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REPORTS. PROFESSOR KOCH ON RHODES.IAN REDWATER OR AFRICAN COAST FEVER. INTERIM REPORT.! I have the honour to submit herewith my first report embodying my observations and investigatio\ls with regard to the cattle disease existing in Rhodesia, in response to your telegraphic request of the 17th March. Hav in g received a letter from the British South Africa Company on 24th December 1902, authorising me to proceed to Rhodesia, via the East Coast. I left Berlin with my two assbtants, Dr Neufeld and Dr Kleine, Army Medical Department, on 12th January 19 03, and landed at Beira on 18th Feb ruary. On the way I availed myself of the opportunity to make in- vestigations and inquiries at the var io us ports at which the steamer caIJed along the East African Coast, at Mombassa, Tangar, Zanzibar, Dar-es-Salaam, Kilwa, lb o, Mozambique, and although the stoppages were brief I was able to colle ct valuable material throwing much light on the subject of the Rhodesian cattle disease, to which I will refer later. I n Beira I was met by Mr Gray, Chief Government Veterinary Surgeon of Rhodesia, and Col. Beal, Assista nt Manager of the Beira and Mashona- land Railways, who kindly arranged everything to enable me to proceed without delay to Umtali. Mr Gray gave me every information about Beira, and about the first outbreak amongs t the imported cattle from New South Wales at the end of 19°0 . On the afternoon of the day on which we arrived we visited the farm of Mr Martini, outside Beira, a nd inspected his cattle, which were of interest inasmuch as they had grazed alongside the Australian cattle and sometimes even mixed with them. \Ve then proceeded to Umtali, where we arrived on 20th February. Here we saw the first case of the disease in a calf, the survivor of a large herd, but we could carryon no further investigations here, as the disease had spent itself, and only a very few head of the cattle were left. A similar state of affairs existed in Salisbury, where we also saw some cases, but, as at Umtali, the epidemic, after having killed off nea rly the whole stock of the township, had temporarily abated. This being the case, we therefore decided to proceed to Bulawayo, wh ere the disease had broken out only some months previously, and where there is every likelihood that for some time to co me suitable material for the study of the disease will be found. Th e Hillside Camp, It miles out si de Bulawayo, which was erected two years ago for the accommodation of the Rhodesian Field Force, but which is now unoccupied, affords an excellent site for a laboratory and for housing experimental animals, although some alterations are necessary to prepare stables in which healthy animals can be kept without danger of infection, by no means an easy matter in such a highly infected neighbourhood. I expect, however, the work of carrying out these alterations will .pe so far advanced in the course of a few days, under the expert Mr Gray, that experiments with healthy animals, with a view to conferring immunit y, can be commenced by placing as many infected animals as possible und er observation. , I This report is dated lIIarch 26th 1903. S

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Page 1: Professor Koch on Rhodesian Redwater or African Coast Fever

REPORTS.

PROFESSOR KOCH ON RHODES.IAN REDWATER OR AFRICAN COAST FEVER.

INTERIM REPORT.!

I have the honour to submit herewith my first report embodying my observations and investigatio\ls with regard to the cattle disease existing in Rhodesia, in response to your telegraphic request of the 17th March.

H aving received a letter from the British South Africa Company on 24th December 1902, authorising me to proceed to Rhodesia, via the East Coast. I left Berlin with my two assbtants, Dr Neufeld and Dr Kleine, Army Medical Department, on 12th January 1903, and landed at Beira on 18th February. On the way I availed myself of the opportunity to make in­vestigations and inquiries at the various ports at which the steamer caIJed along the East African Coast, at Mombassa, Tangar, Zanzibar, Dar-es-Salaam, Kilwa, lbo, Mozambique, and although the stoppages were brief I was able to collect valuable material throwing much light on the subject of the Rhodesian cattle disease, to which I will refer later.

I n Beira I was met by Mr Gray, Chief Government Veterinary Surgeon of Rhodesia, and Col. Beal, Assistant Manager of the Beira and Mashona­land Railways, who kindly arranged everything to enable me to proceed without delay to Umtali.

Mr Gray gave me every information about Beira, and about the first outbreak amongst the imported cattle from New South Wales at the end of 19°0.

On the afternoon of the day on which we arrived we visited the farm of Mr Martini, outside Beira, and inspected his cattle, which were of interest inasmuch as they had grazed alongside the Australian cattle and sometimes even mixed with them.

\Ve then proceeded to Umtali, where we arrived on 20th February. Here we saw the first case of the disease in a calf, the survivor of a large herd, but we could carryon no furth er investigations here, as the disease had spent itself, and only a very few head of the cattle were left.

A similar state of affairs existed in Salisbury, where we also saw some cases, but, as at Umtali, the epidemic, after having killed off nearly the whole stock of the township, had temporarily abated.

This being the case, we therefore decided to proceed to Bulawayo, where the disease had broken out only some months previously, and where there is every likelihood that for some time to come suitable material for the study of the disease will be found.

