530 



NATURE 



[February 15, 19 12 



a ai'hc qua non in the infective process ; in other words, 

 the stumpy type of form developed in this situation is re- 

 garded as the essential propagative phase. It should be 

 mfntioncd, however, that the commission found also that 

 injrition of the intestines only of infected flies, after 

 twf-nty-four days or more had elapsed since feeding, pro- 

 duced an infection in some of the inoculated animals. 

 Mence either the blood-type must occur in the intestine 

 also,' or else some other form or phase is also capable of 

 transmitting the infection. With regard to the latter 

 possibility, there is one point upon which we should like 

 to comment. A characteristic type of parasite, long and 

 very slender and possessing a peculiar elongated nucleus, 

 was found, but not very commonly, in the fore-gut or 

 proventriculus at intervals after twenty days. This very 

 distinct type of form is known to occur also in the life- 

 cycle of other trypanosomes, from widely different verte- 

 bratrs. when in the invertebrate host ; it has been described, 

 for instance, in the case of Trypanosoma brucii in Glossina 

 fusca, in the case of fish trypanosomes in leeches, and in 

 the case of an avian trypanosome in a mosquito ; in these 

 cases it is either known with certainty to be the pro- 

 pagative phase or else is regarded with some probability 

 as such. We think, therefore, that the fact of its occur- 

 rence in Trypanosoma gambiense, as described by the com- 

 mission, should be noted, and the possibility that it may 

 be a propagative form also in this case borne in mind. 

 At any rate, the occurrence of this type in very different 

 species of trypanosomes suggests that it has an important 

 significance. 



It is interesting to compare with the above account of 

 Trypanosoma gambiense in Glossina palpalis the relations 

 of Trypanosoma vivax, a dangerous parasite of cattle, to 

 the same species of tsetse-fly, on which light has also been 

 thrown by the commission. Flies were found to be able 

 to transmit T. vivax after an incubation period of from 

 seventeen to twenty-eight days, a shorter period, it will be 

 noticed, than in the case of T. gambiense. The parasites 

 develop, moreover, in a much larger percentage of flies — 

 in about 20 per cent. A striking point of difference is that 

 the development is restricted to the proboscis and pharynx 

 of the fly, where the parasites occur in large numbers ; * 

 and, further, the predominating type of form met with is 

 not, as in the other case, trypanosome-like. From this 

 brief comparison it will be realised how greatly the 

 developmental cycles of different species may vary even in 

 the same insectan host. 



The second section (B) consists of series of experiments 

 designed to ascertain if, among various animals, including 

 cattle, antelope, &c., there are any which can be regarded 

 as a reservoir or source of T. gambiense ; and the results 

 obtained by the commission have already attracted con- 

 siderable attention, and may prove ultimately to be of 

 great economic importance. The conclusion arrived at is 

 that it is possible both for cattle and antelope living in a 

 fly area to act as a reservoir, and so maintain the in- 

 fectivity of Glossina palpalis in regard to sleeping sick- 

 ness : but up to the present the commission has not been 

 able to prove that this actually takes place in nature. 

 The facts brought forward in this connection, however, 

 are very suggestive. In antelope the parasites are 

 extremely scarce and difficult to find by microscopic 

 examination of the blood, even when the animal was 

 proved by experiment to be infective for flies. In one 

 instance a buck was shown to remain infective for nearly 

 three months. Infected animals remained apparently in 

 good health, even though kept in captivity (in one case for 

 at least four months). It is evident that in antelope and 

 cattle the infection produced by Trypanosoma gambiense is 

 of the chronic type, and apparentlv similar in character 

 to the infection of wild game by T. brucii. In addition, 

 there is the fact, shown by the commission, that the tsetse- 

 flies from the lake-shore have now remained infective for 

 three years since the removal of the population, the zone 



■' Kleine and Taute found blood-forms (apparently not qnite con-espond- 

 ing, however, to those referrd to above) in the intestine of most of their 

 infective flies. Further, »hese workers do not attach much importance to 

 the presence of the parasites in the salivary glands ; in view of the marked 

 correspondence shown by the British Commission between the period when 

 the Trypanosomes were found in the glands and the time when the fiies 

 became infective, this discrepancy is difficult to explain. 



