The Distribution of Glossina in the Ilorin Province of Northern Nigeria
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THE DISTRIBUTION OF GLOSSINA IN THE ILORIN PROVINCE OF NORTHERN NIGERIA. By DR. J. W. SCOTT MACFIE, M.A., West African Medical Service. (PLATES I—VII AND MAP.) With the rapid development of Northern Nigeria, following the British administration and the completion of the railway from Lagos to Kano, problems hitherto of minor importance are continually coming into prominence. Amongst these the abatement of trypanosomiasis is a matter of medical and entomological interest. As the confidence of the people grows there is an increase of inter- communication, which inevitably involves a danger of the spread of such diseases as sleeping sickness from existing foci. In Northern Nigeria these foci are at present peculiarly isolated, but they will gradually lose their isolation as the efforts made to stimulate the agricultural development of the country meet with greater success and the growing demand for roads, feeders for the railway, and better means of transport, is satisfied. In a densely populated and naturally fertile country like Ilorin the problem of avoiding this danger is particularly insistent, but unfortunately also particularly difficult. In the neighbouring province of Kabba sleeping sickness is said to be endemic, and might readily move westwards with the opening up of the interior ; and in a large part of the province of Ilorin itself tsetse-flies already spread disease amongst the cattle and horses to such an extent that these animals cannot live. Nevertheless, during the dry season, herds of cattle pass, day after day, in an almost continuous stream along the highroads on their way to Lagos from the north. How many die on the journey no one can tell, for the fate of those that sicken is to be butchered by the way, and it is a common experience to come across a carcase hewn up and laid out for sale by the road-side (PI. I, fig. 1). The first step towards discovering some remedy for this waste of cattle and horses, and some means of opening up the country safely, would seem to be an adequate study of the distribution of the carriers of the disease, the tsetse-flies ; and it was with this object that, on being appointed to Ilorin in February 1912, I undertook to make a systematic survey of the province. Physical Features of Ilorin Province. The Province of Ilorin, which is estimated to contain some 6,300 square miles and supports a population of perhaps half a million of people, forms part of the south-westerly portion of Northern Nigeria. The greater part of the province lies in the area enclosed by the eighth and ninth parallels of latitude and the longitudes 4° and 6° E. On the north it is bounded by the River Niger and the province of Borgu, on the south and west by Southern Nigeria, and on the east by the province of Kabba. It is divided into three sections, the western, the (29262—2) Wt. P 11—21. 1000. 6/13. D & S. A 2 J. W. SCOTT MACFIE—THE DISTRIBUTION OF GLOSSINA eastern or Patigi, and the southern or Offa divisions. These are known respectively as divisions 1, 2 and 3, and each in its turn is sub-divided into a number of districts. Dr. J. D. Falconer in his " Geology and Geography of Northern Nigeria " thus describes the orographical features of the province :—" The primary watershed of the Niger basin which runs from Kabba to Aiedi und thence westward a few miles south of the Ilorin frontier, is not defined by any range of hills or mountains, but by the crest line of a lofty plain which, like a low, extended arch, slopes gently northwards towards the Niger."* Across this plain six rivers—the Weru, Anwa, Oshin, Oyi, Oro and Kampe—run in an approximately parallel direction northward to flow into the Niger. The ultimate courses of the first two are doubtful and it is probable that before reaching the Niger they join in the manner indicated on the map. " To the west, Ogga [in Kabba] and Eri are set within a cluster of rocky hills, while to the north there is a comparatively rapid fall to the plains of the Kampi. Between the Kampi and the Niger a steep-sided range of sandstone hills, capped by the pinnacle peaks of Bgbom, runs out westward in a succession of rounded ridges two hundred feet above the level of the river, and not until near Share is the river belt of sandstones again bounded by a low escarpment. The Shappa and Orissa Hills form the only prominent range in central Ilorin. The Shappa Hills are of granite, and many of the peaks are gracefully rounded and most