The Hillside Camp, It miles outside Bulawayo, which was erected two years ago for the accommodation of the Rhodesian Field Force, but which is now unoccupied, affords an excellent site for a laboratory and for housing experimental animals, although some alterations are necessary to prepare stables in which healthy animals can be kept without danger of infection, by no means an easy matter in such a highly infected neighbourhood. I expect, however, the work of carrying out these alterations will .pe so far advanced in the course of a few days, under the expert supervisi~t..pf Mr Gray, that experiments with healthy animals, with a view to conferring immunity, can be commenced by placing as many infected animals as possible under observation.

, I This report is dated lIIarch 26th 1903. S

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Meanwhile we have lost no opportunity of studyimg the disease by observing its course in sick animals, by making post-mortems, and by exam­ining the various organs therefrom for the characteristic lesions produced by the specific parasites, and we have also studied the connection of the ticks with the disease, with a view to forming an opinion as to the causes of this epidemic.

Up to now we have had under our care twenty-two infected animals; nineteen of these have died, and upon eighteen we have made most careful post-mortems. Of those surviving two are very sick and will probably die of the disease, while one appears to have some chance of recovering.

These figures show that an extraordinarily high mortality characterises this disease. In Umtali, of 4000 head of cattle scarcely 200 survive, and of the New South Wales imported animals (about 1000) none are now alive. The general opinion is that the percentage of mortality amongst infected animals is from eighty to ninety-almost as high a death rate as that of rinderpest.

The symptoms of the disease and the post-mortem appearances in our cases correspond to those given in the most excellent report of Messrs Gray and Robertson on Texas fever or redwater in Rhodesia, and therefore I do not think it necessary to enlarge on these at great length again.

From the beginning it was noticed by all observers that the Rhodesian disease was very similar to that which attracted public attention first in North America, later also in Australia, South Africa, South America, and Europe, and characterised generally as Texas fever.

The occasional appearance of hremoglobinuria (redwater) and the exis­tence of pear shaped parasites in the red blood corpuscles led to the con­clusion that the Rhodesian disease was identical with Texas fever, or at least one closely allied thereto, although more virulent; but, if one gives the Rhodesian disease a careful consideration, important differences appear, which I think are even more important than they have been considered to be by the majority of observers.

Regarding this, I wish to cal! attention to the following facts :-In Texas fever there appear in the red blood corpuscles, and in its

initial stage without exception, the large pear - shaped twin parasites so characteristic of this disorder, and in the course of the disease a great number of red blood corpuscles perish, so that their normal number, which is six to seven millions in the cubic millimetre, will sink to two or three millions, and even less, and through the destruction of so many red blood corpuscles much of their colouring matter is liberated, discolouring the blood serum, and when this is excreted by the kidneys it gives rise to the condition known as hremo­globinuria or redwater. Besides this, through the loss of so large a number of red blood corpuscles, an important anremia results, which is most character­istic of Texas fever, and upon this anremia the subsequent symptoms and post-mortem appearances depend.

It is quite different with the Rhodesian fever. Here, too, we have found blood parasites as proved by the microscopic examination of the blood of every sick animal submitted to our scrutiny, but these are of different shapes and considerably smaller than the pyrosoma of Texas fever.

In the early stages of the disease they are, as a rule, not very numerous, but their number increases from day to day, so that ultimately in each or in every other red blood corpuscle there are one or more small parasites. In the first days of sickness only rod-shaped or very small ring-shaped parasites are observed, but if the animals remain alive a little longer a number of somewhat larger parasites make their appearance; these are disc-shaped or resemble a leaf in outline. Only in exceptional cases and after a prolonged period of illness do we find, in addition to the smaller organisms, some bigger

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pear-shaped parasites. Amongst our fatal cases here we have only observed one in which the number of parasites present in the general circulation re­mained low throughout the course of the disease (about one parasite to six blood corpuscles). In all the other cases the parasites were very abundant. Only in four cases were the pear-shaped parasites observed; in two of these the disease lasted a comparatively long time (from fifteen to sixteen days); in the other two the duration of the disease could not be assured.

Another difference exists, and is that, although the red blood corpuscles are numerically more abundantly inhabited by parasites than they are in Texas fever, there is not the same destruction of these, and consequently not the same reduction in their number that there is in this disorder.

In a number of cases in which Mr Gray undertook daily count of the number of blood corpuscles, it was found that in some cases no reduction whatever of their number could be observed. In other cases, 3gain, oscilla­tions in the number of the blood corpuscles were observed in which the decrease did not go under 4,500,000 per cubic millimetre. Only in one instance did the number of blood corpuscles fall to 4,200,000, and in another to 2,380,000. As a consequence of comparatively small destruction of blood corpuscles, we only exceptionally observe hremoglobinuria.

Amongst our cases only once was a characteristic hremoglobinuria observed during life, and that was in the case of the animal in which the number of blood corpuscles was most diminished; while in a second case, in making the post-mortem, a light reddish mine was found in which spectroscopic evidence of the presence of hremoglobin was forthcoming. These were the only cases of hremoglobinuria which we saw.

