratherthan a decrease. Both of these sources however, have some degree of bias. Whileboth reflect scientific evidence found through experiment and published inscientific journals, suggesting reliable evidence, both sources had a commonco-author: C.
L.Cheeseman. Upon further research, this scientist was found tohave a vested interest in the study, as a member of badger conservation group,”Team Badger”3,which may introduce some bias into his work researching the papers. However, itmay equally be argued that his anti-culling views exist as a product of hisresearch, rather than the source of his results. As the results he haspublished are widely found in reputable scientific journals and are peerreviewed, it is unlikely this bias is significant enough to discredit hisfindings. These studies also reflect the findings of a similar, earlier studypublished in “Wildlife rabies: the implications for Britain. Unresolvedquestions for the control of wildlife rabies: social perturbation andinterspecific interactions”4,where a similar “vacuum effect” is demonstrated (In this regard described relatingto rabies control) as badgers move into cull areas to fill the territorialvacuum left by a cull. This suggests that culling may lead to increasedexposure of otherwise isolated populations of badgers to each other and tocattle, increasing the likelihood of transmitting Bovine Tuberculosis.
The simplest measure of how effective a cull is inpreventing the spread of Bovine Tuberculosis is how the frequency of outbreaksis impacted by the reduction of badger populations in the area by culling. The directimpact of a proactive cull gives an indication of how heavily badgerscontribute to the spread of Bovine Tuberculosis, as well as whether cullingpresents an effective solution. In “Impacts of widespread badger culling oncattle tuberculosis: concluding analyses from a large-scale field trial”5,a large scale trial conducted over thirty trial areas, each about 100 km²,were used as ten matched triplets, all selected as areas of high cattle TBincidence. Over these areas the impacts of culling on bovine tuberculosis weremeasured.
The treatments allocated to each area (proactive culling, reactiveculling or survey only) were conducted between December 1998 and December 2002,then repeated yearly, excluding delays caused by the national outbreak of footand mouth disease in 2001. Farms in the trial and surrounding areas thenreported any unconfirmed* orconfirmed Tuberculosis breakdowns following the trial. The use of veterinarysurveillance provided by the trial runners allowed the distinction of these twotypes of breakdown to improve the reliability of results gathered. The resultsdemonstrated levels of TB breakdown to be 23.2% lower inside the active cullarea compared to in the survey only trial area, consistent across all tentriplets. This suggests a significant link between culling of badgers within anarea and the decrease in outbreaks of Bovine Tuberculosis, strengthening theclaim that badgers contribute to the spread of the disease. However it was alsoreported that the costs involved in conducting the cull were shown to besignificantly greater than the estimated compensation allocated for farmsexperiencing breakdowns of bTB that were prevented by the cull. Thereby, evenwithin the initial cull area where Bovine Tuberculosis levels are reduced, itis apparent that these culls have no obvious financial benefit to participatingregions.
Left: The economic impact of various badger control options on thediscounted net benefit distribution. Each bar represents the predicted economicbenefit of one simulation, taking into account the economics of the badgercontrol, and cattle disease management. (A) Shooting (50% culled), (B) trapping (70% culled), (C)snaring (80% culled), (D) gassing(80% culled).
5 It is worth noting, however, that the above economic graphsare taken from a simulation rather than experimental data. True values for bothcosts and effectiveness of a cull may vary, despite the use of data fromprevious field trials to generate these predictions. In addition, furthersimulations where immigration of badgers into the control area was prevented (representingareas isolated by rivers or coastline) demonstrated an improved economicbenefit, with 67% of simulations demonstrating an overall economic gain as aresult of culling. This data suggests that the suitability of culling as ameasure of protection against bTB may vary between areas depending ongeographical factors. This means that while a method of combatting bTB may beeffective in one area, it may not be so in another, so it becomes necessary totailor the measures in place to the area in which they are carried out. Whileit appears that bTB levels do decrease within the primary culling area, thisdoes not result in economic benefits to farmers outweighing the costs of thecull.
It would, therefore, be more economically viable to offer financialcompensation to farmers suffering from a bTB breakdown than to conduct a cull.This economic data is provided by independent and impartialauthors representing established and prestigious universities and agencies, assuch it is unlikely to be impacted by bias or conflict of interest.Furthermore, the article cited was published in a recognised scientificjournal: ‘Journal of wildlife diseases’ in20095, suggesting it is a relatively current and reliable source. While the impact in the immediate area ofthe cull is significant when measuring it’s effectiveness, the repercussions onthe surrounding area are of equal importance. Data published by the RoyalSociety6indicates that during the annual cull trial period (Initial culls for eachtrial area between 1998-2002, culling repeated annually with final cull inconcluding 2005) the area bordering the cull zone demonstrated an averagechange in bTB incidence of +25%. Furthermore, the overall average incidence ofbTB during the cull and the following five years after it’s completion showedan increase of +8% relative to pre-cull levels. A further study conductedduring the same cull period and described in “The Duration of the Effects of Repeated Widespread Badger Culling onCattle Tuberculosis Following the Cessation of Culling”7suggests that during the trial period and the 30 months following this wheresignificant impacts remained apparent, the incidence of bTB was 28.
