Nagana (Trypanosoyna hrucei) 



239 



Expenments with dogs. — Of the four dogs inoculated with varying 

 amounts of cultures of the trypanosome, which had been cultivated ap- 

 proximately three years in vitro, three died of Nagana. 



One dog, after receiving five intra-peritoneal injections, each of ten 

 tubes, of generations 140, 141, and 142 in 16 days became infected two 

 days after the last inoculation, or 18 days after the first. After a rapid 

 increase in the number of parasites the dog died on the 44th day. 



The second dog received a single injection of ten cultural tubes of 

 generation 144. Unlike the first and third dogs (table IV), this animal 

 developed a typical chronic course of the disease after a period of in- 

 cubation of only eight days. The parasites were not numerous but once 

 (ten per field) and usually present to the extent of one or two per field 

 with frequent intermissions. Death did not occur until on the 127th day. 



The third dog received but one culture and showed trypanosomes 

 ten days afterwards. He died nine days later of the acute infection 

 following severe sickness. 



The fourth dog received one-tenth of a culture and did not show 

 parasites in its blood at the end of 39 days when he died. 



TABLE IV. Dogs Inoculated with Culture Crown in vitro. 



Inoculation of Rabbits with Cultures Grown in vivo. — Rabbits inoc- 

 ulated with this strain of the trypanosome usually show a period of in- 

 cubation of from two to five days but sometimes the organisms are not 

 seen by the ordinary methods of examination until on the seventh to 

 ninth day, or in very refractive animals as late as the tenth day or 

 even much longer (31 to 49 days in a few of the exceptional cases 

 where the animals received very small amounts of the infective ma- 

 terial). 



Also, depending upon the susceptibility of the rabbit, the duration 

 of the disease varies greatly. Death may occur as early as ten days or 

 it may be deferred as long as two and a half to three months. It will 

 be seen in table V that the average period of incubation is 8.4 to 11.9 

 days, while the average duration of the disease is about 40 days. The 

 number of trypanosomes to be found in the blood of these animals is 

 usually very few and remains so even up to the time of death. The 

 animals run an irregular course of fever and usually show oedematous 

 swellings which may be marked, blepharo-conjunctiva, coryza, ulcera- 

 tion of the skin and alopecia. 



