tag:blogger.com,1999:blog-6885842.post4260643479077554982..comments2023-07-15T10:28:46.810+01:00Comments on Bovine TB: His master's voice - GammaIFNRichardhttp://www.blogger.com/profile/02561483930556493363noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-6885842.post-60894476254892910422008-05-12T07:40:00.000+01:002008-05-12T07:40:00.000+01:00The skin test is repeated every 60 days and it is ...The skin test is repeated every 60 days and it is very likely that the reactors identified slightly earlier by the gamma interferon test would be found at subsequent skin tests. As I said, if a significant number of infected cattle were missed by the skin test then the successful eradication of TB in cattle could never have been carried out anywhere using the skin test. <BR/>The blood test certainly identifies more reactors, but a high proportion of these are never confirmed as having TB and they probably haven’t got it. Of those identified that are infected, most have early disease and are not spreading it, so shooting them earlier does not achieve anything.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6885842.post-1505132004859739562008-04-28T18:07:00.000+01:002008-04-28T18:07:00.000+01:00Well George it all depends what yiou consider sign...Well George it all depends what yiou consider significant doesn't it?<BR/><BR/>You suggest that "There is no evidence that significant numbers of infected cattle are missed by the skin test".<BR/><BR/><BR/>Ever heard of gamma interferon George?<BR/><BR/>The results of the trial of this published on 10 August 2006, showed that in problem TB herds about 12% of animals passing the skin test are testing positive to the blood test and of the blood test positives about 18% are shown to be grossly infected or culture positive in almost half of the herds blood tested.<BR/><BR/>Combined use of skin testing and blood testing resulted in more infected animals being detected than using skin testing alone.<BR/><BR/>http://tinyurl.com/4doqxdAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6885842.post-25038498887376462482008-04-27T07:54:00.000+01:002008-04-27T07:54:00.000+01:00Even if a herd is infected that doesn’t mean all t...Even if a herd is infected that doesn’t mean all the cattle are infected. In fact, the commonest number of reactors is one. Removing that one animal will often solve the local problem - after a 60 day test or two with no further infection the herd can be released from restrictions. So shooting the rest of the herd will achieve nothing. If there are further reactors to be found, the skin test is good at finding them at the subsequent tests – if it wasn’t then the successful eradication of TB in cattle from a number of countries could never have been carried out. There is no evidence that significant numbers of infected cattle are missed by the skin test. Continuing cattle problems happen where TB is found in wild species too. Here the disease has to be tackled in all the major species involved in order to make progress or a lot of money will be wasted. Killing more cattle will achieve nothing, as the disease will constantly trickle back into the cattle from an increasing reservoir in the wildlife.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6885842.post-66297957094614431562008-04-24T18:12:00.000+01:002008-04-24T18:12:00.000+01:00Anon 10.12Yes the herd test is recognised as the p...Anon 10.12<BR/><BR/>Yes the herd test is recognised as the primary diagnostic tool worldwide.<BR/><BR/>* "A herd test - it identifies infected herds."<BR/><BR/>No. It identifies individual cattle within a herd - and the more cattle tested the better - which have had exposure to m.bovis bacteria, in enough quantity (just 70 cfu [colony forming units]) to provoke an immune response in that animal.(see last point)<BR/><BR/>* "The safest route would be to 'remove' infected herds."<BR/><BR/>Not necessary and not effective if the problem is not in the cattle.<BR/><BR/>Herd clearances have been done in the past, (some by default)and restocks several months later have experienced Tb breakdowns. Two farmers known to us personally, had cattle taken with clinical FMD. Farms were disinfected within an inch of their lives, and left fallow for months. In each case the restock was a complete herd, from non Tb areas, and preMT before entry.<BR/><BR/> One had a breakdown within 6 months and the other lasted just a year. The spoligotype identified in the reactor cattle was indigenous to the farm of breakdown, not the area of origin of the cattle, which in each case was several hundred miles away.<BR/><BR/>Another farmer, after several years of restriction, got clear and the farm was sold. After a period of time, the buildings were demolished and a complete new dairy set up built. Within a couple of years the new owner - and his herd were in trouble.<BR/> <BR/><BR/>* "... anything that finds infected animals that the skin test misses should help."<BR/><BR/>That assumes that the skin test used as a whole herd test is missing anything, and that gammaIFN is specific to m.bovis. Neither assumption is backed by fact.<BR/><BR/>* "We're talking about bacteria here - not something that can be seen. Just 'cos there's no VL's doesn't mean no infection."<BR/><BR/>Agree, which is why all post mortem samples are cultured. Open lesions are necessary to facilitate onwards transmission of bacteria and that has proved to be difficult in laboratory trials of confined cattle, and leads everyone except the ISG to the conclusion that in field situations, and with regular testing, cattle to cattle transmission is over stated. <BR/><BR/>We are aware of the argument re 'infectious badgers' i.e those with open lesions, transmitting bacteria and 'infected'- those whose immune system has walled off the lesion ... for a while. Shedding is thus intermittant. A reactor cow is shot. So, with regular testing, little opportunity to get to the 'open lesion' stage. <BR/><BR/>So much cfu bacteria are present in badger samples - 300,000 cfu in 1ml of urine - that a microscope is sometimes not needed, we're told. In fact "jumping off the slide" was the expression used. And just 70 cfu needed to provoke the immune respose to the skin test in a cow.Matthewhttps://www.blogger.com/profile/09293505337441558637noreply@blogger.comtag:blogger.com,1999:blog-6885842.post-81376804582573069652008-04-23T10:12:00.000+01:002008-04-23T10:12:00.000+01:00We all know that the skin test is effective as he...We all know that the skin test is effective as herd test.<BR/><BR/>A herd test - it identifies infected herds.<BR/><BR/>The safest route would be to 'remove' infected herds.<BR/><BR/>We don't do that, so anything that finds infected animals that the skin test misses should help.<BR/><BR/>We're talking about bacteria here - not something that can be seen. Just 'cos there's no VL's doesn't mean no infectionAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6885842.post-50881306732802270752008-04-23T08:04:00.000+01:002008-04-23T08:04:00.000+01:00Anon 12.36.Yes, it would appear from recent challe...Anon 12.36.<BR/><BR/>Yes, it would appear from recent challenges to test results that judges are inclined to decide on procedural failures, rather than tackle head on the fundamental right in common law of an individual to challenge results of statute, which may have the opportunity for error further down the line.<BR/><BR/>Matt<BR/>hmutdsMatthewhttps://www.blogger.com/profile/09293505337441558637noreply@blogger.comtag:blogger.com,1999:blog-6885842.post-7650195270505635352008-04-23T00:36:00.000+01:002008-04-23T00:36:00.000+01:00We have been told on two separate occasions by Def...We have been told on two separate occasions by Defra officials that the longer the interval between taking blood samples and those samples receiving laboratory treatment the greater the risk of a positive result. I understand that the maximum recommended interval is 12 hours ( 8 hours if you are in South Africa!) Here in Cornwall samples have to be taken back to Truro by mid-afternoon for delivery to Bristol the same day providing of course that there are no hold-ups on the motorway, car breakdowns etc. With the best will in the world and keeping to the speed limit they are not likely to arrive during office hours.I am not aware of Defra working overnight so the chances are the samples will not be seen to before the next day, well outside of guidelines. Even if samples are treated the same day the animals tested first would appear to have a greater chance of testing positive than those tested later in the day especially with a large herd taking several hours to complete a test.If I were faced with the huge discrepancy between the skin test and blood test outlined in the recent court case I would be inclined to challenge the actual blood testing procedures.They appear to be a complete lottery.Anonymousnoreply@blogger.com