Diphtheria.—Formerly there was an idea that diphtheria, like scarlet fever, was extremely rare or unknown in the tropics.
The assistance of the laboratory has shown that this old idea is incorrect and that the disease is fairly prevalent in many tropical regions.
Vincent’s Angina.—While not rare in temperate climates, various affections of the oral mucous membrane due to the fusiform bacillus in symbiosis with various species of spirilla are fairly common in the tropics. The best known condition is one in which the tonsils show somewhat the appearance of a follicular tonsillitis but ulceration is more common and severe, with however, less evidence of toxaemia.
The temperature in a case of pure Vincent’s Angina rarely exceeds 101°F. but if there is a mixed infection with other pyogenic organisms the temperature and other signs of a severe infection may be more marked. There is usually more or less swelling of tributary glands. Associated with the angina or alone we may have a gingivitis in which the spongy gums more or less resemble those of scurvy or of pyorrheoa alveolaris. In fact these Vincent organisms have been considered as factors in the development of pyorrhoea alveolaris. In the tropics there have been many reports of organisms of the type of those described by Vincent occurring in skin ulceration or affection of the mucous membranes other than the oral ones, more particularly the pudendal mucous membranes.
The infections are readily and easily diagnosed by a smear stained with any simple aniline dye. Care must be taken not to accept such a finding as the sole cause, as an underlying diphtheria, syphilis or other dyscrasia may be more important.
Malignant Tumors.—It is usually stated that malignant tumors are very rare among tropical natives. The proper solution of this question, however, is complicated by the frequent lack of careful autopsies.
Pneumonia.—Just as with the tubercle bacillus so does the black race seem to have less resistance to the Pneumococcus than does the white one.
Great engineering works employing tropical natives are frequently associated with very fatal epidemics of pneumonia, especially broncho-pneumonia. Again in the black races the infection tends to become generalized rather than localized in the lungs. It is more toxic and insidious in its course than is true of the infection in the white man; it has the fatal trend of pneumonia of the aged. Another tendency is to invasion of the meninges.
Influenza.—In temperate climates we associate this disease with bronchial and coryzal manifestations. In the tropics types almost unrecognized in Europe are noted, especially the gastro-intestinal and nervous ones. The similarity in the clinical picture of dengue with slight eruption and tropical influenza is striking.