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Chapter XIX

Communicable Diseases, Table of Contents

CHAPTER XIX

INTESTINAL PARASITES

The greater number of the different kinds of animal intestinal parasites are of little or no military significance; they may have slight if any apparent effect upon either the health or efficiency of their hosts; they may be so restricted in occurrence as to be of little quantitative importance in the total volume of disease and physical deficiency of the troops. However, in the cases of seemingly healthy carriers of intestinal parasites, the military significance of the diseases which they cause rises in proportion to the facility with which they are spread from the carrier to uninfected men under conditions of camp and of field service. Though the sanitary conditions under military administration in this country are such as to preclude much if any spread of these parasitic infections, under the disturbed and changing circumstances surrounding active campaigning, carriers of intestinal parasites assume an importance proportional to the severity of the disease the parasites produce and the ease and rapidity with which the infection spreads. Viewed in these lights, one disease produced by an intestinal parasite rises to the level where it demands the cure of soldiers suffering from the disease and the elimination of carriers by treatment and cure. This is ankylostomiasis.

Whereas the life of the individual bacillus of typhoid or of dysentery is brief and the rate of multiplication of the individuals very rapid, the life of animal intestinal parasites, even of the Protozoa, is somewhat longer, and their rate of multiplication less rapid. Massive infections, quickly produced, are therefore less predominant among animal parasites than with the bacteria. This is much the more striking in the case of ankylostomiasis. The life of the hookworm is about 7 years in the case of the male and 10 in the female worm. The infection is lasting, the disease chronic, and the clinical symptoms may arise from a relatively small number of individual parasites. These facts of life history make the carrier element in the case of animal parasites one of grave importance in the epidemiology of the disease, tend to diversify the clinical pictures which the disease presents and to obscure the presence of the infection. For this reason the military surgeon may be misled as to the existence of these infections among troops and as to their extent unless he has the assistance of the clinical examination of the feces to determine the carriers.

ANKYLOSTOMIASIS

Ankylostomiasis is of considerable military significance because of the fact that it is in itself a disease which, in severe and chronic cases, may entirely disable the soldier. Also, in light infections it tends to increase the chronicity

aThe data in this chapter are based, in the main, on the following articles: (1) Rapid Method for Detection of Ova of Intestinal Parasites in Human Stools, by Maj. Charles A. Kofoid, S. C., and Maj. Marshall A. Barber, S. C. Journal ofthe American Medical Association, Chicago, 1918, lxxi, No. 19, 1557. (2) The Geographical Distribution of Hookworm Infection in the United States, Detected in Army Recruits, by Charles A. Kofoid. The American Journal of Tropical Medicine, Baltimore, 1922, ii, No. 5, 389. (3) Report on parasites in overseas and home service troops of the U. S. Army, made by Maj. Charles A. Kofoid, S. C., Second Lieut. Sidney I. Kornhauser, S. C., and Second Lieut. J. T. Plate, S. C. On file, Historical Division, S. G. O.


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and severity of other diseases, and to lower the intellectual and physical efficiency of the soldier. Since infection by this parasite may occur directly through the skin on contact with soil or water fouled by the feces of infected men, and since the worm, in the larval stage, may live in the soil for a year after deposition of the eggs in the feces of man, surviving freezing and even brief partial drying up, the spread of the infection among troops in trench warfare becomes distinctly possible, and the consequences of such extension of the infection a matter of serious consequences to the efficiency and health of the troops. The treatment and cure of both disease and carrier cases of hookworm infection is then a matter of military importance sufficient to justify prompt measures to detect the presence of the parasite and to cure all cases detected.

The enlisting and drafting of men for the Army from the known area of hookworm infection and their segregation in certain camps somewhat according to their geographical distribution laid the basis for a mass comparison of men from these regions with those from territory in which this infection was not prevalent. In some instances, as at Camp Logan, Tex., and Camp Wadsworth, S. C., men from the North were in cantonments in the neighborhood of others filled with men from the surrounding territory. They were thus under the same general environmental conditions as the men assembled in adjacent camps from the hookworm area.

A general opinion soon prevailed that the incidence of disease was relatively greater among men from the hookworm area than among the men from outside that region, an opinion since verified statistically by the studies of Vaughan and Palmer, and later supplemented by an intensive comparative study of the incidence of morbidity and mortality among men with hookworm and those in whom it was not detected at Camp Bowie, Tex., by Kofoid and Tucker.

In view of the prevalent opinion, the Surgeon General, on February 23, 1918, directed all surgeons to take all practicable measures for the early detection of ankylostomiasis, and for the adequate treatment of the infected before the men became exposed to the general infections commonly found in large camps. These instructions initiated the hookworm surveys which were made throughout the southern camps, the results of which are the basis of this chapter. Furthermore, as a result of investigations, which were carried on in the Southern Department, and which indicated some infection by the hookworm among northern men who had a year or more of service in the hookworm region and among southern men inducted from Northern States, supplemental instructions were promulgated by the Surgeon General on August 17, 1918. These supplementary instructions were as follows:

All recruits and recently inducted men from the following States or other political divisions should be examined for hookworm as soon as possible after their arrival in your camp: Maryland, Virginia, District of Columbia, West Virginia, Kentucky, Missouri, Oklahoma, Texas, and all States lying to the south of them, and also Porto Rico, Cuba, Mexico, Hawaii, the Philippine Islands, and other tropical countries. Troops coming from other States, who have been serving for six months or more in the hookworm region, should also be examined and, when necessary, be treated for the disease. In addition, all patients admitted to hospital should be examined for intestinal parasites as rapidly as men can be trained for the work.


531

It was the aim to secure data, through the returns from the hookworm surveys made in accordance with the instructions referred to above, in the Army, which would make it possible to map the distribution of hookworm infection in the known area of its occurrence, and to detect its presence elsewhere in the United States, since the drafted men represent in the main an ideal cross section of the population owing to their ratio to the total population and the nature of their selection. It would hardly be possible by any other available method, except by a complete school survey, to secure as representative a group of the population in such a test. However, owing to the fact that Medical Department Form 55 n, used in reporting laboratory examinations of feces, does not give the home address of the patient, and to the fact that the routine hookworm surveys, with few exceptions, were not so conducted as to provide rosters with the home address or place of enlistment of the men examined except in a few isolated organizations, it was not practicable to furnish the geographical data in the amount desired.

METHODS USED FOR THE DETECTION OF OVA OF INTESTINAL PARASITES

Since no orders prescribing the method to be used in the detection of ova of intestinal parasites were promulgated by the Surgeon General's Office, it is appropriate here to describe some of the methods more commonly used throughout the camps, and to indicate their comparative values.

Because of the numbers to be examined, the nature of the available equipment, and the desirability of not encroaching on the duties of a medical staff already occupied with more important work, it was essential that any method used in detecting infection by intestinal parasites, such as hookworm, should be adapted to the utilization of an untrained and changing personnel in large part, and that it should not require elaborate apparatus or extensive laboratory equipment.

