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Chapter 6, Part 2

Medical Science Publication No. 4, Volume II

MALARIA IN KOREA*

LIEUTENANT COLONEL IRVINE H. MARSHALL, MC

Malaria has in times past and in previous conflicts earned for itself a reputation for producing high noneffectiveness in the troops. It was not many years ago, during World War II, that 80 percent of the personnel of certain Indian Army units in Burma were down with malaria at one time; and in Assam, India, there was a thousand-bed Indian Army malaria hospital. Much has been accomplished in recent years by the so-called conventional methods of mosquito and malaria control. With the entrance of the United States and Japan into World War II the supplies of quinine, which for years had been the specific therapeutic and prophylactic drug for malaria, were denied to the United States and her allies. Simmons, et al. (1), reported that atabrine had been utilized prophylactically on a trial basis against malaria in Panama in 1935. It was not until 1945, however, that atabrine was available in sufficient quantities to conduct the mass prophylaxis required for the
U. S. Armed Forces. With the introduction of atabrine suppression in 1945, a great forward stride was made in decreasing noneffectiveness from this disease in troops. This was considered one of the advances in military preventive medicine during World War II. Figure 1 shows the dramatic effect of atabrine suppression in our troops in Assam, India.

Coatney, et al. (2), have recently published a survey of nearly four thousand compounds which have been screened, since 1941, for their antimalarial activity. Although the ideal malaria prophylactic drug has not been produced, further advances in reducing noneffectiveness from this disease have been most dramatic and gratifying.

With the entrance of the United States Armed Forces into Korea in 1950, it was recognized that malaria would be a primary problem. During the period of peace, the U. S. Army troops in Korea experienced malaria with annual rates ranging from 8.3 to 39.2 per 1,000 per annum (3). And these rates prevailed during a period when attention could have been devoted to the control of this disease. This incidence was not as high as the average annual incidence rates expe-


*Presented 29 April 1954, to the Course on Recent Advances in Medicine and Surgery, Army Medical Service Graduate School, Walter Reed Army Medical Center, Washington,
D. C.


271

rienced during 1942-45 in the Mediterranean Theater (49 per 1,000), China-Burma-India (102 per 1,000), the Pacific Ocean area (60 per 1,000) or the Southwest Pacific (70 per 1,000); but had the higher rate (39.2) prevailed from 1950 on, it would have created a significant and costly noneffective rate and a sizable manpower problem.

Little reliable information is available on the incidence of malaria among the native population. Park (4), in a study of Korean deaths for the period 1938-41, which, he feels, provides the most reliable Korean data available, reports that deaths from malaria appear to

FIGURE 1.

be over-reported. Further examination of the five-thousand-odd deaths shows that 4,599 or 91.5 percent of the number reported were certified to by "herb doctors," whose low level of medical education and knowledge of scientific medicine has long been recognized by the profession. Another indication of over-reporting is the fact that 3,984 of these deaths, 79.3 percent, were for children under 5 years of age. It is reasonable to assume that these officially reported deaths are diluted with a significant proportion of deaths due to other febrile diseases.

A couple of malaria surveys have been conducted by U. S. Armed Forces medical service personnel in Korea. During 1951 the Fleet


272

Table 1. Malaria Survey of Korean Civilians on Koje-do, Korea August-October 1951

Population

Number of blood smears examined

Number positive

Number negative

Percent positive

Resident

501

7

494

1.40

Refugee

500

55

445

11.00


Total


1,001


62


939


6.19

Epidemic Disease Control Unit No. 1 (5, 5a), while conducting studies on the island of Koje-do, reported the results of a malaria survey which are summarized in table 1.

In July 1952 reports received at the Headquarters, Eighth U. S. Army, indicated that during the period 25 December 1951 to 24 July 1952 there were 7,280 malaria cases in the civilian population of Kangwon Do province. Certain areas in close proximity to Wonju, a troop concentration center, had reported a large number of these cases and a malaria survey was conducted between 20 and 30 August 1952 by Murdoch and Lueders (6). The results of their survey are summarized in table 2.

