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Chapter 6, Part 5

Medical Science Publication No. 4, Volume II



This report reviews certain important contributions to our knowledge of rickettsial diseases which have been made since the close of World War II. Attention is centered upon aspects which are of particular importance to military medicine. The discussion is concerned mainly with louse-borne typhus and with scrub typhus, the other rickettsial diseases being considered briefly. The period covered is January 1946 through December 1953.

Basic information on rickettsial diseases, available at the close of World War II, has been presented in detail (1). This information has been translated into effective control measures (2). For authoritative accounts of rickettsial diseases, chapters by various authors (3) should be consulted.

Louse-borne Epidemic Typhus

At the close of World War II, the more obvious problems of epidemic typhus were: (a) the need for specific therapeutic agents other than para-aminobenzoic acid; and (b) further clarification of the interepidemic reservoir of the disease. When the possibility that the vector might prove resistant to DDT became an actuality in Korea, the need for effective insecticides was immediate. These problems merit further consideration.

Specific Therapeutic Agents. Three antibiotics are established as effective in the treatment of persons suffering from each of the rickettsial infections: chloramphenicol, aureomycin and terramycin. They are rickettsiostatic, not rickettsiocidal, in action; recognition of this fact is essential to an understanding of their proper clinical use. Although the recommended doses (4) are non-toxic, nausea, vomiting, or diarrhea may accompany their administration. In evaluating reports of the rare occurrence of blood dyscrasias, attributed to chloramphenicol, the very low risk of the occurrence of such complications should be contrasted with the much higher case fatality rate in the rickettsial diseases of military importance. In no known instance

*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.


have any of the three effective antibiotics failed to prevent a fatal outcome, when given a reasonable therapeutic trial in a human case of rickettsial infection. Thus the available rickettsiostatic agents are eminently satisfactory. If further search for antibiotics is made, one would aim at finding a compound which is rickettsiocidal and which is non-toxic to man (4).

Interepidemic Reservoir. The studies of Murray et al (5-7), sponsored by the Armed Forces Epidemiological Board, have verified the hypothesis that Brill's disease represents a recrudescence of louse-borne typhus. It is postulated that viable rickettsiae persist during the latent interval somewhere in the tissues of some individuals. The factors which disturb the immunologic balance in such persons, permitting the sequestered rickettsiae to emerge and again produce disease, are poorly understood.

It has been demonstrated that lice become infected by feeding on patients who have Brill's disease, hence the epidemiologic significance of such persons is obvious. When cases of Brill's disease occur in a louse-infested community, they may serve as foci from which an epidemic of louse-borne typhus can spread to susceptible members of the population. Similarly, they may serve to introduce typhus into an area where it has not been known for some time. Thus, the potential hazard of such persons emphasizes the need for louse control as an integral part of measures designed to prevent outbreaks of typhus in louse-infested populations.

Control of Lice and Lousiness. The principle of vector control as an important weapon in the control of an arthropod-borne disease is well illustrated by experience with louse-borne typhus. The effectiveness of delousing in controlling the spread of epidemic typhus was demonstrated during World War I. Delousing methods in use at that time employed heat to kill the insects and their eggs in clothing and other effects, together with the concurrent cleansing of individuals. Subsequent studies of various chemical insecticides culminated in the use of DDT during World War II, and in the development of effective methods for its application to large numbers of persons (1). A noteworthy property of DDT is its residual effect, whereby reinfestation with susceptible insects is reduced to nil during a period of several weeks following proper application. An insecticide which has these features of effectiveness, ease of application, relative non-toxicity to man, and residual effect, is admirably suited to the control of human body lice.

