PUBLIC RECORD OFFICE
། ། ། ། ། །
Reference :-
C.O.885
18 PUBLIC RECORD OFFICE, LONDON
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH—NOT TO
14
Also a disease (or diseases) called by the natives ruhinyo, muhinya, enya enya, and bihimbo, the names being, apparently, used indiscriminately and interchangeably, has received attention. An epidemic called by one or more of these names had been reported from Ankole, and, when Dr. Bagshawe arrived at Lake Albert Edward to investigate the epidemic there, about the only facts that he could gather were that there certainly was an epidemic, and that it was called ruhinyo.
Since, therefore, ruhinyo or muhinya had been rumoured to exist in the interior of Toro as well as in Ankole, and I had already instructed Dr. Lowsley, the Medical Officer of the latter province, to investigate it there, Dr. Bagshawe was at once directed to examine the inland epidemic of Toro. Dr. Bagshawe thinks, and agree with him, that there is little room for doubt that the epidemic which he then examined is beri-beri, a disease new to our experience in this country, and I append hereto his very careful and interesting report, with extracts from his later reports and also from those of Dr. Lowsley, whose description of the cases which he saw in Ankole is inconclusive, but bears some resemblance to severe dengue, a disease which was epidemic this year in the Protectorate.
I had hoped that an enquiry, as to whether Glossina morsitans and other tsetse flies can convey Trypanosoma gambiense could have been commenced ere this, but it has been found necessary to postpone it. It will, however, in all probability be undertaken shortly.
It is a matter of very grave importance, and especially so in the Nile Province, where, as I found during my term of residence, both Morsitans and Pallidipes are present, and, in some places, abound. They are to be found, probably co-extensive, from Northern Unyoro to the northern border of the Protectorate, and how far beyond this I am unable to say, but they become more plentiful just where Glossina palpalis has its limit, and, if unfortunately they can convey the infection, the epidemic may spread into the Sudan. My own belief is, however, that they will not prove to be natural carriers.
In my report already quoted (Note I.) I pointed out that there is no continuous "fly-belt" across the Uganda Protectorate, but the Glossina palpalis exists in certain circumscribed strips of narrow patches along the margins of lakes, rivers and streams. These areas I proposed to call "fly-areas," and the limit of flight from the waterside (Note 2)* at such places the "fly-range," reserving the term "fly-belt," which had been very loosely used, and had no well-defined meaning, to describe the limits of distribution across the continent. I have already used these terms above and I propose to adhere to the definitions throughout this report.
I also showed that the fly-areas and fly-ranges, both of which are local and vary with the locality, are much narrower than had previously been supposed; that, far from inhabiting swamps, the fly rather avoids them, and is absent or scanty on the truc shore, even if shaded, behind wide belts of swamp, while it is practically never met with on swamps pure and simple nor on swamp-filled rivers and streams (which I shall call hereafter, for the sake of brevity, "swamp rivers "); that the conditions most suitable to them are open water, however small in extent, contiguous shade and a certain amount of raised or definite bank. I recorded also the fact that Glossina palpalis was present on most or all of the inland streams which are open, with running water, wherever there was sufficient shade, and that, in the case of very narrow streams, this might be afforded sometimes by high or over-hanging banks or even by long grass.
I described how it is probable that in most cases sleeping sickness is conveyed from place to place by man, especially along main traffic routes, and from man to man, in suitable localities, by the fly; how in any epidemic area the local intensity of infection varies with certain physical and geographical conditions such as indented coastline, peninsulas, islands, rivers, swamps, shade, cliffs, open water, &c., which affect the fly, and how these conditions again interact with others, which chiefly concern the human inhabitants, to determine the magnitude of an epidemic and the direction of its spread, these last conditions being, chiefly, density of popula tion, relation of dwellings and occupations to local fly-ranges and the methods and frequency of intercommunication; and I showed how certain localities within or
• NOTE 2.-In the term "fly-range " the limits of flight along the water's elge are not taken into consideration. Flight in this direction may reach to long distances and is limited by local conditions. See page 16 below and also Appendix B.
