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This article was published in 1953
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Investigations of Developments in Animal Disease Control in Some Overseas Countries
IAN W. MONTGOMERY, B.V.Sc., I.C.I. of Aust. and N.Z. Ltd., Melbourne
Mr. President and Gentlemen: At the outset I would like to thank you for the privilege of addressing the Annual Conference of your Institute on the subject of animal disease control in some overseas countries I have recently had the opportunity of visiting.
My travels tork me to every veterinary teaching institution in the British Isles and most of the veterinary research organisations. In addition, I had an opportunity of attending in England the Royal Show, the British Veterinary Association Conference, the Royal Dublin Horse Show and a number of divisional meetings of the British Veterinary Association; and after three months in England I had a short fortnight on the Continent attending an International Plant Protection Conference at Paris and visiting veterinary teaching and research institutions in France, Belgium and Holland. I also paid a short visit to Malaya and India on the way overseas, and on my return journey I spent a week only in Canada in the Montreal district, visiting the MacDonald College, and then I had a month in the United States, visiting a number of the United States Departments of Agriculture Research Stations, including their principal organisation at Beltsville and spending most of my time in insecticide investigations in Florida and Texas. I also had an opportunity of seeing two of the veterinary teaching institutions at Cornell University, New York State, and at the University of California; visiting the Berkeley and Davis Sections of this University.
Turning to mere specific subjects, firstly I would like to deal with ANTHELMINTICS. I was impressed particularly that, of all countries visited, it was most notable that the principal anthelmintic research in the world as far as farm animals are concerned is being conducted in Australia at the C.S.I.R.O. McMaster Laboratory, Sydney. My Company is very happy to be able to associate itself in some very minor way in this research in the preparation of special materials for the continued investigations by Mr. H. McL. Gordon and his staff. It was with regard to these investigations that I enquired in all parasitological laboratories visited overseas; as to developments in those places of new anthelmintics or the improvements of the already well known materials.
I am aware that at this conference last year Mr. Gordon mentioned to you confidentially his work in the improvement of the efficiency of phenothiazine by altering the physical nature of the material. I understand that Mr. Gordon told you that this work was giving hopeful indications that the anthelmintic efficiency of phenothiazine might be improved, and you may be aware that this work has been continued and results in general are most promising.
Whilst overseas, I specifically investigated this point and found that, whilst only very little work had been done in relationship to the effect of the variation of the physical nature of phenothiazine on anthelmintic efficiency, what little work had been undertaken, for example at Weybridge by Taylor and his group, had shown that no improved efficiency had been recorded. On further investigation of Taylor's work, it was noted that the material with which he was working was not of the specially fine grades which had shown improved efficiency in the Australian work and it does appear that the specification of the physical nature of phenothiazine is very critical. Whilst I can report that we still have the most hopeful indications that phenothiazine efficiency can be improved, we have yet some distance to go before the complete story is known fully and it will be possible to convert the results of experimental work to full-scale effective field usage.
Of overseas countries, England seems to be leading in general anthelmintic research after Australia, but what work is being done has not produced any new information and would appear to be of rather doubtful value, as it is based essentially on in vitro methods. In England, it can be appreciated that large numbers of sheep, or for that matter other animals, are not freely available for field-scale critical anthelmintic trials, and for that reason English workers have continued to try to develop in vitro methods of screening of new chemicals in an attempt to determine anthelmintic activity. Two organisations particularly are working on these lines; a group at Edinburgh University, where Dr. Parnell is working on field studies, and a research team under Dr. Leiper working for the commercial organisation of Boots Ltd. Both these teams are using in vitro methods. The Edinburgh team are using the common fluke (Fasciola hepatica) and Ascaris lumbricoides. The technique is relatively simple; the fluke or the Ascaris being immersed in a physiological saline and connected to a lever-arm pen for the recording of changes in movements on a recording drum. To the physiological solution is added solutions of various chemicals which it is desired to test. It is rather notable that the Edinburgh team when working with Hexachloroethane had showed that this chemical had no activity against common fluke; whereas in vivo tests have proved it to be highly active. Whilst thousands of chemicals have been tested, practically nothing has shown up and I am rather doubtful that such an in vitro test is a valid method of screening chemicals in the search for new anthelmintics.
