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Concerning spreading of bovine TB in edge areas.

The goverment of the Uk did release the last quartal figures about the situation of bovine TB obtained from APHA.
https://www.gov.uk/government/statistical-data-sets/tuberculosis-tb-in-cattle-in-great-britain

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The figures show that  in high risk areas the top is obviously reached. Since 2012 it is moving between 10% and 12% prevalence. In the edge areas however it seems that bovine tb is spreading unrestrained. We are now at about 5% prevalence. This means that edge areas will sooner or later become high risk areas and the amount of regions with high herd prevalence ist growing. So far there are no signs of a sucsessful control of bovine TB. 

The herd prevalence is calculated by breaking the amount of herds under restriction through the amount of all herds registered on SAM. To get a percentage figure you have to multiply with hundred. 

You can find the the concerning dataset here: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/763660/bovinetb-gb-countries-12dec18.ods

Select the Edge Area Sheet in the file and go to the columns:

“Number of cattle herds registered on Sam” and

“Herds not officially TB free at the end of the period due to a bovine TB incident”

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Then scroll down to the rows with the monthly figures:

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The Excel file the graph above is created with: 

http://wf2g2bm3y.homepage.t-online.de/0012/wp-content/uploads/2018/12/st1.xlsx

 

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How to measure the effect of badger culling

When measuring, we should  use units, that are used to measure the goals we set.

George Eusticen   Minister of State for Agriculture, Fisheries and Food of the UK formulates a goal in the “Written statement – HCWS963”:

https://www.parliament.uk/business/publications/written-questions-answers-statements/written-statement/Commons/2018-09-13/HCWS963/

 

“I want to update the House on the implementation of the government’s strategy to eradicate bovine TB in England by 2038.”

 

I am not sure what kind of definition of “eradication of bovine Tb” George Eusticen is using, I suggest to agree on “prevalence under 1%” as it is in Scotland since ages.

How can we define “prevalence of bovine Tb” within a population of cattle herds?

I suggest: “The part of herds with not OTF-status of the whole population”

 

Here are the graphs for Gloucestershire and Somerset 1996 until 2017:

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George Eusticen also states:

 

“Today the Animal and Plant Health Agency has published data showing there has been a drop in TB incidence in the first two cull areas where the number of new confirmed breakdowns has dropped by around 50%. In Gloucestershire the incidence rate has dropped from 10.4% before culling began to 5.6% in the twelve months following the fourth cull. While in Somerset it has dropped from 24% to 12%.”

What is incidence and what are incidents.

 

I think, that we have to be exact with the terms. Incidents (mind the spelling) rate and incidence is not the same. In the file “bovinetb-southwest-17oct18.ods” provided by APHA and government incidents are: “New herd incidents where OTF status was withdrawn from the herd.”

If new incidents of Bovine TB are decreasing, the disease is perhaps spreading slower, but there is no effect on the incidence or prevalence of bovine TB (Percentage of farms with no OTF-status) So there is not yet a proof that badger culling is decreasing incidence or prevalence of Bovine TB.

So we are not on the way to an incidence or prevalence of Bovine TB under 1% until 2038 or whenever.

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The development in the different risk areas.

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Bovine TB is spreading. The prevalence of all regions classified as high risk area is 2017 at 12.8 percent. The prevalence of all edge areas is at 5.3 percent. In 1996 the prevalence of the areas belonging now to high risk and edge area was under 1%. Because of higher prevalence in certain areas they joined then high risk areas and edge areas. In areas within this categories now the prevalence and risk was raising constantly from 1996 until 2017. Any stricter regulations compared to low risk areas,  like testing in shorter intervals (12 M, 6M or Premovement-tests), did  not show an desirable effect.

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In the southwest as an example vor highrisk areas and the midlands as an example for highrisk and edge areas the prevalence did raise constantly from 1996 to 2017.

 

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This graph is also based on the history of the current three risk areas high, edge and low.

In this case however the number of farms have been  grouped by prevalence “<1%,” “1% to 5% “and “> 5% “ The  number of farms within the concerning group within a year  is calculated and put in relation to the whole number of farms within this year. In 1996 for example the prevalence of all farms (belonging to high, edge and low in 2017) was under 1%. In 1996 100% of the farms are within the group: “< 1%”.

This is changing the following year. On from 1997 to 2004 the percentage of farms in group <1% is about 60%. On from 2004 until 2017 the percentage of farms in group <1% is drops to 40%.  The figures show, that the problems of growing prevalence already start in 1997. From 1997 until 2004 the percentage of 1% to 5%  is 40%. 2005 the “>1% part” is splitting to 20% “ >1% to 5% and about 60 percent to “> 5%.” In 2017 the whole” > 1% fraction” is within the “>5%.”

Starting in the second half of the 90ies farms many farms are moving to categories of high risks areas and higher prevalence fraction. Bovine TB in England  is spreading since 1997 and not under control at all.

sources:

Excel-File the graphs are created with

TB in cattle in Great Britain – GB by country dataset

TB in cattle in Great Britain – headline statistical dataset

TB in cattle in Great Britain – South-West by county dataset

TB in cattle in Great Britain – Midlands by county dataset

 

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Status quo and history of Bovine TB in England, Wales, Scotland and Ireland

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Excel-File the graph is created with

In Scotland the prevalence of “Bovine TB” never went over 1%.  In Ireland it did decrease from 8,1% in 2000 to 3.3 percent in 2016. In Wales it did increase from under 1%  in 2000 to 5.5%, there was a peak at  7.2% in 2012. In England there is an increase of the prevalence from 1% in 2000 to 6.3% in 2017. No significant effect at all  of control of prevalence of “Bovine TB” in England can be seen since 1996.  Just  in Ireland a sustainable decrease over 18 years can be seen. The country did  decrease the prevalence of Bovine TB more than 50%.

 

Sources:

TB in cattle in Great Britain – GB by country dataset

IrelandEradicationProgrammeBovine170518.pdf