Wednesday, March 27, 2013

Repeat, repeat and repeat.

We have spoken of a 'beneficial crisis' created by the zoonosis known as 'bovine tuberculosis' many times. And yet again, this feeding trough has proved lucrative for members of academia. This time the RVC (Royal Veterinary College) with not a little help from FERA, fitted tracking collars to badgers and cattle, and then tabulated the contacts. There were not that many direct contacts, but before our Badgerist friends get too excited, the indirect contacts were tracked too. And there were loads.

The paper reports that indirect contacts were shown
"... to be far more frequent with 383 records of badger visits to latrines located on pasture grazed by cattle, and 1,716 visits by cattle to these sites. “This suggests that indirect contacts might be more important than direct contacts in terms of disease transmission at pasture,” a paper on the research, published in the Cambridge University Press, concluded.
The paper is discussed in this article in Farmers Guardian. But this site is built on the foundation of Owen Paterson's Parliamentary questions posed almost a decade ago. And this is just one which tells a similar tale of 'indirect contact' and its expected consequences.

 6 Jan 2004: Column 248W
Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs what assessment has been made of whether badgers infected by TB may excrete urine from which viable M. bovis bacilli may be isolated; what the typical quantities per millilitre are; and whether such levels are capable of causing infection in cattle through (a) contamination of feed and (b) other mechanisms. [144445]

Mr. Bradshaw: Some badgers develop TB infection in the kidneys 37 per cent. of infected badgers sampled post mortem between 1971 and 1978 m. bovis was isolated from the kidneys and may excrete M. bovis bacilli in urine. Urine is typically left in trails up to a metre or more in length and may be focused at a latrine or distributed more randomly as the badger forages. Concentrations of up to 300,000 bacilli per ml of badger urine have been reported and experimental nasal inoculation of cattle suggests that, at this concentration of viable microbes, less than 0.03 ml would need to be inhaled by cattle in order to promote slow infection.

 Investigations into infection of cattle from feed and other sources contaminated with infected badger urine are lacking. However, risk of infection to cattle by infected badger urine on cattle feed would be a function of the survival of the microbe in the feed (which is dependent on, for example, duration since excretion, moisture content of the environment, exposure to UV rays) the number of microbes consumed by the cattle and the method of consumption (i.e. ingestion or inhalation). I am unaware of measurements of M. bovis survival in cattle feed but the environment inside farm buildings is generally considered to be conducive to longer periods of survival than at pasture, where M. bovis in badger urine has survived for three days in summer and 28 days in winter.
Cattle appear less able to detect badger urine than faeces at pasture away from latrines. In addition, patches contaminated with urine detected by cattle appear to be sniffed more than those contaminated with faeces. Furthermore, some cattle do not select against latrines and freely graze over them. Therefore, potential sources of risk of cattle contact with infected badger urine include the ingestion of contaminated feed from feed stores or in troughs; investigation/grazing at and around latrines; and the investigation/grazing of contaminated pasture.
We are nothing if not persistent, so another slant at the same question,

 Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs pursuant to her answer of 8 December 2003, Official Report, column 212W, what inferences can be drawn from the preponderance of TB lesions found in badgers on post mortem examination arising in the lymphatic nodes of head and chest as to (a) the portal of infection, (b) the possible routes of infection and (c) the risk presented by those badgers to other animals. [150564]
Mr. Bradshaw: Infection with Mycobacterium bovis frequently causes lesions in the respiratory tract and the associated lymph nodes of badgers, which suggests that a common route of infection is by inhalation, or ingestion followed by inhalation. Where there is infection of the respiratory tract, it is probable that there are phases of M. bovis excretion of infected saliva via the respiratory tract, which may contaminate pasture or animal feed containers.
and another:

 29 Jan 2004: Column 482W
 Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs pursuant to her answer of 8 December 2003, Official Report, column 210W, what her estimate is of the typical proportion of badger faeces and urine deposited in latrines from a given social group; what proportion is distributed more generally over grassland; and what risk of M. bovis infection these deposits present to grazing cattle. [150550]  

Mr. Bradshaw: Work carried out by Bristol University suggests that the proportion of faeces and urine deposited at latrines vary with badger density. The proportion of latrines located in different habitats is the subject of current research at the Central Science Laboratory, the results of which will be published in due course.
The majority of cattle actively avoid eating grass contaminated with badger faeces but tend not to select against grass contaminated with badger urine. Since most faeces tend to be deposited in latrines, which are often large and obvious, while urinations tend to trail onto pasture, infected badger urine at pasture might pose a greater transmission risk than infected faeces. However, there is likely to be some risk of onward transmission wherever either infectious faeces or urine are present on land grazed by cattle.
New 'research'? The hell it is. The danger to cattle from the detritus left by badgers infected with tuberculosis has been known for decades and answered quite clearly in these PQs, which are 9 years old and archived under this tag.

It is high time that this lucrative gravy train reached its station and its many passengers disembarked for pastures new. Preferably pastures not contaminated with urine, pus, faeces or saliva from infected badgers, 38 per cent of which were found to be infected in this latest money spinner trial.

Scotland did a similar 'research' in 2009. We covered it in this posting. Their conclusion was slightly different though.

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