346 TRYPANOSOMA PECORUM [CH. 



Trypanosoma pecorum Bruce, Hamerton, Bateman 

 and Mackie, 1910. 



General account. In 1910, Bruce and his collaborators 

 observed a trypanosome in the horses and cattle of Uganda. 

 This parasite was supposed to be identical with T. dimorphon 

 and T. congolensc, and, therefore, all three were united under the 

 name T. pecorum. Laveran, however, has shewn by means of 

 cross-immunity reactions that T. pecorum is a distinct species, 

 but is closely related to dimorphon, congolense and nanum. 



Recently Kinghorn and Yorke have found T. pecorum 

 present in the wild game of the Luangwa Valley, North-Eastern 

 Rhodesia. 



The incubation period in cattle inoculated with T. pecorum 

 is on an average about six to seven days. The duration of the 

 disease may vary from 26 up to as long as 287 days. It is 

 invariably fatal, the symptoms being weakness and emacia- 

 tion, accompanied by anaemia. Cattle, goats, sheep, monkeys, 

 dogs, rabbits, guinea-pigs, rats and mice are all susceptible to 

 infection with T. pecorum, and this constitutes a means of 

 distinguishing it from nanum. Duke's experiments have shewn 

 that the bushbuck is also susceptible and may remain infective 

 for at least 323 days, therefore the wild game may serve as a 

 reservoir for this trypanosome. 



Morphology of the parasite. In the living state T. pecorum 

 is remarkable for its habit of exhibiting alternate periods of 

 quiescence and activity. When quiescent it usually buries 

 itself under clumps of red cells and is thus difficult to detect. 

 The movements are active but, as in the case of T. congolense, 

 not translatory ; therefore, the parasites do not travel across 

 the field of the microscope. 



In stained specimens the trypanosome is practically indis- 

 tinguishable from T. nanum and T . congolense. 



It is a monomorphic species ; the extreme variations in 

 length are 8 to 18 microns, but the average dimensions, 

 comprising the majority of individuals, are 14 microns in length 

 by about 3 microns in breadth, including the undulating 

 membrane. The posterior extremity is rounded ; the anterior 



