BIG-GAME PRESERVATION AND THE SLEEPING SICKNESS.

[To THE EDITOR OF THE "STRCTATOR."]

Si,—In a footnote to Mr. Tallack's letter to the Spectator of December 14th, 1907, on the subject of the approaching extinction of interesting animals, you allude to the "apparent fact that as long as the big game is encouraged so is the tsetse-fly, and that the tsetse-fly is held responsible for the two most terrible of scourges to man and beast,—sleeping sickness and horse sickness," and, while stating that the matter is still sub judice, you add : "If preservation of big game can be proved to prevent the stamping out of sleeping eickness, then the notion of keeping sanctuaries in Africa must be at once abandoned."

The editorial opinions of the Spectator Carry so much weight that I should be very grateful if you could allow me space to try to show that the connexion between big game and nagana, or animal trypanosomiasis, is limited to those parts of Africa inhabited by the tsetse-fly (Glossina morsitans), and that the argument for the destruction of the game cannot apply to vast areas where the fly is absent, and to which it is not at all likely to spread. The possible necessity for sacrificing the game elsewhere would rather be an additional reason for preserving it where the tsetse-fly complication does not come into the question.

It may be as well to point out the great difference between the direct connexion of big game with the dissemina- tion of nagana by Glossina- morsitans, and the alleged, • but

insufficiently proved, indirect connexion of big game with the spread of sleeping sickness, or human trypanosomiasis, by a quite distinct species of tsetse-fly, Glossina palpalis. In the first case, the trypanosome of nagana is very habitually carried

in the blood of game animals, which are immune against its effects, and transferred by Glossina morsitans to domestic

animals, to which it is fatal. In the second case, the trypano- some of sleeping sickness has never been found in the blood of any game animal, and the only argument against the game is that, as the fly (Glossina palpalis) which disseminates it by man-to-man inoculation is known to feed on game as well as on almost any vertebrate animals, it might become extinct for

lack of sustenance if the game were exterminated. To me this seems more than doubtful. In mosquitoes, for instance, strong as the blood-sucking instinct is, there must be incalculable myriads of these insects in desolate African swamps where mammalian life is almost absent which exist and propagate their kind without ever obtaining mammalian blood at all. It is not yet proved that blood is the only food of the tsetse-fly, and how little the presence of big game is essential to the existence of Glossina palpalis may be judged from a passage in which Dr. A. D. P. Hodges* describes a small fly-infested native settlement. The village was situated in a patch of jungle sixty or seventy yards wide on the point of a small peninsula of a few acres in extent :—

"The point itself swarmed with fly as far as the jungle extended The inhabitants were nineteen, of whom all but five children, two women, and one man had sleeping sick- ness, and these people, with four or five goats, and a few fowls, and perhaps an occasional hippopotamus and some wild birds, must have formed the whole available supply of food for the flies on this small area."

Dr. Hodges points out that at regular landing or drinking places of hippopotami, crocodiles, and other game the fly is especially abundant when these places are within its natural limits, and considers that in such localities the game should be killed or driven away. The same Report shows conclusively that more or less open water with contiguous shade and a certain amount of well-defined banks (in the soil of which the pupal stage is passed) are essential to the existence of Glossina palpalis. It shows also how narrow these suitable water.

margin breeding-grounds are, and how short is the flight- range of the fly from them, and emphasises the fact that the destruction of the pest by clearing these breeding-grounds would be by no means such a hopelessly large undertaking as has hitherto been imagined. So much for the connexion between game and sleeping sickness.

Glossina morsitans, the carrier of animal trypanosomiasis, which should in no way be confounded with sleeping sickness, is a fly of wider range, and is found much further away from water than Glossina palpalis. Its distribution, however, is doubtless in a similar manner dependent, not on the presence of big game alone, but in the first place on essentials of environment, and the absence of these probably accounts for large areas of game country being entirely free from it, and secure against its invasion. This fly has never been found to carry the trypanosome of sleeping sickness, and Dr. Hodges expresses the belief that it will not prove to be a natural carrier. As instances of large areas of country well stocked with big game where the question of the teethe-fly and disease is not involved, may I point out that in the Soudan the Sanctuary and the Officers' Reserve, lying between the White and Blue Niles, and the country north-east of the Blue Nile, though inhabited by elephants, buffaloes, giraffes, and antelopes, are perfectly free from tsetse ? Intervening rivers and distance would prevent the game in these areas from extending into and replenishing fly-infested districts, even if it ultimately proved necessary to denude the latter of game. In Kordofan Glossina morsitans occurs within very restricted limits, and not where game is most plentiful. The White Nile from Mongalla northwards is free from tsetse. In the Bahr-el-Ghazal Province alone is Glossina morsitans widely distributed, and responsible for serious loss of transport animals ; and in the southern part of this province G. palpalis also occurs, the various small rivers affording the conditions essential to its existence. In the other large tracts of country

* First Half-yearly Report of the Medical Officer in Charge of the Bleeping Sickness Extended Investigations, to the Principal Medical Officer, East Africa and Uganda Protectorates.

I have mentioned these mem( ry conditions are, in my opinion, absent. In the Soudan, at least, the distribution of the teethe-fly is by no means co-extendent with that of the large game animals. Big game teems in parts where the fly is unknown, and likely to remain so. It is certain that an abundance of buffaloes does not in itself involve the presence of tsetse as an in- evitable consequence.

It is greatly to be hoped that any experiments made as to the benefit obtained by allowing the game to be exterminated in fly-infested areas will be conducted very locally, and the results systematically studied; and in the meantime the case for the preservation of game in districts where the tsetse is non-existent should not be prejudiced, but rather strengthened, by the possibility of its sacrifice in other parts of Africa becoming a regrettable necessity. The connexion between game and sleeping sickness seems slight and indirect, while the connexion with the spread of horse-sickness is direct and proven, but in both cases the connexion ends where the conditions of environment necessary for the existence of the tsetse are absent. And is it not possible that game animals themselves, seeing that they are immune to the disease, may afford the solution of the problem in a serum by means of which their immunity may, by inoculation, be extended to transport Superintendent of Game Preservation,

Khartoum. Soudan Government.