Our present knowledge of the etiology of Mediterranean fever, with special reference to the Royal Navy

Abstract

In 1901 it was definitely proved that the micrococcus melitensis or causative organism was not nearly such a delicate body as was generally believed; having great vitality in water, dust, etc., in the presence of light, cold, and drying, and that it was probably excreted in the urine. It was also found that very minute doses of the living culture were able to set up the disease by artificial inoculation in man after and incubative period of from five to eight days. In 1903 further observations were made, when surgeons Shawn and Gilmour, R. N., at Malta, were able to demonstrate the presence of the micrococcus in the peripheral blood of five out of eight cases suffering from the fever; later in the same year it was found at Haslar in seven out of eighteen patients, up to the 142nd day of the disease. The persistent failure to isolate the organism from the blood in previous investigations was due probably to (1) too small quantities of blood being taken; (2) to the blood being transferred direct to agar surfaces in an undiluted state, when the bactericidal properties of the serum came into play, instead of adding the blood to large quantities of fluid media, as is now done. We ad, then, three important points to work on: (1) the probable escape of the organism by the urine; (2) the resistant character of the organism outside the body; (3) the presence of the organism in small numbers in the peripheral blood, even up to quite late stages of the disease. In 1904 the Royal Societies Commission took up to work under the able management of Col. D. Bruce, C.B., F.R.S.; the working members at Malta being staff-surgeon Shaw, R.N., Major Horrocks and Capt. Kennedy, R.A.M.C., Dr. T. Zammit and Dr. R. W.. Johnstone, of the Local Government Board. The result of the first summer's work was to show the still greater vitality of the micrococcus as a saprophyte, that in dry dust it might be absorbed by monkeys, giving rise to the disease, also that it was frequently excreted in the urine of men suffering from the disease. Dr. Johnstone, in his epidemiological report, was most condemnatory of the general sanitation of the island. In Ul05 further investigations were made showing that the infection did not pass out by the breath, sweat, and skin, but by the urine and alimentary canal, and that infected clothing remained a source of clanger for long period. The most important observations were those demonstrating the wide-spread presence of infection in domestic animals and in apparently healthy natives; the cows and goats passing out the specific organisms abundantly in milk and urine, the natives while doing their usual occupations often infecting areas with urine containing the micrococcus melitensis. Some evidence was also brought forward showing the possible conveyance of infection by mosquitoes. Out. of 896 mosquitoes examined, the micrococcus was found in four, these successful results demonstrating that the organism had not only lived, but that it had been able to multiply after removal from the body in the stomach of the mosquito. Evidence was obtained of infection being conveyed to two monkeys by infected mosquitoes, and once in the case of a laboratory assistant; other modes of infection were, however, possible. The Commission this summer is particularly investigating this question of insect-borne infection. The constant presence of the micrococcus in the blood of patients, even in small numbers, and the fact of growths of the organism having been obtained from the stomachs of several mosquitoes, make it most important to gain further information of this mode of propagation. I have thus rather scantily run over the recent history of the work of experimental investigation still being carried on, let us now pass on to the epidemiological factors.