Ideas which have influenced attempts to solve the problems of African trypanosomiasis

Sor SCI & Med Lol 138 pp 269 to 275

Peremm~ Press Lid 1979 Prmred ,n Great Brmm

IDEAS WHICH HAVE INFLUENCED TO SOLVE THE PROBLEMS

ATTEMPTS OF

AFRICAN TRYPANOSOMIASIS

JOHN FORD

2 Forge Close. Horton-cum-Studley. Oxford OX9 IBL

Abstract-One of the malor diseases affecting human beings and livestock in Africa. trypanosomiasis- known in its common human form as sleeping sickness-remains resistant to general eradication, covermg a wide belt across the middle of the continent. This is true even though the disease’s carriers- several varieties of tsetse flies-and tts need for an animal host IS well understood. This paper sketches the htstory of medical. public health, and development concepts that have attempted and achieved short-term and local eradication with a variety of methods. as well as the ecological consequences of these eradication measures, some quite devastatmg. More ecologically-attuned approaches to development than the simple removal of the tsetse are requtred in the trypanosomiasts belt if resource degrada- tlon and famine are to be avoided.

INTRODUCTION

In June 1925 the British Prime Minister created a sub-committee of the Committee of Civil Research .to prepare a scheme “aimed at controlling the tsetse-fly as a carrier of human and animal trypanosomiasis and as a preventive and curative treatment of the human and animal disease” [I], Some 20 years later Sir Henry Tizard. then Chief Scientific Adviser to His Majesty’s Government. referred to this sub-committee as follows: “The Committee on tsetse fly control was still sitting in 1938 without any noticeable effect on the expectation of life of these pests” [2]. If for 1938 we write 1978 the words are still true. Moreover, the British Committee is now only one of several national and international committees and there have been, since about 1947, a continuing succession of confer- ences and seminars. This year the United States has become the principal mover in setting up yet another body of experts with an object identical with that of Mr Stanley Baldwin in 1925.

This sounds like a record of abysmal failure. Of course it is nothing of the sort. There is a whole range of techniques for getting rid of or for controlling tsetse flies: human and animal trypanosomiasis can be cured and chemoprophylaxis has had many and often large-scale successes in preventing both human and animal infections. In some degree this was true before 1938; since the Second World War those responsible for the direction of studies have not failed to take advantage of new knowledge of the chemistry of pesticides, of advances in pharmacology and immu- nology and so on, while in physiology, ecology and ethology research has enlarged several fields of general scientific interest. But the application of this knowledge is slow-indeed in many areas retrogres- sion rather than progress is the rule. Why is this so? Have we backed the wrong horse? Or even. are we running in the wrong raa?

It is interesting to look back at some of the ideas which have influenced thought and action among those conarned with tsetse-borne disease over the last hundred years or so.

COMMON GENERALIZATIONS

One important idea must be noted. but not discussed. Earlier field workers on tsetse and trypanosomiasis shared the view of their feliow-countrymen. whether French or British, or Belgian. Portuguese or German, that they would succeed where the indigenous peoples had failed and that their successes would lead to spectacular improvements m the stan- dard of living of the inhabitants of the African continent. This confidence was based not upon the results of experimentation but upon the solid conviction of their superiority, moral as well as technicaL over Afri- cans in general. It i’s a view that still persists, but is outside the scope of this paper.

Another general idea was that the apparent back- wardness of African peoples could be attributed to prevalence of endemic diseases, particularly the trypanosomiasis of domestic livestock. The wheel was not used; transport, where there were no rivers or lakes. was by human porterage, since draught or riding animals could not survive. Cultivation was limited because there were no oxen to pull ploughs, to turn mills or to carry produce: and because of these deficiencies nutrition among the Africans was inferior to that of Europeans and Americans. And so on.

THE MORE DISTANT PART

It is only possible to guess at the effects of trypanosomiasis on earlier African history, for there is almost no evidence of specific constramts upon development or health. There have been, in various parts of Africa, a number of relatively highly organized societies which have achieved considerable cultural development in spite of having been located in areas. which, in the 19th century, become foci of both sleeping sickness and nagana. Whether or not their peoples consciously made efforts to achieve protection against infection, one does not know; although Swynnerton’s study [3] on the western border of Mozambique suggests strongly that the Nguni chief Mzila knew what he was about in creating large concentrations of population.

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270 JOHN Foao

The seasonal migrations of the modern Fulani of West Africa show clearly that they have a sound knowledge of the local geography of the fly-belts.