During the Korean conflict, it became apparent that not all strains of human body lice are killed by DDT. During the winter and spring of 1951, routine applications of DDT powder to Communist prisoners of war failed to control their louse infestations. Field and laboratory


studies showed that the lice themselves were resistant to DDT (8). DDT-resistant lice were also detected in Japan (9, 10). Tests of other insecticides were conducted (11, 12). Six formulations of powder, each containing pyrethrum and allethrin as active principles, were found to be effective if applied four times at 5-day intervals. A single treatment of clothing with powder composed of 1 percent lindane (the gamma isomer of hex-chloro-cyclohexane) in pyrophyllite killed all lice for as long as 9 days after application. Laboratory tests indicated, however, that more than one treatment would be required to eradicate a person's infestation under natural conditions (12), since the initial application would have lost its effectiveness by the end of the 10-day period of incubation of louse eggs. Lindane was subsequently used effectively for control of lice in Korea.

Although currently effective insecticides are available, the possible future occurrence of resistant lice must be borne in mind. In other words, although the immediate problem of DDT resistance has been solved, the potential problem of insecticide-resistant lice remains.

Effectiveness of Typhus Control Measures. During the Korean conflict the hazard of infection of troops with epidemic typhus was very real. The widespread occurrence of famine, poverty, disruption of populations, overcrowding and lousiness, during the latter part of 1950, provides environmental factors known to be conducive to the spread of louse-borne typhus (13, 14). The persons at risk included approximately 20 million South Korean nationals, numerous louse-infested Communist prisoners of war, and the personnel of the United Nations.

Appropriate preventive measures were applied to these three population groups. During the period 1 January to 30 September 1951, more than 15 million (75 percent) South Koreans were treated with DDT powder (13, 15), and the newer insecticides were used when they became available. More than 14.5 million South Koreans received Cox-type typhus vaccine (13). Similar measures were applied to prisoners of war (16), and standard preventive measures were employed by military personnel of the United States and other United Nations.

Were these measures effective? It is estimated (14) that the typhus incidence among South Korean civilians rose during early 1951 to an average of 3,228 cases and 473 deaths per month; while estimated monthly averages for the first 6 months of 1952 were 125 cases and 16 deaths.

The experience of United States military personnel is likewise relevant to an evaluation of the typhus control programs. The exposure of our personnel to lice is suggested by the fact that they became infected with relapsing fever in Korea, where the vector is presumably


the louse. During 1951, 69 cases of relapsing fever were reported in United Nations troops in Korea, and 107 cases were diagnosed among prisoners of war (17). The number of cases of louse-borne typhus in United States personnel was, however, essentially nil, there being but one case on record in a heavily exposed member of the Medical Department.

In view of these considerations, it is concluded that the effectiveness of typhus preventive measures was demonstrated by the experience in Korea.

Scrub Typhus

Recent advances in our knowledge of scrub typhus are the outcome of studies made mainly by members of the United States Armed Forces working in Malaya, Japan and Korea. These include the clinical evaluation and development of antibiotics in the chemoprophylaxis and therapy of scrub typhus in Malaya, and important contributions to the epidemiology of the disease in Japan and Korea. Since the studies of antibiotics have been mentioned above, particular attention will be given to the advances made in Japan and Korea.

Japan. Since the close of World War II, our Armed Forces in Japan have experienced two outbreaks of scrub typhus. Between 6 October and 13 November 1948, 27 cases were diagnosed in American soldiers; of these cases, 26 men had been engaged in field exercises near the town of Gotemba and 1 came from a camp on the slopes of Mount Fuji (18). The general locale became known as the Fuji-Susono area. Field studies (19, 20) revealed the presence of several species of chiggers, but Trombicula akamushi was not found. Further surveys (21-23) of this focus resulted in the recovery of Rickettsia tsutsugamushi from pooled tissues of field mice, and in the demonstration of the presence of four species of Trombicula: T. palpalis, T. intermedia, T. japonica and T. fuji.

During the period 20 to 31 October 1953, 57 mild cases of scrub typhus were diagnosed in personnel of the Third Marine Division who were stationed in the vicinity of Mount Fuji (24). In view of the well-documented experience of 1948 together with the availability of effective preventive measures, this occurrence is regarded as an example of lessons not learned.

Studies by Japanese scientists (25) have revealed the presence of scrub typhus on several islands located off the southern coast of Honshu. The name "Winter Scrub Typhus" emphasizes the seasonal occurrence of human cases on these islands. The evidence summarized by the Japanese (25) suggests that T. scutellaris is the local vector.

