September 14, 1905] 



NA TURE 



497 



but I have no doubt his successor, Mr. Gray, from 

 Rhodesia, will continue the good work begun by him. 



East Coast Fever was first studied by Prof. Koch at 

 Dar-el-Salaam, in German East Africa, and he at first 

 mistook it for ordinary Redwater. It seems to occur as 

 an endemic disease along a great part of the East Coast 

 of Africa, but appears to be restricted to a narrow belt 

 along this coast-line. The cattle inhabiting this region 

 have become immune to the disease, and are, therefore, 

 not affected by it. Cattle passing through the Coast 

 •district to the interior, or brought to the Coast district 

 from the interior, are apt to take the disease and die. 

 It was by the importation of cattle, therefore, which had 

 passed through the dangerous Coast district that the disease 

 was introduced into Rhodesia and into the Transvaal. 

 On this map which I throw on the screen I have marked 

 ■out the probable endemic area of this disease, and in the 

 ne.\t slide the present distribution of the disease in the 

 Transvaal is also marked out. 



Nature of the Disease. — This disease only attacks cattle, 

 but in them is an exceedingly fatal malady : in every 

 hundred cattle attacked only about five recover from the 

 disease. The duration of the disease after the first 

 symptoms have occurred is about ten days. 



The cause of the disease is a minute blood parasite 

 called the Piroptasina parvum (Theiler). This parasite 

 lives in the interior of the red blood corpuscles. 



I now throw on the screen a representation of the blood 

 from a case of Rhodesian Redwater, magnified about a 

 thousand times, showing these small piroplasmata in the 

 Interior of the red blood corpuscles. As in the case of so 

 many of these blood diseases, the parasite causing it is 

 carried from the sick to the healthy by means of a blood- 

 sucking parasite. In this particular disease the tick which 

 most commonly transfers the poison or living parasite 

 from one animal to another is known as the " brown 

 tick," Rhipicephahis appendiculatus. Koch supposed that 

 the common " blue tick " was the agent. The credit 

 belongs to Dr. Lounsbury and Dr. Theiler of having shown 

 that it is chiefly the "brown tick" which acts as carrier; 

 but Theiler has proved that R. siiniis is also able to 

 transmit the disease. Without the intervention of a tick, 

 so far as we know at present, it is quite impossible that 

 the parasite of this disease can be transferred from one 

 animal to another. For example, if we take a quantity 

 of blood containing enormous numbers of these piroplas- 

 mata, and inject it into the blood circulation of a healthy 

 animal, the latter does not take the disease. In the same 

 way, if cattle affected by East Coast Fever are placed 

 among healthy cattle in a part of the country where none 

 of these ** brown ticks " are found, the disease does not 

 spread. It is evident, therefore, that some metamorphosis 

 of the parasite must take place in the interior of the tick, 

 and this new form of the parasite is introduced by the 

 tick into a healthy animal, and so produces the disease. 

 In this particular disease the virus or infective agent is 

 not transmitted through the egg of the tick, as is the 

 case in some of these parasitic diseases, but only in the 

 intermediate stages of the tick's development ; that is to 

 say, the larva which emerges from the egg of the tick is 

 incapable of giving the disease. What happens is this. 

 The larva creeps on to an infected animal and sucks some 

 of its blood. It then drops off, lies among the roots of 

 the grass, and passes through its first moult. The 

 nvmpha, which is the name given to the creature after 

 its first moult, is capable of transferring the disease to a 

 healthy animal : that is to say, if it crawls on to a healthy 

 animal and sucks blood from it, it at the same time infects 

 this healthy animal with the germ of E.C.F. In the same 

 way, if a nvmpha sucks infected blood from a sick animal, 

 it is able, after it has moulted into the adult stage or 

 imago, again to give rise to the disease if placed, or if 

 it crawls, upon a healthy animal. 



Tile Life-history of the Brown Tick. — I throw on the 

 screen a slide representing the four stages of the life- 

 history of the brown tick : The egg, the larva, the 

 nympha, and the adult or imago. The eggs are laid on the 

 surface of the ground by the adult females, which deposit 

 several thousands at a time ; and these hatch out naturally, 

 if the weather is warm and damp, in twenty-eight days. 