For those who enjoy speculation about the interac- tions of people and tsetses in the distant past, starting points are provided by Westwood’s [4] paper postu- lating a role for Glossina in the biblical plagues of Egypt. Townshend [S], three-quarters of a century later, is more widely ranging and one should mention, but not accept, the ideas of the great palaeontologist, Osborn, who suggested that the disappearance of the Equidae from the American continent was caused by their encounter with tsetses, the fossils of which have been found in the Oligocene of Colorado.

However, it probably is true that a king of Mali died of sleeping sickness in 1373 or 1374. After that we come to the West African slave trade, in which it was common practice to discard individuals who had swollen neck glands; a precaution which did not prevent the negro lethargy appearing among slaves in the Antilles in the 18th century, although in the absence of a suitable insect vector the parasite could not per- sist. This, however, was not the case with the cattle trypanosome, Trypanosoma vivax, which was trans- ported to America in the 19th century and has become established there, using other blood-sucking insects as vectors, or the camel trypanosome. T. evansi, which is a variety of Trypanosoma brucei which has succeeded in throwing off its dependence on Glossina as a vector and, using other biting flies, has managed to cross Asia to the Mongolian deserts C61.

EARLY SCIENTIFIC INVESTIGATIONS

The interest of scientists in tsetses, apart from the classificatory activities of systematists, seems to have begun with Professor Richard Owen’s Instructions to the Zoologist of Livingstone’s Zambezi Expedition in 1858 [7]. At that time, before publication of the work of Pasteur, it was thought that the tsetse Glossina morsitans killed cattle by injecting a poisbn. Owen wrote “the alleged fatal effects of this insect in the case of oxen and horses subject to its bites, should be determmed with the utmost precision in regard to the number of bites or punctures occasioning death”. If one postulates infective bites rather than poisons, this simple instruction would form a good starting point for study even today. In the same instructions Owen notes that “the presence of the tsetse is a barrier to progress by means of oxen and horses. .” and con- tinues that the fly would prove “a similar obstacle to a settlement in the so infected districts by any colony depending upon cattle or horses for food or transport”.

Note that the obstacle is to the establishment of a colony.

LESSONS FROM ZULULAND

The first effective scientific investigation of tsetse- borne disease was carried out by Dav:d Bruce in 1893 and 1894 in Zululand [8]. He demonstrated that nagana was caused by a trypanosome and that the parasite was transmitted by tsetse flies from wild animals to cattle and dogs. The importance of the flies

had long been known. That Owen’s “poison” was a haemoflagellate was new.

There are two points to make about this first and fundamental research success. The Zulu kingdom col- lapsed in 1879 and in 1887 the country was taken over by the Government of Natal and its kmg exiled to St Helena. The white farmers moved in with their cattle to graze the Zulu pastures. Very soon nagana appeared and the cattle began to die. An account published by the South African veterinarian Curson [9] in 1924 shows that. in the old days, transhumance enabled the Zulus to avoid infection by movmg their cattle into the high veld in the wet summer months and back to the low veld in the dry winter. Such flexibility in the use of pasture could not be practised by farmers each of whom owned his own land. Land tenure was to be a subject which greatly occupied the minds of colonial administrators throughout Africa.

The second point is that it took very little time for the threat of economic loss among settlers to secure the services of an expert. Bruce had made a name a few years earlier by isolating the causal orgamsm of the variously named Malta fever, undulant fever or Brucellosis. His work in Zululand did not lead to the discovery of new methods of control and it was only after many trials of different techniques, spread over half a century, that du Toit and his colleagues [lo] eliminated the Zululand fly-belts by use of DDT.

The prolonged effort in Zululand draws attention to another basic idea which has. throughout most of this century, powerfully influenced the minds of those responsible for tsetse control. Almost from the beginning of colonial effort, two methods of eliminating these insects were known to experts. These were. of course, elimination of wild animals and removal of trees and larger shrubs. They were not used in Zulu- land, except as protective devices inserted between the fly-belts and the surrounding farms, because legisla- tion was invoked to turn the three fly-belts into wildlife reserves. It will be necessary to look again at the idea of conservation m relation to the control of tsetse-borne disease. The concept of the tsetse as the saviour of Africa from its inhabitants is a frequently recurring theme in British colonial literature.