From the evidence before us it would appear that in this disease compara­tively few blood corpuscles perish, therefore no rem3rkable anremia such as characterises Texas fever is likely to set in.

Further, the Rhodesian fever possesses certain post-mortem phenomena which are absent in Texas fever-namely, local lesions in certain organs, which indicate that the parasites accumulate in these parts in enormous numbers, injuring the tissues and obstructing the circulation. To this cause may be ascribed the most characteristic lesions of this disease, the infarcts in the kidneys, lungs, and liver, the swollen and hremorrhagic condition of the dif­ferent groups of lymphatic glands (the crural, tr3cheal, mesenteric, portal, bronchial, and mediastinal glands), and the appearance of local cedemas, especially in the lungs, from which the peculiarly frothy effusion occasionally observed results. That this is caused by the action of the parasites is proved on microscopic examination, as we find in all these different parts the organisms are unusually abundant, and there we have observed a peculiar form which up to now has not been described, a form which leads to the conclusion that here an increase of parasites takes place.

I am of opinion that these differences are sufficient proof that the Rhodesian fever, although allied to Texas fever, and belonging to the same class of diseases, is still a distinctly different disorder, and we may ultimately find that in pyrosomal diseases of cattle we have to deal with a class of disease related to one another in much the same way as the various types of human malaria, formerly classified as one, but which we now know to be caused by infection with the different parasites of the quartan, tertian, and the tropical types of malarial fever. We must, therefore, in describing such pyrosomal diseases of cattle, descriminate clearly between Texas fever and Rhodesian fever, because in these two diseases the casual parasites, the symptoms to which they give rise, and the pathological changes in the organs, are different.

Bearing out my opinion that the Rhodesian fever is a specific disease, I may instance another fact considered of considerable importance at the present day in the classification of infective diseases, and this is that it has been proved through direct experiments by Gray, Robertson, Pitchford, and Theiler

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that cattle from Natal and the Transvaal, which are, as we know, immune against Texas fever as existing in Natal and the Transvaal, and even cattle from Texas itself, will catch the Rhodesian fever and die of it. Were the two diseases of exactly the same character, a complete or at least a certain degree of immunity should have been manifested, but this is not so, therefore they cannot be considered identical, nor is the view that Rhodesian fever is merely a more than usually virulent form of Texas fever a tenable one.

Yet another theory has been propounded, and that is that the Rhodesian fever is not one disease, but a complication of diseases; but in support of this there is no evidence whatever. In the blood of animals examined by us we only found the small parasites characteristic of this disease, and always in such abundance that the course of the disease and the death of the animals could be ascribed to their presen'ce without any hesitation, and there was no necessity to entertain any theory of the existence of any mixed infection.

The question is now if this apparently new disease has arisen in Rhodesia, or if it was imported from some other place, and to answer this question I must endeavour to trace the history of this outbreak.

At the end of 1900 about 1000 head of cattle for Rhodesia from New South Wales were landed at Beim, and, because they could not be forwarded by rail at once, they were sent on the veldt for grazing there. They grazed in the neighbourhood of Mr Martini's farm and mixed with his stock, which were to all appearances in perfect health, and which remained so. Two or three weeks later the disease broke out amongst the Australian cattle, which were then sent to Umtali, and carried the disease with them.

But how could the Australian cattle become infected? In New South 'Wales no such disease is known, and no mortality occurred amongst these animals during their voyage from Australia. There was also no apparent disease at Beira.

The problem would be well-nigh insoluble if there was not one piece of evidence in our possession which I became cognisant of some years back­namely, that the same disease exists on the East African coast as has now broken out in Rhodesia, and that in German East Africa the disease was carried inland in a similar manner to that in which it may have been brought from Beira to Umtali.

The stock on the coast of German East Africa are apparently quite healthy and in the best condition, but as soon as other cattle are brought there from clean districts-for instance, from the inner parts of the country-and graze on 'veldt on which the cattle from the coast have been grazing, these imported animals will get sick and almost all die.

The indications of this disease are the same as those of Rhodesian fever, and in the blood of these infected animals, which I have many times examined, I have always found the same small blood parasites which I have again seen at Umtali, Salisbury, and Bulawayo.

On the voyage out I have had an opportunity of examining three animals which only a few weeks previously arrived at the coast of German East Africa from the interior, and which were showing the first symptoms of the disease, and whose blood contained the characteristic blood parasites present in Rhodesian fever. My assistants also found the same parasites in the blood of several sick animals at Zanzibar. Six years ago, at Tanga, I saw an out­break of exactly the same character as the present Rhodesian one, although of smaller dimensions.· In this case a herd which was brought into the in­fected area at Tanga, and which became infected there, carried the disease thence to Mohesa in the interior.