 But this period of incubation of the eggs may vary very 



NO. 1872, VOL. 72] 



greatly owing to differences in temperature. Immediately 

 after the larva is born it crawls to the summit of a blade 

 of grass or grass stem, and there awaits the passage of 

 some animal. If an ox passes by and grazes on the 

 grass, the tick at once crawls on to the animal, and, 

 having secured a favourable position, starts to suck the 

 ox's blood. It remains on the ox for some three or more 

 days, when, having filled itself with blood, it drops off 

 and lies among the grass. The first moult, under favour- 

 able conditions, takes twenty-one days, when the nympha 

 emerges. In the same way the nympha crawls on to an 

 animal and fills itself with blood. As a nympha it also 

 remains on the animal for about three or four days. It 

 again drops off into the grass, and at the end of eighteen 

 days emerges from its second moult as the perfect adult 

 male or female. The males and females again crawl on 

 to an ox, where they mate. After this the female tick 

 ingests a large quantity of blood, which is meant for the 

 nourishment of the eggs, and again drops off, sometimes 

 as early as the fourth day, into the surrounding grass. 

 .'\fter about six days she lays her eggs in the ground, and 

 the cycle begins again. 



These ticks are very hardy, and in the intermediate 

 stages can resist starvation for long periods, so that a 

 larva or nympha or adult tick may remain perched at the 

 end of a blade of grass for some months without finding 

 an opportunity of transferring itself to a suitable animal. 

 On this account it comes about that even if all infected 

 cattle are removed from a field the ticks in that field will 

 remain capable of transferring the infection to any healthy 

 cattle which may be allowed into this field for a period 

 of about a year. At the end of a year or fifteen months, 

 however, the infective ticks are all dead, and clean cattle 

 may be allowed into the field without any risk. If one 

 takes these facts into consideration it will be seen that a 

 single ox mav spread this disease for a distance of some 

 200 miles, if 'trekking through the country at the average 

 rate of ten miles a day. For example, an ox is infected 

 by a tick ; for fourteen days the animal remains apparently 

 perfectly well ; it has no signs of disease, nor has it any 

 fever. It is capable of doing its ten miles' trek a day. 

 At the end of fourteen days the temperature begins to rise, 

 and the animal begins to' sicken with the disease, but for 

 the next six days the ox is, as a rule, able to do its 

 ordinary day's march. During most of this time the 

 brown 'ticks' have been crawling on to this ox, becoming 

 infected, and dropping off every three or four days. It 

 can readilv, therefore, be seen how much mischief a single 

 infected animal can do to a country between the time 

 of its being infected by the tick and its death some twenty- 

 four days later. As a matter of experience, however, the 

 disease has never been found to make a jump in this way 

 of more than fifty or sixty miles, as, of course, it is very 

 rare that a transport carrier will take his oxen more than 

 that distance during the twenty days. 



.\t the present time it may be said that there are about 

 500 infected farms in the Transvaal. During last year 

 some 15,000 cattle have died of the disease, and in the 

 affected districts it may be said that there are still some 

 30,000 cattle alive. When one considers the value of the 

 cattle dead of this disease, which may be said to be about 

 200,000;., it is evident that money spent on the scientific 

 investigation of the causes and prevention of stock diseases 

 is money well spent. I am informed that all the South 

 African 'Governments are cutting down their estimates 

 this year, and are inclined to reduce their veterinary staffs 

 and 'the amounts devoted to research regarding animal 

 diseases. Ladies and gentlemen, if this is so, I have no 

 hesitation in saying that this is the maddest sort of 

 economy and the shortest-sighted of policies. 



Methods of combating the Disease— During the last 

 three years an immense amount of work has been done 

 in the' elucidation of this disease — how the animals are 

 infected, how the poison is spread from the sick to the 

 healthy,' and so on. In 1903 Prof. Koch was asked by 

 the South African Colonies to study this disease, in order 

 to try to find some method of artificial inoculation or 

 some other means of prevention. He did his work in 

 Rhodesia, and especially directed his energies towards dis- 

 covering some method of preventive inoculation. At first 

 it was thought that he would be successful in this quest. 



