PREVENTION OF THE SPREAD OF STOCKDISEASES.

New Zealand Journal of Agriculture, Volume XXVII, Issue 4, 20 October 1923, Page 243

PREVENTION OF THE SPREAD OF STOCKDISEASES.

FUNCTIONING OF STATE VETERINARY SERVICES.

Presidential Address by Professor H. A. Woodruff, of Melbourne, to the Veterinary Section, at the Annual Meeting of the Australasian Association for the Advancement of Science, held at Wellington, N.Z., January, 1923.

In accepting the invitation to act as President of this Section owing to the very regrettable absence of my friend and colleague Dr. S. S. Cameron I was not unmindful of the duty devolving upon me of preparing an address for your consideration. The choice of a subject was by no means an easy one, but for a number of reasons the one selected was thought to be appropriate : Firstly, because the stock interest, both in New Zealand and in the States of the Commonwealth, is a very important interest, and in relation to world requirements of food and clothing is one of growing importance ; secondly, because of the absence of many of the most serious contagious diseases of animals in Australia, and even more in New Zealand (to use the words of an old writer, “ Let him that thinketh he standeth take heed lest he fall ”) ; thirdly, because of the necessity for the introduction of purebred stock from abroad for the maintenance and improvement of the excellence of our stock here ; and, fourthly, because we as a profession have the responsibility of advising the Governments of our respective States in this matter, and with every increase of our scientific knowledge of the incidence and causation of stock-diseases our advice will require to be modified and adjusted to fit the known facts.

There is little need to spend time in reminding the majority of my audience of the ravages made by some of the more virulent contagious diseases of animals in the older countries of the world, but it may be that some of my hearers are not familiar with the magnitude of the losses which have occurred, and which have compelled Governments in all civilized countries to institute and organize a veterinary sanitary service.

“ In Great Britain up to the time of the invasion of the cattleplague in 1865 it may justly be said that veterinary sanitary science, except in the Army, had no existence so far as the prevention of contagious disease is concerned. In 1865 cattle-plague was -introduced.into England on 24th June. In October it was calculated that 17,000 cattle had been affected. In November only four counties in England were exempt, and the malady was present in nineteen out of the thirty-three Scotch counties. Further, during 1865 and 1866 some 279,000 cattle were reported sick, and 233,000 died or were killed.”* But in addition to cattle-plague other stock-diseases were taking toll of the national wealth. “ Up to 1869, for thirty years since the introduction of the two contagious maladies, foot-and-mouth disease and bovine pleuropneumonia, it was estimated that the loss from these alone amounted to five and a half million cattle, roughly valued at eighty millions sterling.”*

.Even in recent days just prior to the war and with an organized veterinary staff the losses due to foot-and-mouth disease alone in European countries were immense. “ In August, 1911, 37,000 outbreaks of foot-and-mouth disease were recorded in Germany; in July of the same year 12,000 were recorded in Belgium, and 4,000 in Holland ; in. France there were 16,000, and there it was estimated that the loss would amount to over fifteen millions sterling.” (Sir Stewart Stockman.)

, In those earlier days before the advent of a State veterinary sanitary service it is not surprising that contagious diseases of animals should have spread from country to country, and one has only to read the theories of the etiology of what we now know to be specific contagious diseases to understand how entirely uncontrolled and, indeed, uncontrollable they appeared to be. So long as spontaneous generation ” was believed to be possible, and when mysterious miasmatic and telluric influences were thought to be all-sufficient factors in the causation of disease, preventive measures were clearly impossible.

Now, this inability to control the spread of disease coincided in point of time with. a very natural desire on the part of colonists in different parts of the Empire to import high-class pedigree stock from Great Britain in order to establish purebred studs and to improve stock generally. Thus the chances of introducing into Australia and New Zealand the prevailing animal-diseases from Europe were considerable, and it is probably owing mainly to the length of the sea voyage that comparatively few of the animal scourges found their-way in. On this point it has to be remembered that races of animals which have for many generations been free from any particular contagion are, generally speaking, in a highly susceptible condition should the chances of infection ever occur. This, indeed, makes it the more surprising that in the case of some of the actively contagious diseases which have been introduced into Australasia they have not spread far from the primary infected place.