From inquiry which I made, I gathered that this disease has been in­digenous for generations back in German East Africa and the neighbouring islands, and I have good reason for supposing that it also extends still further

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southwards along the coast, and in all probability it also exists in Beira. In Beira I was informed that some time ago cattle were frequently brought there from German East Africa and Madagascar, and that the latter animals, especially when they came from the south of the island, soon became sick and died, while the cattle from the East African coast and the northern dis­tricts of Madagascar remained healthy.

To verify these statements, to see if the cattle from German East Africa and from Beira are immune against Rhodesian fever, which should be the case if my views are correct, I consider it is well worth while bringing a few cattle from German East Africa and from Beira to Bulawayo, and to be tested here as to their immunity.

In conclusion, it seems to me a very reasonable explanation of the cause of the present Rhodesian outbreak is to assume that the highly susceptible Australian cattle landed at Beira, which belongs, I believe, to the infected coast district, became infected there, and carried the disease with them to Rhodesia.

I am of opinion that there is also good reason for supposing that the in­fected area extends still further south to Delagoa Bay, as for some time past the Transvaal has been invaded from its south-eastern border by a slowly spreading disease infecting cattle, which appears from all accounts to be very much like the RhodeSian fever. M. Theiler, Government Veterinary Bacteriologist, Pretoria, whom I asked to send me some blood preparations from infected parts of the Transvaal, most kindly complied with my request, and we have been able to prove that in the preparations from different parts of the Transvaal, (from Nelspruit, Herdepoort and Mooi Plaatz) exactly the same blood parasites are to be found as at present in the blood of animals affected with local Rhodesian fever; therefore, there can be no doubt that the same disease exists in the Transvaal as that which prevails in Rhodesia, but when we take into consideration the position of the infected districts of the Transvaal, and the obstacles to communication which have existed and still exist, the view that the disease extended thither from Rhodesia is, I think, quite untenable. What is very likely, however, is that the disease obtained a foot· hold in the Transvaal in much the same way as it did in Rhodesia, that is, by being imported from the coast, in the one instance from Beira, and in the other from Delagoa Bay. In appearance in Rhodesia the disease has con­formed to a natural law which it has often followed aforetime. It has been hrought inland from the infected coast districts as it has previously been in many other instances, and therefore it appears to me more reasonable to call it " African coast fever, " in preference to calling it " Rhodesian fever."

Taking these facts into consideration, it is advisable that those ports on the East African coast which are now used as ports of entrance for the introduction of cattle to the interior should be carefully examined in order to ascertain whether or no they are infected with" African coast fever," and those which are so infected should be closed against cattle, or the entrance of these animals should only be permitted under such conditions that the importa· tion of infection from the coast to the interior is rendered impossible.

Another important question which arises in connection with the present epidemic is whether anything like lasting immunity against the disease exists in such animals as have recovered from an attack of the disease. It is known that immunity against Texas fever exists, but whether there is any lasting immunity to the Rhodesian fever seems doubtful, as in the report of Gray and Robertson they state, "the few animals which have recovered from a first attack in many instances developed a second attack about three months later which terminated fatally, " and we also saw a case in Salisbury which ended in the death of the animal, which we were assured had got over the disease some months ago. This does not look as if we could reckon upon immunity, but still I am convinced that such a thing exists, because we have had an

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opportunity of seeing and examining a considerable number of animals which have recovered from the disease, and although they have been grazing for some time on infecled veldt they have not sickened again, and must there· fore be considered immune against natural infection .

. A most interesting feature of the examination of these animals was, that al­though they appeared perfectly healthy, and did not show the slightest varia tion in temperature, their blood contained a small number of parasites, which can only be demonstrated satisfactorily by tbe use of a staining reagent (Azur. I I) which, like the Romanowsky method of staining for malaria, colours the chromatin' in the parasites a dark red. By this staining method every single parasite can be identified with certainty, and it is to be hoped that in this manner immune animals can be easily and certainly recognised. An immunity of this description against Rhodesian fever, which is characterised by the presence of a small number of parasites in the blood, resembles very closely that existing against Texas fever, as here, too, parasites exist in a cer­tain number in the blood of immune animals, as the reaction following inoculation with their blood proves. The existence of such parasites in the blood of an apparently healthy animal may be taken as an indication that such animal is not inconvenienced by their presence, and therefore must be immune.

As we know that in the pyrosomal diseases, whereto the Rhodesian fever belongs, ticks playa most important part as agent for the dissemination of in­fection, I have occupied myself thoroughly with this side of the question. For this I have had special facilities, as in my earlier work on the pyro6omal disease at Dares-Saalam, which I have identified with Rhodesian fever, I re­produced it with infected ticks in the far distant Usambara Mountains, and so proved that the ticks are also the intermediary agents in this disease.

Putting on one side a few rare species of ticks, I have found the cattle ticks of Rhodesia to be of the same species which are described commonly as throughout South Africa. They are the following:-

Rhipicephalus decoloratus, rhipicephalus evertsi, and hyalomma cegyptium, and to these we must add rhipicephalus sanguineus, which is the most common tick in Rhodesia. In Umtali we found also amblyomma variegatum frequently on cattle, and now and then we found hcemaphysalis leachi, of which the dog is the usual host.

