CONTROL OF INTESTINAL AND INSECT BORNE DISEASES

CONTENTS

34. General Control Measures of Intestinal Diseases.

The control of intestinal diseases is based on the control of environmental conditions with a view to preventing the transmission of the causal organisms by water and food. General measures for the control of intestinal. diseases include water purification, food protection and control, waste disposal, and control of the housefly. Prophylactic immunization is employed as a routine measure in the control of typhoid fever; at times it may be utilized in the control of other intestinal diseases, particularly paratyphoid lever, cholera, and bacillary dysentery. Immunization of all army personnel against yellow fever is in effect.

CONTROL OF INTESTINAL DISEASES

Water Supply and Field Purification

35. Importance of Pure Water.

The importance of pure water cann9t be over-emphasized. Until the method of spread of intcstiruu diseases was understood and the part that water played in the conveyance of these diseases recognized, they were the largest cause of morbid~ty and sickness in the armies of the world.

36. Potable (Safe) Water.

Pure water is, of course, the quality of water desired but seldom found. Even though a natural source of pure water is available in a given area when a body of troops arrives to occupy it, the likelihood of such a water remaining pure is very remote, as water becomes polluted easily. Contrary to popular impression, it is not possible to determine, by simply looking at it, whether or not a particular water supply is safe £or drinking in its natural state. The cool, sparkling water from the closest spring may be laden with disease producing germs. On the other hand the water from a muddy or discolored stream may be suitable to drink in its raw state.

The only safe method of dealing with water from an unknown source is to assume it to be dangerous until it is proven otherwise. Even water from a community's public water supply system cannot be taken for granted as being, a safe water just because it happens to be from a public supply system. The safety of such a water can be quickly and easily ascertained, and such action should be taken before it is pronounced safe for troops.

37. Sources of Water.

The common sources of water are rivers and streams, lakes, wells, springs, tube borings, and distillation. Water from rivers and streams cannot be considered safe. Lakes, if large, arc usually clean in the center. The action of the sun and of oxygen purifies the water far from the shore. Shore, water is never safe.

Spring water is of two kinds, namely land and main springs. Land springs are formed by water that percolates through the ground and appears at lower levels. It may be heavily contaminated. Main springs are derived from underground reservoirs lying between two impermeable strata, Such water has usually been filtered through a considerable depth of soil and is usually, but not necessarily, free of disease-producing germs. All such water of course contains soil bacteria and is not sterile, though it may be potable and safe for human consumption.

Well water is subsurface water and not necessarily safe just because it is not on the surface. Shallow wells may drain the surface almost directly, and deeper wells in the vicinity of privies and barnyards may, in porous soil, be heavily contaminated. No well water should be accepted as safe until it has been proven so bacteriologically. To be safe, wells should penetrate through an impermeable stratum, be lined so as to exclude surface drainage, covered to prevent ,surface contamination, and equipped with pumps, etc. so that nothing is introduced, such as buckets, from the outside.


PLATE 8 - General Factors in the Control of Intestinal Diseases.

Artesian water obtained by tube borings is usually safe. Such water comes from underground supplies, formed by water draining from hills underneath impermeable strata of soil. It is best obtained in valleys and at the lowest points of plains. Distilled water is bacteriologically pure but is not obtainable in sufficient quantities.

38. Responsibility for Water Supplies.

In the army, the Quartermaster Corps is responsible for the quantity and quality of all water supplies in time of peace, and for the zone of the interior in time of war. The Corps of Engineers is responsible for the quantity and quality of the, water supplies for troops in the theater of operations to divisions and higher mobile units. Organizations below the division generally have to provide their own water supply, usually under the general supervision of the Corps of Engineers. The Medical Department is responsible for determinin1r the potability of, and advising as to the sanitary. suitability of, all water supplies for military personnel at all times and places. The unit commander is responsible for the water discipline of his organization and for the execution of standing orders pertaining to the purification of water by and within his own organization.

