498 



NA TURE 



[September 14, 1905 



as in his second report he announced that he had succeeded 

 in producing a modified form of the disease by direct 

 inoculation with the blood of sick and recovered animals. 

 As you are all aware, the only method of conferring a 

 useful immunity upon an animal is to make it pass 

 through an attack of the disease itself, so modified as not 

 to give rise to above a few deaths in every hundred 

 inoculated. This is the method that has been employed 

 in such diseases as Rinderpest, Anthrax, Pleuro-pneumonia, 

 and many other diseases. The great difficulty in this 

 disease in finding a method of preventive inoculation is 

 the fact that the blood of an affected animal does not 

 give rise to the disease in a healthy one when directly 

 transferred under the skin of the latter. It is only after 

 its passage through the body of the tick that the parasite 

 is able to give rise to the disease in a healthy animal. 

 It is evidently, on the face of it, difficult to so modify 

 the parasite during its sojourn in the tick's body as to 

 reduce its virulence to a sufficient degree. 



Prof. Koch in his third and fourth reports recommended 

 that cattle should be immunised by weekly or fortnightly 

 inoculations of blood from recovered animals, extending 

 over a period of five months. Even though this method of 

 Koch had given the desired result, viz. that it rendered 

 the inoculated cattle immune to the disease, it is evident 

 that the method itself can hardly be made a practicable 

 one on a large scale in the field. The expense and trouble 

 of inoculating cattle on twenty different occasions would 

 be very great. It is apparent now that Prof. Koch fell 

 into error through mixing up East Coast Fever with 

 ordinary Redwater. His plan of preventive inoculation 

 was, however, tried on a large scale in Rhodesia by Mr. 

 Gray, now the P.V.S., Transvaal, and found to be useless. 

 At present, therefore, we must look to some other means 

 of preventing the disease and driving it out of the country 

 than preventive inoculation. 



Dipping. — Much can be done to prevent the spread of 

 this disease by ordinary methods. For example : in the 

 case of Texas Fever in Queensland dipping cattle in solu- 

 tions of arsenic or paraffin, in order to destroy the ticks, 

 has met with very fair success ; but in the case of this 

 disease we cannot expect to get as good results as in the 

 case of Redwater. The species of tick which conveys 

 Texas Fever remains on the same animal through all its 

 moults, instead of falling to the ground between each 

 different one. If it is not possible to spray or dip cattle 

 oftener than once in ten or fifteen days, it is evident that 

 ticks may crawl upon such animals, become infected, and 

 drop off every three or four days, and so escape destruction 

 by the dipping solution. At the same time every infected 

 tick that is killed by spraying or dipping operations is a 

 source of infection destroyed. 



Fencing of Farms. — Again, the fencing of farms must 

 also be useful in the same direction. As the ticks do not 

 travel to any extent when they fall among the grass, it 

 is evident that the cattle on a clean farm which is properly 

 fenced will not become infected by this disease, although 

 all the country round about should be infected. This 

 fencing of farms and subdividing the farm itself into 

 several portions is a most important factor in the preven- 

 tion of contagious diseases amongst stock. It is, of 

 course, impossible that this can be done at once, as the 

 expense would be prohibitive. 



Moving Cattle from Infected Pasture to Clean Pasture. 

 — From a study of this disease and a study of the life- 

 history of the tick it is evident that by a combination of 

 dipping or spraying the cattle so as to destroy almost all 

 the ticks, slaughtering the sick, and moving the apparently 

 healthy on to clean veld — and repeating this, if necessary, 

 a second or third time — it is obvious that by these means, 

 if circumstances are favourable, an outbreak of this disease 

 may be nipped in the bud without much loss to the stock. 



Stamping out the Disease. — In May, 1904, an inter- 

 Colonial Conference held at Cape Town resolved that the 

 only effective method of eradicating East Coast Fever is 

 to kill off all the cattle in the infected areas, and to leave 

 such areas free of cattle for some eighteen months. By 

 this means all the centres of infection would be destroyed, 

 and at the end of eighteen months, as all the infected t'icks 

 would be dead, it is evident that the disease would be 

 completely stamped out. There is no doubt that this 

 NO. 1872, VOL. 72] 



drastic method would be the quickest and most complete 

 one of getting rid of this extremely harassing disease. 