Research workers in Scotland, where internal parasites of sheep appear to be more severe than in England, are undertaking surveys similar to these conducted by Mr. Gordon in Australia, and it was of interest to note that in general phenothiazine did not appear to be as effective in either the British Isles, or for that matter in the U.S.A., as it is in Australia. It was noted also that the qualities of phenothiazine in those two countries appeared to be inferior to the Australian material, particularly in respect to the physical nature of the product. Another point noted was that Nematodirus appeared to be one of the serious parasites of the sheep in Scotland. Phenothiazine apparently was of very low efficiency against this parasite, and there were some unproven indications that phenothiazine even might have been toxic when used for the control of Nematodirus infestations. In the United States, I found nothing new in the anthelmintic field for large stock but there was some work being done in new anthelmintics for small, pet animals. Indications, therefore, at present are that phenothiazine will remain the anthelmintic of choice for a number of years to come and the most hopeful developments in this field are the improvement of the physical nature of phenothiazine itself.
Whilst dealing with anthelmintics. I will mention briefly coccidiostatic chemicals. Control of coccidiosis of poultry is of considerable interest in most countries visited and an appreciable amount of research is being undertaken in both the British Isles and U.S.A. The following points were noted particularly in this field:—
In Britain, Sulphamezathine is still the drug of choice for control of caecal coccidiosis, having high intrinsic activity and low toxicity. There was ample evidence, however, to show that when Sulphamezathine was used too early in an outbreak, before the majority of chickens had developed an infestation, control was only temporary and a general immunity did not result. The chief competitor to Sulphamezathine was Sulphaquinoxaline; that drug being definitely superior in the control of intestinal coccidiosis, though some evidence had been accumulated indicating that in certain circumstances it is definitely toxic. It was also less palatable than Sulphamezathine. Other coccidiostatic materials being used in overseas countries are Nitrofurazone and Nitrophenide, both of which were designed for admixture with foodstuffs and may be used for continuous feeding of chickens, and so prevent the occurrence of coccidiosis. Such a method would hardly be applicable in Australia, but it is very suitable, particularly in U.S.A. where the broiler industry is developed very highly and chickens are fattened rapidly. These materials did not appear to be very satisfactory for the treatment of sick birds as such are disinclined to eat and these chemicals are relatively insoluble.
Insecticides
In view of the vast interest in Australia in improved insecticides for control of external parasites of stock. I spent a considerable time discussing the newer insecticides with research authorities in the United Kingdom and in North America. There is a very considerable body of research work being undertaken on the problem of developing efficient insecticides and in the effective formulation to ensure adequate control of the external parasites of stock, and this work is particularly well advanced in the United States. As you are already aware, there are a large numbei of chlorinated organic insecticides which have been developed since the original effective use of D.D.T. and, later, of B.H.C.; and now being used widely in America are a number of newer products such as Toxaphene, Chlordane, Aldrin and Dieldrin. In addition, there are a number of new phosphatic insecticides which have received some attention, experimentally only, for use in control of external parasites. The two main points noted were: firstly, the rapid and serious increase of the number of insects resistant to one or all of the chlorinated insecticides and occasionally to phosphatic insecticides. The second point of greatest interest to us was the marked improvement in formulation of existing insecticides; noted mostly in the United States, and to a lesser extent in England. Dealing firstly with the resistance problem, some very useful work is being done on this matter, both in England and the States, but to date the real story of why resistance is occurring has not been clarified. However, there is no doubt that this if a very real problem. I had the opportunity of inspecting some dairying establishments in Florida where work is being carried out by a team of workers from the U.S.D.A. in an endeavour to control insecticide-resistant house flies, and it was there that I noted the heaviest density of population of house flies that one could possibly imagine to exist. A veritable cloud of flies existed in all the dairy barns and it was literally possible to brush these away from in front of one. All these flies were completely resistant to all the known chlorinated insecticides, and in some rases