Friday, 28 September 2012

Badger Herpes
For anyone reading this outside of the UK a huge uproar is currently occurring over the imminent start of a trial whereby it will be legal to intensively cull badgers. The hope is that this will reduce bovine TB (bTB) which is rife in 'hotspots' in the south west of England and Wales. The controversy is that a previous culling trial, the Randomised Badger Culling Trial (RBCT), suggested that reactive culling (that is, culling badgers in an area where a bTB breakdown has occurred) disrupted badger communities with the result that bTB incidence increased (incidentally, this itself adds further weight to the fact that badgers are important in bTB epidemiology). However, in areas where culling was proactive (whereby all badgers in an area were culled up front), bTB levels did indeed drop by a significant level (Vial and Donnelly, 2012), so culling works, right? The current trial is aiming to create regions which have been culled to a sufficient extent to reduce bTB incidence by culling within boundaries to badger movement (rivers, busy motorways etc.). Interestingly, the results of culling in Ireland are somewhat more positive, and in previous periods of culling in England (intensively using gassing) bTB levels were low. 

The large proportion of the UK population like badgers and, combined with the contrasting results, there are plenty of people who are less than keen for the culling to go ahead (hopefully they won't cause the level of culling to be insufficient and thereby cause an increase in bTB!).

Brian May is a big fan of badgers.
So what about viruses? A paper by Banks et al (2002) described the discovery of a gammaherpesvirus in a badger from Cornwall in England. The paper reports bits of sequence from the virus; nowadays the complete genome would, in theory, be relatively simple to obtain and report. The badger was negative for bTB (based on histological and immunological examinations) but was in a poor state of health and had pathology in the liver, kidneys and lungs. Of course this doesn't mean it was the virus that caused these effects. It would be interesting, and potentially important, if this virus inadvertently interferes with bTB epidemiology.
According to the phylogeny, badger herpesvirus appears to fit nicely among other herpesviruses, most closely with equine herpesvirus 2.

Bager herpresvirus (BadHV) most closely related to equine herpesvirus in either the gb  (a) or  DpoI (b) genes. From  Banks et al 2002

The virus can be propagated in mink cells so in theory could be manipulated, though my current knowledge of herpesviruses isn't that great. Perhaps a virological-fantasy would be that the virus could be modified in such a way that it induces immunity/resistance to bTB in badgers - release the virus into the wild badgers and let it spread through the population. Simple and effective. 

But releasing a genetically modified virus into the wild......would that really be any less controversial than the culling?

Banks M, King DP, Daniells C, Stagg DA, & Gavier-Widen D (2002). Partial characterization of a novel gammaherpesvirus isolated from a European badger (Meles meles). The Journal of general virology, 83 (Pt 6), 1325-30 PMID: 12029147
Vial F, & Donnelly CA (2012). Localized reactive badger culling increases risk of bovine tuberculosis in nearby cattle herds. Biology letters, 8 (1), 50-3 PMID: 21752812

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