Ti:!'". INFLUENCE OF THE CLfMATIC AND TEL- 

 LURICAL FACTORS ON THE DISTRIBUTION AND 

 SPREAD OF CERTAIN ANIMAL DISEASES, WITH 

 SPECIAL REFERENCE TO THE CONDITIONS 

 OCCURRING IN SOUTH AFRICA. 



By D. Kehor, M.R.CA'.S. 



It is the belief of the writer that the interest attached to the 

 collection of results obtained throug^h specialised researches, and 

 the co-ordination of these in such a way as to jwint out their 

 influence on conceptions reo^arding- the relationships existing" 

 between certain causes and certain effects, is in itself sufficient 

 justification for presentation of a paper of the nature of the 

 following to the members of an Association as ours, consisting 

 as it does of persons who are interested not only in the advances 

 made in their own particular branches of science, but who are 

 also interested in learning of general advances made in fields 

 outside of their own. If, however, justification were needed for 

 the selection of the subject, it is to be found in the marked 

 interest shown by the majority of the members of our commu- 

 nity in South iVfrica in the marked prevalence of certain of our 

 stock diseases luider the rather unusually wet climatic conditions 

 prevailing during the early part of this present and latter part of 

 the past year. At that time one was often asked for an explana- 

 tion of the state of affairs existing in regard to the prevalence 

 of these diseases, and equally often limitations imposed by time 

 enforced a brief reply to such queries. In the paper which 

 follow's, however, an atteiupt is luade to furnish a general reply 

 to questions of this nature, although even here the same limita- 

 tions as those before referred to do not allow of any more than 

 the main points to be dealt with and the outlines of the subject 

 to be indicated. It is, however, hoped that these outlines given 

 here may furnish some ideas of the relationships existing between 

 certain diseases and the environment in which they occur, and 

 if this paper should stimulate an interest in the subject in those 

 who, having no specialised interest in disease problems, }'et have 

 that general interest in all problems aff'ecting the welfare of the 

 community which is demanded from every th.inking individual, 

 the purpose of the writer will have been fulfilled. 



With these remarks we shall, then, first proceed in an intro- 

 ductory fashion to a more general consideration of the subject, 

 later coming to examine the matter in fuller detail. 



Now, many of Our South African, stock diseases are of such 

 a natiu-e that they hapi^en to be included under the headings 

 of tropical or subtropical diseases, and here we meet with two 

 terms which in themselves suggest a classification based on clima- 

 tic distribution. If we enquire into this grouping- more closely, 

 however, we find that a classification of this nature is one founded 

 on considerations of convenience rather than of accuracy, which 