39. Water Requirements.

All living things require water. Experjencc has sbown th11t the minimum amount of water that must be provided for troops under ordinary conditions of march or in bivouac is 1 gallon per mo.n per day, I½ quarts for drinking and 2½ quarts for cooking and drinking with meals, either as water, as coffee,. or other beverage, However, climatic conditions and the effort of march may alter this minimum.. Let us suppose that the commanding officer of a body of troops desire, to move camp to another location. He is anxious to know how much water will be required per man per day during the march and in the new location. The medical officer is asked to estimate these requirements and to advise on the plan. What then arc the water requirements in the various situations, in permanent camps, in semipermanent camps, on the march, or in bivouac? The following will serve as a guide in this estimation. Permanent camps: One should estimate a per capita consumption of 50 gallons pet day where there is a water-borne sewer system and where there arc the usual lawns and other features requiring water. Temporary camps: One should estimate 5 gallons per person per day and 10 gallons per animal. This amount should not be greatly exceeded since waste water must be disposed of by improvised methods and an excess will collect as unsanitary surface water.


PLATE 9 - Location of Water Sources - Stream.

Bivouac and march:
Two gallons per capita are necessary, except under unusual conconditions when 1 gallon is the absolute minimum as indicated above. This is based on 1 gallon for cooking and drinking purposes and 1 gallon for washing. The animals will each require 4 to 10 gallons depending on whether the weather is cold or hot. In combat: The amount necessary to retain efficiency should not be less than the minimum of 1 ½ gallons per capita per day. In extreme conditions animals can be limited to 5 gallons per animal per day.

40. Protection, of Water Supply Sources.

Every source of water supply, civilian or military, should be carefully guarded against pollution. The principal and most dangerous pollution is human and animal excrement or sewage; these wastes are often intentionally placed in water to dispose of them or are washed in from deposits of excrement on or near the surface of the ground. During droughts, surface and ground waters are more likely to be polluted than under average conditions. During floods high water reaches deposits of exc;rement and washes them into the watercourses. Such deposits would not ordinarily be dangerous.

Water supply sources for military forces can be, and usually are, carefully guarded so as to mirumize the possibility of local pollution. Latrines are placed so that surface or underground drainage from them cannot reach the water source. Great care must be taken that the watershed is not contaminated by careless individuals. When streams arc used as a source of water, points along the stream are designated at which water for various purposes may be drawn. Beginning upstream, the following points are designated: water for drinking and cooking, water for animals, water for bathing, water for laundry, and that for washing vehicles (Plate 9). It is often necessary to place a "water guard" to enforce compliance with such instructions.


PLATE 10 - Water Sterilizing bag with Tripos.

41. Purification of Water.

a. The average person surrounded by the benefits furnished by modern public health service gives little thought to the machinery behind it and the efforts that are put out to conserve the public health. The medical officer quickly realizes this when upon him is suddenly thrown the responsibility foli the health of large bodies of troops. In .time of war and of public peril the civilian practitioner or the medical officer may be the ultimate factor in bringing about a successful or unsuccessful outcome, particularly as regards the Army. He becomes a small public health service and is expected to function for the good of bis community in preserving its health. Among his most important duties is the overseeing of the water supply and advising as to its purification. Some practical method must be employed to purify water that is easy to carry out, that can be used with small numbers of troops as wdl as llll'ge, that can be carried on in the field and so be available at all times, and that will be efficient and dependable.

Distillation, while it is a certain method of obtaining pure water, is usually out of the question.

Boiling stailizes water and can be used on a small scale but is impracticable on a large scale. A company of 250 men requires three barrels of water daily for drinking purposes alone, The amount of labor and time required to boil so much water daily is almost prohibitive, so that this method can never be of wide application, specially with moving commands.

