Soo 



NA TURE 



[September 14, 1905 



harm, Just as the rat trypanosome lives in the blood of 

 healthy rats ; but when introduced into the blood of such 

 domestic animals as the horse, the dog, or ox it gives rise 

 to a rapidly fatal disease. The discovery that the wild 

 animals act as a reservoir of the disease accounted for the 

 curious fact that Tsetse-fly Disease disappears from a tract 

 of country as soon as the wild animals are killed off or 

 driven away. 



In 1895 the living trypanosome which causes the Tsetse- 

 fly Disease was sent to England in the blood of living 

 dogs, in order that it might be studied in the English 

 laboratories. These trypanosomes have been kept alive 

 ever since by passage from animal to animal, and have 

 been sent all over Europe and America, so that our know- 

 ledge of this kind of blood parasite has rapidly grown. 



Koch, in a recent address, says that our knowledge of 

 protozoal diseases is based on three great discoveries — 

 that of the malarial parasite, by Laveran ; of the Ptro- 

 plasma bigeminum, the cause of Texas Fever or Red- 

 water in cattle, by Smith ; and, lastly, this discovery of a 

 trypanosome in Tsetse-fly Disease. 



We may therefore, .J think, congratulate ourselves on 

 the growth of our knowledge of this great stock disease 

 during the last ten years. 



Since 1895 many other trypanosome diseases have been 

 discovered in all parts of the world. The latest and most 

 important of these is one which affects human beings, 

 and is known as " Sleeping Sickness." This " Sleeping 

 Sickness," which occurs on the West Coast of Africa, 

 particularly in the basin of the Congo, has within the last 

 few yeais spread eastward into Uganda, has already swept 

 off some hundreds of thousands of victims, is spreading 

 down the Nile, has spread all round the shores of Lake 

 Victoria, and is still spreading southward round Lakes 

 Albert and Albert Edward. This disease is in all respects 

 similar to the Nagana or Tsetse-fly Disease of South 

 Africa, except that it is caused by another species of 

 trypanosome and carried from the sick to the healthy by 

 means of another species of tsetse-fly — viz. the Glossina 

 palpalis. 



I now throw on the screen a map of Africa, showing, 

 so far as is known up to the present, the various fly 

 districts, and you will see from this map that it is not 

 at all improbable that this human Tsetse-fly Disease may 

 spread southward through the various fly districts to the 

 Zambesi, and may even penetrate as far as the fly districts 

 of the Transvaal and Zululand. 



I am sorry to say that, in spite of innumerable experi- 

 ments directed towards the discovery of some method of 

 vaccination or inoculation against these trypanosome 

 diseases, nothing definite, up to the present time, has been 

 discovered. At present there does not seem to be any 

 likelihood that a serum can be prepared which will render 

 animals immune to the Tsetse-fly Disease. In the same 

 way it has also been found impossible, up to the present, 

 to so modify the virulence of the trypanosome as to give 

 rise to a modified, non-fatal form of the disease. Again, 

 all attempts at discovering a medicine or drug which will 

 have the power of killing off the parasites within the 

 animal organism, without at the same time killing the 

 animal itself, have not as yet been successful, although 

 some drugs, such as arsenic and certain aniline dyes 

 (Ehrlich), have a very marked effect in prolonging the life 

 of the animal. As this disease is fatal to almost every 

 domestic animal it attacks, it seems very improbable that 

 there is much chance of cultivating an immune race of 

 horses, dogs, or cattle \vhich will be able to withstand 

 the action of the parasite. It is quite evident that if 

 an acquired immunity of this kind could be brought about, 

 such a race of immune animals would now be found ; but, 

 as a matter of fact, there are no horses, dogs, or cattle 

 in the " Fly Country." In other protozoal diseases, such 

 as the Piroplasmata, this acquired immunity seems to 

 come about fairly readily. 



To sum up, then, the increase in our knowledge of 

 Tsetse-fly Disease during the last ten years, we may say 

 that we have discovered the cause in the shape of the 

 small blood parasite Trypanosoma ; we have found that 

 the reservoir of the disease exists in the wild animals, 

 and that we can blot out this disease from any particular 

 tract of country by the simple expedient of destroying or 



NO. 1872, VOL. 72] 



driving away the wild animals. We still have no means 

 of preventive inoculation or successful medicinal treat- 

 ment in this disease. 



