Malaria, syphilis and leprosy are easily excluded. As regards beriberi, there should be no difficulty if it be borne in mind that it is a disease of the peripheral, whilst trypanosomiasis is a disease of the central nervous system; that beriberi is non-febrile, and that trypanosomiasis is febrile. Kala-azar and trypanosomiasis, especially in their earlier stages, may be more difficult to differentiate; but the presence of enlarged glands, local oadema, and erythema multiforme in trypanosomiasis, and their absence in kala-azar, suffice for distinction. Blood or gland-lymph examination, or, if this be negative, hepatic or splenic puncture, should establish the diagnosis.
In pellagra the erythema is of a characteristic type. It is not ringed or fugitive as that of trypanosomiasis, and it affects principally the exposed parts of the body; the disease is of a much more chronic character, and, instead of lethargy, the mental condition, if implicated, is more that of insanity melancholia alternating with mania and terminating in dementia. Further, in pellagra, the symptoms are aggravated at particular seasons spring and autumn.
General paralysis of the insane,*[1] cerebral tumour, forms of meningitis, have features in common with trypanosomiasis and must be considered in diagnosis.
The microscopical diagnosis of trypanosomiasis is sometimes difficult. Anæmia as well as a large mononuclear leucocytosis occurs in trypanosomiasis. A wet blood preparation exhibits, even to the naked eye, a remarkable clumping of the red corpuscles. Held up to the light, such a preparation has a peculiar granular appearance, produced, as can be seen on microscopical examination, by agglomeration of the corpuscles into heaps and clusters, the usual rouleaux arrangement being absent. Such a disposition of corpuscles is significant of, though not peculiar to, trypanosoma infection. As a rule, the parasites in the peripheral circulation are few in number, many fields having to be hunted before a
- ↑ * The Wassermann reaction is of little avail, as unfortunately the sera of most cases of trypanosomiasis give a positive result.
