166 



Dr. L. Eogers. The Transmission of the 



explain the slow and irregular spread of surra through a stable of horses, 

 by the occasional occurrence of the event of a fly which has bitten a 

 diseased animal being disturbed and immediately going off to bite 

 another healthy one. Further, the proof that infection may take place 

 through flies, brings surra into closer resemblance to tsetse-fly disease, 

 and increases the probability of the two being identical, or, at least, 

 caused by very closely allied species of the same family of parasite. 



II. Latent Cases of Surra in Cattle as a Possible Source of Infection. 



Bruce has shown that the parasite of tsetse-fly disease may be 

 present in the blood of big game animals without causing acute 

 symptoms or definite sign of disease, and that their blood when 

 inoculated into susceptible animals will produce the typical acute 

 affection ; and further that a very protracted form of the disease may 

 occur in sheep and goats, and possibly form a source of infection for 

 animals. Lingard, in his first volume on " Surra," records the case 

 of a bull which he inoculated with surra, and in whose blood the 

 trypanosoma was found for three days only, shortly afterwards, yet 

 guinea-pigs inoculated with the blood of this bull on the 85th and 

 163rd days after the first appearance of the parasite developed fatal 

 surra with numerous trypanosoma in their blood. Further inocula- 

 tions from the bull on the 234th and 267th day proved negative. He 

 has also recorded two naturally acquired cases of the surra in cattle, 

 which proved fatal. These facts suggest the possibility of the latent 

 disease in cattle acting as a source from which biting flies might carry 

 the disease to horses, especially as surra is so frequently met with on 

 the roads to hill stations in India, where numbers of bullock carts are 

 going up and down. It seemed advisable, therefore, to repeat this 

 observation on surra in cattle, so I inoculated a small hill bull intra- 

 venously with a small quantity of blood from a rabbit, which contained 

 numerous trypanosoma. The result confirmed Dr. Lingard's observa- 

 tion, for on the seventh clay after inoculation the organism appeared in 

 small numbers in the blood of the bull, remained present for four days, 

 and subsequently was not detected during the next 161 days of the 

 disease, while the animal, after showing slight signs of illness for about 

 a month, remained subsequently in apparently good health, except for 

 an occasional slight rise of temperature for two or three days. A rat, 

 which was inoculated on the 30th day of the disease, and two rabbits 

 inoculated on the 59th and 141st days respectively, developed fatal 

 surra, with large numbers of the trypanosoma in their blood ; that on 

 the latest-mentioned date having been done during a temporary rise of 

 temperature of the bull without the presence of any trypanosoma.* 



# All the rats used in experiments mentioned in this paper had been first proved 

 to be free from the Trypanosoma sanguinis, except where otherwise stated. 



