Wednesday, September 15, 2010

PCR - The HPA take an interest

UK scientists say they have developed a 'one hour test' for diagnosing TB.
"We’re confident that it will pick up very small amounts and tests so far have show that it seems to be as sensitive as the gold standard of using culture, but there are various aspects which we need to develop further before we can offer it as an off-the-shelf product.”
Details of the work are being presented at the HPA’s annual conference at the University of Warwick.

Story is here.


Anonymous said...

Unfortunately for the healthy badgers that will be killed if the English & Welsh Governments get their way this test is not yet a viable option

"there are various aspects which we need to develop further"

How long before a 'targeted cull of diseased badgers' is posible?

Matthew said...

Anon 5.39
We share your frustration.

"How long before a 'targeted cull of diseased badgers' is posible?"

It is possible now, using the pathology, histology and WLU tracking skills of cattle tests/grazing areas as markers. There is absolutely no need to interfere with any badger group whose foraging area has clean testing cattle. That was the kick start of any badger clearance in the past. The presence of disease, not tied into a cattle movement.

Defra have dragged their collective heels on PCR for years now. Mainly we suspect because when it brings them face to face with a positively ID'd infectious sett, they have the thorny question (for them) of what to do about it. (Other than test and kill more cattle of course}

They seem very good at that. And ignoring spill over into other mammals.

Anonymous said...


The WildlifeOnline web site says the following

"At the badger-to-badger level, M. bovis is probably transmitted as an aerosol (i.e. badgers breathe it in). However, the situation is less clear at the badger-to-cattle level. Currently, the primary route of transmission is considered to be through scent marks, especially urine. Indeed, studies have found that while badger faeces can contain up to 75,000 tuberculosis bacilli per cubic gram and badger pus up to 200,000 per millilitre, urine may contain up to 300,000 per ml. Considering the ranging behaviour of badgers, this implies that cows feeding on grass along the periphery of fields (where badgers are more prone to scent) are at a higher risk of picking up the disease than those grazing more centrally. Moreover, badgers take very precise routes, frequently re-marking the same areas and it is not unwarranted to think that a build up of the bacteria (which can survive on the ground or in faeces for days or months, depending on the conditions, while spores may survive for decades) could occur in these areas and may persist even after badgers have been removed. Consequently, several studies have tried to assess how different parts of a field system might present different levels of infection potential. Overall, it was found that urination was more prolific at crossing points (i.e. the points where badgers cross a linear feature like a fence or hedge) than other parts of a pasture. Pastures with lots of linear features were, therefore, found to have increased contamination with badger urine."

Perhaps some aspect of the badger behaviour described above offers a key to distinguishing healthy setts from unhealthy setts. I wonder if further study of badger behaviour and advancing techniques to streamline the collection and diagnosis of samples will lead to a practical and affective means of identifying unhealthy setts.

I think I may put in a request to DEFRA and other ministries to get a helicopter view of current work and a better appreciation of the current issues which is preventing widespread implementation.

Matthew said...

Anon 6.33
Many thanks for that top up on infectivety. To put that heavily loaded detritis which you describe, in persepctive, PQs confirmed that just 70 units of m.bovis bacteria are needed to promote slow infection in a cow.

It is our personal experience, and this is supported by our PQs, that it is the badgers which have been excluded by their groups which are the biggest problem. TB is endemic in the population, but it tends to wall up, and then break down. Thus within a group a few may be shedding at one time but not all. But as the disease inevitably progresses, these 'dispersers' which are in the last stages of TB, are hugely infectious but do not exhibit the normal ranges or behaviour of the group.

PQs tell us that they have larger ranges (roam further) and are likely to take up residence in or around farm buildings. They are often in single, shallow holes or even within the buildings themselves, or under them. These animals are not in a sett with latrines and scratch / marking posts etc.
Like rats, badgers are also incontinent, thus the urine trails across grassland are dribbled indiscriminately. They void up to 30ml at a time. All this info is on PQs archived in 2004 on this site, and resurrected throughout it..

If startled for example, (or surrounded by curious cattle?) they will spit and spray urine as a fight / flight reaction. A real WMD should TB be present at either end.

Any PQs to keep this question high up Defra's flagpole, would be welcome. And good luck!

Anonymous said...

Thank you for your reply.

This probably isn't a very bright question but what does PQ stand for?

Matthew said...

Anon 8.38.

PQ - Parliamentary Question.

This is where questions are submitted via an MP to the Secretary of State, and where the written answer is recorded in Hansard.
It is a hanging offence to mislead a minister, thus these are a very useful benchmark to see what is known about a subject.
About 500 are archived at the very beginning of this site.
Infectivety of cattle / badgers was one thing which we explored in detail. As was badger behaviour and TB transmission opportunities..