asked the Minister for Agriculture and Food if he will outline the research which has been carried out by his Department into lateral spread of bovine tuberculosis; and the result of such research.
Written Answers. - Bovine Tuberculosis.
39.
Bovine tuberculosis is a classical contagious disease and epidemiological investigations in Ireland and elsewhere have confirmed that under field conditions direct animal to animal transmission is the normal means of spread of infection within and between cattle herds. Cattle with open pulmonary tuberculosis are the source of the infection which is spread to contact cattle by means of infectious aerosols.
Recent limited trials carried out at the Veterinary Research Laboratory over short periods have shown that a number of tuberculosis free cattle maintained in contact with reactor animals under good husbandry conditions did not contact disease. Full details of these trials will be published in due course. The results are not seen, however, as conflicting in any way with existing knowledge on the transmission of disease. It is well established that infection is more likely to be transmitted when the immune defences of the exposed animal are overcome or weakened. This can come about through exposure to overwhelming doses of infection, disadvantageous nutritional or environmental conditions, or the ageing process. The primary role of lateral spread in disease outbreaks remains unchallenged.
The precise factors that lead to the shedding of sufficient virulent tubercle bacilli to infect contact cattle is a complex area of research and one which must continue to receive close attention. As I indicated to the House on 21 April last, the research function is being given a special emphasis in the new arrangements for the bovine TB scheme and adequate funding is available for worthwhile projects.
I would be concerned — and my concern in this respect would be shared by the management board for disease eradication — that recent press reports relating to the research should lead to a general belief that the danger of tuberculosis spread has been over-stated and that we can relax our efforts. There will be no let-up in the campaign against bovine TB and the management board will be pressing ahead vigorously with a comprehensive eradication programme. My Department will continue to emphasise the importance of securing boundary fences, isolating reactor and suspect animals and removing reactors for slaugther without delay. Herd owners should be in no doubt but that failure to follow this advice greatly increases the risk of cattle contracting and spreading disease.