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.