picturesque, while the quartzites and gneisses of the Orissa Hills give more rugged and irregular contours. West of the Orissa Hills lies the great plain of Ilorin, thickly populated and well cultivated, in broad undulations trending generally north and south, with scattered inselberge and many kopjes of granite boulders, but with no conspicuous ranges or groups of hills. The Jebba Hills, which extend southward for some distance towards Ilorin, pass westward into an extensive tract of hilly country, high-lying, little known and largely uninhabited, which forms a natural boundary between Ilorin and Borgu."t The types of scenery are fairly represented by the photographs reproduced in this article to illustrate the haunts of various species of tsetse-flies. Dr. Falconer summarises their characteristics as follows :—" In Kabba, Ilorin, and Borgu, where crystalline rocks of a granitic or gneissic character cover by far the larger part of the surface, the prevailing and most characteristic type of scenery is that of rolling sandy plains with isolated hills or groups of hills rising abruptly above the general level. On the other hand, where sedimentary rocks, such as sandstones and ironstones, cover the surface, as in the river belt of sandstones in Kabba and Ilorin, the characteristic type of scenery is that of steep-sided and flat-topped ranges and plateaux, with detached tabular and conical hills rising from the lower plains."J Throughout the greater part of the province the vegetation is open bush, scattered with hardy trees that are able to withstand the annual bush-fires. The country occupying the whole of the central part of Ilorin may be described generally as undulating park-like land, well-farmed and dotted with trees, with * Geology and Geography of Northern Nigeria, 1911, p. 16. f J D. Falconer, Geology and Geography of Northern Nigeria, p. 18-19. % Op. cit. p. 20-21, IN THE ILORIN PROVINCE OF NORTHERN NIGERIA. only occasional patches of bush, and thin belts of trees along the banks of the streams. Dense forest-belts occur, however, in the low-lying strips of swamp near the edge of the Niger valley, in the neighbourhood of the Kampe River, in the south-eastern corner of the province, and along the southern boundary as far west as Offa. On the whole, the province is thickly populated, but there are in the eastern division two districts which are almost entirely uninhabited, the one lying between the rivers Oyi and Kampe, and the other across the Kampe towards Kabba. These districts, which had been depleted of their inhabitants by slave- raiders, are gradually being reoccupied. The north-western portion of the province is also very sparsely populated. Game is scarce in the more densely populated districts. In the east and the south-east, however, hartebeeste, roan, cob, bushbuck, and duiker occur in fair numbers, and a few waterbuck, reedbuck, and buffalo. Game is also fairly plentiful to the north-west of the River Weru, around Jebba, and in some parts of Shari district. Climate and Rainfall. As the distribution of tsetse-flies is intimately associated with the meteorological conditions, a few words must be said about the climate of Ilorin. For this purpose I reproduce below the table of observations for the year 1909 as pub- lished in the official Gazette. This year has been selected because it is the latest in which continuous records have been returned for the whole twelve months. Meteorological Record, Ilorin, 1909. Temperature. Rainfall. Wind. Shade Shade Range. Mean. Amount Degree of Maximum Minimum. in inches. Humidity. January . 97 53 44 79.5 .79 65 W. February. 99 71 28 84 1.18 69 W. March 98 68 30 83.9 5.30 71 S.W. April 100 67 33 82.3 7.78 76 S.W. May 98 68 30 81.8 7.12 78 S.W. June 94 66 28 80.2 8.32 81 S.W. July . 92 67 25 77.3 9.49 81 S.W August . 92 68 24 77.7 4.92 82 September 90 67 23 78.1 14.12 82 S.Ww.. October ... 95 65 30 80.3 4.74 82 S.W. November 99 66 33 81.8 .23 70 w. December 102 52 50 78.3 1.19 65 w. Averages and 96.3 64.8 31.5 80.4 65.18 75 S.W. Totals. From an examination of this table it will be seen that the climate of Ilorin is humid and equable. The extremes of temperature for the year quoted were 102° F. and 52° F., whilst the mean was 80° F. ; the average degree of humidity 29262 A 2 4 J. W. SCOTT MACFIE—THE DISTRIBUTION OF GLOSSINA was 75, and the rainfall, 65.18 inches, was one of the highest recorded in Northern Nigeria. The province of Ilorin, as might be expected from its geographical position, differs in climate to a marked extent from the more northerly regions.