NATURAL TRANSMISSION OF TRYPANOSOMIASIS. 37 



G.'s pigs were obtained from S. and were exposed to similar conditions, and the 

 outbreak took a similar course. Cattle also remained healthy on this farm.* 



VI. ikf.'s Cattle. Sikombella River, Sebungwe District. 



In this outbreak the sequence of events is so clearly defined and the distance of 

 the farm from any fly belt so great that it constitutes in itself a definite proof of the 

 transmission of this form of trypanosomiasis in the absence of Glossina. The situa- 

 tion of the farm in relation to the fly belts in the district is shown in the accompanying 

 map (Map II). The outbreak occurred in the 1915-16 season and the history 

 of the affected cattle is given by the owner as follows : — 



" In September 1915, four spans of oxen were taken to Sileya's kraal and were 

 employed in transport work between that kraal and Sikombella until 17th December. 

 During October eight of these were taken by a Dutchman into the fly belt on the 

 Sassame River — it may have been the Ensengwe River fly belt in the vicinity of 

 the Sabala River (Bandala's kraal) — and on and off after that were in contact with 

 the remainder of the four spans until 17th December.*)* After this they were running 

 not only with the remainder of the four spans, but with all the cattle on Sikombella 

 farm ; the eight infected oxen were all dead by the end of December, one having 

 died with the first rain at Sileya's on or about 15th November. At the middle of 

 February some twenty head showed sick, but the true cause was not suspected 

 at that time. About 25th February a team of healthy-looking oxen, made up of 

 11 oxen which had been to Sileya's and 5 young oxen which had not previously left 

 the farm, were inspanned and sent to Gokwe with a load in company with another 

 team of 16, which had been to Sileya's and looked fit ; two of these died on the road 

 up, including one of the young oxen, and some six others became sick, including 

 three of the young animals (these three subsequently recovered and are now workingj) 

 I now removed all sick animals to a camp about a mile away, but from time to time 

 I had to keep adding an animal which showed sick amongst the 'healthy herd. 

 Towards the end of March two old cows and my bull (none of which had left the 

 farm) became sick ; the two cows quickly died, one leaving a very young calf, which 

 is alive to-day ; the bull has entirely recovered since. From the end of February 

 the infected cattle were dying at the rate of two or three a week for two months, 

 after which the death rate would be about one a fortnight until the end of September ; 

 some 12 head of infected cattle remaining at that date have recovered and are now 

 working. Some 36 head have died, including the 8 fly-struck animals ; all these 

 showed typical fly sickness. With the exception of the eight oxen taken into the. 

 fly belt, none of my oxen have ever been in the vicinity of a fly belt, having only 

 travelled the main road between Sileya's kraal and Queque ; also the main road 

 between Sikombella Farm and Pondo Mine (years ago) — Mr. Luxat's." 



Cattle had been living in a healthy condition on this farm and near by for years. 

 The writer visited the locality in August 1916, and after exploring the vicinity for 

 three days on the possibility of fly having " come down " to the farm from the belt 



* The location of the preceding five outbreaks is indicated on Map I. 

 f The oxen returned with the waggons from Sileya's kraal to the Sikombella River 

 in December. 



X The disease was diagnosed by Bevan from smears taken from these three oxen. 



