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204 History.—— The earliest description of this disease is by Clarke, who states, in the Assam Sanitary Report for 1882, that as far back as 1869 the attention of administrative officers in Assam had been directed to a peculiar disease called by the natives kala-azar, the ravages of which decimated, and in some instances almost depopulated, numerous districts in the Garo Hills. Notwithstanding its peculiar clinical features, its great fatality, its mode of spread along the lines of communication, the almost constant absence of malaria parasites from the blood, and the inefficacy of quinine treatment, until recently kala-azar was regarded by the majority of physicians as "a bad form of malaria."

In 1889 Giles, who had been appointed to investigate the etiology of kala-azar, denied its malarial nature, and stated that the disease was "neither more nor less than ankylostomiasis," because he found the ova of the hookworm in the fseces of practically all the cases he investigated. Giles's theory furnished a plausible explanation of the peculiar way in which kala-azar spread, and which could not be satisfactorily accounted for by the malaria theory. It was accepted by some, with the reservation, however, that he had under- estimated the malarial element. Dobson strongly opposed the ankylostoma theory. He stated that in 116 cases of kala-azar he had found the hookworm in 75 per cent., in 212 cases of other illness he had found it in 73.20 per cent., and in 146 healthy men he had found it in 67.12 per cent.

In 1896 Leonard Rogers and in 1898 Ronald Ross were appointed to re-investigate the disease. Both agreed as to its malarial nature; the former regarding it as a malignant type of malaria, the latter as malarial disease to which some form of secondary infection was superadded.

In 1903 Bentley endeavoured to prove that kala-azar was a malignant form of Mediterranean fever, a disease which he suggested was probably introduced into India at the time of the Mutiny by British troops from Malta, Gibraltar, and other Mediterranean ports.

Owing to the absence of malaria parasites in the