48 



The differentiation between the Trypanosoma pecaudi, the cause of 

 a North African disease called baleri, and the Trypanosoma dimorplion, 

 which in its smaller not free flagellated forms resemble each other to a 

 certain extent, was also demonstrated by the immunity test. 



In Laveran's experiments,* a sheep after it had recovered from a 

 Trypanosoma pecaudi infection, and its blood was proved to be sterile, 

 was tested with its own strain of virus, which in the meantime had passed 

 some guinea pigs. It was found to be refractory to this injection. It 

 was then inoculated with Trypanosoma dimorphon and developed the 

 infection in typical time, thus proving that the immunity obtained from 

 the former infection did not protect against the latter one. 



The long flagellated forms of Trypanosoma pecaudi resemble Trypano- 

 soma evansi. It was therefore possible that the original animal in which 

 Trypanosoma pecaudi was first found contained a mixed infection of two 

 different trypanosomes, a flagellated and a non-flagellated one, and the 

 former might be Trypanosoma evansi of mbori disease. Laveran inocu- 

 lated a goat, immune against mbori {Trypanosoma evansi) with Trypano- 

 soma pecaudi ; the goat developed the infection and the tAvo forms of 

 Trypanosoma pecaudi appeared again, thus pointing to the true species 

 of Trypanosoma pecaudi. 



Conclusion. 



(1) Recovery from Trypanosoma pecaudi gave immunity which pro- 



tected against this particular virus, and the blood of recovered- 

 animals was sterile. 



(2) Immunity thus obtained did not protect against an infection with 



Trypanosoma dimorphon. 



(3) Immunity obtained through recovery from Trypanosoma evansi 



(mbori) infection did not protect against Trypanosoma pecaudi. 



Trypanosoma dim.orphon was first described as a horse disease by 

 Dutton and Todd. Experiments proved that all stock can be infected 

 with it, and subsequently it has also been found in various species of 

 domesticated animals. The disease runs usually a chronic course, and 

 several animals have been observed to recover. 



Concerning immunity, some observations have been made by Martinf 

 in a goat and a sheep. These animals had recovered from a natural attack, 

 and their blood injected into dogs proved to be sterile ; when reinocu- 

 lated, they again showed the infection. 



Conclusion. — Recovery from an attack of Trypanosoma dimorphon did 

 not produce immunity. The blood of the recovered animal proved to be 

 sterile. 



* Comptes Eendus, 1907. 



j Les Tryp. <le la Guinea francaise : Ann. de I'lnst. Past., I. XXJ, No. .5, 



