Medical Science Publication No. 4, Volume II
MALARIA IN KOREA*
LIEUTENANT COLONELIRVINE H. MARSHALL, MC
Malaria has in times past and in previous conflicts earned for itselfa reputation for producing high noneffectiveness in the troops. It wasnot many years ago, during World War II, that 80 percent of the personnelof 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 conventionalmethods of mosquito and malaria control. With the entrance of the UnitedStates and Japan into World War II the supplies of quinine, which for yearshad been the specific therapeutic and prophylactic drug for malaria, weredenied to the United States and her allies. Simmons, et al. (1),reported that atabrine had been utilized prophylactically on a trial basisagainst malaria in Panama in 1935. It was not until 1945, however, thatatabrine was available in sufficient quantities to conduct the mass prophylaxisrequired for the
U. S. Armed Forces. With the introduction of atabrine suppression in 1945,a great forward stride was made in decreasing noneffectiveness from thisdisease in troops. This was considered one of the advances in militarypreventive medicine during World War II. Figure 1 shows the dramatic effectof atabrine suppression in our troops in Assam, India.
Coatney, et al. (2), have recently published a surveyof nearly four thousand compounds which have been screened, since 1941,for their antimalarial activity. Although the ideal malaria prophylacticdrug has not been produced, further advances in reducing noneffectivenessfrom 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 periodof peace, the U. S. Army troops in Korea experienced malaria with annualrates ranging from 8.3 to 39.2 per 1,000 per annum (3). And theserates prevailed during a period when attention could have been devotedto the control of this disease. This incidence was not as high as the averageannual 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.
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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 costlynoneffective rate and a sizable manpower problem.
Little reliable information is available on the incidence of malariaamong the native population. Park (4), in a study of Korean deathsfor the period 1938-41, which, he feels, provides the most reliable Koreandata available, reports that deaths from malaria appear to
be over-reported. Further examination of the five-thousand-odd deathsshows that 4,599 or 91.5 percent of the number reported were certifiedto by "herb doctors," whose low level of medical education andknowledge 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 reasonableto assume that these officially reported deaths are diluted with a significantproportion of deaths due to other febrile diseases.
A couple of malaria surveys have been conducted by U. S. Armed Forcesmedical service personnel in Korea. During 1951 the Fleet
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Table 1. Malaria Survey of Korean Civilianson 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 |
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Epidemic Disease Control Unit No. 1 (5, 5a), while conductingstudies on the island of Koje-do, reported the results of a malaria surveywhich 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 therewere 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 conductedbetween 20 and 30 August 1952 by Murdoch and Lueders (6). The resultsof their survey are summarized in table 2.
Table 2. Distribution of Positive Malaria BloodSmears by Age and Sex for 817 Korean Refugees, Wonju, Korea, 20-30 August1952
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 |
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It would appear from the meager data available that the incidence ofmalaria in the native population may run up to 11 percent. Considerationmust be given to the fact that in the groups surveyed the refugees wereexisting under the worst living conditions in the country.
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Plasmodium vivax is the dominant strain of malaria in Korea.No other species were reported by Murdoch and Lueders (6), FEDCUNo. 1 (5, 5a), or the 406th Medical General Laboratory (7)in their surveys or studies. P. falciparum and P. malariae caseshave been reported as occurring in small numbers in Korea (8). U.S. Army experience has shown only P. vivax infections. The possibilityof other United Nations troops importing P. falciparum and P.malariae from their homelands has been discussed by persons engagedin preventive medicine and public health; however, no studies were madeof the problem. The Korea vivax strain has a period of latency betweenthe primary attack and first relapse of 6, 8, or 10 months. Alving etal. (9), have pointed out the similarity between the Koreanvivax strain and the St. Elizabeth type of temperate zone vivaxmalaria which is said to be prevalent in Macedonia, Northern Italy,Holland, Central Russia, temperate America, and Madagascar. The factorsresponsible 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 dubiousvalidity and has not been collected in surveys by U. S. Army preventivemedicine units (10, 11, 12) in Korea, although they collected allof the other species. A. sinensis is the primary vector of malariain Korea. FEDCU No. 1 (5, 5a) reported dissection of 930 specimensof A. sinensis, collected on Koje-do between July and September1951, with no positive salivary glands. Murdoch and Lueders (6)reported on the dissection of 375 female A. sinensis, collectedin 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 threephases: (1) measures to prevent infection, (2) the suppression of infections,and (3) the treatment of those potentially infected. The prevention andsuppression of malaria infections, provide the Army Commander with themost important means of reducing noneffectiveness from this disease. Sinceat the present time there is no true malaria prophylactic drug, it is alsoimportant to treat those potentially infected, to prevent the importationof the disease into areas which are free or practically free of malaria.
