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Starting the next morning, both Mr and Mrs Baker suffering from fever, while all their quinine was exhausted, they found that their oxen had been bitten by the tsetse-fly, and were in a wretched condition, unlikely to live. Their guide also deserted them, and the whole of their carriers went off, leaving them on the Island of Patooam, in the Victoria River, to which they had been ferried across.
The tsetse-fly is found only in tropical Africa and is limited in its distribution there to certain very definite, narrow, brushy areas along the water's edge. If these places can be avoided there seems to be little danger. Those who are fighting the disease have found that if the brush in the vicinity of watering-places and ferry-landings is cleared away such places become comparatively safe.
He acknowledged the small progress that had been made in this study. From worms he went to Protozoa-Trypanosomes, sleeping sickness, host tsetse-fly showed life history comparatively, propagated in secondary host or encysting in primary host similarly malarial germs spread by Anopheles mosquitoes all very interesting.
Asses and zebras are still found abundantly and widely scattered, but the wild horse of to-day is seen only in western Asia. What happened to those who remained in America we shall possibly never know. Some surmise that a fly not unlike the tsetse-fly of Africa killed them out.
In a later chapter it will be shown how the tsetse-fly, which is somewhat like the stable-fly, is responsible for the spread of the disease known as the sleeping sickness. This disease is caused by a Protozoan parasite, a trypanosome, which is transmitted from one host to another by the tsetse-fly.
When one spends only a short time in some native huts, it is quite clear how he escapes infection. For the floor is covered with a layer of wood ashes that is usually deadly to bugs and fleas and ticks and other crawling beasts; and the atmosphere is so full of wood smoke that the most enterprising mosquito or tsetse-fly would flee, as we do, choking from the acrid smoke.
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