The direct microscopic examination of a sample of the fecal specimen is inaccurate and inadequate because of the minuteness of the sample used, and impracticable because of the length of time required to make a fair examination. The greater efficacy of the brine flotation-loop, described below, in the detection of the worm ova as compared with the ordinary smear method is shown in Table 89, in which daily examinations for nine-day periods are compared. Only hospital cases, based on records at Camp Jackson, are included in the table. The great variability in the daily hookworm percentages is probably due to the varying proportions of patients from the Northern States. The brine flotation method is obviously inferior in the detection of Strongyloides.

The centrifuge method was at once precluded by the difficulty, if not impossibility, of securing at the time an adequate number of instruments to accomplish a work of such magnitude, and the added difficulty of securing the requisite tubes and other glassware essential to equip and maintain facilities adequate to care for the number of examinations to be made in a survey of troops from the hookworm area of the South. It also calls for extraordinary care in cleaning the glassware used, for hookworm eggs are quite adhesive to the surface of glass. This is a difficulty of considerable importance when laboratory helpers are inexperienced, and adds much to the burden of supervision.


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TABLE 89.-Comparative results in detection of ova by direct smear and brine flotation-loopmethods

ORDINARY SMEAR METHOD

1918, June-


Number examined

Positive hookworm

Percentage positive

Remarks

10

205

13

6.3

During nine-day period the same examinations as that for the hookworm gave these percentages of other worms:

11

132

23

17.7

12

153

24

15.7

13

135

19

14.1

Ascaris

1.1

14

150

11

7.3

Hymenolepis nana

0.6

15

116

9

7.7

Trichuris

0.3

17

144

3

2.1

Strongyloides

0.6

18

106

14

13.2

Oxyuris

0.0

19

99

11

11.1

 

    


     Total

1,240

127

10.2


BRINE FLOTATION-LOOP METHOD

20

109

40

37.5

During nine-day period the same examinations as that for hookworm gave these percentages of other worms:

21

96

34

35.4

22

146

50

32.1

Ascaris

1.1

24

146

48

34.1

Hymenolepsis

0.8

25

152

39

26.2

Trichuris

0.8

26

128

26

20.3

Oxyuris

0.08

27

120

26

21.7

Strongyloides

0.0

28

120

22

18.3

 

29

116

25

21.6


     Total

1,133

310

27.1

The centrifuge is also inaccurate, undoubtedly because of the small size of the samples used. The standard fecal sample collected for this method in the Army is contained in a 2-dram vial. Negatives for hookworm by this method as used by the author in the department laboratory of the Southern Department were examined by the brine-flotation method and found in about 50 examinations to show a 40-per cent increase in infections. That is, the percentage was increased from 10 to 14. This ratio was borne out by the fact that, whereas the percentage of infection by the centrifuge method was about 8 per cent in 7,000 examinations, made in March, 1918, at the department laboratory, Southern Department, it rose at once to from 14 to 20 per cent among troops from the same general localities when the brine-flotation method was applied.

The sieve-sedimentation method of Hall is not adequate to the military necessities because of the fact that it can be operated only in a well-equipped laboratory and requires an expensive, elaborate, and somewhat permanent installation. It seems not to be rapid, and would require great care in cleaning to prevent a carrying on of infection when the sieves are used in rapidly succeeding examinations. Its accuracy in cases of light infections should also be tested. The prime difficulty, however, with this method for hookworm survey is that arising from the possibility of carrying over ova from positive to negative stools and thus reporting a man for treatment who carried no infection.

BRINE FLOTATION-LOOP METHOD

In view of the difficulties, under Army conditions, attending the use of the methods referred to above, the method here described was devised after considerable experimentation. The method finally perfected by Kofoid and Barber


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may be designated as the brine flotation-loop method. It consists in mixing a large fecal sample thoroughly in concentrated brine, in a paraffin paper can of from 2 to 3 ounces capacity, forcing the coarse float below the surface by means of a disk of No. 0 steel wool, and then allowing the can to stand not more than one hour nor less than 10 minutes for the ova to ascend. The surface film is then looped off with wire loops, one-half inch in diameter, and examined on a slide without a cover glass.

The method was tested in the Southern Department under the author's direction in more than 100,000 examinations of varying ratios and degrees of infection by about 75 different examiners, under diverse field conditions, and was found to be efficient and practicable.

TECHNIQUE

The stools for examination were collected at reveille at the company latrines by a collecting squad consisting of 16 enlisted men in charge of a sergeant and under the supervision of a medical officer. The men from a given company were in charge of a line officer. They were marched to the latrine and the roll was called in alphabetical order from the roster by the sergeant in charge of the men. On admission to the latrine each man was identified and given a container, bearing the designation of the organization and his roster number, a sheet of waterproof paper, and half of a tongue depressor as a collecting stick. He was instructed to defecate on the paper and fill the can one-third full of feces. Men unable to furnish a specimen were given salts, under the supervision of the medical officer, and were moderately exercised. The men submitted their samples to the collector for inspection on leaving the latrine to prevent the passing in of empty cans. Substitution was forbidden. In practice this squad could collect the specimens from an entire regiment, make the first delivery at the laboratory at 7.30 a. m., and complete the collections at 10 a. m. On an average from 3 to 10 per cent of the organization on a complete roster failed to furnish specimens by reason of absence, detached service, or failed to defecate.

The receptacles used as containers for fecal specimens for examination for ova of intestinal parasites served not only to receive the fecal specimens at the latrines but also as the mixing dishes from which the ova subsequently were looped for examination, and themselves bore the results of their examinations to the recorder's table. The use of glass or tin containers was precluded by the cost, labor of cleaning, and danger of carrying over of infection by adhesion of ova to the sides of the dish; therefore, paper and pasteboard containers, which would be wasted afterwards, were used. In emergency, paraffined paper drinking cups and standard hospital sputum cups were used, but the most satisfactory container proved to be the standard 2-ounce paraffined paper drug can with tin bottom and paper top. Similar cans with paper bottom and top are more liable to be unsealed by the solvent action of the contents. Tin tops are advisable if specimens are to stand many hours before examination. Open drinking cups permit evaporation and increase the odor and liability of carrying over of ova by flies. Heavy paraffined "Kleen Kup" tumbler-shaped containers used in the grocery trade are satisfactory for shipping specimens some distance.


534

These have disk tops which may be forced into a groove. They are water-tight, preserve their contents admirably, and may be washed and used several times. They are difficult to write upon, except with wax pencil, difficult to open, and have an excess of surface exposure.

