Both sexes are to the same degree susceptible, though men are attacked more frequently for the reason that they are exposed more frequently to the influences which produce the disease.
Malaria spares no age; yet children are attacked much more frequently than adults. The advocates of the air theory explained this by the assumption that the closer the layer of air is to the ground, the more malarial organisms it contains and consequently children breathe in more than adults. The mosquito theorists maintained that the skin of children, as a result of its delicacy, is less resistant to the mosquito's prick, and that children defend themselves less from the insects.
There are numerous publications in relation to the frequency of malaria in children. Among others we may mention that of Borius, which asserts that the high mortality of the natives in Senegal is to be ascribed principally to this disease in children (compare also the section Malaria in Children and Old People).
Occupation stands in the closest relation to malaria . Avocations requiring sojourn in the country, particularly in the region of swamps, marshes, and rivers, especially when connected in any way with the working of the soil, constitute the greatest contingent causes of the disease; while occupations which confine to the city or the house are much less dangerous.
The most frequent sufferers are laborers occupied with the dry ing up of swamps, in building harbors, railroads, foot roads, fortresses, and bridges, fishermen, farmers (particularly rice and tobacco farmers), woodcutters, especially in forest clearing, etc. We must not forget, too, soldiers who, during war time, are obliged to camp in swampy regions.
The loss in colonial armies from malaria can, under circumstances, reach enormous dimensions. As an example we may recall the campaign of the French in Madagascar (1895). Reynaud's report of this expedition states that the loss from deaths-at least 72 per cent, of which were malarial cases-amounted to 32 per cent, of the whole force. These enormous figures could certainly be reached only through an incomprehensible contempt for sanitary laws and regulations on the part of the leaders. Nobody can read Reynaud's instructive book without a feeling of the deepest compassion for the sufferings of the staff. On page 354 we find: "The advance guard, with a force of 2500 men, showed in the first months 25 deaths. The mortality increased rapidly and amounted, during' March, to one man daily, during April to two, during May to four, during June to eight, and at the time of the building of the earthworks, which was done by the white troops of the Second Brigade, it rose during July to twelve, at the beginning of the month of August to twenty four, in the middle of August to thirty four, at the end of August to forty, and during September and October to forty five men per clay."
According to Fayrer, the British army in India, consisting of 64,137 men, had, in the year 1892, a mortality from fever of 6.95 per cent.; the native army, of 2.59 per cent.; the general population, 2.81 per cent. Throughout India, during the same year, 6,980,-785 people died, among them 4,621,583 of "fevers," and of the latter, according to Fayrer's estimation, two thirds of malaria . With what caution these figures must be received we have already pointed out.
The English vessels "Monarch" and "Media" carried, in the summer of 1842, an expedition into the valley of the Xanthus (Asia Minor), in order to make excavations. Among 120 people landed from the "Monarch," 84 were attacked by malaria , and of these, 9 died. Altogether, among 153 landed, 104 were attacked, of whom 10 died and 21 were disabled (Friedel).
Moreover, not alone in the tropics, but even in temperate climes, armies suffer frightfully at times from malaria . It is only necessary to mention the expeditions from England to Holland in 1747 and 1804. On this latter expedition England sent an army of 36,481 men to the island of W'alcheren. Fifty days after landing 10,000 were in the hospitals with malaria, of whom 25 to 80 were dying daily. Altogether 36,000 men were attacked-i. e., almost the entire army (quoted from Maclean).
In the Russian-Turkish campaign (1877-1878) the Russian army on the Danube showed 140,000 malarial cases, with 1092 deaths. In Pola in August, 1864, before the introduction of the sanitary improvements, 27 per cent, of the local force suffered from malaria , and this amounted to 90.6 per cent, of the entire morbidity (Jilek). In the year 1880 the force in Pola consisted of 1416 men, of whom 529 were attacked by malaria (Krumpholz).