The conventional methods of control were applied in Korea as well aschemo-suppression and chemoprophylaxis. Programs were vigorously prosecutedto indoctrinate the soldier in individual protective measures. During 1950and 1951 posters were employed to remind the troops of the dangers of malariaand to stimulate the use of protective measures and mosquito control. InOctober 1951 the pocket
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calendar approach was utilized, rather than posters, as reminders withrespect 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 millionand a half calendars were printed in English, French and Spanish and distributedover a 2-year period. The wearing of proper uniforms was stressed at alltimes as a means of protection against disease-transmitting insects. Bedand head nets were available during the mosquito season and insect repellentfor individual use was in adequate supply. However, the composer of a directiveto implement a malaria control program must have a realistic view of theproblems with which he will be confronted. Certainly that part of the programwhich is most difficult to obtain cooperation in or enforce is the portionpertaining to individual protective measures. Clothing worn by our troopsin the field is very uncomfortable in hot, humid weather and it is difficultto assure that men will wear their jackets when they are engaged in hardphysical labor. Men on the line cannot and will not utilize either thebed or head net since their lives may be endangered by them. Insect repellentis not acceptable to the troops and they will not utilize it of their ownvolition. In Korea one division quartermaster had 9 months' supply of fourbottles of repellent per man per month in storage which had accumulatedfrom the summer of 1951. Recommendations were made that no further stocksof 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 summermonths. Also, drainage was to be established within the unit area to preventthe 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 thedifficulties encountered was the absence of replacement parts for the 2-gallonsprayers which were an item of unit issue. Since no facilities for repairand salvage of spray equipment were established, the preventive medicinecompany, although not a repair agency, set up a maintenance shop for theirequipment. The service they rendered was extended to maintain the equipmentof all forward preventive medicine control detachments and the line unitsprayers which were picked up in exchange by the control detachments. Thisservice furnished by the preventive medicine company and the utilizationof native mechanics, under competent supervision, was most effective inmaintaining sprayers, dusters, fogging equipment, etc., at peak operationalefficiency. The preventive medicine units aided materially in the successof the malaria control program.
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Areas outside of the unit confines were the responsibility of the preventivemedicine detachments. These detachments had equipment for larviciding andfogging with DDT. Their manpower was augmented by the use of Korean ServiceCorps troops made available from units assigned to the various divisions.The control unit officers were advisers to the corps and division preventivemedicine officers and recommended areas to be air sprayed. Aerial spraywas particularly helpful for larviciding mine fields in forward areas.These and other forward targets were sprayed on request by T-6 spray planesof the Air Force's Fifth Epidemiological Flight. In May1952 detachableair spray units for L-19 aircraft were made available and it then becamepossible for the division, using organic aircraft, to spray in the divisionarea. This was of particular assistance when there was a difference inweather conditions and the Fifth Epidemiological Flight planes were unableto fulfill their commitments. Further advantage in the use of the L-19-typeaircraft when compared to the T-6 was its maneuverability in narrow valleys.
The Fifth Epidemiological Flight (13, 14), in addition to servicingthe forward areas with the T-6 spray planes, also sprayed the large urbanareas 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 activationof the Fifth Epidemiological Flight, and the unit record for 1952-53 arepresented in table 3. It will be noted that the dispensing of aerial sprayis dependent upon the weather and the ability to fly the mission. Poorflying weather in 1953 decreased the number of missions flown as comparedto 1952. The cost of 66 cents per acre for this service has been comparativelyconsistent during the 2 years for which costs were computed.
It is impossible to assess the cost of the ground mosquito control programinasmuch as the required accounting system would have been too complexand personnel requirements would not permit such a study. This would befurther precluded by quantities of insecticides used for control of otherinsects, the labor costs in line units, etc.
The suppression of malaria has advanced from quinine prophylaxis throughthe 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 suppressoris evident from figure 2. The data presented in this figure show the casesof malaria which were diagnosed and treated in U. S. Army personnel inKorea. Ample supplies of the drug were available early in July 1950, andon 8 July instructions were issued that it would be taken once weekly.During 1951 through 1953, the period of suppression was from 15 April until1 November with Sunday of each week being the day of issue. It is evidentthat the program in 1950 was not as effective as it might have been whencompared with
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Table 3. Combined C-46 and T-6 Aerial SprayProgram for Korea, 1951-53
| 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 |
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the results in later years. This may be attributed to several factors.During these early days in 1950, the tactical situation made it difficultto conduct a complete program. With a slower moving campaign time can betaken for indoctrination and other media, i. e., newspapers and radio,become available for health education. Supply problems, inherent in theearly phases of a campaign, also played a part in decreasing the effectivenessof the program. Troops, residents and refugees were concentrated withinthe Pusan perimeter where conditions were ideal for transmission of thedisease. The chances for the troops to acquire malaria infections weregreater in this situation than at any later time.
