With healthy cholera carriers the period of the continuance of vibrio excretion is equally short but cases have been reported where periods of from three weeks to two months have been noted. It is usually stated that 97% of carriers become vibrio free within a month.
Greig has found infection of the bile of the gall bladder or ducts in 80 cases in 271 cholera autopsies. When living organisms are injected into the ear vein of a rabbit they pass into the bile. An examination of the epithelial layers of the gall-bladder of such a rabbit shows destruction of the cells and the presence of vibrios in the underlying tissues. While cholera spirilla are soon crowded out by intestinal bacteria, thus explaining the short period during which cholera spirilla are excreted by convalescents, this is not true when the cholera vibrio gets into the bile ducts or gall bladder. Greig found one cholera convalescent excreting cholera vibrios forty-four days after the attack. Of 27 persons who had been in contact with cholera patients 6 were excreting cholera vibrios although apparently well.
A very important matter is that persons who fail to show cholera vibrios may begin to excrete such organisms after the administration of a purgative or following some intestinal disorder. In fact purgatives may set up an attack of cholera in a cholera carrier.
The spread of cholera is intimately connected with the great religious festivals and pilgrimages of Oriental people. Not only do those of India keep up the dissemination of the disease there but pilgrims going from the delta of the Ganges to Mecca carry the infection and transmit it to their fellow pilgrims from Egypt and Algiers. Greig examined a number of cholera convalescents who were about to return to their homes in India and found 30 per cent of these pilgrims excreting cholera vibrios in their stools.
In India cholera accounts for about 1 to 1.5 deaths per 1000 of population. Malaria and plague are other great causes of death.
The intimate commercial relations between Europe and Egypt and Algiers make the introduction of the disease into European ports an easy matter. Of particular importance is the fact that so many sick people make pilgrimages, these being peculiarly liable to act as carriers.
Excesses in eating, often of badly prepared or decomposing food, following periods of religious fasts, predispose the natives of India to cholera.
Lowered resistance, as from disease or from gastric disorder, increases the susceptibility to cholera. Errors in diet and in particular the effects of alcoholic excesses markedly predispose to infection.
Pathology
The cholera spirillum does not produce a soluble toxin, the toxic principle being intracellular. The organism rarely penetrates more deeply than just under the epithelial layer of the glands of Lieberkühn. As a result of the outpouring of the fluid into the lumen of the gut we have an increase in the red cells (7,000,000 per cu. mm.) and leucocytosis of from 12,000 to 50,000. The specific gravity of the blood is greatly raised, 1073 to 1078, and the alkalinity diminished. The blood pressure is markedly lowered, 60 mm. in very severe cases and 75 mm. in less severe ones.