The drug cans which were used most extensively are about 1½ inches in diameter and 2½ inches high and are made up from specially constructed paper tubing made from stock paraffined on the inner face. Their capacity is normally 2 ounces and varies from 50 to 80 c. c. according to the brand or factory. Certain brands either have no coating or are so lightly coated that it was necessary to treat them to a dipping or to an inside coating of hot paraffin or sodium silicate to render them brine proof. Brine-proof cans, paraffin-coated on the inside that will resist soaking up by brine and feces for a number of hours can be obtained from commercial sources and are fairly satisfactory for this method of stool examination. The practical advantage of containers of these dimensions is that they will pack snugly in the compartments of the pasteboard fillers, which hold 3 dozen each, of standard shipping cases for eggs, which hold 30 dozen each. To facilitate the handling of a single filler, specially constructed pasteboard trays with tape loops for handles into which a single filler fits were used. These trays are very convenient for use in the preliminary marking of the cans, the arrangement of the numbered cans, and for subsequent handling at the latrines and in the laboratory.

In the examination of troops in the Army each can was marked with the designation of the organization and the roster number of the man whose specimen it was to receive. Thus, 305 Cav. H-16 was for the sixteenth name on the roster of Troop H of the 305th Regiment of Cavalry. Cans were at first marked on both top and side; the former for convenience in picking out a particular can at the latrine, the latter for use in the laboratory. These cans were marked with wax pencils or on strips of adhesive tape in ink on the tin tops, and the sides similarly marked, or with lead or colored pencil or in ink. Pasted typewritten labels are unsatisfactory, as they may soak off if wet or peel away if dry. The most satisfactory labeling proved to be that written in "Eternal" ink. This is not removed by water or brine, and sinks into the paper so deeply that it can not be rubbed off. It is also clearly visible on the wet can.

The cans for a given organization, such as a company or regiment, were serially numbered, and on receipt at the laboratory from the latrines were usually not in numerical order. In order to detect shortages, eliminate confusion of indistinctly written numbers, and facilitate entering results on the numerically and alphabetically serial roster, the cans were first arranged in numerical order on a number board and then racked in order in the sockets of serially numbered wooden racks holding 10 cans each. They were then passed to the mixing table, where they were prepared for the examiners.

The stool was prepared for examination by stirring the specimen thoroughly in concentrated brine with a small wooden stick until the brine was considerably discolored and the contained ova released from the feces. The amount of stool to be stirred varied with its consistency and composition. Not more than one-third of a canful ordinarily was used; if the sample submitted was too generous


535

the amount was reduced. The can was nearly filled with brine, and the stool, if puttylike and resistant, was broken up against the sides of the can. In some instances of puttylike stools the release of the ova was facilitated by scouring the stool up with steel wool on the end of the stick, against the side and bottom of the can. After stirring until the desired consistency was attained, a circular filter of No. 0 or No. 1 long fiber steel wool was carefully pushed down through the fluid to the bottom of the can with the stick. This effectively removed from the surface the lighter coarser float, broke imp the air bubbles, and left the surface clear of coarse particles and suitable for looping the floating ova. Stirring the stool with the electric soda mixer gives quickly a suspension of the stool, but forms too many air bubbles for satisfactory looping. These may be quickly removed, however, by a few drops of alcohol or ether. If too much wool is used it will interfere with the ascent of the ova; if too little is used it will not remove the float. As a rule a lightly compressed disk, one-eighth to one-fourth inch in thickness, is sufficient. From 1 to 2 pounds are sufficient for 1,000 specimens. Other materials, such as disks of gauze or wire netting, or mats of excelsior and southern moss, will serve the same purpose, but less successfully by far. The southern moss may introduce fresh-water nematodes and their eggs and larvæ.

Since there was danger of cross contamination of adjacent cans through stirring and in putting in the wool by splashing over from one can to another, each can was removed from the rack during the preparation. As an additional precaution to prevent the accidental transfer of a stick from one can to another during the mixing of a rack of cans, it was customary to place sticks in all of the cans at the beginning of the work on the rack and leave them there when not in use until the entire rack was finished.

The specimen was prepared for microscopic examination by looping of the surface film to an ordinary glass slide. The loops for this operation were prepared from unraveled window screen or similar fine galvanized wire. They can be made up rapidly from 6-inch squares of wire netting by unraveling the mesh and twisting the individual wires into the loops. Each loop was formed around a glass tube or wooden cylinder about three-eighths of an inch in diameter, the shorter end twisted around the longer, which formed the shaft to close the loop, which was then bent out at right angles to the shaft. It was customary to let the cans stand for one hour to allow the ova to accumulate in the upper layers.

The following test shows the relative hourly abundance of hookworm ova in the surface film on a can mixed with brine at 8.45 a. m., until they disappeared: The brine and ova were poured off into another can at 9.15, being distributed, by the pouring, throughout the fluid. Four loopfuls were placed on the slide and 10 fields were examined. At 9.15 there were 69 ova recorded; at 10.20, 169, at 11.30, 150; at 1 p. m., 85; at 2.10, 20; at 3.15, only 3; and at 4 p. m., none. The temperature during the period was from 90° to 95°. The maximum number of ova appeared at the surface about an hour after they were uniformly stirred, and seven hours after mixing all had descended from the surface.

From tests made under other conditions it is evident that there is considerable variation in the rate of ascent and descent of the ova in the brine in different stools and at different temperatures.


536

The surface film will usually adhere to the wire when the submerged loop is lifted from the brine. Ova in the film are removed with it. It proved advisable to loop the surface near the sides as well as the center of the can. For this purpose the loop may be molded to the arc of the can on the one side. An acute angle in the loop at the base of the shaft is to be avoided as it tends to break the film.

The number of loopfuls necessary to make a fair sample for microscopic examination depends on the viscosity and contents of the film removed. About 10 loopfuls will skim the entire surface of the can and form a pool of brine conveniently handled on an ordinary microscopic slide with a mechanical stage. One skimming does not by any means remove all the ova, as they are not all in the immediate surface.

To secure the even spread of the looped film on the microscopic slide it is essential that slides be thoroughly cleaned with sulphuric acid-bichromate of potash mixture or with soap to remove all trace of fat. The custom of looping more than one sample on a single slide each in its penciled area is to be avoided because of the droplets which are sprayed about at times by the breaking of the film on the loop, and thus giving rise to cross contamination of the adjacent pool by an infected film.

For a time the author marked off an ellipse 1½ inches by three-fourths inch on the slide with a wax pencil to assist in confining the pool of brine on the slide, but this was later abandoned as unnecessary. It also increased the labor in cleaning the slide.

In the cases of viscid, opaque, and fatty stools, considerable dilution may be required. This may be done on the slide with a few drops of a mixture of equal parts of glycerin and brine stirred into the pool. The glycerin clears the more opaque particles and renders the ova more easily visible.

Contamination of the adjacent cans by droplets of the surface film splashing over from an infected can to a negative one may readily occur when the loop catches on a stray fiber of the steel wool and is suddenly released, or when the film in the loop breaks on contact with the slide. For this reason the can and slide should be moved away from the rack while the pool is being looped off.

The viscosity of the surface film may vary greatly with the nature of the stool. It is markedly decreased by slight additions of such disinfectants as tricresol and phenol (carbolic acid) or by alcohol, which is useful in removing air bubbles from the surface. Formaldehyde solution tends to curdle the mixture, and delays the ascent of the ova and reduces the numbers in the surface film.