Change in the tactical situation and the movement up the peninsula separatedthe combat troops from the reservoir to a large degree. The improved supplysystem and an active chloroquine indoctrination program in 1951 did muchto reduce noneffectiveness from malaria and produce lower rates. Replacementswere started on chloroquine prior to departure from Japan for Korea. Thiswas an excellent stimulus to impress the soldier with the importance oftaking suppressive therapy.
In the fall of 1951 authorization was received to activate survey andcontrol detachments which had been requisitioned earlier in the year. Thepreventive medicine support was thus much improved in the 1952
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season. These units were quite prominent in division areas. They enjoyedgood advertising and their presence in forward areas, along with an activepreventive medicine group, did much to stimulate preventive measures. Itwas necessary at times to change preventive medicine units in divisionmovements. When such took place, the Division Surgeon was not bashful inquoting the requirements of the Commanding General for these units. Divisionand corps preventive medicine officers obtained spot announcements on localArmed Forces radio stations. Sunday, from mid-April until the last of October,being chloroquine day, rated radio spot announcements concerning the takingof chloroquine. Further improvements in the tactical situation, availablepreventive medicine personnel, and facilities for health education aidedmaterially in the 1952 program.
The continued decrease in the 1953 malaria rates evidences the progressionin the suppression program. It has been estimated that better than 90 percentcompliance with the program was obtained during the 1953 season. Stabilizationin the tactical situation has played an important part in increasing theeffectiveness of the chloroquine program in Korea.
Information on parasitemia between seasons, when chloroquine was notadministered, was obtained by Egan (15) during the period 20 Januaryto 1 March 1952. He reported on the examination of blood smears obtainedfrom 1,000 troops of the Marine Division who had arrived in Korea priorto 3 August 1951. Chloroquine was available in this division from 15 Aprilto 18 December 1951. Twenty (2 percent) of this group were found to havea parasitemia, without clinical symptoms, at the time of examination. Seventeenstated that they had taken chloroquine 100 percent of the time, one 75percent of the time, and two had never taken it. Seven hundred and ninety-sixof the total group declared they had taken chloroquine 100 percent of thetime and the other 204 stated they had taken the drug less than 80 percentof the prescribed time.
The effect of parasitemia on the malaria rate can cause concern, particularlywhen cases are reported in February, and practically all of the cases arereported from one unit. During February 1952 at one hospital, the assignedpersonnel were examined and those with parasitemia, or who were thoughtto show a parasitemia, were hospitalized and treated for malaria. As aresult some 65 patients were so treated. Examination of a few availableslides by the Army Field Medical Laboratory for confirmation cast seriousdoubt on the reliability of the diagnosis of many of these patients, whoalready had received treatment. The correct diagnosis is not only of importanceto the statistical and historical personnel, but to the laboratory andpreventive medicine officers at Army level. Erroneous diagnosis indicated
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that there was a lack of information on the Korean vivax malariacycle or that the technicians were misreading the slides. It is believedthat in this particular instance chloroquine suppression might have beengiven from the time of diagnosis, since none were symptomatic. On the otherhand, if as many as 2 percent actually had had malaria, the noneffectivenessin this small group would have presented no serious problem to the unit.
Although the preventive medicine officer of a field army is concernedwith reducing the noneffectiveness from malaria as a means of making manpoweravailable to the command, he is also deeply concerned with the exportationof the disease and its establishment in areas of the United States or othercountries which are free or nearly free of the disease. In 1951, with thereturn of many Korean veterans, the number of cases seen in the UnitedStates began to increase and became of considerable concern not only tothe military but the civilian authorities. Young (16) in 1952 mentionedthat the evanescence of malaria as a major health program in the UnitedStates was dramatized by the action taken by the National Malaria Society,i. e., dissolving itself. This is one of the few times in medical historythat a society has voluntarily ceased to exist because its aims had beenfulfilled. Fritz and Andrews (17) reviewed the imported and indigenousmalaria in the United States in 1951-52 and in summary stated that thecurrent status of malaria incidence in the United States, caused by manythousands of infected servicemen, had brought about renewed malaria transmission.