EXPLORERS. VOORTREKKERS AND HUNTERS

It is useful to revert a moment to the experiences of explorers and hunters who lost draught and riding animals from trypanosomiasis and of the South Afri- can voortrekkers who were turned away from the valley of the Limpopo by Glossina morsltans. These encounters have been well summarised by Fuller [I l] and Dicke [12]. The books of Austen [ 131 and Tabler [ 141 are also valuable.

Four important ideas emerged from these experiences. Firstly, the idea of avoiding infection by choos- ing routes which circumvented the fly-belts, using the knowlege of earlier misfortunes and of local people. The main route to the north avoided the Limpopo fly-belts by passing through eastern Botswana, and one may therefore argue that the tsetses determined the line of the railway between Johannesburg and Bulawayo. It was also possible to avoid the consequences of infection by use of transport not suscep-

Attempts to solve the problems of Afwan trypanosomlasls 271

tible to it. In 1864 the need for an outfet from the Transvaal to the Indian Ocean at I3elagoa Bay prompted the Idea that barges could be used to carry goods along the Maputa and perhaps other rivers [ll, IS]. (Livingstone. 10 years earlier. had had the same notion about the Zambezi.)

Now we must observe that to the pioneers tsetses were important primarily because they compelled people to travel by foot and to move their goods on the heads of porters. Lugard in Nigeria was much impressed by the waste of human energy involved in head porterage [16J. One would have expected therefore that the appearance first of railways and then of motor vehicles would have had a profound effect upon the rate of economic development of tropical Africa. So they did-but this devetopment had an almost imperceptible effect upon the size of the fly- belts. Perhaps, then, the lack of animal transport in the hIstorica past was not, after all. a vital impedi- ment to African advancement? Is it relevant to note that similar deficiencies in the same latitudes in Cen- tral and South America did not prevent the appearance of highly developed civilizations? Certainly the fly-belts did not prevent cattle from penetrating the African tropics from the tsetse-free north to the tsetse- free south [ 17).

However that may be, lack of animal transport certainly was a handicap to Europeans trying to push north before 1895 when the Great Rinderpest so con- veniently removed the tsetse host animals and with them the flies.

The third idea was that of bush clearing. The earliest published statement about the unsuitability of open treeless grassland to the tsetses seems to be that of Andersson [18] who noted that the wide grassy and only rarely flooded course of the Taokhe River prevented the insects from spreading out from the heavily infested Okovanga deha. According to Thomas Baines Cl93 Beers who constructed a “Com- mando Path” to the Limpopo destroyed the bush for several hundred yards on either side of it to make a protective corridor as it approached the river.

This is. perhaps, a suitable place to draw attention again to Swynnerton’s [3] account of the administrat- ive actions of the Nguni chief, Mzila who, to provide disease-free pastures for tribal cattle in the region of the Sabi River ordered, firstly, the concentration of settlement, by ordering his followers to “Draw near to the King” and, secondly. the hunting of al1 animals in the peripheral bush. The first measure created wide areas of bush-free cultivation; the second had the effect of keeping the reservoir of infection at a distance.

THE HUMAN INFECI’IONS

At this point we must take account of the human disease, sleeping sickness. I have noted that human trypanosomiasis had long been known on the West African coast, though not its origin. It was not until six or seven years after Bruce had defined the cause of infection in cattle in Zuiuland that Dutton found Try- panosoma gamhiense in the blood of a patient in Sene- gambia. Shortly afterwards, Castellani recovered the same parasite from the spinal ffuid of one of the vic-

tims of the Uganda epidemtc. Bruce again. in Uganda, revealed the role of the tsetses.

There are a few points to make about the early sleeping sickness epidemics. Explosive outbreaks from about 1870 onwards in Zaire and the surrounding regions (i.e. King Leopold’s Congo Independent State and what was soon to become French Equatorial Africa) and, from 1896 onwards. m Uganda, were very much more alarming and, indeed. frightful than the cattle trypanosomiasis encountered by the explorers and pioneers. Cattie trypanosomiasis did not threaten the imperial idea-it was. in any case, the great age of railways, but sleeping sickness was a different matter. For a while, in Uganda, optimists discussed the notion that white men were not susceptible to infection, but this did not survive the first case. Next it was assumed that settlers in the south-eastern African tropics would be safe because Trypanosoma gambiense seemed only to be transmitted by Glossina palpalis which could not be found on rivers draining into the Indian Ocean. There was therefore much alarm when another. more virulent. trypanosomal infection of man in the Zambezl River basin was shown to be transmitted by Glossina morsitans. Moreover, while it was possible to argue that the gambian disease had no reservoir other than man, it was soon evident that Trypanosoma rhodesiense was primarily a parasite of wild animals.