Therefore some other method must be sought. The most reasonable solution is to devise some method of purifying water chemically, and this is exactly what has been done. An Army medical officer, Major Darnall, discovered the principle of cblorinacion of water and in 1910 originated the liquid chlorine method of purification. Utilizing this knowledge, a small field chlorinating outfit has been devised and is used by the Army. It is one of the most important contributions to military sanitation that bas ever been made. (See Plate 10). This simple and yet important outfit is known as the water-sterilizing bag. Before using chlorination, the water should be clar-ified, if that is necessary, as related in the following paragraph.

Before water is rendered free of bacteria chemically it should be clarified if it is muddy or contains a large quantity of organic material. This may be accomplished by constructing small settling beds or by damming streams. A settling bed may be made by digging out a pool and lining it with a woven brush cylinder, or gabion, a barrel or box with both ends removed, or with stones. The space between the lining and the earth is filled with puddled clay. Water is allowed to settle in such a bed until the major portion of the solids have sunk to the bottom.

Watcr may also be clarified by a rude sort of filtration if the soil on the banks of the stream is pervious. In this case pits are dug alongside the stream and the water is allowed to enter these by seepage. Or water may be strained through gauze or blankets to clear it. While these methods remove the solids they in no way free the water from its bacterial content.

Chlorination is one of the most effective meaiurcs of purifying water from pathogenic organisms. It is an accepted fact that one part of chlorine per milHon puts of water will kill most, if not all, of the bacteria contained in the water, providing sufficient time is allowed for the action to take place. In practice, calcium bypochlorite or chloride of lime is used, preferably the Grade A calcium hypochloritc which contains about 70 per cent available chlorine. The amount used should be such that the residual chlorine in the treated water will be less than 0.5 part per million. Four-tenths part per million produces a marked taste, but more than that amount of residual chlorine in the presence of organic matter will produce a definite objectionablc taste. The use of sodium thiosulphate is not recommended. to neutralize the excess chlorine and to remove tastes and odors, unless strictly supervised by a competent officer acquainted with the procedure. It is best to use a small. amount of Grade A calcium hypocblorite initially, testing it with orthotolidine immediately after the addition of hypochlorite solution until sufficient residual chlorine remains.

b. Purification of water in the field.
An unknown water can be rendered potable in the field by a very simple procedure, that of adding a small amount of chlorine to the water. The efficacy of this procedure (chlorination) bas long been recognized in the military service and is provided for by a simpJe apparatus that is very easily transported and operated.

The equipment consists of a canvas water bag and a chlorine compound {calcium hypochlodte) put up in a small, sealed glass tube. The bag and the chemical are obtained from the Quartermaster Corps, not from the Medical Department. The canvas bag weighs about 7½ pounds, holds about 36 gallons of water (20 inches in diameter and 28 includes inches in length), and is provided with a canvas cover. It is solely a stationary receptacle in which water can be held while it is being. sterilized and from which. it can be distributed through faucets wtthout dipping, these faucets being arranged around the bottom of the bag. This apparatus is issued to troops at the rate of one to each 100 men or fraction thereof.

The procedure is as follows:

(1)	Suspend the bag on a tripod. Fill it with Water to the mark four inches from the top, straining the water through cheesecloth.
(2)	Draw a small quantity of water through one of the faucets into a canteen cup.
(3)	Break a tube of calcium hypochlorite into the canteen cup, stir with a clean stick, then fill the cup two-thirds full of water.
(4)	Empty this solution into the water bag and stir thoroughly with a clean stick which is long enough to reach to the bottom of the bag.
(5)	Draw at least one-half canteen cup of water from each of the faucets and pour it back into the water bag. This serves to sterilize the faucets.
(6)	Wait 10 minutes, then wash out one of the faμcets by allowing a small amount of water to run through onto the ground. Fill a clean canteen cup two-thirds full of water from the same faucet. Add one c.c. (fifteen drops) of orthotolicline testing solution to the water in the cup. Wait five minutes and note the color produced. Below is a guide for reading the color reaction between the free chlorine and orthotolidine:

COLOR	DESCRIPTION
No color	Insufficient chlorination. Add more calcium hypochlorite.
Canary Yellow	Insufficient chlorination. Add more calcium hy,pochlorite.
Deep Yellow	Satisfactory chlorination. This represents about one part per million (ppm) of chlorine.
Orange Red	Overchlorinated. Add more water and re-test.
Bluish green	Alkaline or hard water. Add a few more drops of orthotolidine to get a correct color reading.

