13 Dec 2013, 6:47 PM
An interesting article is reproduced below. It gives a very useful insight into the history of bovine TB; cattle and badgers. It is by Monica Ward of the South Yorkshire Badger Trust.
There is such a focus on badgers that the fact that bovine TB is a cattle based problem has been set on one side. History has shown us that the incidence of TB in cattle can be brought down to a very low level by cattle based measures alone. Add to this the vaccination of badgers in hot spot areas and even their implication can be dealt with.
Although the Royal Commission on Tuberculosis was established in 1907, I am going to begin in 1932 when the Cattle
Diseases Committee of the Economic Advisory Council was appointed to consider measures to reduce disease among milk
cattle, with particular reference to tuberculosis and improvement of milk supply. The committee accepted the widely held view (based mainly on findings in abattoirs and the results of exploratory test in 144 herds) that at least 40% of cows in dairy herds were infected with tuberculosis to some extent and that, on the evidence available, at least 40% of cows yielded tuberculosis milk. It was also stated that tuberculosis was responsible for over 2,500 deaths and for a still larger amount of illness annually among the human population.
While the overall incidence of infection in cows was accepted as 30%, it was realised that there was a great deal of variation among herds even within small areas, ranging from complete freedom to 100% infection. The distribution of cases of clinical disease coming within the scope of the Tuberculosis Order showed that the heaviest infection was in herds situated in or near industrial areas. Many of these herds consisted entirely of cows which spent their milking lives in the confinement of badly ventilated cow sheds.
The Cattle Diseases Committee concluded the total eradication of bovine tuberculosis was the only complete solution to the problem of tuberculosis milk but that the progressive formation of clean areas, based on compulsion at the outset, could not then be undertaken.
The Milk Act of 1934
As it was impractical to slaughter reactors as soon as they were identified it was decided to free as many herds as possible under a voluntary scheme over a period of four years so that, at a later date, when the overall incidence of infection had been reduced to manageable proportions, it would be possible to introduce radical measures to get rid of the remainder.
Attested Herds Schemes 1935
Under these schemes, herds which were free from tuberculosis, as judged by having passed three consecutive TB tests could be registered as attested herds. The farm had to be approved as suitable for the maintenance of an attested herd and the owner was required to give an undertaking to observe a number of rules designed to prevent, as far as possible, the chance of re-introduction of infection into the herd. A bonus of one penny per gallon was paid on milk from an attested herd sold through a Milk Marketing Board. The herd was tested at intervals and any reactors had to be isolated at once and removed from the premises within a stipulated time. Progress was slow and there were only 414 attested herds by 1936. In 1938 this was replaced by a single scheme where a bonus of £1 per animal per year for three years brought the incidence of Tb down to
The outbreak of war in 1939 undoubtedly hampered progress as attestation was restricted to herds which qualified for TT status (tuberculin tested), but on the other hand, it is possible that a shortage of foodstuffs during the war, many animals, unthrifty as a result of TB were disposed of and so reduced the overall weight of infection .
In 1944 the Attested Herd Scheme was fully re-opened, but as there was no corresponding bonus payable to non-dairy herds, it was inevitable that attestation should progress largely in areas in which dairy farming was the main agricultural activity.
At the end of 1947, about 14% of the total cattle population were in attested herds. During that year, the number of cattle slaughtered under the tuberculosis order fell to 6,543. The proportion of those animals infected with tuberculosis of the udder or giving tuberculosis milk, remained fairly constant during the 10 year period 1938-1947.
In 1950 it was decided to introduce an Area Eradication Plan. On a determined date, the area concerned would be declared an area eradication area, and all herds not subject to the rules of the Attested Herds Scheme would be placed under movement restrictions and TB tested, compulsorily if necessary, with immediate slaughter of reactors and payment compensation. When all such herds had been tested twice and reactors disposed of, the area would be declared an attested area. Each year in succession further areas would be selected until the whole country became one large attested area.
By the end of 1959, 95% of animals had come within the scope of the Tuberculosis Order and by 1960 the whole of Great Britain had become one attested area.
The plan went smoothly but TB had still not been totally eradicated, the reasons given at this time were:
1. Residual infection on farms. Many farms do not lend them selves readily to adequate disinfection, except at heavy expense, and the organism may survive long enough in a suitable environment to infect one or more members of a herd.