Bruce’s trenchant demand that all wild animals living in sleeping sickness areas should be slaughtered [ZOJ provoked emotions far more violent and deep than did the deaths from disease of hundreds of thou- sands of Africans. But before looking at the subject of wild life destruction, there is one more point to make about the sleeping sickness epidemics.

The expedition of Doctors Dutton and Todd went out to the Congo from the Liverpool School of Tropi- cal Medicine at the request of King Leopold in 1903. Dutton, who had been the first to isolate Trypano- soma gambiense identified also the causal organism and mode of transmission of relapsing fever and then died of that disease and was buried at Kasongo on the Lualaba. Their joint report was written by Todd [2lf. There is also a useful paper by Lechat [22J based upon Todd’s notes and personal correspon- dence. It makes clear the point I wish to make.

Deserted villages were always a feature of regions afflicted by severe epidemics, for not only was mortality very high, but the survivors adopted the only course open to them to save themselves: they ran away. Not unnaturally it was common for early observers to attribute the depopulation solely to trypanosomiasis. But Dutton and Todd did not fail to note that missionaries. who had been in the infected areas before the epidemics began, asserted that the latter were not the initial cause of the collapse. The epidemics followed declines in popuIat]on density brought about from other causes. “According to the missionaries, always, the sleeping sickness was not responsible for the initial collapse of the population: the causes of it were different.” This observation referred specifically to Lukolela where the missionary, White- head, had lived for thirteen years. Some old men of the district had. moreover, known of the disease in their youth. It was therefore endemic and not an introduction. At the time of Dutton and Todd’s arrival,

272 JOHN FORD

the local people amounted to only 350 survivors and in the previous two months there had been 11 deaths from the disease. But, during the previous eight years and beginning before the epidemic the population had fallen from about 7000. At another place, Irebu, near Lake Tumba, a population, in 1893, of some 3500, had, from that year onward, been decimated and Lechat’s conclusion is that the determining factor of the epidemics resided essentially in a violent change in the human ecology. The environs of Lake Tumba were. in fact, one of the regions which King Leopold had sold to a SociCtt Generale de Cultures (a creation of his own) in which the State (also King Leopold) had the right to collect the natural products of the land and keep two-thirds of the profits from their sale c231.

In most medical thinking, these initiating factors were overlooked and epidemics tended to be ascribed to the arrival in an area of people, or even of one person. carrying trypanosomes in the blood. It is a complex subject. involving not only change in human ecology, which includes man’s domestic livestock, but also the associated changes in composition and behaviour of vegetation and soils, of the wild fauna and of the tsetses which live upon them and, throughout the animal components of this ecosystem, change in their immunological interrelationships. But this is to look ahead and outside the scope of this paper.

THE DESART COMMIITEE

By 1910 the main outlines of the epidemiology of the trypanosomiases. both human and animal, had been much clarified, chiefly owing to the remarkable studies of the Sleeping Sickness Commission of the Royal Society under the direction of David Bruce. The British Colonial Ofice now set up an Interde- partmental Committee under the chairmanship of the Earl of De-sart [ZO]. to take evidence from experts including not only the leading figures in British medicine and related disciplines, but also the principal authorities from other European powers.

Bruce believed that the way to eliminate the infections was to remove the parasite reservoir, the wild fauna. Against him in the debate were arrayed the conservationists and the hunters who, at that time, found eager allies among the entomologists. Their solution was to remove the vectors of the parasites. Towards the end of the hearings Bruce said, despair- ingly, “I suppose the entomologists will win”. And they did.

THE ENEMIES OF MANKIND

The end of the 19th and the beginning of the 20th century saw the emergence of the economic entomologist, especially in the United States. In 1906 a well- known text book by J. W. Folsom [24] recorded that:

“The average loss through the cotton worm, 1860 lo 1874. was S 15.000.000 .” ‘“The Rocky Mountam locust, in 1874 to 1877. caused damage of 5200,000.000. .” “The average annual damage by insects to Umted States crops was estimated to be 3300.000.000.”

Additionally, forest insects caused JE100.000.000 damage each year to trees. And so on.

Statistics of this sort made a great Impressron. A book published in 1916 [25] began with an almost hysterical statement:

“The unrelenting, never ceasing warfare which the maJorlty of insects wage against mankind or his property IS, for the moment overshadowed by the tragedy being enacted on the battle fields of Europe”.

