Nagana (Trypanosoma bnicei) 241 



Inoculation of Rabbit.^ ivitii CuHm-cs Grown in vitro. — While rab- 

 bits suffer from the subacute type of Nagana when infected with the blood 

 strain of the parasite the same does not hold true when the organism 

 has been cultivated upon blood agar for many months. 



Rabbits were not inoculated with early isolations of the trypano- 

 somes. Seven rabbits were injected intraperitoneally with the contents 

 of ten tubes of generations 144 to 148, inclusive, and of this set only one 

 showed the presence of trypanosomes in its blood on the 70th day and 

 again ten days later at which time further examinations were negative. 



Out of six rabbits, each receiving multiple ten tube doses, two 

 developed trypanosomiasis of which one proved fatal as table VI shows. 

 Rabbit number ten, which received four bi-weekly injections of ten tubes 

 each, revealed the presence of a small number (one per field) of trypan- 

 osomes in its blood 12 days after its first inoculation. The number of 

 parasites increased to four per field on the 14th day and then disap- 

 peared until on the 27th, 37th, 44th and again on the 126th day when 

 only a single individual was noted in each examination. This animal 

 showed no symptoms of Nagana more than 500 days after its inocula- 

 tion and was pronounced as recovered. 



Rabbit number nine after receiving ten bi-weekly doses of ten tvibes 

 each also developed Nagana on the 49th day after the first injection or 

 17 days after the last injection. At this time but one trypanosome was 

 found but 7 days later ten parasites per field were observed and two 

 days later death occurred. This animal developed the characteristic 

 symptoms of the disease. 



Inoculation of Guinea-pigs ivith Cultures Grown in vivo. — The varia- 

 tion of the disease which has been noted in the rabbit is also markedly 

 borne out in the case of Nagana in guinea-pigs. The parasites do not 

 increase in numbers regularly or rapidly but they may disappear and 

 reappear several times and finally, usually just before death, may be 

 numerous in the blood stream. The disease, generally speaking, runs 

 a more regular course and the organisms are more plentiful than in 

 the case of the rabbit. Nagana is always fatal for guinea-pigs with a 

 period of incubation from two to four or even as high as eight days, 

 the average being a little less than four days when intraperitoneal in- 

 jections are made and about five days when subcutaneously inoculated. 

 The average duration of the infection is approximately 40 days. 



Out of some 600 guinea-pigs examined the shortest period of in- 

 cubation was 24 hours and the longest eight days. The duration was 

 variable being from seven to 66 days. In the typical course of the 

 disease and also when the infection borders the chronic variety, the 

 guinea-pigs have more or less constant fever and develop conjunctiva 

 which may be purulent and always alopecia which is usually marked 

 especially along the back, around the anus and eyes. Some of the ani- 

 mals become very anaemic. 



Inoculation of Guinea-pigs with Cultures Grown in j'zVro.— Guinea- 

 pigs, like rabbits, because of their refractoriness, develop at best a 

 chronic infection if the parasite has been out of the animal body for 

 several years or the organism has entirely lost its virulence for these 



16—25870 