Table 2. Distribution of Positive Malaria Blood Smears by Age and Sex for 817 Korean Refugees, Wonju, Korea, 20-30 August 1952

Age groups

Male

Female

Total

Positive

Negative

Percent positive

Positive

Negative

Percent positive

Positive

Negative

Percent positive

Under 11

30

95

24.0

13

85

13.2

43

180

19.2

11 to 20

13

82

13.6

10

102

8.9

23

184

11.1

21 to 30

0

5

0.0

5

45

10.0

5

50

9.0

31 to 40

1

28

3.4

3

111

2.6

4

139

2.7

41 to 50

1

23

4.3

2

57

3.5

3

80

3.7

51 to 60

1

17

5.8

4

46

8.0

5

63

7.3

61 to 70

0

10

0.0

1

19

5.0

1

29

3.3

Over 70

0

4

0.0

0

4

0.0

0

8

0.0


Total


46


264


14.8


38


469


7.4


84


733


10.2

It would appear from the meager data available that the incidence of malaria in the native population may run up to 11 percent. Consideration must be given to the fact that in the groups surveyed the refugees were existing under the worst living conditions in the country.


273

Plasmodium vivax is the dominant strain of malaria in Korea. No other species were reported by Murdoch and Lueders (6), FEDCU No. 1 (5, 5a), or the 406th Medical General Laboratory (7) in their surveys or studies. P. falciparum and P. malariae cases have been reported as occurring in small numbers in Korea (8). U. S. Army experience has shown only P. vivax infections. The possibility of other United Nations troops importing P. falciparum and P. malariae from their homelands has been discussed by persons engaged in preventive medicine and public health; however, no studies were made of the problem. The Korea vivax strain has a period of latency between the primary attack and first relapse of 6, 8, or 10 months. Alving et al. (9), have pointed out the similarity between the Korean vivax strain and the St. Elizabeth type of temperate zone vivax malaria which is said to be prevalent in Macedonia, Northern Italy, Holland, Central Russia, temperate America, and Madagascar. The factors responsible for this latency in Korean malaria are not known at present.

Five anopheline mosquitoes have been reported from Korea (8): Anopheles sinensis, A. sineroides, A. koreicus, A. lindesayi japonica, and A. pullus. A. pullus is of dubious validity and has not been collected in surveys by U. S. Army preventive medicine units (10, 11, 12) in Korea, although they collected all of the other species. A. sinensis is the primary vector of malaria in Korea. FEDCU No. 1 (5, 5a) reported dissection of 930 specimens of A. sinensis, collected on Koje-do between July and September 1951, with no positive salivary glands. Murdoch and Lueders (6) reported on the dissection of 375 female A. sinensis, collected in the Wonju area between 20 and 30 August 1952, of which 3 (0.83 percent) were found infected upon examination of the gut.

The control of malaria in military forces may be divided into three phases: (1) measures to prevent infection, (2) the suppression of infections, and (3) the treatment of those potentially infected. The prevention and suppression of malaria infections, provide the Army Commander with the most important means of reducing noneffectiveness from this disease. Since at the present time there is no true malaria prophylactic drug, it is also important to treat those potentially infected, to prevent the importation of the disease into areas which are free or practically free of malaria.

The conventional methods of control were applied in Korea as well as chemo-suppression and chemoprophylaxis. Programs were vigorously prosecuted to indoctrinate the soldier in individual protective measures. During 1950 and 1951 posters were employed to remind the troops of the dangers of malaria and to stimulate the use of protective measures and mosquito control. In October 1951 the pocket


274

calendar approach was utilized, rather than posters, as reminders with respect to certain preventable diseases or conditions. The first 6 months' calendar with do's and don'ts for malaria was issued in 1952. Over a million and a half calendars were printed in English, French and Spanish and distributed over a 2-year period. The wearing of proper uniforms was stressed at all times as a means of protection against disease-transmitting insects. Bed and head nets were available during the mosquito season and insect repellent for individual use was in adequate supply. However, the composer of a directive to implement a malaria control program must have a realistic view of the problems with which he will be confronted. Certainly that part of the program which is most difficult to obtain cooperation in or enforce is the portion pertaining to individual protective measures. Clothing worn by our troops in the field is very uncomfortable in hot, humid weather and it is difficult to assure that men will wear their jackets when they are engaged in hard physical labor. Men on the line cannot and will not utilize either the bed or head net since their lives may be endangered by them. Insect repellent is not acceptable to the troops and they will not utilize it of their own volition. In Korea one division quartermaster had 9 months' supply of four bottles of repellent per man per month in storage which had accumulated from the summer of 1951. Recommendations were made that no further stocks of this item be shipped to Korea as a result of the build-up in supplies.