(7) At the end of thirty minutes wash out the faucets for the final time, running five cups of water through each and returning the water to the bag. The water should now be perfectly safe even i£ it was heavily contaminated.

42. Chlorinating Water for Small Detachments,

Frequently small detachments are separated from the main body and from the supply of chlorinated water at the company messes. Their drinking water carried in cantocns may be chlorinated as follows: Mix the contents of one tube of hypochlorite in a quart of water and preserve in a glass bottle. Do not use a metal container as the concentrated hypochlorite solution has a chemical action on the metal. Add one teaspoonful, or the amount contained in a canteen cap, of this solution to a canteen of water and wait thisrty minutes before drinking. This is known as the canten method.

43. Use of Iodine for Purification of Water.

Water may also be sterilized by iodine. Ten c. c. of tincture of iodine (7 per cent) added to a water-sterilizing bag foll of water, will effectively purify even raw river water in thirty minutes. For individual use two or three drops of the tincture may be added to a canteen of water nnd allowed to stand thirty minutes. Thc,se methods have been subjected to laboratory tests and have been found to be reliable.

There are two possible objections to the iodine method. First there is no reliable method for" titrating the iodine in order to test the sufficiency of the amount added, and second it is somewhat more expensive than hypochloritc. There ate three sources of iodine available to the medical officer:

(1) the regular tincture;
(2) "iodine swabs" or glass ampules containing 1 ½ c. c. of 3 per cent iodine; and
(3) iodine-potassium iodine in dry form in scaled tubes for making 50 c.c. of 2 percent solution.


Food Supply and Mess Sanitation

44. Food Control and Protection.

Food as a factor in the prevention of disease has been briefly mentioned. Generally, the supply and technical agencies will see that the food as issued to troops is of the proper quality. Ration allowances for troops in the field are fixed by higher authority. The supervision of an organization mess is an important duty of the organization commander, who should make frequent inspections to insure scrupulous cleanliness of the followmg: kitchen, mess hall, and surroundings; the persons and habits of the personnel, handling food; the preparation of the food before and during its cooking; all utensils coming in contact with the food; and the serving of the food.

He should see that the men have adequate time to eat their meals without hurrying and should discourage all tendencies of the men to "bolt" their food. He should see that adequate provision is made for washing and sterilizing the dishes, mess kits, eating utensils, and similar food containers used by the men. Whatever the type of mess gear used, he must insure that it is properly washed and sterilized after each meal and properly protected from contamination between meals. The organization commander should fully realize that, in the maintenance of his combat strength in battle,


PLATE 11 - Washing Mess Kits in the Field.

food is next in importance to ammunition. Mess sanitation is nothing more nor leas than good housekeeping. Officers responsible for a soldiers' mess should always bear in mind that sanitary conditions and practices - and the wholesomeness of the food placed before the men - which are not good enough for the officers are not good enough for the men for whom they are responsible.

Disposal of Wastes

45. Importance of Waste Disposal.

The disposal of waste products in the field, camp, or garrison is an im_portant detail in sanitation. People accustomed to living in modernly organized and equipped communities ordinarily give but little, if any, thought to water supply, disposal of wastes, and other public services. They seldom realize that someone is responsible for and operates such services with minimum inconvenience to the public. A military community in the field must provide its own public services, the principal responsibility for much of which usually falls to the organization commander.

