Bovine TB: 5 Cattle Pathogenesis and Diagnosis
5.0.1 The Group attaches a high priority to determining the relative importance of cattle-to-cattle transmission of TB. We consider that this issue has not been adequately addressed in the past and may be of far greater practical significance than has been appreciated. The assumption underlying the long-established controls for cattle TB is that cattle to cattle transmission is of critical importance: that is why movement restrictions are imposed immediately when reactors are found in a herd.
5.0.2 In the absence of any external source of infection, the slaughter of infected cattle identified by regular tuberculin testing, coupled with movement restrictions, could be expected to control the disease. This has happened in many countries, and in parts of Great Britain, but in other regions of this country the disease has persisted. This has been interpreted as evidence for the existence of a wildlife reservoir of infection in these regions. Irrespective of the source of infection the increased risk of infection places greater demands on the testing programme. There is therefore a need to consider whether or not control of the disease is constrained by limitations in current testing procedures. We need to know more about the dynamics of the disease in cattle and its temporal relationship to diagnosis, transmission routes, and the effectiveness of early diagnosis.
5.0.3 The analyses of existing information to identify risk factors will go some way towards identifying the role of cattle-to-cattle transmission but these analyses will be much strengthened by data from the TB99 epidemiological questionnaire and from the trial when these become available.
5.0.4 Some aspects of disease pathogenesis in cattle are being covered in the molecular epidemiology and vaccine programmes but further work is needed. The ISG has prepared a paper which reviews the current state of knowledge on pathogenesis and diagnosis of TB in cattle, and raises a number of questions which will determine future research funding priorities. This can be found at Appendix C. The ISG is holding scientific discussions with experts who can contribute to this work to discuss and design experimental protocols.
5.0.5 The Group welcomes MAFF’s support for this work and, in particular, the immediate provision of funding to initiate studies in this area. The research requirements were published in November 1999.
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12 August 2003
Page published: 5 February 2003