Unit mosquito control measures consisted of monthly spraying of tents, mess halls, latrines, hoochies, etc., with residual DDT during the summer months. Also, drainage was to be established within the unit area to prevent the formation of standing pools of water and other mosquito breeding sites. This phase of the program was well carried out by the units. One of the difficulties encountered was the absence of replacement parts for the 2-gallon sprayers which were an item of unit issue. Since no facilities for repair and salvage of spray equipment were established, the preventive medicine company, although not a repair agency, set up a maintenance shop for their equipment. The service they rendered was extended to maintain the equipment of all forward preventive medicine control detachments and the line unit sprayers which were picked up in exchange by the control detachments. This service furnished by the preventive medicine company and the utilization of native mechanics, under competent supervision, was most effective in maintaining sprayers, dusters, fogging equipment, etc., at peak operational efficiency. The preventive medicine units aided materially in the success of the malaria control program.


275

Areas outside of the unit confines were the responsibility of the preventive medicine detachments. These detachments had equipment for larviciding and fogging with DDT. Their manpower was augmented by the use of Korean Service Corps troops made available from units assigned to the various divisions. The control unit officers were advisers to the corps and division preventive medicine officers and recommended areas to be air sprayed. Aerial spray was particularly helpful for larviciding mine fields in forward areas. These and other forward targets were sprayed on request by T-6 spray planes of the Air Force's Fifth Epidemiological Flight. In May1952 detachable air spray units for L-19 aircraft were made available and it then became possible for the division, using organic aircraft, to spray in the division area. This was of particular assistance when there was a difference in weather conditions and the Fifth Epidemiological Flight planes were unable to fulfill their commitments. Further advantage in the use of the L-19-type aircraft when compared to the T-6 was its maneuverability in narrow valleys.

The Fifth Epidemiological Flight (13, 14), in addition to servicing the forward areas with the T-6 spray planes, also sprayed the large urban areas on a regular schedule with C-46's which were converted for this mission. The summary data of the spray program for 1951, prior to the activation of the Fifth Epidemiological Flight, and the unit record for 1952-53 are presented in table 3. It will be noted that the dispensing of aerial spray is dependent upon the weather and the ability to fly the mission. Poor flying weather in 1953 decreased the number of missions flown as compared to 1952. The cost of 66 cents per acre for this service has been comparatively consistent during the 2 years for which costs were computed.

It is impossible to assess the cost of the ground mosquito control program inasmuch as the required accounting system would have been too complex and personnel requirements would not permit such a study. This would be further precluded by quantities of insecticides used for control of other insects, the labor costs in line units, etc.

The suppression of malaria has advanced from quinine prophylaxis through the tablet of atabrine each day to chloroquine in a dosage of one tablet (0.5 gram) per week. That chloroquine is highly effective as a suppressor is evident from figure 2. The data presented in this figure show the cases of malaria which were diagnosed and treated in U. S. Army personnel in Korea. Ample supplies of the drug were available early in July 1950, and on 8 July instructions were issued that it would be taken once weekly. During 1951 through 1953, the period of suppression was from 15 April until 1 November with Sunday of each week being the day of issue. It is evident that the program in 1950 was not as effective as it might have been when compared with


276

Table 3. Combined C-46 and T-6 Aerial Spray Program for Korea, 1951-53


Year

Total number of missions

Total number of targets

Total gallons of air spray

Total acreage

Total flight hours

Total spray hours

Total cost per acre

Total cost

17 June-Oct. 1951

461

461

94,588

373,038

513:20

209:30

-----

-----

1 May-1 Nov. 1952

646

962

274,672

1,066,316

1446:17

524:35

$0.66

$700,000.00

May-22 Oct. 1953

311

311

142,085

489,803

670:25

312:30

.66

323,317.06


277

FIGURE 2.