to the highly toxic phosphatic insecticide. Parathion or E.605. The workers in this area have found that they have had to revert to molasses and arsenic bait traps to obtain any degree of control of this very serious fly menace. Just why mass resistance has occurred is not at all clear but it appears to be in part due to the indiscriminate, uncontrolled and haphazard use of chlorinated insecticides, possibly in sub-lethal quantities, giving the opportunity for the partially resistant members of the species to survive and thus rapidly build up an insecticide resistant race. With the introduction of D.D.T. many years ago, great emphasis was placed on the residual value of this insecticide in the control of insects over long periods, removing the necessity for constant re-application of control treatments. This, in itself, may have been a serious drawback to the continued successful use of D.D.T., as with the fall in concentration of D.D.T. with the passage of time, the point was reached frequently when those insects with a factor tor resistance survived, and resistant races thus were created.
Evidence now accumulating shows that it is far more important to ensure that insecticides are used at concentrations which will guarantee the highest possible kill and that repeat applications be made to maintain the kill, rather than to rely upon residual efficiency.
The second important factor with the usage of insecticides appears to be efficient formulation and effective application, and it appeared to me that in U.S.A. in particular, and to a lesser extent in the U.K., the different formulations available were markedly superior to those available on the Australian market. It was noted that for control of cattle ticks a B.H.C./D.D.T. combination or a Toxaphene formulation appeared to be the dips of choice, and seeing a little bit of their usage in the field these particular materials would appear to be the more valuable in control of cattle tick; in particular due to the effectiveness of the formulations used rather than to intrinsic value of the insecticide as compared to any other. There was some evidence in England that B.H.C. dips of very small particle size are more effective than the materials usually used and this avenue appears to be a promising advance in the successful usage of modern insecticides.
The third important angle which is being investigated actively in the U.S.A. is comparative toxicity of the various insecticides, and in the States severe restrictive action is taken in the usage of insecticides which may give rise to chronic mammalian toxicity. All new drugs or like preparations are controlled by an organisation known as the Food and Drug Administration, which has absolute authority in prescribing whether a product may be used; and if necessary the restrictions on usage of any product. The regulations of this organisation more or less ban the use of a drug such as D.D.T. where products so treated, for example, milk from dairy cattle, are to go into human consumption.
On the other hand, acute poisons, but such as have no residual or chronic toxicity problems (such as Lindane and Toxaphene), are permitted for general usage as they do not create a public health risk. A useful summary of toxicity has been determined by workers at Kerrville in Texas, and this summary places insecticides in the following order of toxicity:—
Chronic Toxicity
D.D.T.: Technical B.H.C.; Dieldrin; Aldrin; and T.D.E.—All readily stored and residues persistent.
Intermediate Toxicity
Crude Lindane (Beta isomer removed); and Chlordane.
Acutely Toxic
Dieldrin; Aldrin; Lindane; and Toxaphene.
It would appear from overseas work that the two insecticides now made in Australia, D.D.T. and B.H.C., are still amongst the outstanding chlorinated insecticides. The other insecticide which may have definite application, particularly in cattle tick control, is Toxaphene. When the problem of the creation of resistant races is considered and correlated with the factor of residual insecticidal properties of some of the insecticides, and the possibility of such residual property giving rise to an insecticide-resistant race in veterinary application in Australia, it might be said that where usage is not repeated, for example in control of blowfly strike by spraying or jetting or in the control of lice or ked of sheep by single annual dipping, D.D.T. with its long residual action can be used most usefully; provided that the initial concentration is sufficient to give a high biological kill throughout the life cycle of the ked or louse, and provided the formulation is such that the insecticide remains in an effective condition in the dip wash. On the other hand, where repeated applications of insecticides are to be made, such as, for example, in dipping of cattle in Queensland for cattle tick control, a shorter acting but highly efficient insecticide such as B.H.C. may be preferable. Toxaphene in its effect appears to fall somewhere between B.H.C. and D.D.T. in regard to its residual properties and its efficiency of kill of insects such as cattle ticks.