The wonder is not that bovine pleuro-pneumonia was introduced into Australia in 1858 and spread over the majority of the States (Fleming, vol. 1, p. 407), but that, having been introduced into New Zealand in 1864, it did not become widespread. Equally remarkable is the fact that sheep-scab, having been introduced and spread to several of the Australian States, should have been eradicated. Again, it is surprising to learn that foot-and-mouth disease—that most contagious and most elusive disease of stockshould have been introduced into Victoria in 1872, and yet that the outbreak was confined to the initial herd, and following destruction of the entire herd, on the advice of the late Graham Mitchell, M.R.C.V.S., that it spread no further.

In the case of those diseases with long incubation periods, such as glanders in horses and rabies in dogs, . it is extremely difficult to understand the immunity of Australia and New Zealand. Glanders was, indeed, introduced, into Sydney, in a troupe of circus-horses which had been brought over from America. On inspection at the port the existence of glanders was recognized by the late Edward Stanley, F.R.C.V.S., the affected horses were at once destroyed, and the rest of the animals quarantined on an island. But what a stroke of fortune

that the disease should have been in a clinically recognizable form in these ' pre-mallein-test days! For the detection of these enemy aliens and their prompt suppression great credit is due to the early veterinarians. Even the first outbreak of contagious bovine pleuro-pneumonia in Australia was diagnosed by the late Henry Wragge, M.R.V.C.S., while still confined to one herd, and slaughter of the entire herd was advised. Action was, however, delayed pending inquiry by a Royal Commission, and the delay proved fatal indeed.

One factor of importance in limiting the spread of contagion in Australia a generation ago was. probably the . sparseness of. the cattle population and the comparatively few sales and transfers of stock as compared with conditions in Europe.

There are, unfortunately, other diseases, insidious, unknown, unsuspected at the time, which have succeeded in getting in, piroplasmosis or tick-fever being a notable example. In this case there is no authentic information as to how and when the cattle-tick [Margaropus australis was introduced into Australia, but according to the evidence collected by Gilruth it appears probable that Asiatic Brahma cattle imported from Batavia in 1872 were responsible, although the first serious mortality to be recorded was not till 1880, in a mob of cattle introduced from Queensland into the Northern Territory.

■ But now consider some more recent outbreaks of. contagious disease in countries where the diseases although for the time being foreign —quite well known, and therefore more or less thoroughly guarded against. The return of army horses to the United Kingdom after the South African War coincided with an increase in the number of outbreaks and number of animals attacked with glanders, and this marked increase continued from 1901 to 1907. But, besides the dispersal of ex-army horses, another factor operated, and was probably of greater importancenamely, the failure of the authorities to deal with “ incontacts ” after discovering a clinical case, and the private use by the owner of the mallein test, followed by the sale and dispersal of apparently healthy reactors. Therein is a lesson which is capable of application in connection with other diseases.

A further disease of horses, epizootic lymphangitis, was introduced at the same time from South Africa, and it is highly creditable to the veterinary profession that within a year or two it had been completely eradicated and is now unknown in Great. Britain.' Still another example of unconscious introduction of disease into a country is furnished by New Zealand, in the case of anthrax conveyed in bone manure from India and elsewhere. The success of the practice of bone-sterilization and the freedom of the Dominion from anthrax in recent years are greatly to the credit of the veterinary staff of the Department of Agriculture and to our old friend Dr. J. A. Gilruth.

Foot-and-mouth disease has furnished many examples of unconscious introduction despite all kinds of precautions, among them an outbreak in Edinburgh some years ago, which was eventually put down to infection by means of hay or straw either intended for fodder or used for packing eggs from Holland. This latter possibility is one which is not easy to guard against, but must remain under suspicion, to be investigated whenever unexplained outbreaks occur.’