the results in later years. This may be attributed to several factors. During these early days in 1950, the tactical situation made it difficult to conduct a complete program. With a slower moving campaign time can be taken for indoctrination and other media, i. e., newspapers and radio, become available for health education. Supply problems, inherent in the early phases of a campaign, also played a part in decreasing the effectiveness of the program. Troops, residents and refugees were concentrated within the Pusan perimeter where conditions were ideal for transmission of the disease. The chances for the troops to acquire malaria infections were greater in this situation than at any later time.

Change in the tactical situation and the movement up the peninsula separated the combat troops from the reservoir to a large degree. The improved supply system and an active chloroquine indoctrination program in 1951 did much to reduce noneffectiveness from malaria and produce lower rates. Replacements were started on chloroquine prior to departure from Japan for Korea. This was an excellent stimulus to impress the soldier with the importance of taking suppressive therapy.

In the fall of 1951 authorization was received to activate survey and control detachments which had been requisitioned earlier in the year. The preventive medicine support was thus much improved in the 1952


278

season. These units were quite prominent in division areas. They enjoyed good advertising and their presence in forward areas, along with an active preventive medicine group, did much to stimulate preventive measures. It was necessary at times to change preventive medicine units in division movements. When such took place, the Division Surgeon was not bashful in quoting the requirements of the Commanding General for these units. Division and corps preventive medicine officers obtained spot announcements on local Armed Forces radio stations. Sunday, from mid-April until the last of October, being chloroquine day, rated radio spot announcements concerning the taking of chloroquine. Further improvements in the tactical situation, available preventive medicine personnel, and facilities for health education aided materially in the 1952 program.

The continued decrease in the 1953 malaria rates evidences the progression in the suppression program. It has been estimated that better than 90 percent compliance with the program was obtained during the 1953 season. Stabilization in the tactical situation has played an important part in increasing the effectiveness of the chloroquine program in Korea.

Information on parasitemia between seasons, when chloroquine was not administered, was obtained by Egan (15) during the period 20 January to 1 March 1952. He reported on the examination of blood smears obtained from 1,000 troops of the Marine Division who had arrived in Korea prior to 3 August 1951. Chloroquine was available in this division from 15 April to 18 December 1951. Twenty (2 percent) of this group were found to have a parasitemia, without clinical symptoms, at the time of examination. Seventeen stated that they had taken chloroquine 100 percent of the time, one 75 percent of the time, and two had never taken it. Seven hundred and ninety-six of the total group declared they had taken chloroquine 100 percent of the time and the other 204 stated they had taken the drug less than 80 percent of the prescribed time.

The effect of parasitemia on the malaria rate can cause concern, particularly when cases are reported in February, and practically all of the cases are reported from one unit. During February 1952 at one hospital, the assigned personnel were examined and those with parasitemia, or who were thought to show a parasitemia, were hospitalized and treated for malaria. As a result some 65 patients were so treated. Examination of a few available slides by the Army Field Medical Laboratory for confirmation cast serious doubt on the reliability of the diagnosis of many of these patients, who already had received treatment. The correct diagnosis is not only of importance to the statistical and historical personnel, but to the laboratory and preventive medicine officers at Army level. Erroneous diagnosis indicated


279

that there was a lack of information on the Korean vivax malaria cycle or that the technicians were misreading the slides. It is believed that in this particular instance chloroquine suppression might have been given from the time of diagnosis, since none were symptomatic. On the other hand, if as many as 2 percent actually had had malaria, the noneffectiveness in this small group would have presented no serious problem to the unit.

Although the preventive medicine officer of a field army is concerned with reducing the noneffectiveness from malaria as a means of making manpower available to the command, he is also deeply concerned with the exportation of the disease and its establishment in areas of the United States or other countries which are free or nearly free of the disease. In 1951, with the return of many Korean veterans, the number of cases seen in the United States began to increase and became of considerable concern not only to the military but the civilian authorities. Young (16) in 1952 mentioned that the evanescence of malaria as a major health program in the United States was dramatized by the action taken by the National Malaria Society, i. e., dissolving itself. This is one of the few times in medical history that a society has voluntarily ceased to exist because its aims had been fulfilled. Fritz and Andrews (17) reviewed the imported and indigenous malaria in the United States in 1951-52 and in summary stated that the current status of malaria incidence in the United States, caused by many thousands of infected servicemen, had brought about renewed malaria transmission.