No comment is required, but it is to the point that despite three-quarters of a century of increasingly powerful efforts on pest control. a modern expert pro- nounced, only two months ago, that “at least half of man’s crop production is lost each year to his natural competitors, weeds and pests, during growth, storage and distribution.”

Be that as it may, at the beginning of this century the entomologists had been quick to use these formidable statistics. The tsetse, Glossina. was another enemy of mankind. Malaria and the mosquito had, very recently, provided the exemplar. Here is another quotation from the year 1900 [26]:

“During the summer of 1899 it was reported that a syndl- cate had been formed to buy up part of the Italian Cam- pagna. The Campagna is.. . some 1400 square miles in extent with the city of Rome practically at its centre. The part of this once fertile and populous district which the syndicate proposed to acquire lies in the triangular piece of land bounded by the river Tiber to the north and west and the Aino to the south and east, and is now so malarial that the land is almost valueless, cultivation is reduced to a minimum and the scanty population IS sickly in the extreme. Why had this land suddenly become valuable?”

Of course, we all know the answer-that Giovanni Grassi had, the year before. demonstrated that malaria was transmitted by Anopheles-although it was not until 1934, under Mussolini, that the drainage of the Pontine Marshes was completed and Italian malaria eradicated.

We need not pursue the matter: by the time the Desart Committe sat, the entomological argument seemed overwhelming. The 1914 war now intervened: but in 1920, when Great Britain took over the League of Nations Mandate of Tanganyika Territory, C. F. M. Swynnerton was appointed Game Warden. While farming on the Rhodesia-Mozambique border he had built up a reputation as a naturalist and had just completed the remarkable study, which I have already. mentioned, of the land development methods of a branch of the Nguni people. His duties as Game Warden included the special task of setting up a research unit to examine the possibilities of controlling tsetses without killing wild animals.

THE SEPARATION AND REUNION

OF DBCIPLINES

Again I must turn aslde from what is mamly an East African story. The French and Belgians were not impressed by the entomological argument. The great Congo epidemics still raged. In the luxuriant West African forests, bush clearing was obviously imposs- ible and elimination of wild animals pointless when the reservoir of the trypanosome was man himself. It was a problem for the doctors and research was con- centrated upon new drugs and pathology and diag-

Attempts lo solve the problems of African trypanosomlasls 273

nosis. The entomologists were given a very minor role.

In Tanganyika. Swynnerton finally established his team of entomologists in the teeth of bitter opposition from the veterinarians. and there was little liaison between the two, although both were concerned with control of the same disease. The human infection, controlled by the medical department. was similarly isolated.

Different administrations adopted different organizations according to what they believed to be the needs of the colonies and protectorates they served. In Uganda, with memories of the great epidemics. the problem was seen principally as medical and the medical entomologist attended to Glossina palpalis as well as to mosquitoes and other insects of medical importance. When Glossma morsitans began to spread in Uganda and cattle started to die. the veterinary services took responsibility for its control on the basis of advice from Swynnerton. In Kenya there was a similar departmental division. Further south in Northern Rhodesia (Zambia) the task was given to the Game Depart nt. Colonial Game Departments

“& were chiefly revenu collecting organizations, controlling the issue of hunting licences. They had the duty of protecting fa l!pl s from the depredation of wild life and also of preventipg poaching (i.e. of preventing the indigenous inhabiiants from hunting). The advantage of givmg a Game Department responsibility for tsetse control was that it enabled extensive shooting to be done with the unimpeachable object of protecting the African farmer.

Allocation of funds for research on tsetse flies in East Africa from the Colonial Of%e almost all went to Swynnerton’s team in Tanganyika. In return the Tanganyika Tsetse Research team undertook surveys and carried out pilot schemes of control in other East African countries-Uganda. Kenya, Somalia (then ad- ministered by Italy) and in Northern Rhodesia (Zam- bia).

What would have happened if Swynnerton had not been killed in 1938 is diilicult to guess. He had a much wider grasp of the social implications of the tsetse fly problem than most of his colleagues.

After the Second World War the British Govern- ment sent out missions to all its territories to review the position and to make recommendations for more comprehensive research institutes. In 1946, the Portu- guese arranged an international meeting in Lourenco Marques [27] to bring together workers in East and Southern Africa and in 1947 the French held another international conference in Bobo-Dioulasso. Out of them emerged the International Scientific Committee for Trypanosomiasis Research (ISCTR) which held its first meeting in 1949 in London [28].