Such a community brings men close to primitive conditions, and, unless great care is exercised, the occupied area and surroundings will soon be thoroughly contaminated, nuisances will be created, and outbreaks of disease from insanitary conditions may be expected. The wastes to be disposed of include: those from the messing facilities; those from human beings; those from animals; and the general wastes of the community.

a. Messing wastes.
Kitchen wastes consist of the food remnants accumulated after meals and in the preparation thereof, as well as the water in which kitchen utensils and mess gear have been washed. The amount of kitchen wastes vadcs considerably, especially the liquid portion. However, the solids average about ½ pound per person per day and the liquids average 200 to 1000 gallons per t ompany of 200 men per day. These wastes must be disposed of to prevent giving rise to offensive odors and attracting flies and rats to the mess area. Solid kitchen wastes may be disposed of relatively easily, but the disposal of liquids becomes increasingly di.$cult as larger quantities of water are used. For camps of short duration, l night to a l ew days, both liquids and solids may: be disposed of by burial, either in deep pits or in trenches about 2 feet deep. At least 1 foot of cru-th should be refilled over the garbage. The scattering of Lime over garbage is of no practical value.

(1) Disposal of garbage.

Garbage is often disposed of by sale or gift to civilians to be used as food for hogs, and it may be used on military reservations for the same purpose. Its disposal by sale or gift to civilians may lead to insanitary conditions about a camp through spilling in transfer from garbage cans to other containers, leakage of containers, failure of collection, or unsatisfactory cleaning of cans. When thorough cooperation with the contractor can be maintained so as to insure cleanliness in the procedure, there is no objection to this method of disposal. However, the site of final disposition should be far enough removed from the camp that odors and flies will not become a nuisance in the camp area. Garbage should not be transferred from one container to another within the camp area. When garbage is to be used as· food for swine, it is necessary to separate it into edible and nonedible portions, the latter being disposed of by incineration. Except when it is disposed of by burial, it is necessary that ga~bage be separated into liquid and solid portions by passing it through a strainer.


PLATE 12 - Straddle Trench Latrine.

(2) Soakage pits.

Liquid kitchen wastes in amounts not in excess of 200 gallons per day are best disposed of by a soakage pit similar in construction to a urine soakage pit. A hole 4 feet deep and 4 feet square is filled with broken rock, varying in size from about 3 inches in diameter at the bottom of the pit to 1 inch at the top. Tin cans or broken bottles may be substituted for the broken rock. Ventilating shafts similar to those in the urine soakage pit are advisable but not essential. A grease trap is necessary in conjunction with a soakage pit as grease, if not removed from the liquid waste, will soon clog the soakage pit. Two such pits should be constructed for each kitchen if the camp is to last several weeks. A daily rest period of several hours will increase the efficiency of soakage pits. If two pits are available, they should be used on alternate days. In camps of long duration each soakage pit should be given a rest period of 1 week every month. If. in spite of these precautions, the pit becomes clogged with organic material, the application of 5 gallons of 10 per cent solution of either calcium hypochlorite or caustic soda may clear it. It is desirable to locate soakage pits near to the kitchen if suitable soil can be found there. If not, they must be located where satisfactory drainage can be secured.

(3) Soakage trenches.

If the ground water level or a rock stratum is encountered near the surface of the ground, a soakagc trench may be substituted for the soakage pit. This trench consists of a central pit 2 feet square and 1 foot deep, from each corner of which a trench radiates outward for a distance of 6 feet. These radiating trenches are 1 foot wide and vary in depth from 1 foot where they leave the central pit to 18 inches at the outer end. The central pit and the rad iating trenches are filled with broken rock. A grease trap must be empl.oyed in conjunction with this trench.

(4) Soakage pit under field Range.

Another optional method is to construct a soakage pit under the firebox of a field range. Liquids are thus disposed of by evaporation. as well as by soakage.