These variables, which affect the opacity of the film examined and contents of the loop and the number of ova it removes, render any uniformity of looping and resulting thoroughness of examination practically impossible. In practice, from 3 to 7 loopfuls are generally used; but the number in the course of numerous examinations will vary from 1 to 20. It is obvious that these variables will introduce a margin of error in the detection of ova only among the lighter infections.

The surface of the pool of brine is thoroughly searched with the aid of the mechanical stage. To reduce the amount of focusing, the convexity of


537

the surface of the pool may be reduced by spreading it over the slide and extending the amplitude of the movements of the mechanical stage.

The microscopic equipment most useful is the typical high-grade instrument with 16 and 4 mm. objectives and x 5 or 6.4 and x 10 oculars or their equivalents. The searching is done with the low-power objectives and low-power ocular, since the latter is less tiring in long-continued examinations. For closer scrutiny the 4 mm. objective may be used with care on objects in the surface film without cover glass.

To render the ova more distinctly visible it is essential that the microscope be provided with a substage condenser and that the illumination be reduced by closing the iris diaphragm or lowering the condenser so as to increase the sharpness of definition of all objects in the field and to bring the egg membranes into relief. This assists in the quick differentiation of ova from objects of similar shape and opacity. The amount of searching necessary to make a fair examination is a function of so many variables that no arbitrary rule can be laid down. The degree of dilution, stirring, flotation, the amount of the surface fluid in the pool, its extent and convexity, the consistency and opacity of the fluid and its solid contents, the nature and number of the particles floated to the surface, the number and size of air bubbles, fat cells, oil globules, and starch cells all combine to complicate the search for ova. It is advisable to search a considerable area rapidly, and especially, in the case of opaque fluid and confusing particles, to search a part of the area minutely or make an additional dilution. Experienced examiners on an average give from two to three minutes to the examination of a specimen containing on an average four or live loopfuls spread over an area of approximately 1.5 square inches on the slide.

Infected stools, or positives, are usually detected in the first field or run across the slide examined. In a test case of 550 positives of hookworm, most of them very light infections, in Oklahoma and Texas recruits, detected on five consecutive days by five experienced examiners and recorded as found or not in the first run across the slide, there were 180, or 30.5 per cent, reported as seen in the first run. Infections obviously reduce the time required for examination in most cases. In a relatively few cases, estimated at not more than 5 per cent, with the examination of more than 150,000 men in the Southern Department (Texas, Oklahoma, New Mexico, and Arizona), several ova only were found in the whole slide examined. In rare instances only a single ovum is found. These very light infections and the negatives require more time for a complete examination than do other positives.

It is obvious that the rate of examination and daily score of the examiner will be in part a function of the ratio of positives to the whole and of the average degree of infection. With numerous positives and heavy infections, which are usually coincident, the rate of the expert examiner may easily be doubled over that when positives are few and infections are light. The experience, skill, industry, and thoroughness of the examiner are also factors determining his daily score, as well as the nature of the stools as conditioned by diet and modified by the skill or lack of it on the part of the mixers.

A skilled examiner will complete from 150 to 250 examinations daily under average conditions. With the assistance of a looper the rate can be


538

speeded up to one per minute; or over 400 per day, but the resulting eye strain renders this inadvisable as a daily routine. A staff of 15 examiners can maintain a rate of from 2,000 to 2,500 examinations daily and attain 3,000 under favorable conditions of cooperation and effective supervision of the mixers. A staff of 20 examiners can complete a full regiment daily. Supplemental aid of approximately one man in the field collecting squad, in case the collecting is done by the men attached to the surveying board, and one man in the laboratory and clerical squad for each examiner is necessary to collect, prepare, record, and dispose of the specimens and attend to the policing of the laboratory.

The time required for the physician inexperienced in laboratory work to become efficient in this method is brief. Enlisted men with some experience in college, university, or Army laboratories acquired a reliable degree of accuracy with several days' training and supervision, as shown by test. Insistence upon focussing upon the surface film and a preliminary exercise and testing out in stools with known infections are essential in preparation for this work.

The ova of parasites such as Ancylostoma duodenale, Necator americanus, Ascaris lumbricoides, Oxyuris vermicularis, Trichuris trichiuria, Tænia solium, Hymenolepis nana, Hymenolepis diminuta, and Dipylidium caninum and of trematodes, are floated up by the brine into the surface layer of the pool without distortion or noticeable change in appearance during the usual period of examination. Cysts of Entamoa coli and histolytica and of Giardia intestinalis are also floated up. Since the ova are at the surface, it is not advisable or necessary to use a cover glass.

MODIFICATIONS OF THE BRINE FLOTATION-LOOP METHOD

The exigencies arising in the Army from the shortage of supplies for the brine flotation-loop method, and the devices of officers responsible for the hookworm survey gave rise to a number of modifications of the original method. The simplest of these is Barber's method, in which a good-sized lump of feces is mixed with glycerin and saturated sodium chloride solution (proportions not important) and a drop of the mixture placed on a slide ringed with a wax pencil. The eggs float to the surface and rise to the center of the drop.

The following modification of the brine flotation-loop method was made at Camp Jackson, S. C., for routine hospital examinations and for a number of stools sent from the camp:

Specimens were sent to the laboratory in tin containers provided with lids. Brine flotation and loops were used exactly as in the method described above, but instead of filtration by steel wool the coarser floating particles were skimmed off by means of a spoon before the ova had time to rise. The spoon was scrubbed with a brush and carefully washed under the hot-water tap after each use. When cans were used a second time they were very carefully cleaned and dried.

It is obvious that the main advantage of this modification is in the saving of materials rather than of labor. Further, it is adapted only to work on a comparatively small scale and in a laboratory supplied with trained workers and with a hot-water tap for the proper cleaning of utensils. It is not to be


539

recommended for field work on a large scale or for any work in which pasteboard containers and steel wool are obtainable, or where expense for labor is a factor. The possibility of removal of some of the ova by this method is not precluded.

The lack of the drug cans led to the use of standard hospital sputum cups for collection and stirring in brine. These answer the purpose, but they are less substantial than the drug cans, more difficult to stir in, attract flies (because they have no cover), permit the stools to dry up on standing, and owing to their proportions they give a greater dilution of the ova in the surface film. For these reasons they are to be avoided when feasible.

ACCURACY OF THE BRINE FLOTATION-LOOP METHOD

The accuracy of the method may be reviewed from the standpoint of its relative efficiency as compared with other methods, considered above, with the conclusion that, with the exception of the culture method, it offers the highest attainable degree of accuracy, with a maximum rapidity, and a minimum amount of labor in cleaning and loss by breakage, and a minimum of expense for materials used.

