TRYPANOSOMIASES OF RHODESIA. I |5 



natural cases. Again, certain infected cattle, having been re- 

 moved from a " tly belt/' were depastured in a district free 

 from " tsetse " where some of them succumlDed. The Govern- 

 ment therefore placed ten young oxen from a clean district in 

 constant contact with them. Tabanidcc, Hcvinatopotcc and 

 Stomoxys were here present in vast numbers, the former con- 

 stituting a veritable plague to man and beast; nevertheless, none 

 of the young oxen became infected. 



On the strength of the vast accumulation of evidence 

 exonerating the biting flies other than the " tsetse," the Govern- 

 ment felt justified in rescinding these very irksome regulations — 

 a step which there has been no reason to regret. 



In this connection it should be metioned that Jowett. work- 

 ing in Cape Town with the trypanosome of Portuguese East 

 Africa, claimis that in one instance the parasite was conveyed 

 from a rat to a sheep by mechanical transmission. 



Under the term Tr. pcconiin, Bruce includes the t'rypano- 

 somes of dimorphic type which I have previously referred to, 

 and one which be found in domestic animals in Uganda, the 

 carrier of which he considered was most probably a Tabaiins 

 and not a Siomo.vys. If his suspicion is correct, the animal try- 

 panosomiasis of Southern Rhodesia must be excluded from the 

 group. 



A similar unfortunate uncertainty exists as to the method 

 of transmission of the human trypanosomiasis of Rhodesia and 

 Nyasaland — i.e., the disease caused by the so-called Tr. rho- 

 dcsicnsc. This is a fact greatly to be regretted, inasmuch as 

 the metliods of dealing with sleeping sickness based upon the 

 supposition that the sole transmitter was the Glossina palpalis, 

 may be quite inadequate, if, as is suggested, the disease is con- 

 tracted in the absence of this species. But our experience in 

 Southern Rhodesia points to the great necessity for care in de- 

 termining whether " tsetse flies " are inhabitants of a district. 

 It is not sufficient to make a hurried search through a locality 

 or to visit it only at long intervals. 



Areas, well known as " fly belts," have been visited time after 

 time without a Glossina being enicountered. Thus Air. Jack 

 visited the Lomagundi district in November and found Glossina 

 morsitans in considerable numbers on the banks of certain dry 

 streams. Returning to the same places in March, he found few 

 if any " fly " in the old situations, but some isolated specimens 

 distributed about the veld— chiefly in Mopani belts. 



In the apparent absence of Glossina palpalis, Glossina mor- 

 sitans has been accused of transmitting the human maladv, but 

 up to the present definite confirmation of the suspicion is not 

 forthcoming. It may be that the Commission, under the skilful 

 direction of Dr. Kinghorn, may put the matter to definite proof. 

 It certainly seems strange, if so widely distributed a fly a.^ 

 Glossina morsitans is the offender, that cases are not far more 

 numerous. Of course, we know that the usual method of trans- 

 mission of trypanosomes by Glossina is " cyclical " rather than 