Of real importance amongst these ticks there are only the different species of rbipicephalus, and of these most particularly the rhipicephalus decloratus or blue tick, because this insect is most closely allied to ticks which in America (rbipicephalus annulatus) and in Australia (rhipicephalus australis) carry the Texas fever, and also because it is known to be the tick which disseminates Texas fever in South Africa. For this reason we may suspect that rhipice­phalus decloratus is also the intermediary agent in Rhodesian fever. Up to now there have been no direct experiments made, and there is a possibility that the other two species of rhipicephalus may also act as carriers. Experi­ments have already been begun to decide this question.

With regard to the rhipicephalus decloratus, it is known that it differs from the American and the Australian species in possessing only six rows of teeth on its sucking apparatus (labium), instead of the eight rows common to both the others. Up to now the general opinion was that the area for the rhipice­phalus decloratus on the East African coast extended far to the north; I there­fore made a collection of ticks at the various ports of call on my journey down the coast, and found that from Mombassa to Beira, with the exception of the Island of lbo, everywhere specimens of rhipicephalus were obtained, and amongst these a kind which would appear to a casual observer to resemble the rhipicephalus decloratus, but which on more careful examination was found to have eight rows of teeth, and is therefore more closely related to the American and Australian varieties than the African rhipicephalus decloratus. This specimen is found all along the east coast of Africa as far south as Beira,

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and I suspect it may also exist in Delagoa Bayand beyond. Of the real rhi­picephalus decloratus I have not found a single specimen on the coast, but in Rhodesia, as far as my investigations went, only the rhipicephalus decloratus, with six rows of teeth, exists. Nor have I found in Rhodesia any specimens of the eight rowed coast species. This fact goes to prove that in carrying the disease from Beira to Rhodesia the Australian cattle only brought to Umtali the parasite which produces the disease, and not the coast tick which carried it; but, unfortunately, it turned out that there was already in Rhodesia a variety of tick, probably the rhipicephalus decloratus, quite as capable of acting as a carrier as is the coast rhipicephalus.

Lastly, I come to the question of how the disease will further devtlop, and in what way we can combat its spread. If nothing could be done against the disease, it would, without any doubt whatever, permanently infect every locality in which it breaks out, and in time the whole of Rhodesia will suffer as se\'erely as Umtali, Salisbury, and other places have already done.

There will be only 10 to 20 per cent. of the cattle left alive, but these animals will be immune, and will be progenitors of an immune breed which will thrive in Rhodesia as they now do on the coast. The same situation will be developed as now exists in the .southern states of North America, in Queensland, and on the East African coast; the locally bred cattle will not become visibly sick, they may appear strong and healthy, but the progeny of ticks reared upon such animals will be pathogenic for cattle which come from clean countries. This state of affdirs can hardly be considered a satisfactory one. Besides this, there is to be feared that this natural immunising process will progress very slowly and fitfully, and as a result the cattle breeding industry in Rhodesia will not develop materially for many years to come. As this is the alternative, it is absolutely necessary not to let the pest take its own course, but to fight against it by every means in our power. A radical measure would be the destruction of all ticks, but this has been attempted for years in the Texas fever countries, but unfortunately without marked success; because, while it is possible with the help of dipping tanks and sprays to destroy most of the ticks on an animal, some remain, as we have noticed on a few regularly dipped cattle here, and very few ticks will suffice for the production of a large number of young ticks which will ensure further spread of the disease.

Therefore, experts in North and South America, as well as in Australia, came to the conclusion that it would be well to protect the animals against the sickness by inoculation. At first these inoculations were not always satisfactory, as 'sometimes the blood used for inoculation purposes was too weak to protect, or too virulent. It was only when blood could be obtained from such immune animals as gave a sufficiently severe reaction to confer immunity, and when this standard of virulence could be maintained, that produced satisfactory results were forthcoming. Such a line of action must be adopted to combat Rhodesian fever, and our endeavour must be to find a suitable virus-a matter of no little difficulty on account of the extreme virulence of the Rhodesian fever; and when once the fact is ascertained that natural immunity to this disease actually exists, there is no doubt the line of lIcatmellt necessary to produce immunity artificially will be forthcoming sooner or later.

What remains to be done is to discover a standard virus of such strength that it will confer a maximum immunity with a minimum of loss from inocula­tion. Should such a virus be unobtainable by any other means, then an effort must be made to attenuate the vir,ulcnce of the parasite, for example, by passages through animals other than cattle, or in some other method by which we may hope to procure the desired protection. That this is possible is shown by the fact that the experiments which I have formerly made in East Africa accidentally placed in my hands a method of immunisation to which I

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subjected certain cattle which subsequently resisted a natural infection when exposed thereto.

Of course it is my intention to do my utmost to obtain a suitable stock vaccine as soon as possible.

I will experiment simultaneously in many different lines in order to save time, and for the purpose many healthy cattle will be required.