15
in contact with fly-ranges are reciprocally infective, while others, beyond the fly- range, can be infective only via the fly-ranges, the chances of the spread of infection varying with the distance therefrom and the frequency and facility of communication therewith; also that it is possible for settlements well outside the local fly-ranges, if so situated as to be in frequent and easy communication with them, perhaps on several sides (as often happens in an island or a peninsula), to show a very high percentage of infection among their inhabitants, although the transmission of infec- tion is impossible within their precincts, and I attached diagrams to illustrate these points and also to show the probable method of extension of the Lake Victoria opidemic, the most probable connection between it and the Lake Albert and Nile epidemic and the probable direction of spread in the near future.
I will now give a short summary of what the various medical officers engaged in the extended investigations have recorded.
All agree that the haunts of Glossina palpalis are close to open water with shade, especially that of undergrowth and scrub. Dr. Bagshawe notes that the banks are often steep and generally have a decided slope. Dr. Densham mentions that most of the inland streams on which the fly abound (which are always open, flowing streams) have steep or definite banks. Dr. Wiggins describes a peculiar distribution on the Mpologoma River (which is so extensive that it more nearly resembles a great lake, the greater part of which is choked with sudd), where fly is absent on the numerous creeks, which run inland often for miles, choked with swamp and having no definite banks, while, in the few places where it is present, it is found on the true shores or those parts or points nearest the main body of the lake where, in all probability, the banks would be comparatively firmer and higher and there is more likelihood of the existence of patches or strips of open water at the sites of ferries, landings and dipping-places. Dr. Van Someren describes one of the few inland streams in his district on which fly was present as having very well-defined banks. We may take it, then, that the essentials of a typical fly-area are more or less open water, with contiguous and especially overhanging shade, preferably of scrub (though in very narrow streams high banks or even high grass may be sufficient), and a certain amount of fairly well-defined bank or shore, this last being essential, in all probability, for the breeding-grounds.
All the medical officers agree as to the absence or only occasional presence of fly on the true shore behind wide belts of papyrus or other luxuriant and close- growing swamp-vegetation, even though this shore may be well shaded and other- wise favourable to it, but they differ as to the width of such a belt necessary to ensure its absence. Dr. Van Someren found in his district that 30 yards and upwards was sufficient, and that flies are seldom seen either on the lake or shore side of such a belt, while the only width of belt mentioned by Dr. Wiggins behind which fly was absent is 100 yards. No doubt the necessary width varies in different localities and with other factors such as the abundance of flies, the amount and kind of food supply, the existence of canoe or other traffic through it with neigh- bouring fly-areas from which a certain number might be "imported," and with the length or extent of the belt along the shore or bank.
All are agreed that if, as occasionally is the case, especially where the sudd or swamp has floated in from elsewhere and has not grown out from a low, swampy shore, there remain patches or strips of open water at the true foreshore behind the swampy-belt, fly may be found at these places if the other conditions are favour- able to it, but that on the outer margins of even a moderately wide belt the fly is not found. Narrow belts of papyrus or other such vegetation are not antagonistic to the fly, nor are open reeds, nor other small or sparsely-growing water-weeds. I may add that the presence of ambatch-bushes at the true shore or in the water near it, since other vegetation seldom penetrates them to any great extent, always means the existence of a little comparatively open water, and is thus favourable to the fly, but by no means an invariable sign of its presence.
