Badgers and Bovine TuberculosisDamien Adams, James Alford & Emily May

What is Bovine Tuberculosis?Bovine TB is a disease of mammals caused by Mycobacterium bovis. Closely related to M. tuberculosis the agent causing TB in humans, M.bovis causes lesions in the lungs, with symptoms manifesting as high fever, weight loss, coughing and eventually death. Due to the economic impact that the death of cattle as a result of TB has on the beef farming industry, this disease has been primarily identified as “bovine” TB, though it actually infects many mammals, including the European badger Meles meles.

TransmissionThought to be primarily via the aerosol- inhalation route. 1-5 inhaled bacterium capable of producing lesions in sheep lung vs 13 million bacteria via oral route. May replicate in oral- pharyngeal region As Droplet Nuclei- residues of small droplets that dry down to a size that persists as airborne particles capable of being inhaled.

Badger Badger 2-12% of a badger population is infected with bovine TB Mainly assumed to transmit via respiratory route. Serological evidence indicates mother to cub vertical transmission.

Badger Cow Presumed to be via oral route- badger urinates on cattle feed in field or in barns and is ingested by feeding cattle. Aerosol route also likely. By contact – badger to calf, shown in the wild and experimentally. NOT ABSOLUTELY CLEAR HOW IT IS TRANSMITTED

It’s not my fault!

Bovine TB incidence has been increasing over the past 20 years, so in a bid to reduce TB in cattle and therefore yield loss, farmers have been given permission to cull badgers in farming areas in hope of reducing transmission from badger to cow. However, the

Conclusion• Government decision to halt the culling of badgers to control bovine TB appears correct based on the scientific evidence provided by culling trials. • Bovine TB still needs much more research, a working and cost efficient vaccine, better methods of diagnoses and farmers need to take responsibility themselves for implementing methods of separating livestock from wild badgers.• The ISG’s randomised culling trials stated in 2007: “badger culling cannot meaningfully contribute to the control of cattle TB in Britain”

The Culling DebateBadger culling to reduce the incidence of bovine TB has been undertaken for more than 30 years, though its true impact on the prevalence of bovine TB in cattle has been contentious. A hearing in Parliament in July 2008 has indicated a new take on policy to target bovine TB that will no longer focus on badger culling but rather vaccination against the disease (£20M will be donated for vaccine research is the next three years), fencing to keep badgers out of the proximity of cattle and better surveillance of the prevalence of disease in both species. This decision is based on a 10 year long study conducted by the Independent Scientific Group (ISG) who’s conclusion it was that culling would not help reduce the incidence of TB in cattle. This decision comes as a disappointment of many farmers, politicians and researchers who maintain the belief that there is sound evidence for culling badgers for the purpose of reducing bovine TB in cattle.

ARGUMENTS IN FAVOUR OF CULLING

Badgers are a reservoir for Bovine TB, and may transmit to cattle. Culling of reservoir host mammals in Ireland and New Zealand proved successful at decreasing TB prevalence. Statistical benefits- The ISG’s randomised trial showed that inner areas of culling areas exhibited some decrease in incidence of TB in cattle. There is no available vaccine for cows or badgers

ARGUMENTS AGAINST CULLING

The ISG randomised trial showed that bovine TB transmission and incidence over the 10 year study period continued to increase despite the culling of badgers. ISG trial showed that culling actually increased TB prevalence in outer areas of the culling zone- due to culling altering badger social behavior so that their contact with cows actually increased. Economic: The cost does not outweigh the gain. Culling is labour intensive and expensive so farmers only receive 1/40 of the cost back from culling on any cows saved. Badgers may not transmit TB to cattle at all. Transmission route has not been convincingly proven. Cattle control is cheaper and more scientifically proven to work. i.e. fencing, locking cattle in barns at night etc. Ethical: is it really appropriate to kill badgers for the farmer’s economic gain? Especially as all the research has shown that it rarely decreases TB incidence in cattle at all. It is likely that bovine TB is increasing mainly due to large scale movement

transmission route between badgers and cows is not well understood and many of the badger culling trials have in fact resulted in an increase, rather than a decrease in TB in cattle populations.

What we need now• Vaccination for cattle and/or badgers. Should be available by 2014. • New methods of diagnosis are needed for current EU legislation against vaccination to be lifted. At the moment vaccination interferes with diagnosis of TB outbreaks, so more funding and research needs to be redirected into this field to allow for a long term control for disease to be developed.• More research is needed to determine the routes of transmission between cows and badgers for more effective control strategies to be developed. • A more centralised data programme to collate information on cattle movement and TB incidence in populations of badgers and cattle around England.

References

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