Probably the main impetus for these events was provided by discoveries stimulated by the war. in various fields, but particularly in pharmacology, im- munology and chemical pesticides. At the 1949 ISCTR the British welcomed, with obvious relief, the discovery of an apparently efficient drug for cattle trypanosomiasis, which offered an escape from the burden of tsetse control. Shortly before this, however, the first trials m the use of DDT in the field were made at Swynnerton’s old laboratory in Tanganyika [29]. The first large-scale success using aerial appli-

cation of this pesticide was that of du Toit in Zulu- land [IO]. Also in the early fifties, Wilson began his work on the elimination of a focus of human trypanosomiasis by ground application of insecticide to river- ine bush in Kenya [30].

Another event at the first ISCTR was the an- nouncement by the principal French delegate, Profes- sor Roubaud. that France intended to recruit entomologists. Probably both French and Belgians began to turn again towards entomology because it had become evident by the middle forties that the successful mass survey and inoculation with tryparsamide and suramin had achieved their maximal result 131,321. The epidemics had been controlled and the incidence of new infections reduced by over 80%; but the curve was flattening out. Fortunately a new drug, pentamidine (lomidine). which also had prophylactic properties, turned out to be highly efficacious in continuing the reduction of gambian sleeping sickness c331.

I do not intend to relate the numerous achieve- ments of research workers in both human and animal trypanosomiasis since the Second World War. How- ever. all this work has had very little effect upon the over-all tsetse infestation of the African tropics, nor, as was seen in Zaire and in the south of the Sudan Republic in the sixties, in preventing the recurrence of violent. widely-spread epidemics of great severity. when the appropriate political conditions were created.

DISCUSSION AND CONCLUSIONS

The British Broadcating Company has recently produced a film illustrating some interesting new de- velopments in tsetse control. The programme printed in the Times newspaper says that it shows “what is being done to eradicate the insect that holds up the agricultural development of 15 million square kilometers of fertile African land”.

I do not believe it. Gillman [34] many years ago pointed out that the enormous Glossina morsituns belts of Tanzania did not exclude man, but that the tsetses flourished (and that means their wild hosts flourished) where man could not. This is not to say that these vast woodlands are useless; but in terms of their development for productive exploitation the tasks of the agricultural or water engineer, of pasture creation and maintenance or of cultivation for crops, are far more formidable than that of the applied entomologist in eliminating trypanosomiasis. When Gill- man said man could not survive in the miombo he meant, of course, African subsistence cultivators using only axe, hoe and fire.

Little has been said about methods used in Rho- desia. (I do not use the name Zimbabwe in this con- text. If there is anything to say about the impact of freedom struggles upon the trypanosomiases it 1s that the former are commonly followed very quickly by epidemics and epizootlcs.) The Rhodesian methods were successful. Clearance of tsetse by destruction of wild life was begun experimentally in 1919 not, as Bruce had wanted, to get rid of the trypanosome reservoir, but to remove the food of the flies.

In 1930 large scale shooting was begun and by 1950 some 26,000 square kilometres had been freed. Most

274 JOHN FORD

of the reclaimed land was subsequently occupied, the better parts by white farmers, the inferior by so-called “native reserves”. The operations had originally been started because it became evident, around 1914, that the Zambezi valley fly-belt, which had been reduced to a few small foci after the Great Rinderpest, was recovering rapldly. Reclamation continued until lack of demand for the still infested land and political opposition to the shooting brought it to an end. Henceforth work tended to be confined to maintain- ing a defence line.

The quality of the land still infested was poor. I have told elsewhere [35] of a conversation overheard between two Rhodesian politicians, one black, one white, while flying over the Zambezi fly-belt. The white said “Look at all that. You people are always demanding more land. Why don’t you come and take this?” The black replied “If it had been any use at all. you people would have taken it long ago”.

I want to draw attention to an aspect of control by shooting which is seldom mentioned, although it was quite fundamental in the thought of colonial administrators and settlers. Devotion to the goddess Artemis is deeply rooted in human Whaviour. She was the patron goddess of hunters, but also the protectress of wild animals. The cult is often allied to aristocratic behaviour and privilege: game preservation. correct behaviour such as refusal to shoot sitting birds. prose- cution and punishment of poachers, etc. It was clear, in Rhodesia, that the main political opposition to tsetse control by shooting came from men who were great “sportsmen”. What they found intolerable was not the mortality among wild animals, but that the hunting was done by Africans, the lower classes.