All are agreed that Glossina palpalis does not exist on swamp-rivers; and it is either absent or very scanty on the swampy parts of comparatively open rivers. Since practically all the inland waters of Uganda proper, Buddu, South and East Unyoro, and Western Usoga are of this nature, the very important fact remains that practically the whole interior of these regions is fly-free, and therefore "safe," country. The only notable exception to the above rule is part of the main trunk or basin of the Mpologoma which, as has just above been mentioned, is really a lake. There are also streams in South Usoga, apparently of a swampy nature, on some
Page 840Page 841
PUBLIC RECORD OFFICE
Reference :-
C.O.885
18 PUBLIC RECORD OFFICE, LONDON
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO
18
of which fly was found. It is not, however, clearly stated whether patches of open water existed in their course, but only that thick, overhanging shade and dense surrounding jungle were the rule upon their banks. Further, they were examined under the abnormal and most unusual conditions of flood and lake-level, referred to elsewhere. Dr. Uffmann records the presence of fly on streams near Munyunyu which were narrow and edged with papyrus, but with a clear central channel over- hung by shade. In my own experience the smallest trickle of a forest-stream is more likely to harbour fly than acres of stagnant swamp or miles of swamp-choked river.
Several of the Medical Officers give as their experience that the fly is absent from cleanly kept native banana plantations unless these abut directly on a water side, and that, even then, they are usually seen only at the edge of the plantation nearest the water. This accords entirely with my own observations, which showed that banana plantations 20 or 30 yards from the water, if there is little or no inter- vening bush or scrub, are safe, and that bananas by themselves, unless at the water's edge, do not afford sufficient cover for the fly. Small patches near the water and shut in by dense forest or jungle, or placed directly between this and the water, are, however, most dangerous.
Drs. Bagshawe, Van Someren, and Uffmann specially note, and I have often observed myself, the absence of fly along the shore at the open grassy spaces which form breaks in the jungle or forest-fringe of lake or river, and that at such spaces, even when comparatively narrow, there are definite gaps in the distribution of the fly. The two former note its absence both on the lake-shore and also at the forest edge, when the forest is separated even by only 20 or 30 yards of clear ground or It moderately short grass from the water, and this observation also I can confirm. is important in clearing to remember that the long-shore range is naturally, and can be artificially, limited by open spaces (see Note p. 14, and also Appendix B.).
Dr. Van Someren describes one very curious and unusual condition under which Glossina palpalis was absent from the lake-shore. The Gwamba swamp, which is long and very narrow, stretches for some miles along the coast of Buddu, separating the beach, which is a thin, sandy strip of slightly higher level than the swamp itself, and over which the lake washes in rough weather, from the forest or jungle fringe inland by a distance which is often only from 20 to 40 yards. This beach consists of a shelving bank, on the top of which are scrub, small trees and grass, all of which, the lake being open at this part and free from sudd, are favourable to Glossina palpalis, and yet it was never found either on the beach or at the forest edge except It at a few points where there were many open pools in the intervening swamp. it evident, therefore, that swamp, unless it contains open water and shade, is just as inimical to the presence of the fly as clear ground or open grass.
It was found that Glossina palpalis was never present in isolated patches of scrub or forest not contiguous with the water side, and I think it seems pretty certain that it is absent from all forest unconnected with lake-shore or river-bank unless such forest includes streams or open pools within its own precincts.
31
While the conclusions as to the habitat of the fly show little divergence, the recorded experience as to its local range, though varying a good deal, shows a satis- factory agreement with regard to its average extent, since no doubt one would naturally expect a greater local and seasonal variation of the range than of the physical conditions of the very circumscribed localities affected by the fly.