The more animals ·we have for this experimental work the sooner we may hope to bring our labours to a satisfactory termination.

SECOND REPORT.!

In presenting this, my second report on African Coast fever, allow me to supplement it by stating that at this stage of our work I cannot furnish what may be looked upon as a complete record of results, but I can only indicate the direction in which our researches are being prosecuted, how they proceed, and at what stage they have arrived. Experiments in African Coast fever require much longer than rinderpest experiments. In rinderpest negative or positive experimental results are forthcoming in every case in from one to two weeks, whereas in African Coast fever four weeks are necessary, as the in­cubative period of the disease is still uncertain, and in the case of tick experi­ments the time taken up is even longer, one or two months being occupied in hatching out the ticks, and one month more elapsing before the experiment can be considered concluded-this brings the total period necessary for tick experiments up to two or three months.

Soon after sending in my first report a series of experiments on healthy animals were inaugurated. For these experiments our animals were drawn from the Plumtree District, in the South of Rhodesia, which is at present free from disease. Our healthy animals were forwarded by rail from Plumtree and detrained in Bulawayo, whence they were driven by road to Hillside Camp. On their arrival there, to prevent any likelihood of accidental infection en route, each animal was well sprayed with a 25 per cent. solution of paraffin in water, and then all were placed in buildings enclosed by a wire fence surround­ing these at a distance of four yards. To prevent any possibility of ticks being harboured within the enclosure, all vegetation and grass has been removed withiri the fence, and the cattle are fed upon imported forage brought from Kimberley, a disease-free area. That these precautions area sufficient protection is shown by the fact that no case of extraneous infection has occurred amongst these animals since they arrived in Bulawayo.

On the arrival of each lot of healthy animals, their blood was submitted to a preliminary microscopical examination. This examination revealed the remarkable fact that the blood of many of them contained the ordinary pear­shaped micro·organism of common Texas fever or redwater, indicating that in the Plumtree district ordinary Texas fever is an endemic disease.

Amongst the first batch of Plumtree animals received, numbering eighteen, pear-shaped organisms were present in no fewer than eight cases, although all the animals were apparently in perfect health, indicating that their infection with the disease was not of recent date, but was rather of long standing. This fact has an important bearing upon the whole investigation, and must be taken into consideration in our further work.

Some experiments made with the blood of these animals which contained the micro-organisms of ordinary redwater, and data furnished me by Chief Veterinary Surgeon Gray, prove conclusively that ordinary redwater infection has existed along the main transport roads throughout Rhodesia, between Bulawayo and the South, between Bulawayo and Salisbury, and along other trade routes, for a long time, and therefore every ox which has worked along

1 This report is dated 28th May 1903.

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these roads for any lengthy period may be reasonably suspected of harbouring in his blood the organisms of redwater.

N ow, we know that animals of this class, living in a region where Texas fever is endemic or which have come therefrom, may have relapses of this disease. These relapses are indicated microscopically by the appearance of numerous Texas fever organisms in their blood, and are most likely to occur if such animals are attacked by any other febrile disorder by which their vitality is lowered, as such a lowering of their vitality gives the Texas fever organisms a chance to multiply. An experience of this sort is not uncommon in rinderpest, as it has been found that when an animal immune to T exas fever and retaining in its blood the organisms of that disease is attacked by rinderpest, it may develop not only rinderpest but at the same time Texas fever. Much slighter causes than attacks of a serious disease of this class may induce relapses in specially predisposed animals which have at some previous time suffered from redwater, mere elevation of temperature, such as may result from overwork, sometimes being sufficient.

This being our experience, it might be expected that such predisposed animals which had previously suffered from redwater might again show symptoms of it if attacked by African Coast fever; and, starting with such a hypothesis, a very simple explanation is forthcoming for certain phenomena which have been observed during the present epidemic, such as the presence of large pear-shaped organisms in the blood in certain cases, and the occur­rence of hremoglobinuria. These pear-shaped parasites are not found in all cases of African Coast fever, nor do they appear simultaneously with the bacillary organisms, but they show themselves in the later stages of the disease, while the hremoglobinuria which we have observed occasionally we have only seen in cases in which the pear - shaped organisms, hitherto considered characteristic of Texas fever, have been found along with th e organisms of the bacillary type.

Irtall, we have examined th e blood of ninety-one sick animals. In every instance we have found the small parasites of African Coast fever, but only in ten cases have we found these parasites in conjunction with the larger pyriform organisms, and in six of the latter cases we have observed blood­coloured urine.

These observations bear out the view that amongst the animals whose blood we have examined there were a certain number of specially predisposed animals salted to ordinary redwater, which again developed this disease as a result of the high temperature produced by an attack of African Coast fever.

Evidence in support of this theory can also be adduced from a consideration of the outbreak which carried off the imported Australian cattle. Here we had animal s susceptible to, and exposed to, infection both with redwater and African coast fever. Probably some were more susceptible to ordinary red­water, or probably the incubative period of African coast fever is longer than that of Texas fever; and, for one reason or the other, redwater of the usual Colonial type first appeared amongst them, while the "atypical " cases observed later on were probably the result of a predominant infection with African coast fever.