From these various observations in Japan, the following points emerge: (a) previously unrecognized foci of the disease have been


discovered; (b) human cases of scrub typhus can occur during the autumn and winter months; and (c) it is very likely that Trombicula akamushi is not the only Japanese chigger which carries scrub typhus to man. These points are pertinent to our consideration of the findings in Korea.

Korea. During June 1951, two cases of scrub typhus were diagnosed in troops of the British Commonwealth forces (26). The patients exhibited eschar and local lymphadenitis, their sera agglutinated Proteus OXK, and they responded to chloramphenicol. During November 1951, a case was diagnosed in a U. S. Marine Corps sergeant who was presumably exposed near Masan, Korea (17). Strains of Rickettsia tsutsugamushi were recovered from two patients with scrub typhus whose acute illnesses occurred during late October and early November 1953 (27).

The causative rickettsiae have been recovered from the common Korean wild mouse, Apodemus agrarius, on repeated occasions (27). This rodent is known to be a suitable host for the larvae of several species of chiggers; however, species of chiggers proved to be vectors elsewhere have not been found in Korea, despite intensive collecting. These facts suggest that one or more of the local Korean chiggers may be functioning as vectors among rodents. The search for a vector to man, other than T. akamushi, is indicated in the light of the epidemiologic and ecologic patterns of scrub typhus in Japan and Korea.

Other Rickettsial Diseases

Murine typhus has not been a problem of importance in the Far East Command. Tick-borne rickettsial diseases have not been recognized among our personnel operating in Korea. The recovery of Rickettsia akari from a Korean rodent (27) extends our knowledge of the geographic distribution of the causative agent of rickettsial pox but the ecologic interpretation of this finding requires additional data. The infection has not been identified in human beings in Korea. During the latter part of World War II, Q fever was an important disease in American troops in Italy (3). Although the causative agent is now known to have a worldwide distribution and a broad host range, Q fever has not been diagnosed among United Nations troops operating in Korea.


Since the close of World War II, much has been learned about rickettsial diseases. The following points are of direct concern to military medicine:

1. Chloramphenicol, aureomycin and terramycin have proved their effectiveness in the specific therapy of these diseases.


2. Persons with Brill's disease (recrudescent louse-borne typhus) may serve to initiate typhus epidemics in a louse-infested community.

3. The occurrence of DDT-resistant body lice in Korea posed a problem in typhus control which has been solved, for the present, by the use of lindane. The possibility of recurrence of insecticide-resistant lice should be borne in mind.

4. The effectiveness of current methods of typhus prevention and control was demonstrated by experiences of the Korean conflict.

5. The known geographical distribution of scrub typhus has been extended to include Korea, where a non-classical occurrence of human cases during autumn months has been noted. The causative rickettsiae have been found in a common and widespread species of wild Korean mouse. One or more species of chigger, not previously recognized as a vector, is probably responsible for the transmission of scrub typhus in Korea.

6. These important contributions to our knowledge of rickettsial diseases were made since World War II by personnel of the Military Service or by investigators who were sponsored by the Armed Forces Epidemiological Board.


1. American Association for the Advancement of Science: The Rickettsial Diseases of Man, pp. 1-247. Am. Assn. Advancement of Science, Washington, 1948.

2. American Public Health Association: The Control of Communicable Diseases, Ed. 7. Am. Pub. Hlth. Assn., New York, 1950.

3. Snyder, J. C., Cox, H. R., and Smadel, J. E.: Chapters of Viral and Rickettsial Infections of Man, pp. 578-664. Rivers, T. M., Ed. J. B. Lippincott Co., Philadelphia, 1952.

4. Ley, H. L., and Smadel, J. E.: Antibiotic Therapy of Rickettsial Diseases. Antibiotics and Chemotherapy. (In press.)

5. Murray, E. S., Baehr, G., Schwartzman, G., Mandelbaum, R. A. Rosenthal, N., Doane, J. C., Weiss, L. B., Cohen, S., and Snyder, J. C.: Brill's Disease. I. Clinical and Laboratory Diagnosis. J. A. M. A. 142 : 1059-1063, 1950.