(5) Sullage pit.

Attempts to dispose of liquid wastes by merely digging a deep hole in die ground into whid1 liquids are poured will meet with little success. Filling with rock or similar material is necessary to secure efficient operation of a soakage pit.

(6) Grease traps.

The water before being placed in the soakage pit must be passed through a grease trap to remove food particles and as much grease as possible; otherwise, the side walls of the pit will soon become coated with grease and debris and the leaking of water into the soil is prevented.

b. Human wastes. The human wastes to be disposed of include waste bath and ablution (wash) waters, and human feces and urine. The disposal of. bath and ablution waters is not a great problem as they are not, in themselves, dangerous from a health standpoint. They often create nuisances and mosquito breeding places, unless properly handled. In the absence of available sanitary sewers the best method of disposing of human feces and urine is to bury them. Although Mose.s is credited wjth devising this method of disposal, it never has been basically improved upon. On the march the soldier should dig a small hole, void his excrement into the hole, and cover it with earth. In bivouac or other camps of short duration-a week or less-the straddle trench may be used, each man covering his own excrement with earth immediately after depositing


PLATE 13 - Pit Latrine for Temporary and Semi-Permanent Camps.

it For camps of a week or ten days duration, when flies are n0t a memrne, the open pit latrine may be used. In general, for camps of more than one week's duration, the deep pit latrine, with By-proof box or cover, should be constructed and used. This device is simply a multiple-seat privy. Every effort must he made to deny to flies any access to fecal deposits, remembering that fecal matter and food are both attractive to ffies; that they will go from one to the other at the slightest opportunity, and that they are careless about which one they visit first. The fly-proof bot also furnishes seating facilities. The latrine seats should be washed with 2 per cent cresol solution daily. The bottom of the pit and the sides and interior of the box should be sprayed daily with aude oil.

Urine is ordinarily deposited in latrines, Urine soakage pits are a convenience and save latrine space for fecal matter. Night urinal cans containmg one inch of 2 per cent cresol may be placed in the company street at night for the convenience of the men and to prevent them from soiling the tent or quarters area. They are emptied and cleaned every morning. When straddle trenches and pit latrines are


PLATE 14 - Urine Soakage Pit.


PLATE 15 - Composting Manure.

abandoned they should be filled in with earth and plainly marked to give warnmg of their presence to subsequent occupants of the site.

c. Animal Wastes.
Animal wastes or manure Is cllsposed of by drying and b,urning or by composting; that is, placing it in thick piles so that it "heats." The principal objective in manure disposal is to prevent fly-breeding.

d. Trash.
The general wastes of the community are usually burnable trash. Burning is the best and most effective method of disposal. Control of. Insect Borne Diseases

46. General Control Measures for Insect Borne Diseases.

The various preventive measures to be employed must be directed toward the accomplishment of the following objects: protection of the patients and carriers of the causative agents from the bites of insects capable of transmitting such agents, protection of healthy persons from the bites of insects infected with the causative agents, eradication of insects capable of transmitting the causative agents, and eradication of cawative agents from the persons of patients and carriers.

47. Insect ControL. Insects of one kind or another are likely to be a problem throughout the year-flies and mosquitoes in warm weather and bedbugs and lice all the year.

a. Flies. Flies are filthy in their habits and spread disease by mechanically transferring


PLATE 16 - The Serbian Barrel for Disinfectation of Clothing.

germs on their feet from one place or person to another. They breed in and live on putrescent material of any kind-garbage, feces, manure, and other wastes. Fly control is best accom.plished by the elimination of their breeding places. A mixture of crude oil and cresol solution is an effective larvacide, used especially in compost piles and latrines. Adult flies are destroyed by By traps, swatters, poisons, By paper and fly sprays. A fly will not go where there is nothing for it to eat.

