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mostly in places where the natives admitted the infection, I conclude that it is hard to find trypanosomes in goat's blood. Very likely they appear for a day or two and disappear again.
There is some evidence that goats have or are acquiring a certain amount of immunity. Nkoka told us that his goats used to die, but have now stopped; and Minamsanzwa says that his goats died last rains and he expects them to die in the rains again, but during the dry season they have done well.
Sheep. It seems that before the European occupation the natives did not possess sheep. They have been recently introduced (?where from). The fly seems to be very fatal to them. At many villages they have all died; others have a few only.
The natives give the symptoms as wasting without loss of appetite, but also mention swelling of the head and neck. I did not see this. Very likely it occurs in rapidly fatal cases.
I found six animals infected out of 24 examined. One of the six in which trypanosomes were very numerous died a few days after I saw it. Another was driven 40 miles to Kariyangwe and seen there three weeks after the first examina- tion. I believe it died soon afterwards. A third sheep was examined on October 22nd and again on November 13th, three weeks later. Trypanosomes were harder to find at the second examination than at the first. It seems, therefore, that try- panosomes are much more easily found in sheep than in goats, and at an earlier stage of the sickness.
Table of Sheep and Goats examined.
Manjolo
Buwampu
Sinasitonka
Siandola
Chabota
Nkoka
Simseu
Sheep.
5
Goats. 4
8
3
3
3
1
Sinombo
2
Siasadoto
12
Chamaiyua
2
Minamsanza
3
Mlonko
1
3
Silubu
3
3
Pashu
1
Sinachungwe
1
4
Mpengwe
1
3
24
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Animals from above list found to be suffering from Trypanosomiasis.
At Buwampu, one goat; not obviously ill. Trypanosomes, two in three films. Animal died a few days afterwards.
At Siandola, two sheep. (1) Numerous trypanosomes. Animal died a few days later. (2) Scarce trypanosomes. Animal was alive a month later at Kariyangwe (rabbit inoculated). At Kariyangwe trypanosomes were numerous. I believe the animal died or was killed after inoculation of rabbits.
At Saboda, one goat. Died a few days later. At Nkoka, two sheep. One was very ill.
and would die soon. Trypanosomes plentiful.
In the other, trypanosomes scarce.
Chief said it had been ill for a month
At Simseu, one sheep. Examined October 22nd, when trypanosomes were plentiful. November 13th, same animal had scarce trypanosomes.
At Minamsanza, one dog, belonging to Mr. Trotter.
At Sinachungwe, one sheep, in
poor condition.
Dogs.
One sees in the kraals outside the fly many dogs with a large admixture of European blood. In the fly very few dogs are to be seen, and my impression is that
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most of those are pure native. But the pure native dog seems to have only a slight degree of immunity. Two or three animals is the most one sees in villages where fly is numerous.
It is hard to find cases, because the disease is rapidly fatal. Dr. Fleming found one case at a village visited.
Mr. Trotter took two dogs into the fly on September 17th and was in the fly with them until October 1st. On September 30th one dog, a greyhound, was thin and languid, blood negative. The other, a mongrel, partly native, appeared well. The greyhound died on October 18th without being further examined. The mongrel died on October 21st; trypanosomes numerous in blood just before death.
Trypanosomiasis in Game.
Blood was examined from the following animals shot in the fly:
Duyka...
Elephant
Roan
Zebra
1
1
1 4
Eland Mpala Warthog Waterbuck
4
2
2
5
Trypanosomes were found in the blood of two waterbuck, the other animals being negative. Two of the trypanosomes were found by Mr. Bevan, who kindly looked through our slides.
The waterbuck were :-
(1) A young adult bull from Siandola. Mr. Zunkel, who shot the animal,
remarked that it was in poor condition.
(2) A calf less than half-grown, in good condition, from Mbele Hill.
(3) A big herd bull from the Seng'wa, close to the Busi junction, in good
condition. Siandola is in the centre of the fly-belt, Mebele Hill at the western extremity of plentiful fly, and the Seng'wa near the eastern boundary of the fly.
The Trypanosome.
As seen in fresh films, whether from men, small stock, or dogs, it is a long, slender and active trypanosome. On one occasion only, in the blood of a sheep, saw a single trypanosome which appeared to be truncated at the posterior (aflagellar) extremity.
One can distinguish three kinds of movements, which, however, pass into each other :-
(1) The trypanosome goes steadily forward flagellum first, with rhythmical sinuous movements. This movement is only seen when the blood is quite fresh.
(2) The trypanosome lashes about irregularly, and moves flagellum first, but
sometimes backwards or sideways.
(3) The trypanosome lashes about irregularly without progressing, though
there is no visible obstruction.
We reckoned that a trypanosome travelling with the first movement would cross the field in about 20 seconds. (It is difficult to observe this directly because the organism never keeps on one course for the diameter of a field. The method we followed was for one to count seconds allowed, while the other looked down the micro- scope.) The diameter of field used was 0'24 mm., so that the pace was approximately 0'01 mm. per second.
Habits of the Tsetse Fly.
I have no original observations to record, but, with a view to considering the question of prophylaxis, I propose to recapitulate what is generally believed and accepted.
If you sit down in the bush by yourself, not happening to have any flies on you, even in a place where flies are numerous, probably one or two flies will find you out and attack you, but in order to be attacked by numerous flies it is necessary to walk about. Some observers (e.g., the Administrator of Northern Rhodesia) maintain that if one stops walking and sits down the flies will leave one, but I do not myself admit this. At any rate, it appears that the tsetse does not fly much or far in search of blood, but waits for an animal to come its way. When an animal comes a hungry fly bites immediately, and if not disturbed gorges itself and flies away, settles, pro- bably on the underside of a leaf, and proceeds to digest. Digestion is, perhaps,
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