The cycle of transmission between badgers and cattle

My new office in Bristol is round the corner from the BBC studios and yesterday I got to visit to talk about some work on bovine TB transmission between cattle and badgers. Thanks Farming Today! I thought they did a great job! http://www.bbc.co.uk/programmes/b05vwpw4

Here's the paper I was talking about.

The Parliamentary and Scientific Committee Discussion meeting: BADGERS!

This evening I attended the Parliamentary and Scientific Committee meeting on badgers and bovine TB. Lined up to talk were Adam Quinney, Vice President of the NFU, Christl Donnelly and Rosie Woodroffe. I heard it was a good turn out for these meetings, and there were quite a few MPs and peers there (although I think a few were kept away by the terrorism bill in the commons). 

Adam Quinney claimed he was not going to talk about the science, but then preceded to talk about the science as he understands it. Over dinner the question was asked about cattle herds in hotspot areas that did not have TB. What were they doing differently? Adam Quinney responded that in the Southwest, in fact 80% of commercial size farms had had TB in the past 5 years. Interesting statistic, and it made me realise that it's important to have the numbers and statistics at my fingertips if the debate is going to be accurate. I'll check it tomorrow. 

Vaccination was presented as almost an ultimate solution and explained in terms of measles and rinderpest. I'm extremely sceptical about the benefits of vaccination at a population scale - we haven't seen it work in humans so why should we in cattle and badgers? Given that Adam Quinney said that in some areas 50% of badgers are infected, so why don't we see a reduction in infective pressure, if vaccination would be likely to work? Christl cited the evidence of badgers cubs being protected when the adults in a social group are vaccinated. Will have to think about that. 

A good question from Stephen Mosley MP: given that vaccination is a way off, what would you do tomorrow to control spread? No one seemed to have an answer. 

Ian Boyd, Chief Scientific Advisor to Defra said the solution would be 25 years off. I thought that was pessimistic, after all it's only 8 years since the 2001 FMD epidemic that saw the massive jump in cattle cases. I would think that a good solution would be able to control the disease within 10 years. 

On an unrelated note, I was given the pregnancy menu option for dinner: no red wine vinegar on my salad?? That seems unnecessary!!

Reading the RBCT - post 2

On to page 24, recommendations for cattle controls. The report recommends the parallel use of the IFN gamma test and recommends differentiating in terms of control herds with one or two reactors and no history of infection and herds with multiple reactors and a history of infection. This also chimes with my issue with Defra terminology; describing a herd as TB free when it has had TB in the past is possibly inaccurate and makes identifying the source of infection very confusing for all concerned. The report also suggests culling the whole herd in extreme cases. 

Ha! Recommendation 29: "Surveillance should be heightened by more frequent testing of herds in low risk areas". That goes against what is being proposed for herds in Scotland - that some herds can be exempt from testing completely. Barlow et al. nicely demonstrated that increased testing in low incidence areas was more effective that more testing in the high risk areas. 

Data analysis should be improved and be made systematic so that the impact of control policies can be assessed. Totally agree. 

They discuss Bang’s method of eradication as practised in Denmark: calves were removed from their dams immediately and reared separately; when they calved they were milked and kept as an isolated group. As time went on, and clinical cases were removed, the clean herd eventually replaced the infected herd. It'd be interesting to know if there is any data that went with this approach.

Randomised Badger Culling Trial (RBCT) post 1

I have decided to read the RBCT report in its entirety. All 287 pages. Although it's 6 years since it was published, there is so much misunderstanding about bovine TB transmission and the results of the RBCT. I have recently started thinking about bovine TB as a two host problem and I think that it would be useful to understand the trial as the main source of information connecting badger and cattle TB. It'll be interesting to see how what we know has developed since the RBCT. 

Day 1. John Bourne's summary. Two main conclusions. 

1. Badgers are clearly a source of cattle TB [...but] badger culling can make no meaningful contribution to cattle TB control in Britain. 

2. Weaknesses in cattle testing regimes mean that cattle themselves contribute significantly to the persistence and spread of disease in all areas where TB occurs

Interesting that attention has focused domain the first point, and I wondered whether I'll agree that badgers are clearly a source of infection. Bourne say that operations in Defra will have to change and that the farming and veterinary communities have to accept the scientific findings. 

Point 4. "Our practice has been to concurrently release all relevant data in order that a full assessment of our work could be made by any interested member of the scientific community". That's me! Shame that more analysis hasn't been done using the RBCT data

Point 10. Discussion of cattle testing. Says that infected cattle remain in a herd following testing with the comparative skin test. This has been confirmed by Andrew's study and also my model. Report says the IFN test should be used and that concerns about the specificity are unwarranted. I don't know that I've seen that analysis. I wonder what Kat's analysis says about IFN testing and recurrent and prolonged breakdowns. It doesn't seem that they looked at IFN testing. 

The final numbers:

1. Proactive culling was associated with an estimated 23% reduction in cattle TB incidence inside the proactive areas

2. Proactive culling was associated with a 25% increase in the incidence of cattle TB on neighbouring un-culled land

3. Reactive culling was associated with a roughly 20% increase in cattle TB incidence.

The report's conclusions are unequivocal that badger culling can make no reasonable contribution to TB control, either in terms of reducing TB in cattle or in economic terms. I have to say I'm a little surprised given the strength of the statements here, that so many people still refer to this document in support of badger culling.