I TRYPANOSOMA 49 



settlements. The effectiveness of this will be conditioned by the extent, 

 at present undetermined, to which animals other than antelopes act as 

 natural carriers of the trypanosome. 



(3) The local extermination or at least reduction in numbers of 

 the transmitting Glossina (see p. 253). The most effective measure to 

 this end is probably the clearing away of shade-giving brush and trees 

 along the margins of rivers and lakes. Low thatched shelters may be 

 constructed over loose dry soil near the water's margin so as to attract 

 the flies of the neighbourhood, and induce them to deposit their pupae 

 where they can readily be collected and destroyed. A further palliative 

 may be found in the encouragement of fowls, Francolins and other 

 scratching birds which are useful for unearthing and destroying the 

 buried pupae. 



(4) The withdrawal of the human population from the fly-infested 

 zone along the margin of the fresh water. This, the most practical 

 method, has actually been carried out on a large scale in the Uganda 

 region, and has resulted in a reduction in the number of sleeping- 

 sickness cases to comparatively small dimensions. 



Of recent years (1909) " sleeping sickness," of a particularly virulent 

 form, has made its appearance in Rhodesia and East Africa. In this 

 region the transmitting agent is apparently Glossina morsitans and it is 

 suspected that the trypanosome concerned is not T. gambiense but either 

 a separate species (" T. rhodesiense ") or a local strain of T. brucii which has 

 developed the capacity of living in the blood of man. In either case 

 the outlook is an anxious one owing to the wide distribution of the 

 transmitting insect upon the continent of Africa. 



r.i cruzi. In 1907 a new species of human trypanosome — T. cruzi 

 — was discovered in Brazil. An interesting feature of the discovery was 

 that the trypanosome was first observed as a parasite in the alimentary 

 canal of a large bug (Conorhinus). By experiment it was determined 

 that monkeys became infected with the trypanosome when bitten by 

 the bugs, and the discoverer — Chagas — then proceeded to examine the 

 blood of the human inhabitants of the district (Matto grosso) from which 

 the infected bugs had been obtained. He found that the trypanosome 

 was regularly present in the blood in cases of a severe illness particularly 

 prevalent amongst children of the district. He also was able to make 

 out that the transmission is cyclical, the bug not becoming infective 

 until 10-25 days after sucking infected blood. A striking characteristic 

 of T. cruzi is that the process of fission takes place normally not in the 

 blood stream but in the substance of the muscles and other organs, the 

 1 Often called Schizotrypanum instead of Trypanosoma. 



E 