2. The failure of the test to disclose infected animals. The margin of error in this direction is extremely important and very difficult to determine. An animal with a slight non progressive infection and in which tuberculin reactivity has largely or completely disappeared is of great danger in a herd if, under conditions of stress, reactivation of the earlier infection takes place followed by generalisation. When this happens, a large number of reactors may be expected among animals in contact. Approximately 70% of reactors from attested herds examined post mortem during the past 7 years showed lesions of tuberculosis.
Reservoirs of infection in other species.
Progressive tuberculosis in goats and swine is usually due to a bovine strain of the organism, probably acquired from cattle. In goats the disease is very uncommon, but on one occasion a goat kept in a cowshed and which died from generalised tuberculosis appeared to have been responsible for infecting the herd of cattle. The disease is much more common in swine but as the incidence in cattle has declined there has been a corresponding decrease of incidence in swine.
The eradication of Bovine tuberculosis in Great Britain by W.D. Macrae, MRCVS, DVSM (Ministry of Agriculture, Fisheries and Food,) published in 1961.
Scotland is a designated TB free area with no badgers culled; just stringent measures to keep Scotland TB free, such as regular testing and not allowing any cattle into the country without prior testing.
1960-1970 After the completion of the Area Eradication Scheme cattle were tested annually and the number of cattle with TB dropped dramatically and remained more or less level until 1990 when the number of herds tested was relaxed countrywide. At the same time milk was being pasteurised or sterilized, thus reducing the number of people catching TB from milk. Bovine TB is no longer a health risk in this Country with only about six people a year contracting the disease, and these are usually slaughter house workers who catch the disease from handling infected carcasses. TB is now also curable with the development of the drug streptomycin.
1971 - TB was first identified in a badger in Great Britain on a cattle farm undergoing a prolonged breakdown. (Annex A of the official consultation document Bovine TB, its epidemiology and history of its control in England, Defra, Sept 2010) Since then the focus has been on badgers instead of on the disease itself.
From 19751986 Badgers were gassed in their setts as part of a clear ring policy in the south west which remains a TB hotspot and where 27 years later they are still culling badgers. It is very important to note that the level of TB had dropped to under 1,000 before badgers were gassed.
Why was TB not completely wiped out at that time? As well as the same reasons given back in 1960 we could add badgers but more probably anergic cows. The latter are cattle that are so early in the stage of the disease that they test as non-reactors and so remain in the herd to cause breakdowns as the disease develops (for more detailed information about this see
http://www.badgersandtb.com Appendix 6).
1990 - Because TB was brought down to a low level, the number of herds tested countrywide was relaxed and the numbers of infected cattle started to rise.
1993 The BSE outbreak when testing for TB was interrupted causing the levels of TB to rise to 2,455 cases.
1998 Start of badger culling trials. TB toll 5,844.
2001- During the foot and Mouth Epidemic testing was once again interrupted because vets were too busy, but because there were no cattle movements the number of cases remained level.
However, restocking farms without prior testing brought the cases of TB up to 8,353. Cases of TB in Cumbria for the first time were linked directly to the areas in the south west where the re-introduced cattle had come from.
2006 Zero tolerance of backlogs and movement controls imposed
2008 More tests and better tests (Gamma Interferon) at shorter intervals discovered more disease in the short term.
2010 - TB toll 6,211 which is a 15% reduction, because more infected cattle had been identified and killed, there were tighter cattle controls and regular cattle testing , and
without any badgers being culled.
FOR 16 YEARS THERE HAD BEEN NO CATTLE MOVEMENT CONTROLS. This was between 1990 and 2006 apart from during the
foot and mouth epidemic. We accept that a minority of badgers develop bovine TB and because of this a BCG vaccine has been developed which is now being used in hotspot areas. This is an injectable vaccine, administered by trained badger group members by cage trapping badgers. It is hoped that an oral vaccine will soon be ready for field trials.
A cattle vaccine, which is the obvious answer, is already being trialled in Wales. It would not only target cattle but would be so much easier to administer than to a wild animal. The problem that a vaccinated animal cannot be differentiated from an infected one could be overcome by the use of DIVA (Differentiate Infected and Vaccinated Animals.) Evidence to support international validation of the DIVA test has been submitted to the World Organisation for Animal Health but as yet it has not been fully accepted. Is there a problem with the EU?
Could not cattle bred for the British market be vaccinated?