Conquest of malaria : the views of Surgeon-General Gorgas / interviewed by William Macdonald.

  • William Crawford Gorgas
Date:
[1914?]
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Licence: Public Domain Mark

Credit: Conquest of malaria : the views of Surgeon-General Gorgas / interviewed by William Macdonald. Source: Wellcome Collection.

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    PROTECTIVE MEASURES. Kindly teli me something about these ameasures?’—You are aware, of course, that malaria is due to a minute micro- scopic parasite that gets into the blood of the human being and causes the symptoms which we know as malaria. kurthermore, it has been proved posi- tively that the parasite is transferred from person to person by a certain species of mosquito—the anopheles—and is trans- ferred in no other way. There are several species of mosquito, but this one alone transfers malaria. The knowledge of the life habits of the malarial para- sites and of the mosquito has enabled man to work out methods whereby he can protect himself from malaria and eradi- cate the disease in any given locality. The most practical and feasible of these methods is that of destroying the mos- quito during its larval stage. Wiuth this object the ground around every dwelling in a malarious country should be care- fully drained for a space of two hundred yards. All water containers of all kinds within this space should be at the same time destroyed, such as old cans, bottles, etc. We have adopted the limit of two hundred yards as that is about the ex- tent of a single flight of an anopheles mosquito. If for any reason there are within this limit collections of water that cannot be done away with, paraffin oil can be used. The oil acts by smothering the larvae. Every minute or two the jarvae has to breathe, and for this pur- pose it has to rise to the surface of the water. Paraffin oil spreads in a thin coat over the surface of the water. When the larvae next rises to the surface to obtain air the oil enters its breathing ap- paratus and smothers the insect. If oil is not suitable, as on the grassy edge of a stream, some poisonous larvicide can be used. These methods are all directed against the mosquito in its larval stage. Is the destruction of the mosquito lar- vae the most important measure 7—Yes ; it is by far the most important anti- malarial measure we have at our com- mand. Of measures directed to the des- truction of the larvae, drainage is much the most important and should always be carried out as completely as local con- ditions will allow. It is obvious in this connection that it is well to locate the dwellings on as high ground to the windward side and as far from water as circumstances will permit, because under such circumstances there will be the less anti-mosquito work to do. My experi- ence has taught me that man can protect himself from malaria anywhere. If it is absolutely essential that he should locate his dwelling on the edge of a swamp or dank of a Tropical stream he can do so. But the care necessary for his pro- tection in such a locality is very much greater than if he were on high ground away from water. ADULT MOSQUITOES. What about the adult mosquito ?—That is the next point; the anopheles mos- quito is very lable to destruction by wind and the direct rays of the sun. For this reason she seeks bushes, shrubbery, house or any shelter that will protect her against the wind and sun. It is, therefore, very important to clear off such material within the two hundred yards limit round the dwelling. | When the mosquito reaches the cleared space she is unable to fly across. If there is no breeding place within the cleared area, the dwelling will be pretty safe from malaria. Only the female mosquito has a biting apparatus, and therefore she alone is concerned in the transmission of the disease. Do you advocate the use of mosquito nets ?—Most certainly. It is almost al- ways the case that the above measures cannot be made absolutely perfect; some mosquitoes will get to the dwell- ing. To guard against this, the house should be made mosquito proof. This can be done by using wire-netting on the doors and windows, and closing all crevices so that the mosquito cannot gain access. With a little care the poorest cabin can be made as safe from the mosquito as the best house. Some mosquitoes will overcome all these obstacles and get into the house. Such mosquitoes hide during the day in dark places about the dwelling, and can be very easily killed by anyone with a little experience. When the mosquito gets in from the outside she is generally uninfect- ed, and has to bite somebody with malaria before she can do any harm. And it is known from experiment that at least twelve days must elapse from the time she got in till the period at which the bite would give malaria. Therefore, if every day the. mosquitoes in a properly screened house are carefully killed, there is very little chance of an individual mosquito surviving suffi- ciently long to become infected. At Pana- ma we found these measures most effective. Still some mosquitoes will pass all these lines of defence. The anopheles is a night- biter; she seldom bites during the day time. She, therefore, generally infects the individual when he is asleep at night. If we can protect him during this period of the twenty-four hours his chances for con- tracting malaria are much lessened. <A properly constructed mosquito netting over the sleeping quarters will generally do this very thoroughly. My experience has taught me that the best netting is that of canopy shape having no slit, and well
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