The cases of malaria diagnosed and reported in the United States by the U. S. Army (3) and to the National Office of Vital Statistics (18) are presented in figure 3 for the period 1951-53. These cases, in a high percentage, were due to the return of troops from Korea. The decrease can be attributed definitely to the institution of primaquine therapy. Alving and his group (9) came to the Far East in August 1951, and returning by surface vessel in September, carried out the first primaquine program for the treatment of returnees. It was not until late December 1951 that primaquine was established as a routine measure for troops returning by ship. As with any program, there is a time interval until it is progressing smoothly. However, it was not until August 1952 that at least 90 percent effectiveness was attained in its administration. It is obvious that those returned by air would not have sufficient time to take the full course of therapy, which consisted of 1 gram of chloroquine followed by primaquine administered in doses of 15 milligrams (of base) over a 14-day period. The efficacy and rationale of this therapy has already been presented by Alving, et al. (9).


280

FIGURE 3.

There are administrative difficulties in providing such a program to troops in the field prior to their departure from the actual theater of operations. It would be desirable to give each individual who is due to return home this treatment by roster, except that the matter of departure is usually in a state of flux until the individual actually departs his unit. It has been generally agreed that the program must be instigated upon the arrival of the troops at the port of embarkation.

The cost of a suppression and prophylaxis program is most important in considering not only the benefits to military returnees but also in planning programs for residents of endemic areas. The cost of chloroquine suppression in Korea for military personnel is 77 cents for


281

one season (not including shipping and handling costs). The cost of primaquine therapy per man en route home is 29 cents. Considering the average time spent in Korea as one year, it is possible to reduce the noneffectiveness due to malaria and decrease the number of cases imported into the United States to a very low figure for $1.06 per man. With this drug combination and its administration during one season to the residents of a country where the temperate zone type of malaria is endemic, a tremendous salutary effect on the health of the country would result. With a 10 percent incidence in a Korean population of 22 million, it would decrease noneffectiveness in over 2 million individuals, not for one year, but for many years. It is interesting to conjecture what the effects would be if one dollar per person were invested in the prophylaxis of malaria in such a population.

Discussion

As a result of the advances made by the use of chloroquine and primaquine, we are confronted with the status of the conventional methods of mosquito and malaria control which are now employed as adjuncts to suppression and prophylaxis in Korea. Malaria in a military force has been reduced to such a degree that it no longer presents a serious problem to the commander or the associates of the veteran upon his return home. The effects are rendered even more dramatic when one considers that the production and introduction of primaquine was accomplished in the short space of a year. Although we may have an effective means of controlling this temperate-zone-type malaria, there remain other strains for which true prophylactic drugs have yet to be developed. In addition, mosquitoes act as vectors of other diseases for which there are, at present, no specific therapeutic drugs. While the control of mosquitoes as a preventive measure with respect to malaria in Korea may not justify the expense of the conventional methods, certainly mosquito control will have to be continued in the face of other diseases for which they are vectors.

With reference to the use of repellent by the individual, it has been evident that the soldiers will not use it either freely of their own volition or when it is force issued. A high-powered sales and advertising program for chloroquine and primaquine is not conducive to encouraging the soldier, who may bathe once in 3 days, to smear certain exposed parts of his anatomy with an oily repellent.

Personnel to conduct training, aid in insect control programs, advise with reference to air spray, check equipment, etc., were in constant demand in Korea. Experiences with a preventive medicine company show it to be well organized and admirably suited to perform its mission. It is believed that there should be a company of three or four control sections per corps, depending upon the number of divisions


282

assigned to the corps and at least one for the army area, rear of corps, and such units as are required in the communication zone.

Summary

1. Chloroquine has been effective as a suppressive for Korean vivax malaria and has reduced noneffectiveness from this disease in a field army to a degree that it presents no problems.