Not all positives can be determined by any method short of autopsy after sudden death, for worms may be voided during sickness as a result of, or treatment for, disease, or males only may be present. Owing to variations in the physiological states of host and parasite, ovaposition is subject to irregularities resulting in marked changes in numbers of ova discharged in the stool, with the result that quite independently of the accuracy of the examiner or of the technique employed, the infection is not revealed in the stool. Within an as yet unknown and presumably variable range of materials, the size of the sample examined, as determined by the size of the sample collected, on the one hand, and by the amount of material subjected to uniform scrutiny by the examiner, on the other, sets a certain limit to the accuracy of the work. Large samples will yield more positives than small ones in light infections, but no method in itself will reveal ova in the stool when the worms are not ovapositing. Repeated examinations on successive days, or at intervals, are necessary to establish a negative.

The relative accuracy of this method, among examiners and specimens, depends on a number of variables, the size and consistency of the specimen, the thoroughness of stirring, the proper amount of steel wool, the care in looping, the opacity of the fluid, and the extent and thoroughness of search made of the material on the slide. Much depends on keeping the focus directly on the surface of the fluid during examination and in training the eye to detect quickly every object resembling an ovum.

The cases of infection which escape detection are the very light ones in which only a few ova can be found on a slide. Some slides prepared from such infections may have no ova, or the ova may be hidden or overlooked.

Reexamination of slides and cans that are reported by an experienced examiner as negative will sometimes reveal a positive, lightly infected. Men reported as negative on a first examination may appear as positive on a second, and vice versa. This raises the question as to the uniformity of distribution of


540

the ova in the stool and as to the possibility of internal states of host and of parasite influencing the rate of deposition of ova in successive stools.

With a view of testing out the possibility of light infections having been overlooked, an examination was made of 100 negatives from colored troops at Camp Travis, Tex. Infections in the battalions from whom these negatives were drawn were only 68 in 1,495, or 4.8 per cent. The infections were also light, as a rule. The top fluid of 50 cans was drawn off into a tall cylindric liter graduate and the surface film of this column examined. The cans had stood after stirring for less than three hours, and no brine from thick or viscous stools was used, so as to avoid entangling any ova that might be present. This was repeated on a second 50 and the top fluid of the two lots combined in a slender 50 c. c. graduate. An examination of the surface film of each of these concentrations gave negative results. A subsequent examination within two hours of flotation of 150 negatives by the same method from white troops, showing 219 positives, or 8.7 per cent, in 2,505 examinations, revealed 1 case of an ovum in 1 lot of 50. The other two lots remained negative. In another test of 3 lots of 50 each from white and colored troops showing 110 infections, or 5.7 per cent, in 1,914 examinations, all remained negative. In a total of 550 negatives, or 11 lots of 50, of light and therefore presumably easily overlooked infections, only one lot showed evidence of an undetected infection on this test.

It appears from these tests that the number of positives escaping detection by the brine flotation loop method is small. These tests were made in the negatives from 16 examiners, 13 of whom were enlisted men and 8 of whom had only from 3 to 9 days experience with hookworm examinations.

No opportunity occurred for a comparison of this flotation method with the culture method to compare their relative accuracy on identical stools.

GEOGRAPHICAL DISTRIBUTION OF HOOKWORM INFECTION IN THE UNITED STATES

Examinations of recruits for hookworm in the Army camps, conducted by the Medical Department in accordance with the instructions previously referred to, afforded unique opportunities of detecting the extent and distribution of infection by this human parasite. The distribution thus detected is not that of the infected population of the country as a whole, but rather that in a selected group of able-bodied men, most of whom had already run the gantlet of one or more medical examinations, and were, at the time of the examination, in Army camps on duty as able-bodied soldiers, or in some stage preparatory to this status. They presented, therefore, to a considerable degree, a selected group, since the obviously sick had been excluded.

The data also include only males, presumably the sex most exposed to infection. Furthermore, the males included were not those of all ages, but only those of military age, the general body of whom were between the ages of 21 and 30, with certain numbers below 21 and above 30. They represented a fair sample of able-bodied young men of the United States of southern residence or exposure with but slight modifications due to selective factors and class of occupation. These selective factors would tend to modify somewhat the representation of classes most liable to infection, especially in some cases, such as agricultural exemptions, which tended to counteract the inclusion of the normal representation from agricultural districts in the hookworm area.


541

Not all of the States are represented equally in the data, since the orders of the Surgeon General's Office covering these examinations provided only for the examination of men who entered the Army from the hookworm area, or had resided there for six months or more, or who had formerly lived in that area but had emigrated to other States of the Union. Percentages of infection therefore which appear for States other than those of the hookworm area are not representative of the normal population of those States, but rather of a selected group of persons who lived within the area of distribution of hookworm and thus came within the possibility of exposure to infection by hookworm.

Our data, therefore, are fairly representative of the normal population of males of military age only for States of the hookworm area and only those males of military age who in other States might have acquired the infection by reason of southern residence.

The total number of men examined for hookworm in the United States Army during the war and so reported to the Surgeon General was 501,472; of these, 56,740, or 11.3 per cent, were found to be infected with this intestinal worm, upon one examination as a rule. Had repeated examinations been made by the brine flotation method in all cases this percentage would have been increased, perhaps from 25 to 50 per cent. Unfortunately the Army records did not permit the allocation of these men to the States of their birth, residence, or enlistment in most of the cases. This was feasible, however, in the case of 126,140 men.

In order that the contrast between the different areas of the United States may be set forth in their relations, the statistics have been grouped under four heads: States in the hookworm area (16 and District of Columbia); 10 of the Northeastern States; the 13 States of Northern Mississippi Valley, or Middle West; and 10 of the Pacific Slope, including Alaska.

TABLE 90.-Hookworm infection in States in the hookworm area

State of birth


Per cent positive

Number positive

Number of men examined

State of birth

Per cent positive

Number positive

Number of men examined

Alabama

29.4

656

2,223

North Carolina

27.1

3,402

12,558

Arkansas

6.4

787

12,292

Oklahoma

6.9

607

8,686

District of Columbia

1.6

2

121

South Carolina

23.5

1,918

8,135

Florida

31.8

1,202

3,778

Tennessee

12.6

1,233

9,722

Georgia

32.6

1,265

3,872

Texas

11.7

3,494

29,837

Kentucky

16.3

376

2,301

Virginia

6.7

65

969

Louisiana

27.3

2,010

7,348

West Virginia

3.7

36

972

Maryland

2.1

12

584

    

Total

17.01

19,464

114,408

Mississippi

27.1

2,358

8,684

Missouri

1.8

41

2,326

TABLE 91.- Hookworm infection in the Middle West-Mississippi Valley

State of birth


Per cent positive

Number positive

Number of men examined

State of birth

Per cent positive

Number positive

Number of men examined

Illinois

1.4

17

1,153

North Dakota

0

0

82

Indiana

1.7

10

582

Ohio

3.5

45

1,277

Iowa

.4

2

418

South Dakota

1.6

1

63

Kansas

.8

3

354

Wisconsin

.7

2

278

Michigan

1.0

7

665

Wyoming

0

0

41

Minnesota

1.5

5

325


     Total

1.69

96

5,664

Montana

1.2

1

81

Nebraska

.9

3

345

 