The cases of malaria diagnosed and reported in the United States bythe 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. Thedecrease can be attributed definitely to the institution of primaquinetherapy. Alving and his group (9) came to the Far East in August1951, and returning by surface vessel in September, carried out the firstprimaquine program for the treatment of returnees. It was not until lateDecember 1951 that primaquine was established as a routine measure fortroops returning by ship. As with any program, there is a time intervaluntil it is progressing smoothly. However, it was not until August 1952that at least 90 percent effectiveness was attained in its administration.It is obvious that those returned by air would not have sufficient timeto take the full course of therapy, which consisted of 1 gram of chloroquinefollowed by primaquine administered in doses of 15 milligrams (of base)over a 14-day period. The efficacy and rationale of this therapy has alreadybeen presented by Alving, et al. (9).
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There are administrative difficulties in providing such a program totroops in the field prior to their departure from the actual theater ofoperations. It would be desirable to give each individual who is due toreturn home this treatment by roster, except that the matter of departureis usually in a state of flux until the individual actually departs hisunit. It has been generally agreed that the program must be instigatedupon the arrival of the troops at the port of embarkation.
The cost of a suppression and prophylaxis program is most importantin considering not only the benefits to military returnees but also inplanning programs for residents of endemic areas. The cost of chloroquinesuppression in Korea for military personnel is 77 cents for
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one season (not including shipping and handling costs). The cost ofprimaquine therapy per man en route home is 29 cents. Considering the averagetime spent in Korea as one year, it is possible to reduce the noneffectivenessdue to malaria and decrease the number of cases imported into the UnitedStates to a very low figure for $1.06 per man. With this drug combinationand its administration during one season to the residents of a countrywhere the temperate zone type of malaria is endemic, a tremendous salutaryeffect on the health of the country would result. With a 10 percent incidencein a Korean population of 22 million, it would decrease noneffectivenessin over 2 million individuals, not for one year, but for many years. Itis interesting to conjecture what the effects would be if one dollar perperson 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 mosquitoand malaria control which are now employed as adjuncts to suppression andprophylaxis in Korea. Malaria in a military force has been reduced to sucha degree that it no longer presents a serious problem to the commanderor the associates of the veteran upon his return home. The effects arerendered even more dramatic when one considers that the production andintroduction of primaquine was accomplished in the short space of a year.Although we may have an effective means of controlling this temperate-zone-typemalaria, there remain other strains for which true prophylactic drugs haveyet to be developed. In addition, mosquitoes act as vectors of other diseasesfor which there are, at present, no specific therapeutic drugs. While thecontrol of mosquitoes as a preventive measure with respect to malaria inKorea may not justify the expense of the conventional methods, certainlymosquito control will have to be continued in the face of other diseasesfor which they are vectors.
With reference to the use of repellent by the individual, it has beenevident that the soldiers will not use it either freely of their own volitionor when it is force issued. A high-powered sales and advertising programfor chloroquine and primaquine is not conducive to encouraging the soldier,who may bathe once in 3 days, to smear certain exposed parts of his anatomywith an oily repellent.
Personnel to conduct training, aid in insect control programs, advisewith reference to air spray, check equipment, etc., were in constant demandin Korea. Experiences with a preventive medicine company show it to bewell organized and admirably suited to perform its mission. It is believedthat there should be a company of three or four control sections per corps,depending upon the number of divisions
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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 vivaxmalaria and has reduced noneffectiveness from this disease in a fieldarmy to a degree that it presents no problems.
2. Primaquine prophylaxis for Korean vivax malaria has effectivelyreduced to a minimum the potential of importing this disease into areasfree 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. PublicHealth Service Publication No. 193.
U. S. Government Printing Office, Washington, D. C., 1953.
3. Medical Statistics Division, Office of The SurgeonGeneral, Department of the Army, Washington, D. C. Official reports forperiods presented.
4. Park, Chai Bin: Studies on Korean Deaths. Unpublisheddata.
5. Activities Report of Fleet Epidemic Disease ControlUnit No. 1 for the month of August, 1951. Fleet Epidemic Disease ControlUnit 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. FleetEpidemic 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 PreventiveMedicine 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 December1945, Washington, D. C.
9. Alving, A. S., Arnold, J., and Robinson, D. H.: Statusof Primaquine. 1. Mass Therapy of Subclinical Vivax Malaria withPrimaquine. 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 AerialSpray 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.
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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." EpidemicDisease 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 IndigenousMalaria 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.
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