The probability that African coast fever has a longer incubative period th an Texas fever, and the occurrence of cases in which the organisms of African coast fever and of ordinary redwater co-exist in the blood of certain animals , offers an explanation for the apparently positive results obtained by certain artificial infection experiments, which seemed to point to ordinary redwater as the sole cause of the present outbreak; as, if blood for inoculation was taken from an animal suffering from two diseases, one of which has a shorter incu­bative period than the other, the disease with the short incubative period will be the first to declare itself, and, if the reaction produced is one with charac-

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282 REPORTS.

teristic peculiarities, the outcome ot such an inoculation experiment may be most misleading.

vVhen we began our experiments upon healthy animals we expected to be able to produce the disease without difficulty by subcutaneous inocula­tion with blood taken from sick animals, an easy matter in ordinary Texas fever, in which the injection of 5 cc. virulent blood almost always induces a severe and frequently a fatal attack; and, as we understood inoculation with virulent blood in African coast fever had had a like effect, our surprise was the greater when we found that such inoculations were ineffective when we injected subcutaneously blood containing an abundance of the small parasites. As it was important to establish beyond dispute that such inoculations do not communicate the disease, many experiments were made with varying doses of blood, and in various ways. Instead of using defibrin­ated blood as we did at first, warm fresh blood drawn directly from the jugular vein was tried, injections being made subcutaneously, directly into a vein, and into the peritoneal cavity. In some cases the injected blood was mixed with an emulsion of spleen pulp and of lymphatic gland, as these organs contain large numbers of multiplication forms of parasite, as I have mentioned in my first Report. In others virulent blood in large volume was injected, doses of 2000 cc. being introduced subcutaneously, and 500 cc. intravenously, but by none of these methods did we succeed in producing the disease. N one of the inoculated animals became sick, nor could the parasites be discovered microscopically in their blood. Even in those cases in which blood containing innumerable parasites was injected directly into the vein we were unable to find a single parasite the following day. .

All our experiments, and they were many. indicate that the direct inoculation of healthy susceptible animals with the blood of animals suffer­ing from African coast fever will not reproduce the disease, and this remarkable fact separates still further African coast fever and Texas fever. In the one case no result follows blood inoculation, while inoculation with blood from the less fatal Texas fever is attended by most serious results.

Although such inoculations in African coast fever fail to communicate the disease, they are nevertheless not without effect. Inoculated animals do not become sick, and parasites are absent from their blood, but when these animals are subjected to a second inoculation with virulent blood the result of the second inoculation differs from that of the first, as we have observed that while the first injection of virulent blood produces either an insignificant rise of temperature on the two following days, or no rise at all, after the second inoculation a temperature reaction follows immediately, which persists for one or two days, and which we may look upon as arising from the inocu­lation; but, what is still more important, after an incubative period of from ten to twelve days, a mild attack of African coast fever supervenes, characterised by the appearance of the usual small parasites in the blood, and generally by a temperature rise of some days' duration. In the course of twenty-one ex­periments we have succeeded in ten instances in producing a mild attack of the disease, which clearly shows that such a result is not accidental, and we have now to determine which is the most certain method of producing this mild attack, what doses of virulent blood should be given, and what interval should elapse between the doses in order to be certain of inducing such an attack in every instance. Whether the incidence of such a mild attack con­fers any immunity, I cannot say at present, but a consideration of the effect upon the animal organism produced hy mild artificially induced attacks of other infectious diseases leads me to think that some degree of immunity may result.

How great this immunity may be, we will only be able to state when we have discovered a certain method of artificially reproducing the disease in the viru-

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lent form which it assumes when arising from veldt infection, and this is another problem which has not yet been solved, although I hope we will over­come this difficulty, either by a modification of some method of direct infection with virulent blood or by working indirectly on the lines in which natural infection occurs, through the medium of the tick.

W ith this object in view, and for th e purpose of ascertaining with certainty what tick may be responsible for the spread of this disease, numerous tick in­fecti on experiments have been initiated. Young ticks of all suspected species are being hatched from eggs laid by mature females taken from sick animals, and many have been placed upon healthy susceptible animals, but these experiments have not reached that stage at which we may expect to get con­clusive results, tick infection experiments, as I have already remarked, being particularly tedious and taking up much time.

Concurrently with this work, we are conducting experiments with a view to obtaining a curative serum. At first I intended to prepare an antitoxic serum which would tend to neutralise the toxic products of the organism. For such a purpose the animal whose serum it is proposed to use is inoculated with gradually increased doses of virulent blood ; and, working on these lines, we have now several animals which are high ly fortified, but since we have discovered th at healthy animals are also able to resist large doses of virulent blood, I have also decided to prepare animals by inoculation with successive large doses of virulent blood for the purpose of obtaining a cytolytic serum. Such a serum possesses the property of directly attacking the specific parasite, instead of neutralising its products as an antitoxic serum would do, and we have now a number of animals fortified for producing such a cytolytic serum, but more time is required in order to enable us to produce a sufficiently pcwerful serum of this class for our experiments.

