TRYPANOSOMA VIVAX 559 



an observation made independently but shortly after by Kingliorn and 

 Yorke (19126) in the Luangwa Valley. Bruce et al. (19146) found that 

 G. hrevipalpis might be naturally infected with this trypanosome. They 

 also showed (1913cZ) that the wart hog {Phacochcerus cBthiopicus) was the 

 natural reservoir. They found that the course of development in the fly 

 was similar to that of T. congolense, the usual period of about twenty days 

 being required before the fly becomes infective. The development 

 commences in the stomach. Finally, the labial cavity is infected, where 

 crithidia forms are evolved. These invade the hypopharynx and develop 

 into metacyclic trypanosomes (Fig. 231). 



(c) Trypanosomes which Develop only in the Proboscis of Tsetse Flies — 

 Monomorphic Trypanosomes provided with Flagella. 



Trypanosoma vivax Ziemann, 1905. — Synonyms: T. cnsalbouiLa,VGran, 1906; 

 Trijpanozoon vivax (Liihe, 1906); Trypanosoma bovis Kleine, 1910; T. angolense 

 Broden and Eodhain, 1910; Buttonella vivax (Chalmers, 1916). 



As with so many of the pathogenic trypanosomes, there has been considerable 

 confusion over the correct name of Trypanosoma vivax. Ziemann (1905) described a 

 very active trypanosome from the blood of cattle, sheep, and goats in the Cameroons. 

 It was of wide distribution, and was seen many times in the area he investigated. 

 With blood taken from infected animals a series of inoculations was made. Eight 

 grey rats which had suffered from T. lewisi infection were inoculated, and died in 

 eight to eleven days. One white rat was inoculated, but did not become infected, 

 nor did a cat. A dog showed scanty trypanosomes after ten days, but these quickly 

 disappeared, and did not recur. Laveran (1906) gave the name T. cazalboiii to a 

 ver}^ similar trypanosome which Cazalbou had studied in cattle in the Upper Niger 

 region. This trypanosome, though inoculable to sheep and goats, was not inoculable 

 to monkeys, dogs, guinea-pigs, rats, and mice. 



The question is whether this form is identical with Ziemann's T. vivax. If it 

 be regarded as identical, it has to be explained how Ziemann infected his eight 

 rats, for all subsequent workers are agreed that the trypanosome of this type 

 is not inoculable to these animals, and it was chiefly for this reason that the new 

 species, T. cazalboui, was created. It is just possible that Ziemann mistook T. lewisi 

 in the rats for T. vivax, for he states earlier in his paper that when T. brucei and 

 T. leivisi exist together in the rat, they are easily distinguished, whereas with T. vivax 

 and T. lewisi this may be very difficult unless stained Alms are examined, and no 

 details of the infection in the rats are given. 



That the eight rats died is again explicable from the fact that wild rats frequently 

 die in captivity quite apart from any infection. Whether this will explain the dis- 

 crepancy or not, it may be noted that in the other inoculations — namely, the white 

 rat, the cat, and the dog — only a slight transitory infection took place in the dog, and 

 this is in agreement with all later observations on T. vivax. Laveran and Mesnil 

 (1912) state very emphatically that it is impossible to identify a trypanosome 

 inoculable to rats (T. vivax) with one which is not thus inoculable (T. cazalboui). 

 They consider that T. vivax cannot be employed as a name for any known trypano- 

 some. Bruce et al. (1910e), on the other hand, came to the conclusion that T. vivax 

 and T. cazalboui are identical. They compared the Uganda strain, which Laveran 



