ANIMAL HEALTH Its Immediate Problems

Press, Volume XCVII, Issue 28701, 26 September 1958, Page 5 (Supplement)

ANIMAL HEALTH Its Immediate Problems

By

J. W. McLEAN

Our contributor, Professor J. W. McLean. B.V Sc.(Sydney), M.Agr. Sc., Ph.D. (Calif.), is associate professor and head of the department of veterinary science at Canterbury Agricultural College, Lincoln.

Apart perhaps from immediate problems of marketing, in no other sphere than m certain aspects of animal health is farming nearer the crossroads. '

Such major animal health problems face the sheep farmer at the present time that literally he does not know which way to turn.

Often at great cost to himself in effort, worry and spending, the progressive farmer has increased carrying capacity by the application of artificial fertilisers and the sowing down of more highly productive' strains of pasture species, only to find that his anticipated return of more meat and wool is whittled away in increasing stock losses. He has grown more feed, but for various reasons the stock cannot utilise it.

True, fortunately, this experience is not universal; but it is sufficiently widespread to be of national importance. Nor is this all: the potential danger is even greater, for much of the evidence available indicates that such problems are likely to become increasingly serious in the future with each successive rftep in the farm improvement p-ogramme and the extension of these methods to other farms. <

These problems must be solved, lest the farmer lose confidence in the future and take a side road that would lead to a slowing up of his effort to produce more on every acre of land, a process on which, in the long term, the future prosperity of the country must still depend. < In this category of diseases seemingly associated with “improved” farming fall, such things as the ill-thrift complex, white muscle disease, trace-element deficiencies of one kind or another, facial eczema and other photosensitivity diseases, and bloat. 11l Thrift Of these, undoubtedly lamb and hogget “ill-thrift” is the most important, for it occurs generally throughout both islands. The environmental conditions "that lead to its appearance in some districts of the North Island are fairly clearly defined so that reasonably effective methods of control can be devised. In the South Island, however, much more work is necessary to determine its essential nature and cause, and to differentiate it from known trace-element deficiencies and parasitic infestation. White Muscle , White muscle disease, a condition almost wholly restricted to the South Island, is certainly on the increase. Recent evidence indicates that, while the disease in hoggets and ewes is probably caused by a deficiency of vitamin E in the diet, the condition in young lambs cannot be explained in this simple fashion. This form appears to be associated with the feeding of high legume diets to the ewe during pregnancy, and possibly also to the lamb; that is, with lucerne hay feeding and grazing, and the grazing of clover dominant pastures which are such a common feature of improved light lands. The possibility exists that, Under certain special circumstances, the legume constituents produce a “toxic” substance which either, destroys vitamin E or operates in some other way to produce the disease. Whether or not such “toxic” substances are produced only when there is a

deficiency of certain trace elements is being investigated at the present time. Facial Eczema With regard to facial eczema, notable progress has been made by the recent discovery that the primary cause of the disease is a toxin produced, not by the pasture itself as was previously believed, but by a common fungus growing on dead pasture foliage under certain special climatic conditions. This finding in itself does not solve the problem of control, but it does suggest lines along which further research should be directed to achieve this end. r Bloat Bloat is another problem that is being intensively investigated at the present time, and while much progress has been made towards a better understanding of its nature and cause, effective control measures that can be easily applied are not yet available to the dairy farmer. These are but four, probably the most important four, of the health problems facing the animal industry at the present time; there are many others. There is no more important work than scientific research directed towards their solution. Effective Control Passing now to a second category of diseases, for which reasonably effective control measures are known, the picture is a little brighter. The problem here lies in the effective application of the control measures under New Zealand conditions. This group includes diseases such as tuberculosis, brucellosis, hydatid disease, and lice and ked infestation. Concerning tuberculosis, marked progress has been made by the compulsory testing of all cows in city milk supply areas. Recent legislation extending control, on a voluntary basis, to factory supply herds is a significant step forward towards eradication. Entry into this scheme is a voluntary arrangement between the farmer and his veterinarian, but once the farmer joins the scheme he accepts responsibility for seeing it through. Provision .is made for compensation to be paid for condemned stock, and in herds where the incidence of disease is high, the farmer is given time to make suitable arrangements for replacing condemned stock. It is to be hoped that the scheme will go forward smoothly and steadily to the ultimate goal of eradication of this disease, which is important not only to the economics of the animal industry but also in public health.

Bovine brucellosis occupies a similar position. Control by vaccination of young dairy stock is now fairly widely adopted on a voluntary basis, but it is clear that further steps will ultimately have to be taken if the disease is to be brought under control within a reasonably short time.

Commendable enthusiasm has been shown in the last few years in renewed efforts to eradicate hydatid disease and other tapeworm parasites of dogs. Voluntary control schemes now cover most of the South Island and large parts of the North Island. Recent research by the Hydatids Research Unit of the Medical Research Council indicates that the control measures advocated can be expected to bring about a significant reduction in incidence, and that a co-ordinated and concerted effort along these lines can ultimately lead to eradication.

The position regarding lice and. tick infestation in sheep is not so promising. Undoubtedly both these parasites could be eradicated if the incentive were great enough and an organised attack made, lor the means for doing it exist. ’.Phe stage has been reached when these diseases can no longer be afforded by our animal industry. Exotic Diseases In the third category fall a number of diseases which fortunately do not occur in New Zealand. For example, foot-and-mouth and other vesicula diseases, swine fever, rindepest, bovine pleuropneumonia, rabies, fowl pest, blue tongue, and many others. At all costs these must be kept out, but if by some mischance any one of them does get in, then the organisation must exist to handle them expeditiously so that they can be stamped out. With modern methods of transport the risks of introducing these exotic diseases are immeasurably greater than they were in the past. The Animal Industry Division of -the Department of- Agriculture and the veterinary profession in the field are fully conscious of the enormous responsibility they carry in this respect. This responsibility should be shared by everyone, particularly those associated with the farming industry. The Future

Viewing the future in relation to the expanding animal population, it is clear that greater numbers of veterinarians are required; first, in the field to provide efficient service to the industry, not only in practice, itself, but also in instruction in methods of disease control; second, in State departments to administer the regulations concerning schedule diseases, and the thorough inspection of our primary produce from the point of view of quality and freedom from disease; third, in research organisations to find better methods of control of some of the important diseases already mentioned; fourth, in public health activities to assist the medical profession with diseases transmitted from animals to man; and fifth, in additional diagnostic stations to provide the rapid and accurate diagnosis that is so vital to the control of certain diseases whether indigenous or exotic. In summary therefore our efforts in the future should be directed towards three main objectives. Vigorous research to find methods of prevention for those diseases that cannot yet be successfully controlled. More effective control of diseases that are preventable by methods already known. Maintaining the optimum vigilance to protect New Zealand against the introduction and spread of serious epidemic diseases from abroad.