164 



Dr. L. Rogers. The Transmission of the 



urra, with a view to contributing towards the solution of the question 

 of the identity or otherwise of the two diseases, and the following is a 

 brief account of the results obtained while I was in charge of the 

 Imperial Bacteriological Laboratory at Muktesar, during the absence of 

 Dr. Lingard on sick leave. 



I. The Transmission of Surra by the Bites of Horse Flies. 



It was proved some years ago by Bruce that the Trypanosoma Brucei 

 is carried from one animal to another by the bites of the tsetse fly. 

 As surra can be certainly produced in susceptible animals by the 

 application of infected blood to the smallest scratch in the skin of 

 another susceptible animal, it appeared to be likely that horse flies 

 might carry the infection from one animal to another. A series of 

 experiments were carried out to test this possibility with the following 

 results. Horse flies were caught and kept for varying periods of time 

 after having been allowed to bite and suck the blood of an animal 

 which was suffering from surra, and whose blood at the time contained 

 the Trypanosoma Evansi in considerable or large numbers. They were 

 subsequently allowed to bite a healthy animal, dogs and rabbits being 

 used in the experiments, and the former were kept in a different- 

 house at some distance from the infected animals, and the latter in 

 separate cages during the incubation period. In every case in which 

 the flies had been kept from one to four or more days after biting the 

 infected animals, no disease ensued in the healthy ones. Many such 

 flies were dissected and microscopically examined, but in no case was 

 anything which might be taken for a development of the trypanosoma 

 in the tissues of the insect detected. A rat was also fed on a number 

 of flies, which had bitten infected animals at varying periods pre- 

 viously, but no infection was thus produced. 



When, however, flies which had just sucked infected blood were 

 immediately allowed to bite another healthy animal, positive results 

 were obtained after an incubation period corresponding with that of 

 the disease produced when a minimal dose of infected blood is inocu- 

 lated into an animal of the same species. The result was uncertain if 

 only one or two flies were allowed to bite, and especially if ' they were 

 allowed to suck as much blood as they wished without being disturbed. 

 If, on the other hand, several flies, which had just sucked an infected 

 animal, were induced to bite a healthy one, and especially if they were 

 disturbed and allowed to bite again several times, infection was always 

 readily produced in both rabbits and dogs, the fur of the latter having 

 been carefully cut, without abrading the skin, at the site over which 

 the flies were applied. The following is the chart of a typical experi- 

 ment of this kind. The dog was bitten by twelve flies which had just 

 previously sucked blood from a dog, which was swarming with the 



