Both methods should be tried. Malarious patients should, so far as possible, be treated with quinine, and no effort should be spared to free their system from the parasite. Special precautions, such as hanging up mosquito curtains, etc., should be taken to prevent the access of the mosquito to the patient; otherwise he acts as a centre of infection. It is almost equally important to protect the healthy man living in a malarious place. The mosquito net must be carefully made, and let down over the bed well before sunset; its free edges should be tucked under the mattress, and the greatest care should be taken to prevent the ingress of a mosquito, especially when slipping within the curtains. Punkahs should be employed as much as possible; they certainly tend to keep the Anopheles at a distance. In the summer of 1899 an experiment was initiated by Sir Patrick Manson which must convince even those least open to conviction that malaria is preventable if proper precautions be taken. That the bite of an infected mosquito can convey malaria may be taken as proved by the voluntary submission of Mr. T. P. Manson to the experiment, as recounted in the Times.[5] This gentleman allowed himself to be bitten, in this country, by insects previously fed on malarious patients; and in due course the disease—tertian ague—showed itself in him. To prove the other side of the case required even more courage and endurance. During the spring of 1899, Dr. Low and Dr. Sambon, of the London School of Tropical Medicine, with Signor Terzi, an Italian artist, and two servants, have been living in a mosquito-proof hut, near Ostia, in the Roman Campagna, and remained in perfect health. The spot selected for this experiment is so malarious that the Romans regard spending a single night there as equivalent to contracting a virulent type of malaria. Yet, when Professor Grassi and several other experts visited the mosquito-proof hut on September 12, 1900, they found the inhabitants in perfect health—a fact which they telegraphed, with their salutations, to Sir Patrick Manson, ‘who first formulated the mosquito-malarial theory.’ The conditions under which Dr. Low and Dr. Sambon and their Italian companions lived were all directed to the avoidance of being bitten by mosquitoes. During the daytime they were allowed out of their hut, because the chance of being bitten in broad daylight is so small that it may be neglected; but they were ‘gated’ an hour before sunset, and were not allowed out until an hour after sunrise. The mosquitoes were kept out of the hut by the use of wire-gauze doors and windows. By these precautions contact between mosquito and man has been avoided, and man has now lived for months in one of the most malarious spots in Europe without acquiring a trace of malaria. It is most satisfactory to record that a similar success has attended the efforts of the Italian authorities to improve the state of things in the great plain of Salerno. Visitors to Paestum and Battipaglia cannot fail to have noticed how malaria has marked that district as its own. By taking such precautions as are indicated above, the peasants and railway signalmen have, during the last few years, for the first time, escaped the disease; whilst for the first time newcomers to the district have failed to contract it. The intelligent activity of the Italian Government, and the well-known interest taken in the question by the King and Queen of Italy, cannot fail to have a profoundly beneficial effect upon the lives of some of the poorest and most hard-working of European peasantry.
The problem in Africa is more complex, owing to the fact that the native population is thoroughly permeated with the parasite. Mr. Christophers and Dr. Stephens, in their ‘Further Reports to the Malaria Committee,’ have shown that the children of natives are in the great majority of cases infected with malaria. In one village where the Anopheles was found in ‘considerable numbers,’ 90 per cent. of the babies suffered, 57 per cent. of the children up to eight years, 28 per cent. of the children up to twelve years, after which age the children were ‘very rarely infected.’ This is but one example out of many, all tending to show that after a time a certain immunity to the disease is acquired, and, further, that travellers should as far as possible avoid the neighbourhood of native villages, and, above all, decline to sleep in native huts.
The destruction of the mosquito, at any rate in neighbourhoods inhabited by man, is a matter of difficulty, but is worth attempting. To expect to destroy the mature insect seems a vain thing, but the larva can be more easily dealt with. Anopheles—unlike the common gnat, which breeds close to houses, in cisterns, garden fountains, old tubs, drains, etc.—prefers rain-water puddles, natural hollows by the roadside, small ponds, and rice-fields. We have occasionally found the larvæ of Anopheles and Culex in the same water in England, but this is probably exceptional. In England, so far as our experience goes, the Anopheles larvæ are usually met with in shallow water easily heated by the sun’s rays; and we have always found them in association with the common green water-weed Spirogyra, though they are not known to eat this.
Attention to the standing water round houses or near towns will do much to diminish the scourge of mosquitoes. All pots and pans containing water should be regularly turned out once a week, and puddles should be brushed out. The larva takes some seven days to develop, so that once a week suffices to destroy each brood. All useless water should be drained away and stagnant ponds filled up. The introduction of fish has markedly diminished the number of mosquitoes around the late Mr. Hanbury’s celebrated garden at La Mortela on the Riviera. They eagerly devour the larvæ, and should be made use of in all large areas of water. For smaller areas some ‘culicide’ should be tried, and more experiments in this direction are urgently needed. One of the simplest remedies known is kerosene oil. A piece of rag tied to a stick should be dipped into the oil, and then applied to the surface of the water. The oil diffuses in a fine film over the surface and clogs the breathing tubes of the larval insect; it possibly interferes with the action of the surface tension—at any rate, the larvæ die. Fresh tar has the same effect. This ‘painting’ of the water must be renewed once a week. Wells and cisterns should be kept closed. A more careful selection of the site for houses, and a more liberal use of wire-netting mosquito shutters, will do much to minimize the risk to Europeans in malarious districts.
The various remedies suggested above have been tried with success in different parts of the world. The writer has been assured by an old inhabitant of Colombo that the mosquitoes have distinctly diminished in number in parts of that town since the custom of storing water near the houses was abandoned. During the summer of 1900 the authorities at Sassari in Sardinia claim to have ‘practically exterminated the mosquitoes ... by killing the larvæ in the swamps with petroleum, and the flies with chlorine and other destructive chemicals.’[6]
The extinction of malaria in England is a kind of by-product of the draining operations which restored to the agriculturist large tracts of land in the fen districts and elsewhere. The breeding-places of the mosquitoes were dried up and their numbers materially lessened; at the same time the parasite was killed in an increasing number of patients. Thus the mosquitoes which survived had fewer opportunities of infecting themselves, and as time went on the parasite was ultimately eliminated. Anopheles, though in diminished numbers, is still with us, and is especially to be found in those parts of England once infested with the malaria; but the parasite has disappeared.
‘INFINITE TORMENT OF FLIES’
Where the water is stopped in a stagnant pond,
Danced over by the midge.
R. Browning: ‘By the Fireside.’
The last few years of the nineteenth and the first few years of the present century are marked in the annals of medicine by a great increase in our knowledge of certain parasitic diseases, and, above all, in our knowledge of the agency by which the parasites causing the diseases are conveyed from host to host.
Chief among these agencies in carrying the disease-causing organisms from infected to uninfected animals are the insects, and, amongst the insects, above all the flies. Flies—e.g., the common house-fly (Musca domestica)—can carry about with them the bacillus of anthrax, and, if brought into contact with a wounded surface, may thus set up an outbreak of woolsorter’s disease. Flies, ants, and other even more objectionable insects, are not only capable of disseminating the plague bacillus from man to man, and from rat to man, but they themselves fall victims to the disease, and perish in great numbers. They are active agents in the spread of cholera, and the histories of the South African and Cuban wars definitely show that flies play a large part in carrying the bacilli of enteric fever from sources of infection to the food of man, thus spreading the disease. They are also accused of conveying the inflammatory matter of Egyptian ophthalmia, and of the ‘sore-eye,’ so common in Florida, from one human being to another.