Committee Reports > List of Committees > Dáil > 1986 > Committee on Public Expenditure > Report - Review of Public Expenditure for the Eradication of Bovine Tuberculosis

APPENDIX IX

Submission to the Committee on Public Expenditure on the Bovine Tuberculosis Eradication Scheme on behalf of the Faculty ofVeterinary Medicine, University College, Dublin.

Introduction

The Faculty of Veterinary Medicine by virtue of its role in veterinary education and research is keenly interested in diseases endemic in this country and is particularly interested in disease eradication programmes pertaining to the National Herd. Members of this faculty contribute to research in infectious diseases in general and tuberculosis in particular. Their role is intended to be constructive in the formulation of policies pertaining to disease eradication.

Responding to the Committee on Public Expenditure’s request, as relayed by Mr. John McCarrick, the Faculty selected three members, Professor J. D. Collins, Dr. K. Dodd and Professor P. J. Quinn to present a report on the Bovine Tuberculosis Eradication Scheme *.

* Members of the Study Group:

Dr. K. Dodd, M. V.B., Ph.D., M.R.C.V.S.,

Lecturer in Veterinary Epidemiology.

Professor J. D. Collins, M.V.M., M.S., Ph.D., M.R.C.V.S..

Associate Professor of Veterinary Preventive Medicine.

Professor P. J. Quinn, M.V.B., Ph.D., M.R.C.V.S.,

Professor of Veterinary Microbiology and Parasitology,

(Chairman of the Study Group).

Appraisal of the Current Bovine Tuberculosis Eradication Programme

Animal disease eradication programmes are the responsibility of the Department of Agriculture. The Faculty of Veterinary Medicine is a resource facility which can assist with decision making and become involved at a consultative level in the evaluation of the progress of disease eradication programmes. A realistic expectation of any such programme is that there be a progressive decrease in the prevalence of the disease. To assess progress, therefore, the prevalence of the disease in the National Herd at a particular time has to be compared with its prevelence over a comparable period after a realistic interval, i.e. the number of herds with infected animals would be expected to decline as eradication proceeded. The essential criteria for evaluating success in an eradication programme are:-

(i)a significant and sustained decrease in the prevalence of the disease being eradicated;

(ii)the maintenance of the disease-free status of those herds established on scientific grounds to be clear of the disease.

As the cost to the Exchequer for the implementation of such a programme must be considered, realistic targets must be set at each stage to justify the considerable expenditure required. Targets, therefore, should be determined by the prevailing prevalence of disease and should be aimed at:-

1.Reducing the prevalence of infection in the National Herd

2.Keeping clean herds free of disease.

Identification of Infected Animals

We need to have full confidence in the methods used to determine when a herd formerly known to be infected can be declared a clean herd. Current methods used for identifying cattle infected with tuberculosis are based on the application of tuberculins in skin-testing procedures. The test procedure is applied at five different levels:-

-the herd test as used for monitoring purposes

-premovement test

-reactor retest

-special check test

-test for intra-community trading purposes (bovine tuberculin alone is the basis of this latter test).

Interpretation of these test procedures varies to take into account (a) the known disease status of the herd and (b) the destination of the animal. It follows, therefore, that the interpretation results are influenced by the purpose for which the test was carried out. There is an urgent need to standardize the interpretation of the tuberculin test irrespective of the reason for carrying out the test. Only by this means can the extent of the disease be reliably determined. Meanwhile, the complications arising from sensitization with other mycobacteria will require elucidation through research. The reliability of test results may be affected by variation in testing procedures depending on the personnel involved and the conditions under which the test is performed. It should be understood that in its various forms, the tuberculin test, in common with other biological tests is subject to biological variation. Published data indicate the reliability of the tuberculin test to be in the region of 80 - 85 per cent

Spread of Disease

In the present eradication scheme, there should be greater emphasis on local investigation on each farm where breakdowns have occurred. The collation of this information should be undertaken by the recently established Epidemiological Unit suitably funded and staffed in consultation with field staff. Such an investigation should take into account:-

1.the modes of entry of the organism into the herd or onto the farm.

2.the spread within the herd.

3.the persistance of the agent within the environment.

4.the steps taken to clear the agent from the environment.

Each can be considered under the following headings:

1.Modes of entry of the organism into the herd or on to the farm

(a)purchase of infected animal - each purchased animal should have passed a pre-movement test;

(b)contact with contiguous herds which is further facilitated by fragmentation of holdings and inadequate fencing;

(c)wildlife;

(d)water;

(e)slurry spreading on pasture;

(f)human contacts.

2.Spread within the herd

(a)the only monitor of this is the frequency of checking of the herd for disease (the tuberculin test and post-mortem inspection at time of slaughter at export plants are the only two methods currently in use);

(b)management of the herd and housing may be contributory to spread of disease within a herd;

(c)slurry utilization

(d)inability to segregate reactors and suspect animals.

3.Persistence of infection

(a)persistence of infection within the animal can occur where infected animals are not detected by the tuberculin test, i.e. anergic or unresponsive animals. This state arises due to the nature of the infection, the type and age of an animal, previous history of the herd, frequency of tuberculin tests and other factors;

(b)persistence can occur in the environment - soil, water, slurry, in buildings and fittings;

(c)wildlife;

(d)people.

4.Removal of infected animals

Segregation of infected or suspect animals immediately they are identified is necessary followed by their removal under permit directly for slaughter.

Disinfection

The agent may persist for long periods in the absence of an effective cleaning and disinfection programme.

Additional Considerations

Particular care should apply to all animals from known infected herds. For the duration of restriction, all animals deriving from an infected herd should be consigned to a meat plant designated by the Department of Agriculture, to ensure thorough monitoring of each at meat inspection including laboratory examination as necessary. Undue reliance is frequently placed on the tuberculin test for the identification of tuberculosis in cattle without the necessary local investigation to ensure that all sources of infection are uncovered. In some instances infected herds may appear to clear up following the implementation of current control procedures, but breakdown is a common experience. This demonstrates the weakness of an almost total dependence on one test procedure for the success of an eradication programme, as operated prior to 1985.

Present limitations to the success of the bovine tuberculosis eradication programme

1.There is a need for the implementation of an overall national plan.

2.There is a lack of field staff to implement testing and detailed investigation of herd breakdowns.

3.The resources at the laboratory and research levels are seriously inadequate.

There is a defined need for a greater awareness on the part of the agricultural community of the factors contributing to the spread of tuberculosis in cattle.

Conclusion

The first phase of the Three Year Plan initiated in 1985 has identified with some success the extent of the problems of tuberculosis in the National Herd. Any diminution in the deployment of resources at this time can only lead to a deterioration of the tuberculosis status in the National Herd as infected herds which would otherwise be identified will be missed. Therefore, we support fully the completion of the programme outlined in the National Plan for the eradication of tuberculosis in cattle. Furthermore we consider that there are defined and urgent needs for:-

-more staff to be deployed for field work;

-resources to be devoted to defining and improving our testing procedure.

In addition, there is an urgent need to develop ancillary diagnostic tests to complement the present tuberculin test.

May 26, 1986.