Even more insidious was the introduction of foot-and-mouth disease virus in vaccine (“ Vaccinia ■’) lymph imported commercially into the United States from Japan in 1902 and 1903. The long period during which the vaccine remained infective, and the very mild type of foot-and-mouth disease set up, increased, the difficulty of proof, and remain serious factors to be reckoned with in the importation of biological sera and vaccines from abroad.. Many more recent outbreaks of this disease in Great Britain,are of unexplained origin, but with the great prevalence of the disease in neighbouring countries this is not so difficult of understanding, and we in Australasia can reckon on a much greater immunity because of our much greater distance from infected places.

Another disease of some concern .to us must be mentioned-namely, dourine of horses. With its pristine home in Asia, this disease has also been prevalent for a long time in North Africa, and was apparently introduced into Europe by means of Arab stallions in the early years of the nineteenth century. The disease was first suspected in the United States in 1885, and recognized by W. L. Williams in 1886. The introduction was traced to a Percheron stallion ‘ imported from France in 1882. From Illinois State the disease spread to Nebraska, and for over twenty years various outbreaks —more or less serious were traceable to this primary importation. Canada became affected in 1904, but by strenuous measures had the disease well under control by 1909, and eventually successfully stamped it out. A fresh outbreak was discovered in the United States in 1911, in Iowa, and this in turn was traced to the importation of a Percheron stallion from France in 1909. France is being continually reinfected by the movement of stallion asses to and from Spain, where the disease is commonly prevalent. ...

The recent introduction of rabies into Great' Britain after a period of freedom lasting .many years is not difficult of explanation. The extraordinary traffic to and from the Continent during the war/and especially the home-coming of many thousands of soldiers anxious in many cases to retain canine pets and mascots,, readily account for the introduction of so wily an invader as rabies. Australia and New Zealand ran considerable risk of suffering the same invasion, but the strictness of the authorities and the general good sense of officers and men returning home were successful in preventing, what would have been a very serious occurrence. The veterinary authorities in Great Britain are tobe congratulated on the success of the energetic policy of control and eradication, and once again Great Britain can be declared free from this disease. . .

The last outbreak of contagious disease to be mentioned in this group of surprise importations, and in many ways the most dramatic, is that of cattle-plague in Belgium, in August, 1920. This disease had been unknown in Western Europe since 1870. It had been the cause of the initiation of veterinary sanitary services in most European countries, and all chances of its reintroduction were thought to be well guarded against. The facts are that a cargo of zebras from British India and consigned to Rio de Janeiro touched at Antwerp, where the animals were disembarked at the quarantine station pending reshipment on another boat. Some of these animals died in the quarantine station, but no ■post-mortem examinations were made, and

cattle-plague was not suspected. The survivors were transhipped and proceeded on their voyage. Then other shiploads of cattle imported for food purposes came into Antwerp, passed through the quarantine station, and were distributed to various abattoirs. In the Ghent abattoir the disease broke out— its real nature was still unsuspected -and then by one unfortunate happening the general spread of infection began. A consignment of German cattle sent over for reparation purposes came into the Ghent abattoir, and were then dispersed to various country districts. So the disease spread, and its real nature was discovered. . The lessons to be learned are sufficiently obvious.