Swynnerton who, as Game Warden in Tanganyika in the twenties, had the responsibility of issuing licences for hunting, refused to issue them to Africans on the grounds that they were not “sportsmen” [36]. Nevertheless. he had been at pains to point out in his paper [3] on Mzila’s methods, that the latter, while calling upon his people to kill or drive out all animals from the neighbourhood of their cultivation, at the same time demarcated reserves in which all hunting was forbidden. The Artemis complex is probably as strongly developed among Africans as it is among Europeans and Americans. Perhaps I should add that Swynnerton. who was a fair man, also recorded that some Europeans were not sportsmen either, by which he meant that they would not bother to follow up and kill wounded animals.

Two other points remain to be made. It was and perhaps still is an experience of officials responsible for implementing anti-tsetse operations, whether by shooting, by clearing or by use of insecticides. that no sooner are discussions begun about reclaiming an area from tsetses. than the conservation authorities declare it to be a wildlife reserve. If the tsetses were to be removed, their role as protectors of Africa against the Africans had to be taken over by government.

The second point is that until the middle fifties when insecticides came into wider use. the research efforts of British glossinologists in Africa were mainly directed towards perfecting Swynnerton’s technique of control by partial bush clearing. Having learned from his historical studies that human settlement, if sufficiently dense, would eliminate tsetses. Swynnerton

proceeded to demonstrate it in the Sukuma country just south of Lake Victona. The result was entirely successful and was continued by the local people and has achieved a high degree of permanence. However, it is very clear that only a small portion of the African wooded savanna is capable of supporting human populat:on in sufficiently high density permanently to suppress the bush. Moreover, the method exter- minated wildlife just as surely as intensified hunting.

Swynnerton had been much influenced by Ameri- can ecologists in the early part of this century. The names of Clements and Sheiford come at once to mind. The notions of plant succession and, particularly, of the biotic community or ecosystem appealed greatly to him. It was certam that tsetses could not survive in open, treeless, grassland. Therefore it must be the case that a woody vegetation was, in some way, essential to them, for example by offering shade and shelter or, simply, perching places. If, therefore. one could induce modifications in the natural vegetation it might be possible to render it unsuited to Glossina.

though not to the host animals. The notions of partial clearing, that is, the removal of vegetational elements which field study suggested were essential to the insects or of wholesale modification by exclusion of grass fires, were advanced and tested. Both achieved incomplete success. Fire exclusion was too difficult to be practical or, if successful for one species of tsetse tended to create an environment favourable to another. Partial clearing worked for some species but had limited success for the principal species, Glossina morsirans. The reasons for failure were never fully explored, because of the advent of insecticides; but the successes, it now seems, were achieved because the clearings destroyed the habitats of the principal host animals, especially the wild pigs.

This paper attempts no forecast on future trends in trypanosomiasis control; but the history of the last 150 years does not suggest that its achievement will open up vast rich lands for exploitation. Trypanoso- miasis controL especially tsetse control, or elimination, has to be considered as part and often a small part only, in development programmes. In some regions it will have to take second place to provision of water, of new transport and communication networks. of markets and marketing facilities and of education of people into new social patterns. In other areas it will have a high priority but unless local life- styles and economics can be changed to fit the new environment it will induce. removal of tsetse-borne disease will lead only to further resource degradation and larger famines.

REFERENCES

I. Economic Advisory Council. Tsetse Fly Commlftee: Seventh Report. E.A.C. (cl 76, London. 1932.

2. Blackett P. M. S. Tizard and the science of war. Nature. Land. 185, 653, 1960.

3. Swynnerton C. F. M. An exammatton of the tsetse problem m North Mossurisse, Portuguese East Afrrca. Bull. ent. Res. 11, 315. 1921.

4 Westwood J. 0. Observations on the destructtve species of Dipterous insects known in Africa under the names of tsetse. ztmb and tsaltsalya. and thetr sup- posed connectton wtth the fourth plague of Egypt. proc. Zoo/. Sot Land. 18. 258. 1150.

Attempts to solve the problems of African trypanosotmasls 275

5

6.

7.

8

9.

IO.

12

13.

14.

15.

16.

17.

18.

19.

20.