542

TABLE 92.- Hookworm infection in the Northeastern States 


State of birth


Per cent positive


Number positive


Number of men examined


State of birth


Per cent positive

 


Number positive

 


Number of men examined

 

Connecticut

1.1

4

265

New York

 

.7

11

1,479

Delaware

8.7

 

2

23

 

Pennsylvania

.3

4

1,074

 

Maine

.9

2

216

Rhode Island

 

1.3

1

73

Massachusetts

.1

9

813

Vermont

1.1

1

84

 

New Hampshire

14. 2

2

47


     Total

 


.84


37


4,358

New Jersey

.3

1

284

 

TABLE 93.-Hookworm infection in the Pacific Slope States


State of birth


Per cent positive


Number positive


Number of men examined


State of birth


Per cent positive

 


Number positive

 


Number of men examined

 

Alaska

0

0

1

New Mexico

 

2.6

9

345

Arizona

3.1

 

4

128

 

Oregon

2.4

2

81

 

California

2.0

11

527

Utah

 

3.2

2

61

Colorado

2.4

9

368

Washington

2.1

3

137

 

Idaho

2.7

1

38


     Total

 


2.5


43


1,710

Nevada

8.3

2

24

SUMMARY

Total number of men examined 

126,140

Total number positive 

19,640

Per cent infected 

15.5

The number of men examined, according to these tables, is 126,140, among whom 19,640, or 15.5 per cent, were found to be infected by hookworm. The percentage of infection in the men outside the hookworm area owes its origin to two factors, the relative importance of which it is not possible, owing to the nature of the data, to disentangle from available records. These two factors are infection due to birth or residence in childhood or later life in States of the hookworm area, on the one hand, and, on the other, to exposure in southern Army camps or service on the Mexican border on the part of recruits in the Army in the years prior to the World War, and service in Army camps in the hookworm area for more than six months after the United States entered the war. Owing to the sanitary supervision in Army camps, it is highly improbable that many cases of hookworm infection could have been acquired by men of the latter group during their period of Army service. The inclusion of these two groups of men among those accredited to States outside the hookworm area undoubtedly has tended to decrease the percentage of infection reported for these States. Had the examinations been limited to men of southern birth or residence outside of Army service the percentage would possibly have been higher, because of the varying degrees of sanitary supervision during periods of residence and the tendency for many of these periods of residence to have been more prolonged than those of Army recruits.

In view of these considerations, it is evident that the degree of suspicion of hookworm infection which attaches to persons of birth or residence in the hookworm area and subsequent migration to States outside of that area must be somewhat higher than that suggested by the percentages of infection here reported. Thus, for example, in the State of Illinois, in which 1,153 men were examined, there were 17 men, or 1.5 per cent, found to be infected with hookworm. It happens that Illinois recruits at Camp Logan, Tex., who had been


543

there for more than six months, were examined for hookworm and constituted a considerable proportion of the persons accredited to that State. In that camp, among 7,539 patients at the hospital, 7.4 per cent were found to be infected, while in 4,807 men on duty in the 15th Division, the percentage was 2.4. This percentage is higher than that accredited to the State of Illinois, because of the infiltration into this camp of other recruits, largely from the hookworm area. It is impossible to determine the extent to which the 2.4 per cent among troops on duty in this camp was due to infections acquired during residence therein, or to determine in what degree the 1.5 per cent accredited to the State of Illinois was due, on the one hand, to migration from the South into that State, and, on the other hand, to local infection acquired by recruits born in Illinois and subsequently residing in the southern Army camps. The presumptive evidence is against the acquirement of the infection in the camps, owing to the sanitary supervision of food and of latrines and the wearing of shoes. Only under the most exceptional circumstances would a recruit be exposed to infection by contact with polluted soil or food or water.

Certain sources of error are inevitable in so large a mass of data as this, gathered under circumstances so diverse. These errors arise from varying methods of examination. All of the examinations are subject to errors arising from a single test. Repeated tests would undoubtedly have increased the number of infections perhaps as much as 30 per cent, and 10 per cent if examined by the brine-loop method. The lighter infections by few worms are often overlooked or undetected in cases of a single examination only. The percentages of infection here reported fail to represent adequately the degree of infection prevalent, because of the fact that the group of men included are of the age in which infection acquired in childhood is gradually dying out, especially in cases under consideration in which changes ensued from rural to urban life and from barefoot days to those of the constant wearing of shoes. These changes cut off the opportunities for renewed infection, and combined with the dying out of worms from old age, tend to eliminate in the older men of the group the infection of earlier years.

Imperfect as these figures of necessity are, still they indicate that there is much to be done in sanitary supervision, not only in military camps but by local and State boards of health, by educational agencies, by industrial organizations, and by other institutions interested in the improvement of the sanitary conditions and of the health and efficiency of the community.

INTESTINAL PARASITES IN CERTAIN OF THE OVERSEAS AND HOME-SERVICE TROOPS

In the Army laboratory, port of embarkation, New York, from December 28, 1918, to July 1, 1919, examinations were made of 2,300 men of the United States Army who had been overseas and of 576 men from home-service troops. The overseas troops examined were sick and wounded soldiers in transit through Debarkation Hospital No. 3, New York City; they were drawn from over 800 different military organizations, and therefore were fairly representative of our overseas troops. They came from every State in the Union and constituted approximately a fair example of our population. Only a small fraction of them saw service on the Mexican border.


544

The home-service troops were mainly cooks, bakers, and food handlers from the port of embarkation, principally from the Medical Department. Of the total of 576 men examined, about 30 per cent were of foreign origin-Russian, Polish, Italian, or Spanish-or were negroes from Florida. This group, therefore, was less typical of the American troops as a whole than was the overseas group examined. They presumably presented a higher degree of infection by reason of their origin than would a fair sample of our population.

The relative degree of infection in these two groups of men was striking, as will be shown later, but it is obviously impossible to determine what proportion of the infection detected in the first group was acquired overseas and which was of home origin.

For the determination of infections, reliance was placed mainly upon the microscopical analyses of ova and cysts in the fresh stools. Different methods for the protozoa and for helminths were used in this analysis, the ova of the latter appearing in only a small number of cases in the direct smear method, which proved most useful for the former. For the protozoan examination a modified Donaldson's iodine-eosin stain was used. The smear is prepared for microscopical examination by rubbing out a minute bit of the feces by rolling it on a round applicator stick in a small drop of normal salt solution and then in an adjacent drop of the iodine-eosin stain. A single cover is placed on both drops and the smear is ready for immediate examination. Living flagellates, active amebæ, and unstained cysts appear in the unstained part. In the stained area the bacteria, fecal particles, and the smaller intestinal yeasts stain at once. Against the pink background the protozoan cysts stand out clearly as bright, greenish spherules, which soon become tinged by the iodine to varying tones of yellow. When glycogen-laden vacuoles are present they become light or dark brown, according to their mass. The nuclei, which at first are scarcely if ever visible, become more clearly defined as the iodine penetrates, expecially in Entamoba coli and histolytica. They are detected with difficulty in this stain in E. nana.