In addition to these more serious contagious diseases there are a number of parasitic diseases which require consideration at the hands of the State veterinary authorities. Notable examples are the conditions due to the ox-warble (Oestrus bovis), the sheep ■ nasal bot (Oestrus ovis), and the worm nodule of cattle (Onchocerca).- The failure of the ox-warble to become acclimatized in Australia, despite its inevitable importation in the early days and its escape from quarantine on several occasions during recent years, is not readily explained. Symons, in a paper read before the Australian Veterinary Association in Sydney last year, brings forward evidence to show that in no country in the Southern Hemisphere is the ox-warble established. On the other hand, the nearly related nasal bot-fly of sheep has got a firm hold in Australia, and is proving a source of considerable loss, in lowering the condition of sheep, although it rarely causes any mortality. What are the factors which account for the different behaviour of these two parasites in a new country I am quite unable to say. In the case of Onchocerca it may be said that the species common in northern Australia, ’ or nearly related species, are found in many other parts of the world. There is, however, no evidence to show that the infection is spreading southward in Australia, and in Victorian . cattle, at any rate, cases are practically unknown. There, again, the lifehistory and the vital factors are as yet unknown. J

But now the question arises, Are we, through ignorance or inertia, or both, allowing the introduction of various fresh contagious diseases of animals into our erstwhile clean country ? Are we perpetrating similar disastrous errors to those committed by our forefathers ? I think that with regard to at least two diseases of cattle we shall have to plead —namely, contagious abortion of cattle and Johne’s disease or pseudo-tubercular enteritis. With respect to the former, the mischief has already been done. We erred through ignorance in the days before definite diagnosis was readily possible. With regard to the latter, we are probably now sowing the seed—largely for want of serious concern—of a harvest -whose magnitude it is impossible to assess.

About bovine tuberculosis I have said nothing, since the distribution is already practically world-wide, and also because tuberculin testing of imported cattle is practically universal. Some regulation of inter-State traffic will be called for in Australia if and when a forward movement commences in any State for the eradication of the disease. In this connection the procedure under the accredited herd system and the standardization of the tuberculin test in the United States deserve careful study.

A POSITIVE POLICY.

And now, having surveyed very cursorily the field of possible importations, may I be allowed to put forward the . positive policy which it is the main object of this address to commend to you. It may be stated in a number of propositions as follows : (i) The chances of the importation of infection are numerous, and every known chance has to be guarded against ; (2) the interests involved are economically very important; but (3) the necessity for pedigree - stock exchange between the various States and countries is also extremely important ; and. (4) the modern scientific methods for the detection of diseaseinfection are incomparably greater than those of a generation ago, and they are being improved and added to daily; (5) thus it behoves the veterinary profession in general, and Government veterinary advisers in particular, to revise continually their methods and regulations, their prohibitions and exemptions, so as to allow the maximum facilities for trade and for importation and exportation of stock, while at the same time affording all the protection which science can devise. This protection will not only apply to well-known recognized dangers, but will look forward to possibilities of danger from sources hitherto unsuspected. .

Veterinarians in Great Britain have often been taunted that their most important instrument for the control of contagious disease was the pole-axe. The further taunt has been applied to Government .veterinary officers that their only policy to exclude contagious .disease was rigid exclusion of all animals from abroad. I venture to put forward the view that our increased scientific knowledge should be used wherever scientifically possible .in relieving this drastic and rigid policy. In order to be in a position to approve this view, let us briefly survey the various methods available for the exclusion, of infection from a foreign source.

(1.) The first method is the most obvious and direct—namely, the prohibition of importation of live animals from any country where contagious disease of animals exists. Rigidly interpreted and administered, this method provides a very real protection against the introduction of infection, but it is a serious restrainst upon trade in general and upon the introduction of pedigree stock in particular. It relieves the . Government veterinary advisers of a great deal of responsibility, and it affords absolute protection in the fiscal sense for certain vested interests within the country. ■

An excellent . example is afforded by the embargo on the importation of Canadian store cattle into the United Kingdom, an embargo which has just been removed. The avowed reason for the embargo was the fear of the introduction of contagious disease into Great Britain, and the particular disease which was used as a stalking-horse was contagious bovine pleuro-pneumonia. As a matter of fact, all the evidence available pointed to the entire freedom of Canada and the United States from this disease for many years, but two factors prevailed until a few months ago to keep the embargo in being. The one was the political influence of the vested interests, particularly in Ireland, which did not desire an invasion of Canadian store cattle, and the other was the departmental shirking of responsibility on the part of the Ministry of Agriculture with or without the advice of their veterinary staff.

