AuGusT 12, 1915] 
NATURE 
601 

Royal Society in 1896, and at that time found its way 
into many laboratories, and much of the earlier work 
on trypanosomes was founded on it. The parasite 
causing the Rhodesian and Nyasaland form of sleeping 
sickness, and which had been named T. rhodesiense, 
is considered to be identical with T. brucei. Various 
strains, Zululand, 1894 and 1913, Nyasaland and 
Uganda, are compared, and the conclusion come to 
that they are identical in morphology. 
SusceprTisitity oF ANIMALS TO T. brucet. 
horses, mules, 
oxen, goats, sheep, monkeys, dogs, and 
many others, are attacked by this parasite. Birds and 
the cold-blooded vertebrates, such as _ crocodiles, 
lizards, and frogs, are quite unaffected by it. A single 
trypanosome seems to be just as efficacious in setting 
up infection as a million, and it does not seem to 
matter whether the kind of trypanosome injected is 
one of the long and slender forms or one of the short 
and stumpy. 
Many mammals, including man, 
donkeys, 





Table I.—Giving (a) the Average Duration in Days 
of the Disease in Various Strains of T. brucei. 
jy ot eh a 
| S w | 4 
: | fol > Zils 
Strain EI Z g 4g 2 & a eu 2 
2/e fo) $o/§/Q|'s |3e4 a 
De le ae 
Human o | go | — 134 42 | 26 | 34 | 28 | 67 | 30 
Wild pame ake wf — | — Gil 385] 4r-| — |) 32 
Wild Glossina morsitans | — | — \Recovered| 54 | 38 | 29 | 47 | 8r | 26 
Zululand, 1913 -. | — | 38 310 77. | 29 | 18 | 33 | 44! 27 
(b) The Number of Animals Employed. 
Human... a oly | small I 2 | 20| 25/7/15 | 22 
Wild game a we | — | — 5/ 9/23|/—|—] 6 
Wild Glossina morsitans \ —- | — 2 16 } 14 | 25 3.| 10 | 19 
Zululand, 1913 -|—| 3 I 7| 8|17| 8 | 10] 23 








Table I. gives the average duration in days of the 
disease caused by various strains of this trypanosome, 
also the number of animals employed. From this it 
will be seen that this disease runs a fairly rapid course 
in man, killing him as a rule in three or four months. 
This, as we shall see, is in marked contrast to the 
much more chronic course of the Congo sleeping 
sickness caused by T. gambiense. In horses, donkeys, 
and mules nagana runs its course on an average of 
thirty-eight days. | No opportunity of studying the 
disease in horses occurred in Uganda or Nyasaland, 
as horses are very seldom seen in these countries. In 
the ox the disease is chronic and a certain proportion 
recover. In the other animals it may be said broadly 
that the disease runs a fairly similar course, and that 
little or no difference in the virulence is seen between 
the different strains. 
Nagana is, as a rule, a fatal disease. With the 
exception of the oxen, almost all the other animals 
die. Out of 318 employed in these experiments only 
three recovered. ° 
From its action on animals, then, just as from its 
morphology, it is apparent that T. brucei as it occurs 
*n Zululand differs in no way from the Nyasaland 
strain called by Stephens and Fantham T. rhodesiense. 
Tue INnrectivity oF WiLp TsETSE-FLIES 
(G. morsitans). 
The tsetse-flies in Nyasaland were examined in 
order to find out how many of them were naturally 
infected. There were fifty-six experiments, and 10,081 
tsetse-flies (G. morsitans) were employed. In the fifty- 
six experiments T. brucei was found twenty times 
(35-7 per cent.). Nine monkeys, fourteen dogs, and 
eleven goats were infected. This gives a proportion 
of 1 in 500, or 2 flies per 1000 caught in the sleeping 
NO. 2389, VOL. 95] 

sickness area, Nyasaland, infective with nagana. This 
is only allowing one infective fly to each series of 
flies fed on the experimental animals, and is therefore 
the irreducible minimum. 
TRYPANOSOMES FouND IN THE BLoop oF WILD 
AnimaLs LIVING IN THE SLEEPING-SICKNESS AREA, 
NYASALAND. 
When an animal was shot a small quantity of its 
blood was taken in a sterilised bottle containing citrate 
of potash to prevent coagulation. Smear preparations 
were made at the same time. As the animals were 
often shot thirty or forty miles away from the camp, 
a motor-cycle was used to get the blood up the hill as 
quickly as possible. When the blood arrived at the 
laboratory it was at once injected into a goat, a 
monkey, and a dog. In this way 180 specimens of 
blood of wild game living in the fly area were 
examined, and fifty-seven were found to harbour patho- 
genic trypanosomes (32 per. cent.). 
This is, however, probably much below the actual 
percentage. A wild animal is only examined once, 
and that often under unfavourable conditions. If it 
were possible to examine the same animal several 
times it is probable that many. more would be found 
infected. The parasites come and go in the blood ; 
one day they may be present, the next day absent. 
The big game live in the “Fly Country’ among 
swarms of infected flies, and are constantly liable to 
infection and re-infection. 
The following table (Table II.) represents the num- 
ber of times T. brucei was found among the 180 wild 
animals examined, and the species of game which 
Table I1.—This Represents the Number of Times be 
brucei was Found Among the 180 Wild Animals 
_ Examined and the Species of Game which Har- 
boured it. 
Number Number 
Species of Number _ infected Species of Number infected 
animal examined with animal examined with 
T. brucei ‘ T. brucet 
Eland LO (a) Duiker.. 7 I 
Sable ene ds ° Buffalo.. 9 o 
Waterbuck 13 3 Lion I to) 
Koodoo ..- 3 to) Hyena.. 3 o 
Bushbuck... 10 o Elephant 2 o 
Hartebeeste 35 5 Warthog 33 I 
Reedbuck... 19 3 Wild cat 3 (0) 
Oribi Mo IS} I Porcupine 1 to) 

From this it will be seen that fourteen 
animals among the 180 harboured the nagana para- 
site (7-8 per cent.), and that the waterbuck, harte- 
beeste, reedbuck, and duiker seem to be the most dan- 
gerous neighbours to man. Twenty-three per cent. of 
the waterbuck, 14 per cent. of the hartebeestes, 16 per 
cent. of the reedbuck, and 14 per cent. of the duiker 
had T. brucei in their blood. If, then, the contention 
that this parasite found in the wild game is the cause 
of Nyasaland sleeping-sickness be proved to be true, 
then it is abundantly obvious how dangerous these 
wild animals are to man; and it must be borne in 
mind that in this Nyasaland fly area T. brucei is only 
one of the pathogenic species of trypanosome found in 
the wild game. Other three species pathogenic to the 
domestic animals are also found, T. pecorum, ie 
simiae, and T. caprae; T. pecorum in 14-4 per cent., 
T. simiae 1-7 per cent., and T. caprae in 11-1 per cent. 
of the wild game examined. It is self-evident that 
these wild animals should not be allowed to live in 
“Fly Country,” where they constitute a standing 
danger to the native inhabitants and the domestic 
animals. It would be as reasonable to allow mad 
dogs to live and be protected by law in our English 
towns and villages. Not only should all game laws 
harboured it. 
