J. G. Thomson and Sinton (1912)[64] have obtained in cultures the various trypanosome forms of T. gambiense seen in the fly’s main gut.
Duke (1912)[65] found T. gambiense in a species of antelope, the situtunga (Tragelaphus spekei), on Damba Island in Victoria Nyanza. Wild G. palpalis could be infected therefrom. The antelope may then act as a sleeping sickness reservoir in that district, but men are apparently the chief reservoir.
Trypanosoma nigeriense, Macfie, 1913.[66]
Macfie has recently (August, 1913) described a human trypanosome from the Eket district of Southern Nigeria. It is common in young people. The disease produced does not seem to be of a virulent type in Nigeria, and does not occur in epidemic form. In the early stages the glands of the neck are enlarged. In the later stages—cases of which are rarer—lethargy appears. The parasite is a polymorphic trypanosome, morphologically almost indistinguishable from T. gambiense, though it may be slightly shorter. Macfie recorded the occurrence in his preparations of a few trypanosomes appearing to have a flagellum free during their whole length. Some of the parasites, as seen in a sub-inoculated guinea-pig, are very small (8 µ long). Other trypanosomes have their nuclei displaced somewhat anteriorly. This parasite may only be a variety of T. gambiense. The parasite is perhaps spread by Glossina tachinoides.
Trypanosoma rhodesiense, Stephens and Fantham, 1910.
The parasite was found in the blood of a young Englishman who had contracted sleeping sickness in the Luangwa Valley, North-eastern Rhodesia, in the autumn of 1909. The patient had never been in an area infested with Glossina palpalis.
(1) Morphology.—The morphology of the parasite in man and sub-inoculated rats was studied by Stephens and Fantham in 1910.[67] They pointed out a morphological peculiarity in the presence of certain trypanosomes with posterior nuclei in sub-inoculated animals, that is, parasites in which the nucleus (trophonucleus) was situated towards the posterior or aflagellar end, close up to or even beyond the blepharoplast or kinetic nucleus (fig. 31, 4, 5). When the nucleus was beside the blepharoplast, the former was seen to be kidney-shaped (fig. 31, 4). The posterior nuclear forms were of the stout and stumpy variety, and about 6 per cent. of the stumpy forms were found to have their nuclei displaced from the centre. The anterior or flagellar end of these trypanosomes often contained chromatoid granules. T. rhodesiense varies in length from 12 µ to 39 µ[68]; short stumpy forms vary from 13 µ to 21 µ, intermediate forms from 21 µ to 24 µ, and long, slender forms from 25 µ onwards. The average length is 24·1 µ.
Fig. 31.—Trypanosoma rhodesiense. 1, Long narrow form; 2–4, nucleus passing to posterior (aflagellar) end; 5, nucleus quite posterior. × 1,800. (After Stephens and Fantham.)