Prohibit and keep out of trouble and responsibility seems to have been the departmental slogan. I . suggest that “ Importation whenever possible without danger” should be the watchword of an efficient veterinary staff, for, as has been pointed out elsewhere, while any fool can prohibit and avoid responsibility, it needs a trained man to allow importation under regulations.

(2.) Combined with prohibition of live-stock there must be prohibition of entry of animal products such as hides, hoofs, horns, bones, wool, &c., either absolute or' except after efficient sterilization of such materials. Such other materials as hay, straw, and manufactured foods such as oil-cakes may also have to be provided against, and, as we have seen in the case of foot-and-mouth disease, vaccines and sera of animal origin are potential dangers. Suitable regulations and certificates, continual vigilance with regard to the- valence of animal-disease in foreign countries, and power to promptly exclude such products as and when their importation appears to be dangerous, afford the necessary precautions in relation to these matters. Assuming now, however, that total exclusion of live animals of different species is not in operation, but that importation with safeguards is allowed, what are .these further safeguards ?

(3.) In the case of many diseases infection or non-infection can be determined by means of certain biological tests. The most commonly applied is, of course, the tuberculin test, and in this connection a degree of reliability ' can now be attained which leaves little to be desired. A standardized method of testing, using the best combined test (a matter well worthy of discussion in light of world experience), and using efficient tuberculin" applied either by the official veterinary representative of the importing country or by a Government official of the exporting country, should be required from the country of origin of the stock. In order to be able to give the necessary guarantee,- both in the interests of the exporter and the importer, the British Ministry of Agriculture has established a testing-station where animals for export may be tested prior to shipment. Mallein testing of horses,. asses, and mules can be applied in a similarly reliable manner, and in both cases the tests can be applied at the port of entry. Other tests which might well be applied to the animals concerned are the avian tuberculin tests for Johne’s disease, the agglutination test for contagious abortion of cattle, a similar test recently worked out by Heslop for pleuro-pneumonia of cattle, and the complement fixation test for dourine in horses.

These immunological tests will surely be used increasingly, and the list of diseases allowing of their application is also increasing yearly, so that the certification by trustworthy persons in the country of origin of an animal for export will become of more and more importance. As has been pointed out, these same tests can, if desirable, be repeated at the port of entry.

(4.) Another time-honoured measure of protection is that of quarantine at the port of entry. This is a very valuable measure in the case of -- animals which have been only a short time in transit, and in connection with diseases with a short incubation period. It is, however, by itself an inadequate safeguard against such, diseases as tuberculosis, glanders, Johne’s disease, bovine pleuro-pneumonia, and. rabies, while

such parasitic conditions as warbles have often outlived the regulation period. Quarantine, then, while useful, cannot be relied upon alone.

(5.) Veterinary inspection at . the port of entry is, of course, an essential precaution, and if this is made , to include a reference to the ship’s log for any history of disease or mortality during the voyage,.and repeated inspections during the quarantine period, together with application of the laboratory and biological tests previously mentioned, it affords the most solid measure of protection possible.

(6.) There are still one or two further methods by means of which a State desirous of importing pedigree stock can secure protection against infection. One of these is to require what may be called a certified history of the particular animals from the date of birth. Such a. history is furnished by the breeder and owner, and is to be endorsed by the veterinary officials of the exporting Stated The method rests upon the mutual honesty and integrity of stockowners and departmental officers, and, while it is necessarily limited, it does , provide a means for the inter-State exchange of pedigree stock. Another method, that of the buffer State, can sometimes be applied. If, for example, it is desired to import Queensland cattle into Victoria the latter State is safeguarded by the dipping regulations of the State of New South Wales, and by requiring a period of three-months stay of the cattle in New South Wales. This three months in the buffer State serves the purpose of quarantine.