For the production of antitoxic and cytolytic serum only immune animals can be used, as susceptible animals tend to break down under repeated injec­tions of virulent blood, and for our work the immune animals taken over from the Transport Department, Salisbury, which survived the outbreak there, and whicn have since been grazed continually on infected veldt, have been most valuable. Of their immunity I think there can be little doubt, as none of them have shown any signs of indisposition after repeated injections with large doses of highly infected blood.

Our experience with the anim:11s which we found here on our arrival has been less satisfactory. These animals lent by Bulawayo farm ers many months ago had been subjected, previous to our arrival, to a series of inoculations, beginning with recovered and finishing with virulent blood, with a viewto confe rring immunity on somewhat similar lines to those by which animals are immunised against ordinary Texas fever. Most had been turned out on the Commonage for exposure to natural infection after the final inoculation, and an examination of their blood on our arriva l revealed the presence of a few small parasites, which I stated in my first report led me to believe they might be immune, but this unfortunately is not the case, as several (13 out of 29) have since developed acute attacks of African Coast fever and died. From this we must conclude that the discovery of single small parasites in the blood of cattle exposed to infection with African Coast fever only proves that these animals have come in contact with some infecting agency, but does not indicate that they are capable of resisting further infection, as we previously supposed. Herein lies another point of difference between African Coast fever and Texas fever, as the discovery of isolated pyriform organisms in the blood of animals which have been affected with Texas fever can generally be, considered to indicate that under ordinary circumstances such animals will resist further infection with this disease, a conclusion unwarranted in dealing with African Coast fever when we detect the presence of isolated orga nisms in the blood of apparently healthy animals.

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The presence of such small parasites in every case in which they are found can be taken, I believe, as a proof that the cattle whose blood contains them certainly come from areas where African Coast fever infection exists. All our investigations on this point bear out such an assumption. Single parasites have been found in the blood of forty animals which have come from the infected areas of Salisbury and Bulawayo, while no such parasites have been found in thirty blood preparations sent from the Cape Peninsula, an area free from both Texas fever and African Coast fever. For the specimens sent from Cape Town I am indebted to Dr Hutcheon, Colonial Veterinary Surgeon, who kindly arranged to have them forwarded to Bulawayo. In the blood of sixty-four animals from the clean district of Plumtree no such single parasites have been demonstrated, nor did an examination of blood prep lrations of other twenty-four animals, taken in the same district, reveal their presence; while it is particularly interesting to note that in the blood of seven animals brought from Beira, and of the six brought from Dar-es-Salaam (German East Africa) for the purpose of testing their immunity, we found the same small parasites which were present in our local animals.

For the preparation of animals, in order to obtain antitoxic and cytolytic serums, much virulent blood was necessary, and at first its scarcity somewhat retarded our work; but latterly, thanks to the efforts of Mr Marshall Hole, Civil Commissioner, Mr Taylor, Chief Native Commissioner, and Mr Gray, Chief Veterinary Surgeon; to the liberality of certain farmers in the Bulawayo district; and to the energy of Messrs Fynn and M'Donald, in charge of the Fingo Location, Bembesi, who have sent in large numbers of sick cattle, contributed by the Fingoes, we have had no difficulty in carrying out this part of our work.

In all, 78 sick animals have been obtained, which have been of material service, enabling us to carry out a systematic observation of animals while sick, and to obtain virulent blood for fortification purposes while they lived, while such as died furnished valuable material for careful jost-mortem examinations.

ROYAL VETERINARY COLLEGE, LONDON.

INAUGURATION OF THE WINTER SESSION, 19°3-19°4.

The winter session of this institution was opened on Thursday, 1st October, when the inaugural address was delivered by Mr J. ASTLEY BLOXAM, F.R.C.S., The large lecture theatre was filled to overflowing, the audience comprising many members of the profession, in addition to Governors of the College, members of the teaching staff, and students.

Mr A. C. COPE, Chief Veterinary Officer to the Board of Agriculture, presided, and, in introducing the lecturer, said that Mr BLOXAM had a two­fold claim on their attention. In the first place, he was a distinguished member of the medical profession, and, in the second place, he was one of the Governors of the Institution.

Mr BLOXAM then delivered the address, as follows :-"Mr CHAIRMAN AND GENTLEMEN-In glancing at the reports of intro­

ductory addresses which have been given here by distinguished members of your body in previous years, I have been.much struck with the evidences of progress in veterinary science which they display. It is no part of my intention to attempt to rival these admirable reviews and comprehensive surveys. I am free to confess that my own particular field of work has not brought me, except as an amateur, into contact with your own. But years ago, when assistant-surgeon in the R.oyal Horse Guards Blue, accompanying the veterinary surgeon on his rounds there, I first learned to appreciate the value of the services which veterinary science