PROTOZOA IN BRITISH EAST AFRICA 
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introduced in cattle from India towards the end of 1901. 
In 1908, 2251 head of cattle and 965 equines died of this 
disease, which in Mauritius is spread by the agency of Stomoxys 
geniculatus. 
Trypanosoma vivax. Ziemann. 
Distribution. Probably widely distributed in Africa. It 
is known in the Cameroons, in Northern Rhodesia, and in 
Uganda, and a form found in Italian Somaliland is possibly 
of this species. Laveran has created T. cazalboui for a try- 
panosome very closely allied. Its existence in East Africa 
is only suspected ; parasites seen in preparations of ox blood 
sent by Mr. A. G. Doherty, the Veterinary Officer stationed 
at Marsabit, towards the Abyssinian frontier, being morpho- 
logically very similar. 
Hosts. Cattle. Other domestic ruminants are susceptible. 
Dogs, rabbits, guinea-pigs are immune. 
Morphology. Stained preparations measure from 20 /a to 26/a 
in length and from 2/a to 8* 5/a in breadth at the widest part. 
The posterior end is commonly bluntly rounded, and shows 
a well-defined kinetonucleus. The undulating membrane is 
poorly developed, being represented by a narrow structure 
which shows very slight tendency to fold. The free flagellum 
is relatively short, rarely more than 6/a or 7/a in length. In a 
fresh preparation the movement of this trypanosome is quite 
distinct from that of most other mammalian forms. Its 
movement is so rapid and the change in direction so sudden 
that it is impossible to retain any one organism in the field of 
vision for more than a very short time. 
Biology. The insusceptibility of mice, white rats, guinea- 
pigs, rabbits, dogs and monkeys is characteristic of the group 
of trypanosomes which contains T. vivax , T. nanum and T. 
cazalboui. These laboratory animals are as a rule susceptible 
to all other mammalian trypanosomes. 
Transmission. Ziemann incriminated Tabanidae in the 
transmission of this species, and Cazalbou has also laid stress 
on the importance of this family in the spread of the disease 
‘ La Soumaya,’ of which the Trypanosome named after him is 