There are literally hundreds of chemicals with insecticidal activity.
Few of them have reached commercial application and many of them are extremely toxic to mammals; the most interesting developments being amongst the phosphatic insecticides which are extremely effective in certain plant protection applications, but in view of their acute toxicity have little application at present in control of ecto-parasites of stock. A further development being followed particularly in the U.K. and on the Continent is that of the systemic insecticides, which act through the systemic circulation and are so far applicable only to plant protection work.
Further matters of interest, particularly in the veterinary field, are developments in the control of metabolic diseases of cattle and this was of particular interest to us in Australia. I found however, that the position was even more obscure than we believed many years ago and that, whilst many are working on this problem, very little in the way of new knowledge is at present available. One can add nothing to help elucidate the problems as they exist in Australia.
One of the interesting developments overseas is that of antibiotic feeding and this has been particularly marked in the U.S.A. where already a commercial market amounting to 36 million dollars per annum has been created for the sale of foodstuffs based on antibiotic materials. Whilst these developments have been investigated very fully in the U.K., as yet no commercial usage has been possible as the sale of such materials still is prohibited by law. Summarising briefly the results obtained, both in the U.K. and the U.S A., it can be noted that the beneficial results occur from feeding of very small quantifies of antibiotic materials to young stock, particularly pigs and poultry, but such beneficial results seem to occur only when such stuck are being fed or maintained in other than ideal conditions.
To quote figures, it was noted that the Agricultural Research Council's results showed an 18% body weight improvement and an 11% increased foodstuff utilisation ratio in young stock fed on normal farm rations.
At this stage I might mention briefly one or two other interesting points noted. Firstly, in U.S.A. in particular, considerable attention is being given to the use of soil improvers which are based on hydrolised polymers of Acrylonitrile. These products are not fertilisers but are used mainly in heavy clay or silty soils and have the effect of producing porous, granular soil structures and so assist better crop growth. Soil improvers of this nature are very expensive and are applicable only at this stage to market gardens, nurseries and household gardens.
Another interesting task undertaken was to investigate the developments of weedkillers; and particularly to have a look at the problem of control of secondary jungle growth in Malaya, where such undergrowth proves to be an ideal ambush cover for insurgents in the Malayan jungles, when roads or railways are cut through, some light entering the cleared areas permits a dense secondary growth in the jungle about ten or twelve feet high and extending inwards 100 to 120 feet. This secondary growth is known as Belukar and it has been the objective of the Security Forces to try to destroy the secondary growth with weedkillers, and so eliminate potential ambush areas. For some time now various hormone and total weedkillers have been used, and whilst partially effective in killing secondary jungle growth, the great difficulty has been to apply such materials in such dense, massive growth.
It was noted that a new weedkiller known as C.M.U. produced in U.S.A., has extremely high efficiency as a total weedkiller and is the most effective soil sterilant yet discovered. C.M.U. is non-hazardous, non-toxic and is not inflammable or corrosive. Whilst at present expensive, it appears to be a very useful development for the eradication of unwanted growth in areas which are to be kept clear, or for control of many of our difficult-to-eradicate weeds.