b. Mosquitoes. Mosquitoes spread certain communicable diseases, such as malaria, yellow fever, and dengue, by furnishing a biological link between the person sick with the disease and the well person. They arc best diminatcd by destroying their breeding places and habitations. As mosquitoes must have water in which to breed, drainage of standing water, or oiling water that fannot be drained, destroys their breeding places. The elimination of tall grass and underbrush destroys their habitations. Screening of sleeping quarters and the use of mosquito bars (bed nets) may have to be resorted to to keep mosquitoes away £rom the men.

c, Bedbugs. Bedbugs are sometimes found in the sleeping quarters of soldiers. They are introduced by individuals whose recent environment was not of the best. Once established, it is difficult to eliminatc bedbugs completey. They are obnoxious and are strongly suspected of being agents in the spread of certain communicable diseases. Control is best accomplished by fumigation with hydrocyanic gas, which destroys the adult and the eggs. If hydrocyanic acid gas is not available or practicable, sulphur dioxide gas is next best. Liquid insecticides of various kinds are effective against bedbugs if applied thoroughly, forcing the liquid into places in which bedbugs seek protection or lay their eggs. All methods except bydrocyanic acid gas fumigation require repetition every few weeks as some of the eggs will usually escape destruction, hatching out to form a new generation.

d. Lice. Lice have been a problem to military communities foe hundreds of years. They are definitely known to carry typhus fever from one individual to another. There are three varieties of lice: the head louse, body louse, and pubic louse. Body and pubic lice arc also known as "cooties" and ''crabs," respectively. The best protection against lice is cleanliness of person, clothing, and bedding. Individuals who bathe daily and sleep in night clothing need have little fear of louse infestation. Frequent sunning and airing of the bedding will usually destroy them. It is no disgrace to get lice; it is a disgrace to keep them. Large organizations of men which become infested with lice arc frunimcd with steam delouscrs (portable) through which all clothing is passed in order to kill the lice. This process is known as delowsing. If portable delousers are not available, a Serbian barrel can be constructed. It consisu of a barrel or cask with holes drilled in the bottom and set on top of a boiler. The clothes are placed in the barrel, the lid placed on, and the clothes steamed for 45 minutes after steam begins to escape around the edges of. the top or bottom of the barrel.

e. Fleas. Fleas arc agents of transmitting plague and typhus fever. They are eliminated by eradication of the animal host which infects them. Fleas resort to man when the normal host is not available, and, if his former host was infected, the disease will be transmitted to the human host. As man may be closely associated with domestic animals be is apt to be bitten by fleas, normally parasitic on such animals. If the fleas arc traced. to rats, then effective rat control measures must be employed. Measures of control arc designed to prevent the migration of rats to a community.

If they are already present measures are taken to destroy them or force them to leave. All buildings should be rat-proofed; all openings to buildings which permit entrance of rats should be closed; all drains leading from the building should be constructed to prevent the entrance of rats; building material used should be nondestructible by rats. The storage of food and food wastes should be such as to prevent access to them by rats. Food must be stored in metal containers, garbage cans should be kept covered, and the garbage should be disposed of promptly. Fumigation with hydrocyanic acid gas is the most effective means of exterminating rats and in addition destroys the lkas which are using the rats as hosts. Trapping rats has the disadvantage in that the Seas leave a dead rat, migrating to a living host as soon as one is available. Other rodents may also carry fleas. They arc eradicated by destruction of their habitat and by hunting, trapping, or poisoning.

QUESTIONS

1	What is the minimum amount of water that' must be provided every day for each soldier in the field?
2	Who is responsible that the men of an organization have su$.cicnt water fit for their needs?
3	Is every public wator supply a safe source of water for troops?
4	How are unknown waters made safe (potable), for soldiers in the field?
5	How would you obtain safe water for your men in the absence of the usual water sterilizing facilities?
6	What arc the dangerous elements of human and animal wastes?
7	What is the best protection against infestations, such as bedbugs a~d lice?