■• This localised type of 'development has been termed by Roubaud " Evo- 

 lution par fixation directe." 



being given ever to the wild game. Unfortunately, th- 

 commission was able to shoot only five buck, which w»r' 

 negative in respect of 7^. gambiense; from such a small 

 number it was impossible, of course, to draw any con- 

 clusion. If the further investigation undertaken by Sir 

 David Bruce proves that the wild game in the district i- 

 naturally infected with the parasites, a very serious etio 

 logical factor is introduced, since the removal of inf' 

 human beings from the zone of the fly will not be sulV. 

 to cause the disappearance of the trypanosome. 



We have dealt somewhat at length with the first hal: 

 of the report in view of the widespread interest and import- 

 ance attaching to all research that bears in any way upoi: 

 the serious question of sleeping sickness. Consequently, 

 we are unable to refer as fully as might be desired to the 

 remaining half of the volume, which contains much that 

 should be noted by workers on trypanosomes and trypano- 

 somoses in general. It must suffice to indicate briefly the 

 scope of the other sections, permitting ourselves to remark 

 upon one or two particular experiments. 



The third section (C) describes series of miscellaneous 

 experiments carried out, for the most part in connection 

 with Glossina palpalis. One of these series (No. 22) was 

 to ascertain if laboratory-bred G. palpalis become infected 

 with flagellates when kept in the same cage with, or in 

 contact with cages containing wild flies infected with, 

 Trypanosoma grayi. The commission found that the 

 laboratory-bred flies did not become infected with T. grayi 

 (or other flagellates) after being kept for six weeks in 

 dissociation with the infected flies, and after having had 

 ample opportunity to foul their proboscides with the excre- 

 ment of the wild flies. T. grayi is known to form cysts, 

 which presumably pass out with the dejecta of the fly ; 

 hence the above evidence, so far as it goes, points to the 

 flies not becoming infected directly from the cysts, the 

 function of which remains to be determined. The idea 

 originally put forward by Minchin was that they might 

 serve for a contaminative infection of the vertebrate host. 



Section D is devoted to a consideration of certain well- 

 known disease-causing trypanosomes of cattle in Uganda. 

 Much attention is paid to the morphological characters of 

 the different forms, and the limits within which they vary 

 in the case of " strains " from different districts, with 

 the view of distinguishing clearly between different species. 

 A trypanosome found in oxen from a particular locality is 

 regarded as a new parasite, and named T. uniforme. 

 Section E consists of experiments designed to ascertain '■ 

 certain Tabanidae act as the carriers of Trypanosov: 

 dimorphon (termed by the commission T. pecorum). Specie; 

 of Tabanus were apparently unable to transmit this parasite 

 " mechanically," but these flies did not live long enough 

 in captivity for it to be determined whether they could act 

 as true hosts or not. We may point out that the flagellate 

 parasites which were found in some of the (wild) Tabanids 

 were most probably phases in the life-cycle of a trypano- 

 some of some vertebrate, quite possibly a natural (i.e. 

 harmless) parasite of the cattle themselves : * such a form 

 would not be likely to live in rats. Sections F and G 

 describe trypanosomes (including new species) and other 

 parasites from various animals. Section H is concerned 

 with the disease of natives known as " Muhinyo," which 

 turns out to be Malta fever. Section I is a veni' useful 

 account of the distribution, so far as it is known up to 

 the present, of biting flies in Uganda, illustrated by a map 

 in the case of the more important species. ^ Lastly, 

 Section J, together with the appendices, furnishes an 

 epitome of the commoner diseases of cattle occurring in 

 the different districts of the Uganda Protectorate. 



It will be evident from the above digest that a mass of 

 very useful information is contained in the latest report, 

 which in our opinion is one of the most valuable of the 

 series. No elaborate study of the numerous experiments is 

 required to realise the very considerable amount of time 

 and labour their prosecution must have entailed. The 

 members of the commission are to be congratulated on the 

 addition of an important quota to the ever-growing sum 

 of our knowledge of the devastating trypanosome diseases 

 of tropical Africa. 



5 Knuth and Rauchbaar have recently shown that a Tr>T>anosome occur* 

 naturally in cattle in Germany ; this is most likely transmitted by Tabanids 

 (e.g. Hsematopota spp.), from which. In fact, flagellate phases have long been 

 known. 



NO. 2207, VOL. 88] 