The last method of protection to be mentioned is just that of common honesty, both in the inter-State and international relations. Honest international notification of the existence of contagious disease among animals at the earliest possible moment is still the best policy, for it becomes reciprocal, and, to apply another proverb, “ Forewarned is forearmed.”

VETERINARY TRAINING,

And now I desire, in conclusion, to suggest two directions in which this professional duty of allowing the fullest facilities for international trade in live-stock compatible with the safety of our own flocks and herds affects the problem of veterinary education.

Firstly, it must be clear that for the efficient performance of the duties of a State veterinary officer special . qualifications are necessary. The training required for a general practitioner is not enough. The special. qualifications required may no doubt be attained to a considerable extent after appointment to. a junior post by the man who will read and who takes study leave for practical work in a laboratory. But I venture to suggest that a special course of training not verv long after graduating is the best equipment. It is just a matter of choice between practical experience first, followed by hardly acquired scientific and technical training in a post-graduate course on the one hand, and a four-years graduation course followed by a specialized fifth year adapted solely to the scientific technical work of the State sanitary veterinarian. The one method is exemplified in the regulations for the fellowship (in this branch of work) of the Royal College of Veterinary Surgeons. The other is the method set out in the post-graduate diploma courses of some of the English universities, such as the D.V.H. of Liverpool, or the course for the degree of M.V.Sc. of Melbourne. * - ’

Just prior to the war a departmental committee was appointed by the President of the Board of Agriculture in England “ to inquire into the requirements of the Public Services with regard to officers possessing veterinary qualification; and to consider whether any further measures can with advantage be adopted for the selection and training of students with a view to such employment/’ The committee reported that, with regard to the Indian civil veterinary department and the colonial veterinary services, in both cases there was a deficiency of suitable candidates. Further, “ it was generally agreed among the professional witnesses that the course for the qualifying diploma was not of itself sufficient training for future officers in the Government service. At least a year in postgraduate work and study would be a great, advantage.”

This criticism of the ordinary course applies specifically to the four-years course leading to the diploma of M.R.C.V.S. in any of the affiliated British veterinary schools, but it must be equally true in principle of any graduation course which is on general lines; and a year of specialization in the laboratory, with as much field-work in the abattoir and on the dairy' farm and in the quarantine station as may be, is, in my judgment, the minimum requirement for an appointment as a Government veterinary officer.

The second effect this broader view of the State veterinary officer’s duties must have upon -his education is that he will have a desire to continue and extend it. The British departmental committee referred to above suggest several inducements to university students possessing a thorough grounding in general science to enter the veterinary profession and the State service. Among these they rightly include special facilities for research work. I have suggested elsewhere in this address that increasing knowledge makes for increasing security and diminishes the risks of importing infection. But there are many hiatuses in our knowledge of the causadon and prevention of contagious diseases of animals. Who are to fid he gaps ? To the scientifically trained veterinary officer there must cor.:- practical problems demanding scientific investigation and research. It I-' is of the right type such problems come as a challenge. He may be qualified to carry out the research .more or less alone ; or he may find iv necessary to seek the collaboration of the bacteriologist, or pathologist, or parasitologist, in the laboratory. What is certain is that the practical knowledge of the field officer must be combined with the scientific and technical knowledge of the laboratory worker before many of the problems of contagious disease can be solved. Further...it requires the scientifically trained officer in many cases to see the • roblem in its proper proportions, and in order that, he may go on seeing difficulties and appreciating risks some facilities for special investigation and research must be given him from time to time.

I close, then, with a plea for an opening door to inter-State and international stock traffic, because with increase of knowledge there is increased security, and with the further plea for the employment of men of the highest standard obtainable, who with reasonable facilities and encouragement for research will continually add both to our knowledge and our security. - - ' ■ . .. •.

* Veterinary Sanitary Science and Police, vol. 1. (George Fleming.)