CO885-(21-23) — Page 562

PUBLIC RECORD OFFICE

Reference :-

C.O. 885

22 PUBLIC RECORD OFFICE, LONDON

ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO

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The origin of the disease is, of course, a matter of conjecture, but it seems clear that it came from the south, i.e., from Uganda proper, and was apparently intro- duced at first by the domestic herds. (See Part II. of this report.)

In previous times, 15 to 30 years ago, all this district was a thriving cattle country-the Hoima District and Butiabwa, especially the latter, are so still. I have not had the opportunity of examining the herds myself, but European and native accounts all concur in saying that there are large and healthy herds in these places. The deductions being (1) that serious permanent foci do not exist at the present time in these parts (viz., the Hoima and Butiabwa Districts); (2) that the infection of the Masindi country is relatively speaking recent, i.e., within the last 10 years.

The evidence for supposing that the trypanosome diseases have spread to the game from domestic cattle in the first instance lies in the fact that the Butiabwa District contains fly, game, and cattle all in the usual close contact without the disease having appeared, the reason for this immunity being apparently that the game, which travel round the bush to the north and east of Masindí from the Kafu District, In other are checked by the escarpment, and do not travel into the Butiabwa area. words, as the game area is not continuous there is no continuity of the reservoir of trypanosome diseases. Similarly the game area on the south of the Kafu, in the Buruli District of Uganda, is not continuous with the game area on the north of the Kafu, and one seems justified in concluding that domestic herds were responsible for bringing the trypanosome diseases into the country north of the Kafu. The moving of diseased domestic herds must, therefore, be looked upon as an important link in the connecting up of game areas separated by natural barriers. (For addi- tional evidence see Part II.)

A close study was made of the country round Masindi, more especially of a small area comprising the Bigando Hills. There had never been any sign of cattle disease up to 1912.

This country contains a good number of villages well separated from each other by the configuration of the hills; they are all reckoned to be outside the fly-belt, but the limit of the cultivation runs into the bush.

In almost every case the cattle are herded on the bush side of the villages, but do not go further afield than at most a mile, generally much less. The herdsmen never admit to seeing tsetse, but they generally say that" mbara" and "bijuju " are present, meaning, roughly. Hæmatopota and Tabanide. Unfortunately neither Europeans nor natives seem, in the ordinary course of events, to distinguish between the common brown Hæmatopote (H. hinta) and tsetse. My fly-boys followed the herds here for days, and never caught a single tsetse, although a very fair number of Hæmatopota and Tabanide were always brought Chrysops was never seen in the Masindi District. An examination of these herds gave practically the same result, roughly 15 to 20 per cent, of all the cattle showed T. vivax. (Details of all herds examined are given in Part. II.)

Kiamugweri, Bigando, Kisoga, Kibali, Butobe, and Kijambura had all an almost identical history. The cattle had been in their present herding places for years, no cattle had been brought since about 1903, when one man had got some cattle from Bukedi. There were no changes of any significance in the pasture lands or watering places, and up to 1912 there had only been occasional deaths among calves from "

Makebe" and rare isolated deaths clearly due to other causes. In every case these Bigando herdsmen placed the beginning of the disease during some part of the year 1912. One man did not seem to have recognised the disease though his herd proved infected when examined. This suggests that in this instance the first infection occurred in the early part of 1913.

It may be mentioned in passing that with very rare exceptions information was readily given; in many cases the clinical symptoms of trypanosomiasis were well known and accurately described. Herdsmen varied greatly in intelligence and observation, but in many instances recognised quite early cases, and asked very perti- nent questions. On two occasions I was asked, if the fly were responsible for the disease, would the man who herded the cattle not take it also if bitten?. Native observation has connected the game with the disease, but says it is the saliva left by the game upon the grass that infects the cattle. The danger of mixing sick and healthy herds was often, though not always, well understood, and in some instances spontaneous protests were raised against the moving of herds or even of individual cattle from sick to clean districts.