In commenting on veterinary education overseas, one's first impression is the magnificent facilities and equipment of overseas, and particularly American, veterinary teaching establishments. One realises immediately the difficulties of Australian teaching schools when our limited facilities are compared to those available in European or American countries. However, on the other hand, whilst the teaching of clinical veterinary medicine and surgery overseas may be by virtue of the facilities available better provided than that in Australia, for our Australian requirements I feel that our teaching courses are equivalent to or better than anything encountered. I rather feel that our graduates may not be quite as adept as the American or British graduate in the handling of surgical or straight medical problems, but I feel certain that in dealing with disease on an economic level amongst our livestock, our graduates are placed better than the majority of our overseas' colleagues.
I had a few days with Professor Beveridge, who at present has the worries of the building of a new veterinary school at Cambridge; and whilst he has been in the last year or so restricted in his finance and cannot complete the whole of his plans, from what I saw of it the new veterinary school at Cambridge should be a very adequate establishment. I was particularly interested also in the veterinary school at Glasgow which recently has come under the command of Professor Weipers. The result of his energy almost has completed a magnificent new field station for the training of students in their final years. Professor Weipers has a young and energetic staff and the teaching fraternity at Glasgow are undertaking extremely interesting and advanced studies. A new field station has been opened recently at Bristol, and again facilities for teaching of the final years of veterinary science are excellent. The equipment of the new school of the Bristol University is outstanding. However, most of the field stations of the British Veterinary School are designed for the teaching of medicine and surgery and are not comparable in this respect to the facilities available, limited as they may be, at the Sydney University's station at St. Marys for the teaching of general animal husbandry.
I should mention the two schools I visited in U.S.A., Cornell and Davis, of the University of California, where it would be hard to describe the excellent facilities available for teaching; but like the British schools the teaching of clinical medicine and surgery takes pride of place.
Last year's British Veterinary Association's Conference was held in the Midlands of England at the town of Harrowgate. It was attended by some 600 veterinarians from the British Isles and overseas and was extremely well organised. It was an enjoyable conference, although for a speaker on the last day of the conference extremely difficult to survive. The British conference is much more a social affair than our conference in Australia; a large proportion of wives attending with their husbands, presumably to keep them out of mischief, but there is so much in the way of entertainment that one finds little time for serious scientific discussion. The conference opens on a Sunday with a reception by the local division at night; the official opening being on the Monday with some scientific papers and Mayoral reception and dance at night. Further papers are given on Tuesday, with a Presidential reception and dance at night; Wednesday morning further papers, and then a sports afternoon with a dinner at night; Thursday, further papers and a further dance at night; Friday, some papers (and in my case a theatre party at night); and Saturday morning the closing sessions. A very full week and most enjoyable, and notably attended by a very high proportion of field officers and practitioners, who tend to make the conference a week's holiday and a get-together of the profession in England generally.
Following the B.V.A. conference, I went to the Third International Crop Protection conference in Paris, where some 800 delegates from all countries outside the Iron Curtain attended and I was the only Australian. I was somewhat disappointed in the organisation of this conference, where some six hours were spent in rather magnificent opening and closing sessions with orchestras, bands and flags flying; a further six hours in the presentation of four or five principal papers, and six hours only devoted to some 200 sectional papers divided into nine sections. As these papers were possibly the most important contributions to the conference, it is a pity that such a limited time was allowed; practically prohibiting discussion. In view of continued alterations in the programme, it was impossible to attend those sections which might have proved of much value.
Finally, a note on the Royal Show in England; held in a different locality every year and in 1952 hampered by the lack of cloven hoofed stock due to the foot and mouth outbreak. However, the Royal Show is a magnificent achievement; the ring and the stands, the buildings for the administrative offices, overseas clubs, the Royal party and all the necessary facilities for the housing of stock being completely portable and being transferred from area to area each year. The Royal Show is taken to the people of England rather than people having to attend a central position each year. Last year it was virtually a trade exhibition in view of the absence of stock, but the trade exhibition itself was staged magnificently and hundreds of firms exhibited their wares most effectively; many interesting stock and crop protection products and machinery being displayed for inspection.