The average
"natural range (which term I will define presently) is put by Drs. Van Someren and Densham at 10-30 yards from the water, and the same distance over water to a passing or incoming boat, while Dr. Uffmann puts it at only 10 to 15 yards. Dr. Densham mentions that he has only once seen a fly in his camp, which was at the time 50 yards from the water, and that he has frequently attended to numerous sick natives in his various camps, at a distance of from 50 to 150 yards from water, without once seeing a fly, though he was always on the watch. On the other hand Dr Bagshawe found by direct experiment, at one of the rivers running into Lake Albert Edward, that flies came from the water to a distance of 50 to 80 yards, in a very short time, and in fair numbers, and bit some of his porters whom he had placed at these distances. Dr. Wiggins, too, while in South Usoga, frequently found fly, at any rate in one neighbourhood, half a mile, some- times a mile, and on one occasion two miles, from any known water, though in other parts of Usoga, e.g., on the Mpologoma, Nile and a few inland streams, he found much the same average range as the other observers, namely, 10-20 yards. His
17
observations in South Usoga, however, were made under such abnormal conditions as might not occur again for many years. Both Dr. Wiggins and Dr. Bagshawe have occasionally noticed Glossina palpalis in their camps or tents at distances of 300 yards or more from water, while Dr. Van Someren found fly at 300 yards from water on one occasion only, in a densely-wooded locality on the Sese Islands.
Dr. Bagshawe states, as a general rule, that wherever he has found a fly there has always been water, with overhanging shade, either on the spot or within 300 yards. All seem to be agreed that the distance which flies will follow from their haunts after their victims does not, as a rule, exceed 300 yards from water, though, on a few occasions, where they have found special facilities for shade, single flies have followed or been carried more than twice this distance.
The range over water seems to be much the same as on land, and Dr. Van Someren says that he finds 80 yards about the limit to which flies will "follow or accompany a canoe from the water's edge. This is very likely true for the majority of flies, as it is also on land, but a few will follow for longer distances, while individuals, especially such as are gorged, may, if they can find shade where they can remain undisturbed, as under the unoccupied thwart of a boat or in various parts of a vessel of any size, be carried for great distances. It is very unlikely, however, that, on a native canoe, where there is little shade and generally constant movement, flies would be carried more than a few hundred yards, and then it would be only occasional ones.
Several medical officers, and I myself also, have observed that Glossina palpalis can bite through clothing such as khaki or a flannel shirt, but they seldom attempt it, and much prefer feeding on the bare skin. No evidence has been adduced of their feeding on anything but vertebrate blood, with regard to which they are, so far as my observations go, omnivorous. Dr. Bagshawe has noted their abundant presence in regions where there were no crocodiles. There is general agreement that Glossina palpalis, though a lover of shade, is more active during bright sun- shine and less so in dull, cloudy weather, while during rain and high wind it retires almost completely. It is also less active, and, unless in places where it is very numerous, seldom seen, before 8 to 8.30 a.m. and after 4 to 4.30 p.m., though no period of the day is entirely safe from it.
This confirms what I have previously recorded (Note I.) and Dr. Van Someren mention's, in addition, that he has noticed a much decreased activity towards noon and lasting till 1 or 2 p.m. He also gives some interesting counts which illustrate what has just been said :-
7.30 a.m.
10 to 10.30
10.30 to 11
...
No flies
Two females six males Two females two males
11.30 to 12.30 p.m. Nil
A.M.
Cloudy and dull
Sunshine at intervals. Heavy rain
This count shows very
well the influence of dull weather in the sinall number captured and these only in bright intervals.
The following three counts were made at the same place on consecutive days :-
(1)
Hour.
Flies Caught.
e
(2)
Hour.
Flies Caught
A.M. A.M.
(3)
Hour.
Flies Caught.
A.M.
A.M.
7.45 to 8.45
2
7 to 8
4
A.M. 7.15 to 8.15
+
8.45
9.45
7
8"
9
25
8.15
9.15
4
31
19
9.45
10.45
17
9"
10
5
9.15 10.15
21
"
}}
10.45
11.45
21
10 »
11
10.15
11.15
11
"1
"
P.M.
P.M.
"
11.45 12.45
6
From 9-10 dull and
11.15 12.15
9
11
P.M.
8
cloudy. About 10 rain began and the flies disappeared.
P.M.
12.15 1.15
17
1.15 "
2.15
2.15 "
3.15
3.15 »
4.15
12.45 1.45
11
Bright sunshine con- tinued all the time.
:
Sunshine with cloudy
intervals.
5
3
28167
No comments yet.
Private notes are available after approval.