(2) Trypanosomiasis of Cattle. 



This disease seems to be widespread over all South 

 Africa. It cannot be said to be of much practical import- 

 ance, as the cattle infected do not seem to be seriously 

 affected by it. It is caused by a species of trypanosome 

 remarkable for its large size, which was discovered by 

 Dr. Theiler some years ago, and named T. theileri. 



Dr. Theiler states that it is conveyed from animal to 

 animal by the common horse-fly, Hippabosca rufipes. 



This, then, is a short account of the trypanosome 

 diseases which affect South .Africa. 



Of late years the Tsetse-fly Disease has become of less 

 practical importance to the Transvaal, from which it has 

 practically disappeared. This is due to the disappearance 

 of the game, killed off by Rinderpest ; but with the 

 preservation and restoration of the reserves with big game 

 the disease is certain to reappear. Why the fly should 

 disappear with the game is not known. 



B. Parasite unknown. 

 I. Rinderpest. 



We now turn our attention to the important diseases- 

 of the second group. In these the parasites causing them 

 are unknown — that is to say, no parasites can be detected 

 by the microscope or by culture — but it is equally true 

 that they must be present in the blood and fluids of the 

 sick animals in some form or other. In all probability 

 they are ultra-microscopic — too small to be seen with our 

 present instruments. This is borne out by the fact that 

 they are able to pass through the pores of porcelain 

 filters, which keep back the smallest micro-organisms we 

 are able to recognise. 



The first of the second group of diseases is Rinderpest, 

 which has overrun and devastated South Africa within 

 the last ten years. 



Rinderpest has been known from time immemorial in 

 Europe and Central Asia, and is an exceedingly fatal 

 disease, killing go to 100 per cent, of the cattle attacked. 



The recent epidemic, according to some, originated in 

 the Nile provinces, and slowly crept southwards, reaching 

 the Transvaal in 1896, after a journey lasting some fifteen 

 years. Great efforts were made to oppose its passage, 

 but nothing seemed to avail. In parts of the country 

 where there were few or no cattle the epidemic spread 

 by means of the wild animals — particularly the buffalo — 

 which have been exterminated in many places. 



Ten years ago the symptoms and contagious nature of 

 this disease were well known, but nothing was known as 

 to methods of prevention, and it is to the investigation of 

 this epidemic in .South Africa that the discovery of prac- 

 tical methods of immunising cattle, and in this way of 

 stamping out the disease, is due. 



As soon as it was apparent that the epidemic was spread- 

 ing into South Africa, all the Colonies made strenuous 

 efforts to combat it. The Transvaal Government invoked 

 the aid of the Pasteur Institute, and Messrs. Bordet and 

 Danysz were sent out to discover some method of pre- 

 vention. They worked near Pretoria, and were assisted 

 by Dr. Theiler, then the Principal Veterinary .Surgeon. 

 Before they arrived on the scene the Natal Government 

 had dispatched Mr. Watkins-Pitchford, their Principal 

 Veterinary Surgeon, to the Transvaal, where he also at 

 first had Dr. Theiler as his colleague, and where he did 

 some good pioneer work in the serum therapeutics of the 

 disease. In the Cape Colony Dr. Hutcheon, the Principal 

 Veterinary Surgeon, and Dr. Edington, the Government 

 bacteriologist, were no less active. It is, however, to 

 Prof. Robert Koch, of Berlin, that the honour is un- 

 doubtedly due of first publishing a practical method of 

 immunising cattle against Rinderpest. He arrived at 

 Kimberley on December 5, 1896, and in the incredibly 

 short space of time of two months was able to report two 

 methods of immunising, viz. bv the injection of Rinder- 

 pest bile, and, secondly, by the injection of serum from 

 immune animals. I have always thought that the dis- 

 covery that the injection of bile taken from an animal 

 dead of Rinderpest rendered cattle immune was particularly 