There was a definite seasonal incidence in the case of some herds, suggesting that the infection takes place in the rainy months.

Examining the herds in June and July, I found quite recent cases. These can be recognised by the presence of the trypanosome and the absence of macroscopic signs

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of disease. All fairly recent cases up to three or four months more or less can be diagnosed by direct microscopic examination; this is also true of rapid virulent cases up to the end. Chronic cases, however, may live for some months in an enfeebled emaciated state without showing trypanosomes in the blood-subinoculation may even fail to reveal them-the animals always die in the long run,

The interest in the Bigando herds lies in the fact that one has clearly got a new Locus-not a sudden epidemic, but the gradual arrival of the disease, and the estab- lishment of what is now a definite centre of infection without the introduction of sick cattle from other parts, and without any alteration of the conditions under which the herds were kept.

As the trypanosome found in the Bigando District was T. vivax, it pointed clearly to tsetse as the carrier. Nevertheless Glossinidæ were never brought in, and the contact between the cattle and the carrier appeared to be so excessively slight that the infection seemed difficult to explain.

An investigation was then made into the condition of the fly in the morsitans belt and the following extraordinarily high percentage of infected individuals was found, namely 94 per cent.

From the foregoing analysis it may be said that if in the course of a year a herd of cattle met 200 Glossina morsitans from this fly-belt and supposing each fly bit only one individual of the herd, the chances are that 188 would be exposed to the infection of one or other of the trypanosomes represented in the district.

This is a fair enough way to handle the probabilities, for while it may be pointed out that no allowance has been made for morsitans carrying trypanosomes which are not yet in the infective state, this is more than balanced by the fact that, once infective, a tsetse continues to infect at every feed until the end of its existence. which may comprise a period of several months.

I may point out that 200 tsetse is an absurdly small number for a herd to meet in

the course of a year, granted that tsetses are present at all.

The very high co-efficient of infectivity among the morsitans was found equally among individuals caught in the very centre of the uninhabited area quite ten to twelve miles from herds of any kind, and those from the nearest point where fly were to be caught in satisfactory numbers. The food of the flies from the centre of the belt is the blood of the wild game, which is very plentiful in the bush, and one is led to the obvious conclusion that the wild fauna must constitute the reservoir for the trypanosomes in question. I have no doubt that were subinoculations to be made from game shot in this district the percentage of infected individuals would be found to be relatively very high.

There is no reason to assume that the flies round the Bigando Hills have increased in number in the last two years or so. There are very few at present, so few that only prolonged search during the wet season would show any at all. I only found one single specimen and the fly-boys never brought me any from this part of the country during June and July, though the rains had not yet ceased.

Bigando herds probably meet approximately the same number of flies as hereto- fore, only now their infectivity that is, the percentage of individuals carrying try- panosomes has risen to such a pitch that even the slightest contact between the herds and the morsitans is sufficient to cause a serious yearly loss among the cattle in this district.

All the above evidence seems to justify the deduction that the disease has spread through the game from the south, fly and game infecting each other, so that now there is a large area so heavily infected that herds cannot be kept in safety any- where in the vicinity. (See Part II.)

It is obvious that cattle transport in such a country is a grave danger to clean districts as an example of this I need only cite the eight transport cattle working from Masindi Station to Butiabwa along the Hoima road. On examination on July 9th, four of them showed trypanosomes (T. vivax and T. pecorum were the species involved), and in addition one animal, although not showing trypanosomes, was so emaciated as to leave no doubt that it was suffering from the disease; it died in the course of the next fortnight. These cattle were never worked through the fly-belt on the Masindi road.

The risk of these cattle carrying trypanosome disease into the fly ridden but apparently still clean area at Butiabwa is obvious this cattle transport has now been stopped.

The country to the north of the Masindi-Hoima Road appears to be free from disease, at least in the well-cultivated parts near the Hoima Rond.

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