The component solutions of this stain were prepared in physiological salt solution and the proportions of iodine as given in the original formula were reduced. The formula is used as follows:

 


Parts

Saturated solution eosin in normal salt

2

Five per cent KI in normal salt saturated with iodine

1

Normal salt solution

2

Also the concentration method of Cropper and Rowe (1917), as modified by Boeck (1919), was used on over 2,000 stools as supplemental to the direct smear, but less than 10 per cent was added to the number of infections detected by the direct smear method. A few trials of the Carles-Barthelomy (1917) citric-formalin method also were made. The added infections were mainly of E. coli, which is rarely abundant, a few light infections of E. nana, and a few cases of Giardia. It is probable that the detection of light infections of E. histolytica would be facilitated by these methods, but the time required is greater and the percentage of infections detected thereby very small. The direct smear is simple, rapid, and in our experience both efficient and reliable for practical purposes. Concentration methods were useful in research and in following up difficult and suspected cases.


545

In nearly all cases of infections with Entamoba histolytica and with the smaller races of E. nana preparations were made by the wet smear and stained with Heidenhain's slow iron hematoxylin. This also was used to confirm the analyses made in all doubtful cases.

Examinations for ova of intestinal worms were made by the brine-loop method.

A single examination only was made in most cases. The exceptions to this were 60 men from overseas and 71 of the home-service troops, from whom two or more samples were secured for examination. In the overseas group the reexamination of 60 cases with a total of 129 examinations, or 2.15 examinations per individual, increased the number of different infections detected from 75 to 123, or from 1.25 to 2.05 per individual. Thus the first examination revealed 60.9 per cent of the infections found in 2.15 examinations. In the home-service group the examinations of 25 cases, with a total of 57 examinations, or 2.3 per individual, increased the number of infections detected in these cases from 47 to 93, or from 1.9 to 3.7 different infections per individual. In this group the first examinations revealed 50.5 per cent of the infections found in 2.3 examinations per individual.

In view of the large percentage of cases in which it was possible to make only one examination, it is highly probable that the total percentage of men infected among those examined is considerably higher than our records indicate, particularly for protozoan infections.

There has been little, if any, selection of cases for examination. The data represent the average run of the sick and wounded men received at Debarkation Hospital No. 3 from overseas, and of food handlers, etc., of the port. They were not, as a rule, dysenteric patients, though many of the positives carrying cysts of Entamoba histolytica reported one or more attacks of diarrhea or dysentery, in some cases with treatment, while on duty overseas.

TABLE 94.-Summary of infections by intestinal parasites in 2,300 overseas troops and 576

home-service troops of the United States Army

CASES OF INFECTION


546

As shown in Table 94, the infected men (1,533 or 66.6 per cent) were relatively more numerous in the overseas group than among those who had only home service (345 or 59.9 per cent) and on computation it appears that overseas men averaged 1.2 infections by different parasites per man as contrasted with 1.03 infections for men having home service only. These results indicate that many of the infections were presumably carried overseas and not acquired there in the first instance, although there is some evidence that many overseas men carried heavier infections than did home service troops. In determining the significance of this difference the source of the home service troops previously referred to should be considered. It may be that the percentages of infections found among them were somewhat higher than they would have been in the more representative troops on their departure overseas, and that the infections acquired abroad were in reality more numerous than our data reveal.

An analysis of the data in the tabulation given above exhibits certain very significant features. In the first place the men with hookworm infections were all, with 13 exceptions, from the known areas of hookworm occurrence in this country. There is thus slight indication of the acquisition of this infection overseas.

In the case of Trichuris trichiura, a different condition is found. In home service troops there were 14 infections, or 2.4 per cent, while in the overseas troops there were 136 infections, or 5.9 per cent. In the home service troops seven of these infections were in recent immigrants from Europe and two were in negroes from Florida. Deducting the number of these immigrants, the percentage of infection in the remaining falls from 2.4 to 1.2, but even this percentage is probably not representative of our troops on departure overseas. An examination of the stools of 145,016 men in the Southern Department revealed only 162 cases of infection by Trichuris trichiura, or 0.1 per cent. These were men mainly from Texas and Oklahoma, but representatives of every State in the Union were included. In a total of 501,472 examinations reported to the Surgeon General there are 1,945 cases of Trichuris, or 0.38 per cent.

HELMINTH INFECTIONS IN OVERSEAS AND HOME SERVICE TROOPS

The infections which are of significance have already been referred to in the discussion of fecal infection in overseas troops. A more detailed account of the results of the examinations for helminths in the two groups of soldiers will now be given.

A tabular summary of 437 examinations of home service men and 2,253 from overseas follows.


547

TABLE 95.-Infections by hookworm and Hymenolepis nana in men from Northern States

State


Overseas

Home service


Hookworm

Hymenolepis nana

Negative

Totals

Hookworm

Hymenolepis nana

Negative

Totals


Number

Per cent

Number

Per cent

Number

Per cent

Number

Per cent

Arizona

1

16.7

0

0

5

6

0

0

0

0

1

1

California

1

1.9

1

1.9

51

53

0

0

0

0

9

9

Colorado

1

6.2

0

0

15

16

0

0

0

0

3

3

Connecticut

0

0

0

0

33

33

0

0

0

0

4

4

Delaware

0

0

0

0

2

2

0

0

0

0

2

2

Idaho

0

0

0

0

7

7

0

0

0

0

1

1

Illinois

0

0

1

.7

140

141

0

0

0

0

18

18

Indiana

0

0

0

0

61

61

0

0

0

0

10

10

Iowa

0

0

0

0

55

55

0

0

0

0

3

3

Kansas

0

0

0

0

43

43

0

0

0

0

2

2

Maine

0

0

0

0

15

15

0

0

0

0

15

15

Massachusetts

1

1.2

1

1.2

79

81

1

3.1

0

0

31

32

Michigan

1

1.2

0

0

79

80

0

0

0

0

30

30

Minnesota

1

1.3

0

0

73

74

0

0

0

0

8

8

Montana

1

5.9

0

0

16

17

0

0

0

0

0

0

Nebraska

0

0

0

0

11

11

0

0

0

0

2

2

Nevada

0

0

0

0

1

1

0

0

0

0

0

0

New Hampshire

1

9.1

0

0

10

11

0

0

0

0

5

5

New Jersey

0

0

0

0

57

57

0

0

1

2.6

38

39

New York

2

.7

1

.4

264

267

1

1.1

1

1.1

85

87

North Dakota

0

0

0

0

9

9

0

0

0

0

2

2

Ohio

1

.8

0

0

122

123

0

0

0

0

12

12

Oregon

1

5.9

0

0

16

17

0

0

0

0

2

2

Pennsylvania

0

0

1

.5

186

187

1

1.7

0

0

56

57

Rhode Island

0

0

0

0

15

15

0

0

0

0

2

2

South Dakota

0

0

0

0

9

9

0

0

0

0

1

1

Utah

0

0

0

0

8

8

0

0

0

0

0

0

Vermont

0

0

0

0

8

8

0

0

0

0

6

6

Washington

0

0

0

0

29

29

0

0

0

0

3

3

Wisconsin

1

1.7

0

0

58

59

0

0

0

0

17

17

Wyoming

0

0

0

0

7

7

0

0

0

0

0

0


     Total

13

.9

5

.3

1,484

1,502

4

1.1

2

.5

368

373

 