7% lowerwithin proactive cull areas than in the surrounding no-cull area. At no pointwere the impacts (positive or negative) on bTB levels in the area surroundingthe cull zone shown to reach statistically significant levels demonstrated byerror bars.Left:Comparative impact of incidence of bTB inside culling area and in adjoininglands7. Culls were conducted on an annual basis with initial cullsoccurring between 1998 and 2002, with the final cull concluding in 2005 Overa 7.5 year period with no culling conducted, an average area of 150 km2, with 1.25 herds per km2 and a background bTBincidence of 0.
08 breakdowns per herd per year would anticipate 112.5 herdbreakdowns. Over the same time scale, surrounding land of 99 km2 falling less than 2km outside the sample area would experience74.
3 breakdowns, ie a total of 186.8 across both areas. During a five-yearculling period, annual proactive culling in the trial area would prevent anaverage of 23.2% of 75 breakdowns inside a culled area (ie 17.4 breakdowns),while causing the number of breakdowns on adjoining land to increase by anaverage of 24.
5% (ie 12.1 additional breakdowns), giving an overall reductionof 5.3 breakdowns during the 5 year cull. In the 2.5 years following the cull,the incidence of bTB inside the cull zone would reduce by 42.0% (15.8breakdowns prevented), and the number on adjoining lands would be reduced by6.0% (1.
5 breakdowns prevented), giving an overall total of 17.3 breakdownsprevented in the years following the cull. Therefore, the total impact ofculling an ideal area of land would be the prevention 22.6 breakdowns over 7.
5years. This corresponds to a saving of £610,200 (approximating a loss of£27,000 for each breakdown). In comparison to this, the cost of conducting fiveannual culls over the same 150 km2 area, assuming a typicalvalue of 75% accessibility for culling, is estimated as £1.35 million forsnaring or gassing (the most cost effective methods of culling). This indicatesthat culling is not an economically viable solution, as it would result in a£739,800 greater loss than the absence of culling over a 7.
5 year period. It istherefore apparent that while there is an overall reduction in the total numberof breakdowns as a result of culling, this does not balance the economic costof the cull. Furthermore, isolating the data for the no-cull adjoining landsalone, we see an overall increase of 10.6 additional breakdowns over the fulltime period studied. This demonstrates an extremely high cost relative to thebenefits of the cull on levels of bTB overall, which throws further doubt ontothe already contravertial topic of badger culling.
Furthermore, the study goes on to state that36 months following the cessation of culling, no further impact was seen inoverall levels of bTB, positive or negative, despite the £739,800 additionalloss incurred by culling relative to compensating farmers for breakdowns. Thissource was published in an established scientific journal, by authorsrepresenting reputable research organisations (Imperial College London, Instituteof Zoology London). The article is also accompanied by a declaration ofcompeting interests stated by the authors, which shows them to hold no vestedinterest in the outcomes of the study. The source is therefore likely to beunbiased and reliable. 1 (Rosie Woodroffe, Christl A. Donnelly, D. R.
Cox, F. John Bourne, C. L. Cheeseman, R. J. Delahay, George Gettinby, John P.
McInerney and W. Ivan Morrison, 2006)2 (Stephen P Carter, Richard J Delahay, Graham C Smith, David W Macdonald, Philip Riordan, Thomas R Etherington, Elizabeth R Pimley, Neil J Walker, Chris L Cheeseman, 2007)3 (2017, Team Badger ©, 2017)4 (Macdonald, 1995)5 (Christl A. Donnelly, Gao Wei , W. Thomas Johnston , D.R.
Cox,, 2007)* Cases whereone or several cattle tested positive for TB in Tuberculin test but this wasnot confirmed at post-mortem or by culture6 (H. Charles J. Godfray, Christl A. Donnelly, Rowland R. Kao, David W. Macdonald, Robbie A.
McDonald, Gillian Petrokofsky, James L. N. Wood, Rosie Woodroffe, Douglas B. Young, Angela R. McLean, 2013)7 (Helen E. Jenkins, Rosie Woodroffe, Christl A.