lM-'LL"liXCli OF CLIMATE Oi\ ANnJAL DlSliASlC. 4S7 



Bruce made his original observations, the disease is stih cxi-tent. 

 Following- the outbreak of the epidemic of rinderpest which, 

 entering the northern portion of South Africa in the }ears 1896 

 and 1S97. s\\-e])t down tlirough this country, the number of Clos- 

 siiia tiies is said to ha\'e decreased in Zululand simultaneously 

 with the decrease in number of the game animals killed there 

 by the epidemic. Since the time, however, that the rinderpest 

 disappeared, both the " tiy " and game have increased in number 

 up to the present day. In tlie Transvaal, on the other hand, and 

 following the same epidemic, trypanosomiasis and the " tiy "" 

 carrying it disappeared entirely from the east i)ortion of 

 this territor}-. I^revious to the rinderpest the tly was well k'nown 

 in this part of the country, and that it ma\- h.ave had a wider 

 distril:)ution is indicateil l)v a fact referred to by Theiler, which is 

 that on an old map of the Transvaal, ])ublished by Jeppe many 

 years ago, the country above a certain line is m;irked as infested 

 with " fly." This line has its lower extremity situated near the 

 jimction of the Marico and Crocodile Rivers, and from here 

 runs north-east through the Waterberg district u]) to the Lim- 

 popo. Theiler also mentions certain " voortrekkers " as having 

 told him that 30 or 40 years ago they n;et with tlie " fl\' '" north 

 of Pretoria, and not far from the Magaliesberg. Into this point;, 

 however, and also the explanations suggested tb accoiuit for the 

 disappearance of the " fly " from the North-East Transvaal, we 

 cannot further enter here, but these remarks, ho\\ever, made 

 here chiefly because of their general interest, will also show that, 

 whatever parts certain hosts may play in determining the distribu- 

 tion of flies of the genus Glossiiio. the climatic and tellurical con- 

 ditions of the North-East Transvaal Avere suitable to the existence 

 of the " fly " there some years ago — and they ma}' still l)e so — 

 and that in Zu.luland they are suitable to the fly even at the 

 present day. 



Let us then now pass from trypanosome diseases and pro- 

 ceed to consider the two other diseases needing no introduction 

 in South Africa, namel\-, horse-sickness and the disease of sheep 

 known as blue tongtie or malarial catarrhal fever. 



To commence with horse-sickness, we may note that it is 

 not a disease peculiar to Southern Africa, but has also been 

 recorded along the East Coast as far ui^wards as the Italian 

 Colony of Eritrea; in the Soudan; in some ])laces towards more 

 Central Africa ; and on the West Coast up to St. Paul de Loanda. 

 So far, it is not known fin-ther north on this latter coast — as, for 

 instance, in the Congo region — but its prevalence in what was 

 knowai as German South-West .Vfrica has been l)r()Ught home 

 forcibly this year through the numbers of e(|uines dying from 

 the disease dtu-ing the operations of the Union forces in that 

 territory. 



It has been noted in the areas where the disease is i)resent 

 in South Africa that it does not present the same degree of 

 severity in every year, "and certain epizootic ravag^es have even 

 become historical. One of the earliest of these referred tc is 