Townshend C H. T. The tsetse problem S. dfi J. nur. M?nates of Ewdence, Cd 7350. H.M.S.O. London. Hzst. 4. 36 & 139. I923 1914. Hoare C A The spread of African trypanosomes beyond their natural range. 2 Troprr~rnrd. Parusrr 8. 157. 1957. Walhs J P R. (Ed.) 7% Zunzfi~,-i ~~p~~t~~o~~ of Dutxd Lwmgstone 1858-1863 Chatto and Wmdus. London. 1956.

Dutton J E. and Todd J L Dlstrlbutlon and spread of sleepmg sickness m the Congo Free State. Mem. Lpool Sch trap. Med 18. 1906 Lechat M F. tiher ~abj~arts 1963, p. 589. Instttut de Medecine tropicale “Prince Leopold”, Antwerp, 1963.

Bruce D Further Report on the Tsetse F/y Disease or nagana rn Zululund. Harrison, London. 189; Curson H H Notes on GIossCza puiilpld~s m Zululand 3111 em Res 14, 445. 1924. Du Tott R M. The eradication of the tsetse fly (Glos- slna pallrdlpes) from Zululand. Unron of South Africa. Adr. cet SC& 5, 221. 1959 Fuller C Tsetse rn the Transwai attd Surroutrdmg Ter- ritortes. 4tz Hzstorteai Review. 9th and 10th Reports of the Dtrector of Vetermary Educatron and Research Pretoria, 1923 Dlcke B H The tsetse fly’s influence on South African history. S. Afr. J. Scr 29. 792. 1932.

Austen E. E. A Monograph of the Tsetse-Flies genus Glossina. Westwood based on the collection m the British Museum. Brittsh Museum (Natural History). London, 1903. Tabler E. C. The Far Interior: Chrorncles of proneeriny m the Matabele and Mashona eowtries 1847-I879. Bal- kema. Capetown. 1955. Walker E. A A Huror)’ of Southern Africa Longmans, London. 1957.

Slade R Kmg Leopold’s Congo Oxford University Press. London, 1962. Fotsom J. W. ~ntornol~~ wrth speclaf wference to its bzologieui and economtc aspecrs. Rebman, London. 1906. Ealand C A. lnsecr Enemres Grant Richards, London, 1916.

Lugard F D. The Dual Ma,ldute in Brrtrsh Troprcal

Africa. Blackwood. Edinburgh. 1922. Ford J. Proc. Ist Federal Science Congress. p. 357.

Saiisbury, 1960. Andersson C. J. Lake Ngamr or Exploratton and Dwco- veries duringfour years wanderrngs m the wilds of South

Western Apica. Hurst & Blackett. London. 1856. Baines T The Gold Regions of South Eastern Africa.

Stanford. London. 1877:’ Desart. Earl of (Chairman). Report of rhe Interdeport-

mental Commrtree on Sleeprag Stckness. Cd 7349 and

21

22

23

24

25

26.

‘7

28.

29.

30

31

32

33

34

35

36.

Christy C. ~o~~zroes and Malana. The Trmes of Indlo Press. Bombay. 1900. Conferencia Intercolon~al sohre Tripanossomiases 1Y46 Lorenco Marques, 1947. In~ernortonal Sclentrjc Committee for Trypanosomiasls Research. Firsr Meerznrr. London, 1949. WhItesIde E F An exp&ment in control of tsetse wtth DDT-treated oxen. Bull. em. Res. 40. 123. 1949.

Wilson S. G. The control of Glossi& palpahs fuscrpes Newst m Kenya Colony. Bull. ent. Res. 44. 711. 1953. van Hoof L. Observations on trypanosotmasls m the Befglan Congo. Trans R. Sot trap Med. Hyg 40, 728, 1947.

Lotte A. J. Hlstorlque du foyer de trypanosormase de Nola. Pubis Bw. perm. mrerqfi Tsh-tsl: 194/O, 1952. Neutean G. Practical Aspects of the control of human tryp~no~miasis m the ‘Republic of the Congo (Leo- ooldvilie). Bull. WH.0. 28. 797. 1963.

billman C A population map of Tanganyika Terra- tory. Geogr. Ret). 26. 353. 1936. Ford J. The role of the trypanosomrases m Afircan Eco- logy. Clarendon Press. Oxford. 1971. Swynnerton C. G. M. Draft Transcript Memoran- dum to Government of Tanganyika Territory. Tsetse Res. Archs. E.A.T.R.O. Laboratory. Tororo, Uganda, 1921.

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Ideas which have influenced attempts to solve the problems of African trypanosomiasis

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