September 14, 1905J 



NA TURE 



501 



brilliant. Up to that time no one had dreamt that bile 

 could possess such a quality. It is true that both Trans- 

 vaal and Orange Free State Boers are said to have used 

 a mixture of bile and blood from dead animals before 

 Koch's researches, and also that Semmer in 1893 showed 

 that serum might be used for protective purposes ; but still 

 to Koch is due the credit of making these processes prac- 

 tical. .After he left South .Africa his work was continued 

 by Kolle and Turner, who greatly improved the methods : 

 and it is to them, and to the other workers mentioned 

 above, that we owe the fact that Rinderpest has now lost 

 its terrors. 



In the last recrudescence of this disease in the Trans- 

 vaal, in 1904, Mr. Stewart Stockman, the Principal 

 Veterinary Surgeon, and Dr. Theiler, thanks to the ex- 

 perience and knowledge gained during the last ten years, 

 were enabled to stamp out the disease rapidly and com- 

 pletely. It is to them also that we owe our knowledge 

 of the dangers of the intensive method of inoculation, 

 much used in the past and due to Kolle and Turner, and 

 the introduction of the fighting against the plague by the 

 inoculation of the healthy cattle by injections of immune 

 serum alone. 



In the Tsetse-fly Disease our advance in knowledge has 

 been in regard to the causation of the disease, and not 

 in its prevention; it is quite otherwise with Rinderpest. 

 The contagion or cause of Rinderpest is absolutely un- 

 known. We know it exists in the blood, nasal, mucous, 

 and other secretions of the sick animal, as all these are 

 infective, but no one has seen it. The smallest quantity 

 of blood will give the disease if injected under the skin 

 of a healthy animal. We also know that the contagium 

 is not very resistant. Blood soon loses its virulence after 

 it leaves the body, and the effect of drying or the addition 

 of chemical preservatives, such as glycerin, act also 

 injuriously to the contagium, whatever it may be. It 

 evidently belongs to the ultra-visible sort of micro- 

 organisms, as it is said to pass through a porcelain filter. 



How the contagium passes from the sick to the healthy 

 is assumed to be by contact. No experiments have, so far 

 as I am aware, been made as to whether it is conveyed 

 by insects as well ; but, as Prof. John MacFadyean says, 

 as it spreads in all countries and climates and seasons, 

 and the contagium is easily carried on the persons or 

 clothes of human beings, it is improbable that insects have 

 anything to do with it. 



it is in the methods of protective inoculation that the 

 great advance has been made in our knowledge of this 

 disease. Ten years ago no means were available to stay 

 the progress of this plague ; now it has lost its terrors. 

 As soon as it appears it can be immediately attacked and 

 stamped out. This is done by rendering the surrounding 

 cattle immune to the disease by injecting immune serum. 

 This serum is prepared by taking immune cattle and hyper- 

 immunising them by the injection of large quantities of 

 virulent blood, so as to make their blood serum as anti- 

 toxic as possible. If there are no immune cattle at hand, 

 cattle can be immunised by Koch's bile injection method 

 and then hyper-immunised ; but, of course, in practice — 

 for example, here in the Transvaal — large quantities of 

 Immune serum are kept ready for emergencies, and a 

 herd of immune cattle kept up for the supply of the serum. 

 This satisfactory state of affairs, so far as this disease 

 is concerned, is, of course, the outcome of an immense 

 amount of thought and experiment, and I have already 

 mentioned the chief scientific men to whom this country 

 owes this great boon. 



Different methods of immunising have been tried during 

 these years. Up to 1903 the prevailing custom was to 

 use what was known as the virulent-blood and serum 

 method. That is to say, immune serum and virulent 

 blood were injected at the same time, in order that the 

 animal might pass through a modified attack of the 

 disease. Since 1903, however, in the Transvaal this 

 method has been stopped, and the " serum alone " method 

 introduced. This method is based on the fact that the 

 virus of Rinderpest does not retain its infective property 

 outside the body for more than a day or two ; that it dies 

 out in the animal, as a rule, in fourteen days, but in 

 chronic cases only after thirty days, and that therefore 

 the healthy cattle in an affected herd must be protected 



NO. 1872, VOL. 72] 



for this length of time. Now " serum alone '' only pro- 

 tects for about ten days, and therefore the cattle must be 

 inoculated three times at intervals of ten days. The doses 

 of serum must also be large — from 50 c.c. to 200 c.c. — 

 so that this method of stamping out Rinderpest, although 

 quite efficacious, entails a good deal of labour. It is 

 necessary, then, to spare no expense in making the 

 Veterinary Department efficient, and any cheese-paring 

 legislation in this direction may be disastrous. 