TABLE 96.-Infections by hookworm and Hymenolepis nana in men from Southern States

State


Overseas

Home service


Hookworm

Hymenolepis nana

Negative

Totals

Hookworm

Hymenolepis nana

Negative

Totals


Number

Per cent

Number

Per cent

Number

Per cent

Number

Per cent

Alabama

18

40.0

1

2.2

26

45

1

16.7

0

0

5

6

Arkansas

4

11.8

0

0

30

34

0

0

0

0

3

3

Florida

10

37

0

0

17

27

2

13.3

0

0

13

15

Georgia

25

50

0

0

25

50

3

43.3

0

0

4

7

Kentucky

10

18.2

0

0

45

55

0

0

0

0

4

4

Louisiana

8

19.5

0

0

33

41

0

0

0

0

4

4

Maryland

0

0

0

0

21

21

0

0

0

0

5

5

Mississippi

6

17.1

0

0

29

35

0

0

0

0

0

0

Missouri

0

0

0

0

78

78

0

0

0

0

5

5

New Mexico

0

0

0

0

7

7

0

0

0

0

0

0

North Carolina

13

26

0

0

37

50

2

40

1

20

2

5

Oklahoma

6

11.5

1

1.9

45

52

0

0

0

0

0

1

South Carolina

13

33.3

1

2.6

25

39

1

100

0

0

0

1

Tennessee

10

22.2

0

0

35

45

1

100

0

0

0

1

Texas

7

7.3

1

1

88

96

0

0

0

0

3

3

Virginia

11

26.8

0

0

30

41

1

20

0

0

4

5

West Virginia

1

3

1

3

33

35

1

33.3

0

0

2

3


     Total

142

18.8

5

.6

604

751

12

18.5

1

1.5

51

64

 


548

As shown in the above tables, there were only 13 cases of infection by hookworm, or 0.9 per cent, among 1,502 men from Northern States from overseas, and 4 among 373 home service, or 1.1 per cent. In the case of 757 men from the hookworm area, with overseas service, there were 142 infections, or 18.8 per cent, while in 64 home-service men from that area there were 12, or 18.5 per cent. The differences between infections in home-service men and overseas men by hookworm are not the probable error and do not show any clear evidence of any increase in the infection due to overseas experiences. There is likewise no evidence that overseas men had an increased infection of Hymenolepis nana. In fact, among home-service men, largely food handlers, this infection was heavier than among overseas men, both among the northern and southern men.

In the case of infections by Trichuris trichiura, the case is different. We have here an infection carried to new human hosts in the unhatched egg stage. The ova are discharged in an undeveloped stage, and do not hatch to a larva stage until taken into the digestive tract of man. After discharge with the feces, the egg of Trichuris may live in moist earth or water for not less than five years under experimental control. Presumably at any time in this period, if taken into the digestive tract of man, it develops into the adult worm.

Whenever sanitary provisions for the proper care of human sewage are defective or imperfectly observed, wherever night soil is deposited in fields or gardens which drain into water supplies or near springs used for drinking purposes, opportunities for infection may be afforded. Wherever flies have access to freshly deposited or accumulated feces and at the same time to kitchens and mess halls, or food in any stage of its preparation prior to cooking, they may carry the ova on their feet from the feces to the food and thus infect it.

The degree of infection of any population or body of soldiers by whipworm is a measure of the effectiveness of the sanitary protection from infection by organisms of human feces under which they have been living for several years prior to the examination. The same conclusions may be derived from the degree of infection by Ascaris lumbricoides for similar reasons.

The infection by these two helminths in the United States does not have a distribution similar to that by hookworm, but is affected by two diverse factors: Immigration from the more highly infected regions in the south of Europe, and by sanitary conditions in the Appalachian Mountains region, especially in coal mining and cotton mill centers. Eastern Kentucky and Tennessee and West Virginia appear to be centers of infection by these two helminths.

The total number of infections by Trichuris and by Ascaris reported in all records compiled in this report were 1,862 and 3,013, respectively, for over 450,000 examinations, or 0.4 and 0.6 per cent, respectively. In the overseas men the total infections by these two helminths were 136 and 26, or 5.9 and 1.1 per cent, respectively. This is a fifteenfold increase in the case of Trichuris in overseas men as compared with the body of troops surveyed and a twofold measure in Ascaris. Since the southern men formed only about one-third of the overseas men examined and made up the greater part of the surveyed before going overseas, it is highly probable that the increase in infections by these helminths as a result of the overseas service was in reality considerably


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greater than we have computed it to be. This increased infection by these helminths appears to have been the direct result of overseas service, and to have been caused by fecal infections of food and water.

The presence of such carriers of amebic dysentery constitutes a menace to the health of armies in field operations, of troops in camps, and of the communities in which they may reside later, especially where sanitation is neglected and the fly nuisance prevails. The number of cysts discharged daily by a carrier of amebic dysentery varies greatly according to the degree of infection. A moderately infected case of Entamoba histolytica was kept under daily observation and examination for 42 days and the whole stool stirred to a uniform suspension and diluted to 500 and 1,000 c. c. in normal salt solution. The numbers of cysts of Giardia, Entamoba histolytica, and E. coli were determined in the counting chamber of a hemocytometer and computed for the stool as a whole, with the result that E. histolytica cysts were found on 26 of the 42 days in numbers ranging from 330,000 to 45,000 per day, averaging 14,520,000 for the 26 days, or 8,145,000 for the whole period of 42 days. Cysts of Giardia intestinalis were present on only 17 of the 42 days in numbers varying from 5,000,000 to 3,625,000,000 per stool, and averaging 925,200,000 per day. Entamoba coli was much rarer, being found in this case on only 3 of the 42 days, with an average of 3,110,000 cysts per day for the 3 days. The margin of error in these computations is large, but after due allowances are made for this, the number of cysts discharged by carriers is still large enough to provide for a wide dispersal of the cysts by flies or other agents. The sizes of these cysts range from 5 to 20 microns in the main, most of them are from 7 to 15 microns in diameter, and are thus of such volume that they could easily be carried on the foot of a fly. Computations show that 100 to 150 of the larger cysts and 500 to 2,000 of the smaller ones could be crowded in the area of a fly's foot in a single layer.

The possibility that the carrier problem in the case of amebic dysentery and other human protozoan infections is a much larger one than hitherto recognized is raised by the data here presented. Furthermore, the findings among home-service troops are indicative that the endemic area of infection by Entamoba histolytica in the United States is not confined to the Southern States.