 If compensation were given, it could be done at a cost of, 

 say, a quarter of a million. The Government decided, 

 however, that on account of the difficulty of carrying out 

 such a drastic scheme another policy had to be considered. 

 This policy provides for the fencing-in of infected farms, 

 places, lands, or roads, on generous terms ; the compulsory 

 slaughter of stock with compensation in the case of isolated 

 outbreaks ; the removal of all oxen from infected or 

 suspected farms ; and, lastly, the stabling of milch cows 

 in infected areas. It is quite evident that under this less 

 drastic policy the final stamping-out of the disease will 

 be a much slower process than if the more drastic scheme 

 of compulsory slaughter of all cattle on infected areas 

 had been carried out. The benefits, however, from the 

 modified scheme are undoubted ; and if carried out 

 thoroughly and intelligently for a period of several years 

 will probably result in the stamping-out of the disease. 



Allow me to sum up in regard to the advance in our 

 knowledge of this important stock disease during the last 

 ten years. Ten years ago nothing was known. Now the 

 causation of the disease has been .made out very fully ; 

 the parasite that causes it is known ; the ticks which carry 

 the infection are known. Although no method of con- 

 ferring immunity on healthy cattle has been found out, or 

 any medicinal treatment discovered which will cure the 

 sick animal, yet our knowledge of the life-history of the 

 parasite and the ticks enables regulations to be framed 

 which, if patiently carried out, must be crowned with 

 success. 



(2) Redwater or Texas Fever. 



I may dismiss this disease in a few words. It is a most 

 interesting disease and of great importance to stock 

 farmers. It only affects cattle. 



Geographical Distribution. — It is a disease found in 

 almost every part of the world. It was first studied in 

 North America ; hence the name Texas Fever. Tc 

 Kilborne and Smith is due the honour of elucidating the 

 causation of this disease, and their work forms one of 

 the most interesting chapters in the history of pathologica.- 

 science. They discovered that it was caused by the 

 presence in the red blood corpuscles of a protozoal para- 

 site closely related to the parasite found in E.C.F. — the 

 Piroplasma parvum. This organism is called Piroplasma 

 bigeminum. They further discovered that this parasite 

 was conveyed from sick to healthy cattle by means of a 

 tick. They also showed that the cattle born and bred in 

 certain southern districts are immune to the disease, 

 whereas cattle in the northern districts are susceptible. 

 Hence, if southern cattle were driven into the northern 

 district, they gave rise to a fatal disease among the 

 northern cattle ; and, vice versd, if the susceptible northern 

 cattle were driven into the southern district among the 

 apparently healthy cattle of that district, they took Texas 

 Fever and died. 



Texas Fever was introduced about 1870, and is now 

 endemic throughout most of South Africa. For many 

 years the native cattle have been immune to the disease ; 

 that is to say, on account of being born and bred in a 

 Texas Fever localitv thev had inherited a degree of resist- 

 ance to the disease which enabled them to pass through 

 an attack when they were young, and so they became 

 immune. But there is one peculiarity about Texas Fever 

 which does not occur in Rhodesian Tick Fever, and that 

 is that the blood of an animal which has recovered from 

 Texas Fever remains infective — the germs remain latent 

 — and so the native cattle of South Africa, although 

 apparently healthy, are capable of infecting imported 

 susceptible cattle with this very fatal malady. This is 

 what makes it so difficult to import prize stock into this 

 country. 



When the Boers visited Mooi River, at the beginning 

 of the war, they found a prize short-horn carefully stabled 

 in Mr. P. D. Simmon's farm. They killed most of his 

 stock for food, but left this short-horn bull alive. When 

 they left the farm they turned this bull into the nearest 

 field, in order, of course, that it might procure food. 

 They had much better have eaten it. It promptly took 

 Texas Fever and died. 



This disease, then, has become of secondary importance 



