PUBLIC RECORD OFFICE
Reference :-
EL CO. 885
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO
24 PUBLIC RECORD OFFICE, LONDON
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reser-
infective flies is increasing. Certainly the antelope presumed to serve as voirs" are increasing numerically, and many more flies feed upon them than for- merly. At points, too, the fly is also increasing numerically as years pass.
The
3. There is also every reason for believing that in this region Trypanosoma gambiense is wholly dependent upon Glossina palpalis, its alternate host and vector. and that to exterminate the fly would be to eradicate the disease. environment supplied by the lake shore is frequently very favourable to the repro- duction of the fly. As long as it remains so any suppressive measures short of complete extermination can have but momentary effect, and complete extermination is quite impossible. But if the environment can be rendered permanently unfavour- able to numerical increase the fly is permanently suppressed. It depends upon its environment for food and protection; if it can be deprived of either the desired end is attained by indirect methods. These are much more likely to succeed than any direct methods of attack-i.e., as by trapping or catching the flies or destroying their young-for the reason above given.
4. In the course of the bionomic investigations it was found that whenever certain wild vertebrates occurred in connexion with vegetation of certain types, and not too far distant from certain combinations of soil and shade, Glossina was invariably found, and its distribution and numbers could easily be shown to be governed by the character of "shelter," by extent, character, and location of breeding grounds" which afford necessary protection to adults and young, respect- ively), and by abundance and distribution of its hosts (any one of which may be its sole source of food, and during all its stages). It is believed if any one of these three requisites were absent that it could not exist. There are, therefore, three methods by which it may be suppressed, any one of which will suffice if thoroughly carried out:-
5.
(a) By extermination of hosts, or by preventing the fly having access to
them.
(b) By clearing away of shelter.
(c) By destruction of breeding places.
The second mentioned, under the designation of "clearing measures," has long been employed for local protection. Bush or forest is cleared from roadsides. ferry heads, boat landings, etc., in infested regions; the flies avoid the spot, and traffic is safeguarded. The actual number of flies inhabiting the region is not necessarily reduced unless breeding places are included in the cleared area or hosts interfered with in some way. Nothing has been done except to deprive the fly of easy access to one of its hosts-man.
The extermination of favoured 6. The point is one that merits attention. hosts (crocodile, varanus, etc.) would be difficult, if not impossible, to accomplish locally, on account of their amphibious habits and freedom of movement from place to place. But the success of local clearing measures above mentioned has proved that Glossina palpalis can be prevented from feeding on any particular hosts locally. It will be unnecessary to exterminate the hosts, and sufficient to keep host and fly apart.
7. In logical extension of such local clearing measures. much larger clearings have been made at the several lake ports, when it is requisite that they should be inhabited. The largest is at Entebbe, where several miles of foreshore are included. The results are very satisfactory, but they are not altogether attributable to clearing of shelter, because, in addition, very extensive breeding places have been destroyed, and the wild hosts driven away or the fly separated from them. All of the possible methods for indirect suppression have thus been more or less thoroughly carried out, although any one of them alone ought to have been equally efficient. It
really due. is quite impossible to state to what the successful outcome
away
Formerly
8. As an object lesson the clearing at Entebbe is most valuable. the shore was in no particular respect different from many of the more dangerous Now, in place of densely infested bush and forest, are reaches in the closed area. broad expanses of sward, which afford safe pasturage to numerous herds of cattle At several points are native villages and plantations; at another the Government gardens, with successful experimental plots of rubber, cocoa, coffee, and other tropical crops. It is a complete demonstration, not merely of the efficiency of indirect methods of suppressing Glossina, but of the many varied uses to which the land may be put, and of its great potential value for supporting human life.
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9. The work at Entebbe was undertaken as a sanitary measure, with the Whether or not the land was primary object of safeguarding public health. utilized for agriculture was a secondary consideration. But the facts are that, once cleared, it was thus utilized, and it is demonstrated capable of supporting a dense population and producing a great diversity of crops. Most significant of all, prac- tically all of it is proved capable of producing something, if nothing more than pasturage for cattle or goats. If the primary object had been to make use of the land to somewhere near the limit of its productivity it would have been similarly cleared as a necessary preliminary, and the fly, which stands as the only obstacle to reoccupation of similar reaches of shore, would have been completely eradicated without the expenditure of an extra penny.
10. To eradicate the tsetse as a mere incident in connexion with the economic development of infested regions is the ideal solution to the problems, but it is not immediately possible to do this. It is necessary to use all the land, not bits of the best of it scattered here and there; and not all of it is good. The country, in pro- portion to its capabilities for supporting life, is very sparsely populated, and back from the lake large areas of better land than much of that along its shore are lying equally idle. There are not people enough in Uganda, nor nearly enough, to make it worth anyone's while to cultivate the poorer acres. If there were more people, if economic pressure sufficient to make utilization of the idle land worth someone's while could be diverted from some other region and brought to bear in Uganda, there would be no tsetse problem.
11. The writer must confess to a conviction that the ultimate and only satis- factory solution to this problem will be found to lie somewhere in the direction thus indicated; i.e., in a thorough study of the economic situation, and in some scheme for the development of the agricultural resources of the region along truly economic lines. There are a great many other obstacles and impediments than the tsetse to development along present lines. Some are very serious. It is not improbable that some of these others would be found amenable to precisely the same treatment as this the tsetse. The practical difficulties opposed to any such course are numerous : is freely admitted; but if the practical benefits to be derived in the end are likely to he out of proportion greater, the problem is certainly worthy of further considera- tion in this light. But it is not within the writer's province to attempt such consideration. He must accept the economic status quo, and consider how, without modifying it in any way, Glossina palpalis can most. effectually and cheaply be suppressed.
It
12. The present Principal Medical Officer for Uganda, to whom credit for most of the success of local operations against the tsetse is due, and who realized that such thoroughgoing work as was done at Entebbe is capable of very limited application, has proposed a modification of it* which, in brief, limits clearing operations to a belt 200 yards in width along the shore. This revised scheme would, if it proved successful, represent a very long step in the interest of economy, but it has not been given a practical test. It might not, though it probably would, succeed; but, in the existing state of knowledge, it was impossible to give precise reasons why it would be likely to do so. Like the work done at Entebbe it involved not only clearing of shelter, but destruction of breeding places, and, in addition, it would serve to separate the fly from some of its most favoured amphibious hosts. appeared to the writer that a better understanding of the real effect of such clearing measures was essential to their economical application; it further appeared probable (at this particular stage in these studies, when the importance of the point brought out in paragraph 6 was not recognized) that the principal effect of clearing limited to 200-yard belts would be due to destruction of breeding places, the most and best of which are located in this area. But, taking the lake shore as a whole, only a small part of the 200-yard belt is good breeding ground; therefore, it might be pos- sible to reduce the requisite amount of clearing still further, and perhaps to bring the cost to within the limits set by the present economic situation. This was the motive actuating such of the earlier investigations as had an economic rather than a bionomic purely technical objective.
13. It was an open question, with partisans on either side, whether Glossina palpalis is equally dependent upon breeding places as upon food and shelter.
*
"Sleeping Sickness Clearing." Pamphlet by Dr. A. D. 1'. Hodges, C.M.G., Principal Medical Officer, Uganda Protectorate, dated 8th November, 1911.
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