II. Horse-sickness. 



The next stock plague I would bring before your notice 

 is Horse-sickness. This is a disease which only affects 

 equines — the horse, mule, and rarely the donkey. It is 

 a very fatal disease, carrying oft thousands of horses 

 every year. It is one of the most important diseases in 

 South Africa, and, if it could be coped with, would enable 

 the Transvaal to become one of the best horse-breeding 

 countries in the world. .At present it is dangerous for 

 anyone in Natal and many parts of the Transvaal to 

 possess a valuable horse, the chances of losing it by Horse- 

 sickness being so great. 



In 1895, when I went to the north of Zululand with 

 the Ingwavuma Expedition, we lost all our horses with 

 this disease. We started with a htindred horses, and had 

 to march back on foot, every horse having died. 



Ten years ago, vi'hen I arrived in South Africa, our 

 knowledge of this disease was confined to the disease 

 itself ; nothing was known as to its causation or pre- 

 vention. Credit is due to Dr. Edington for having 

 accurately described the lesions and shown its ready in- 

 oculability, period of incubation, &c. He, however, fell 

 into the mistake of attributing its causation to a species 

 of mould fungus. 

 I Etiology : Geographical Distribution. — Horse-sickness is 

 widely distributed throughout Africa. It is common in 

 Natal, Zululand, the greater part of the Transvaal, 

 Rhodesia, Bechuanaland, and Portuguese East Africa. In 

 Cape Colony it occurs in epidemics, with intervals of ten 

 to twenty years. It is undoubtedly a disease which prevails 

 chiefly in low-lying localities and valleys, and is but rarely 

 met with in elevated exposed positions. It, however, is 

 met with now and then in river valleys up to an elevation 

 of some thousands of feet. Season has also a remarkable 

 influence on its development, being exceedingly common 

 in summer and disappearing on the appearance of the 

 first frosts of winter. 



Ten years ago various theories were held as to the 

 cause of this disease. Some people thought that it was 

 due to eating poisonous herbs ; others, to some peculiarity 

 or state of the night atmosphere ; others, to eating grass 

 covered with dew ; and still others, to the eating of the 

 spiders' webs which may be seen on the grass in the 

 morning. It was known at that time not to be con- 

 tagious in the ordinary sense of that term ; that is to say, 

 a horse could be stabled alongside a case of Horse-sickness 

 without incurring the disease, or a horse might be placed 

 without danger in the same stall in which a horse had 

 recently died of Horse-sickness. 



Nature of the Disease. — A horse which has been exposed 

 to infection shows no signs of the disease for about a 

 week. Its temperature then goes up rapidly, and it dies 

 after four or five days' illness. Very often the horse 

 appears perfectly well until within a few hours of death. 

 For example, iny horse was the last one to die on the 

 Ingwavuma Expedition. On the day of his death I rode 

 him until noon without noticing anything amiss. He 

 then became rather dull in his movements, and I handed 

 him over to the groom to lead. He died that evening 

 immediately after we got into camp. It is, therefore, a 

 very rapidly fatal disease, and almost every horse which 

 is attacked Ijy it succumbs. I have never seen a case of 

 Horse-sickness which had been brought on by artificial 

 inoculation recover. But there can be no doubt that a 

 small percentage of horses infected naturally do recover, 

 and these recovered horses are, more or less, immune in 

 future to the disease. There is no necessity for me to 

 describe the symptoms of this well-known disease, as 

 everyone who has to do with horses in South Africa is 

 perfectly familiar with it, and everyone has seen dead 

 horses with the characteristic mass of white foam issuing 