2. Primaquine prophylaxis for Korean vivax malaria has effectively reduced to a minimum the potential of importing this disease into areas free or nearly free of the disease in the United States.

References

1. Simmons, J. S., Callender, G. R., Curry, D. P., Schwartz, S. C., and Randall, R.: Malaria in Panama. Monograph No. 13. Am. J. Hyg., 1939.

2. Coatney, G. R., Cooper, W. C., Eddy, U. B., and Greenberg, J.: Survey of Antimalarial Agents. Public Health Monograph No. 9. Public Health Service Publication No. 193.
U. S. Government Printing Office, Washington, D. C., 1953.

3. Medical Statistics Division, Office of The Surgeon General, Department of the Army, Washington, D. C. Official reports for periods presented.

4. Park, Chai Bin: Studies on Korean Deaths. Unpublished data.

5. Activities Report of Fleet Epidemic Disease Control Unit No. 1 for the month of August, 1951. Fleet Epidemic Disease Control Unit No. 1, USS LSIL 1091, c/o FPO, San Francisco, California. FEDCU 1/A9-4/JMC: fch, Serial: 318-51, 15 September 1951.

5a. Activities Report September and October 1951. Fleet Epidemic Disease Control Unit No. 1, USS LSIL 1091, c/o FPO, San Francisco, California. FEDCU 1/A9-4/JMC: hwa, Serial: 354-51.

6. Murdoch, W. P., and Lueders, H. W.: Monju Malaria Survey. Symposium on insect and rodent control in Korea. The Military Preventive Medicine Association in Korea, 8 April 1953, pp. 6-8. APO 301, c/o Postmaster, San Francisco, California. Mimeograph, pp. 43.

7. Annual Report, 1951, 406th Medical General Laboratory, APO 500, c/o Postmaster, San Francisco, California.

8. Medical and Sanitary Data on Korea. TB MED 208, 6 December 1945, Washington, D. C.

9. Alving, A. S., Arnold, J., and Robinson, D. H.: Status of Primaquine. 1. Mass Therapy of Subclinical Vivax Malaria with Primaquine. J. A. M. A. 147 : 1558-1562, 1952.

10. Monthly Reports, 207th Preventive Medicine Detachment, APO 301, c/o Postmaster, San Francisco, Calif. August 1951-May 1953.

11. Monthly Reports, 37th Preventive Medicine Company, APO 301, c/o Postmaster, San Francisco, Calif. October 1951-May 1953.

12. Monthly Reports, 37th Preventive Medicine Company, APO 59, c/o Postmaster, San Francisco, Calif. March 1952-May 1953.

13. Muchmore, H. G., and Reed, R. E.: The 1952 Aerial Spray Program in Korea. Symposium on insect and rodent control in Korea. The Military Preventive Medicine Association in Korea, 8 April 1953, pp. 30-33. APO 301, c/o Postmaster, San Francisco, Calif. Mimeograph, pp. 43.


283

14. Annual report on Korean Aerial Spray Program, 1953. 5th Epidemiological Flight. APO 67, c/o Postmaster, San Francisco, Calif. 29 October 1953.

15. Egan, J. F.: "Project Bitterpill." Epidemic Disease Control Unit, 1st Medical Battalion, 1st Marine Division, FMF, c/o FPO, San Francisco, Calif.

16. Young, Martin D.: Malaria during the Past Decade. Amer. J. Trop. Med. and Hyg. 2 : 327-359, 1953.

17. Fritz, R. F., and Andrews, J. M.: Imported and Indigenous Malaria in the United States, 1952. Amer. J. Trop. Med. and Hyg. 2 : 445-446, 1953.

18. Weekly Morbidity Report, F. S. A., P. H. S., N. O. V. S., Vol. 2, No. 53, 17 Feb. 1953, Washington, D. C.

Morbidity and Mortality, D. H. E. W., P. H. S., N. O. V. S., Vol. 1, No. 54, 26 Oct. 1953, Washington, D. C.

Morbidity and Mortality, D. H. E. W., P. H. S., N. O. V. S., Vol. 2, 1953, Washington, D. C.