6. Murray, E. S., and Snyder, J. C.: Brill's Disease. II. Etiology. Amer. J. Hyg. 53 : 22-32, 1951.

7. Murray, E. S., Psorn, T., Djakovic, P., Sielski, S., Broz, V., Ljupsa, F., Gaon, J., Pavlevic, R., and Snyder, J. C.: Brill's Disease. IV. Study of 26 Cases in Yugoslavia. Amer. J. Pub. Health 4l : 1359-1369, 1951.

8. Hurlbut, H. S., Altman, R. M., and Nibley, C., Jr.: DDT Resistance in Korean Body Lice. Science 115 : 11-12, 1952.

9. Barnett, H. C., and Knoblock, E. C.: Chemical and Biologic Studies on DDT Resistance of Lice. U.S. Armed Forces Med. J. 3 : 297-304, 1952.

10. Kitaoka, M.: DDT-resistant Louse in Tokyo. Jap. J. Med. Sci. Biol. 5 : 75-88, 1952.

11. Eddy, G. W.: A Report on the Effectiveness of Certain Insecticides against DDT-resistant Body Lice in Korea. Confidential Report, Office of The Surgeon General, U. S. Army, 1951.


12. Eddy, G. W.: Effectiveness of Certain Insecticides against DDT-resistant Body Lice in Korea. J. Econ. Ent. 45 : 1043-1051, 1952.

13. Van Bommel, L. B.: Epidemische vlektyphus on haar bestrijding in Zuid-Korea. Nederl. Tijdschr. v. Geneesk. 96 : 2562-2565, 1952.

14. Office of The Surgeon General, U. S. Army: Korea: A Summary of Medical Experience, July 1950-December 1952. Reprinted from Health of the Army, 1953.

15. Maclaren, J. P.: Insect and Rodent Control Activities of UNCACK. Military Prev. Med. Assoc. Korea, 8 April 1953. Mimeographed Proceedings: 28-29, 1953.

16. Dews, S. C.: Mass Delousing of Personnel. Military Prev. Med. Assoc. Korea, 8 April 1953. Mimeographed Proceedings: 8-10, 1953.

17. 406 Medical General Laboratory: Annual Historical Report for 1951.

18. Thompson, A. H.: A New Endemic Area of Scrub Typhus in Japan. Bull. U. S. Army Med. Dept. 9 : 871-879, 1949.

19. 406 Medical General Laboratory: Annual Historical Report for 1948.

20. Kuwata, T., Berge, T. O., and Philip, C. B.: A New Species of Japanese Larval Mite from a New Focus of Tsutsugamushi Disease in Southeastern Honshu, Japan. J. Parasitol. 36 : 80-83, 1950.

21. 406 Medical General Laboratory: Annual Historical Report for 1950.

22. Fukuzumi, S., Obata, Y., and Kagiwada, R.: On the Trombiculid Mites and Rickettsiae Discovered in Mt. Fuji Foot Plain. Kitasato Arch. Exper. Med. 23 (4) : 11-22, 1951.

23. Hayashi, H.: On the Causative Agent of Tsutsugamushi Disease Isolated from Field Voles, Apodemus speciosus speciosus, Inhabiting the Foot Area of Mt. Fuji in Japan. Kitasato Arch. Exper. Med. 23 : 13-19, 1951.

24. Outbreak of Scrub Typhus: Medical News Letter, United States Navy 23 (5) : 33-35, 5 March 1954.

25. Yosano, H., and co-workers: Studies on Shichito Fever. Winter Scrub Typhus of Izu Shiohito Islands, Japan, 125 pages (pp. 91-125 in English), Tokyo, 1953.

26. Munro-Faure, A. D., Andrew, R., Missen, G. A. K., and Mackay-Dick, J.: Scrub Typhus in Korea. J. Roy. Army Med. Corps 97 : 227-229, 1951.

27. Army Medical Service Graduate School, Division of Communicable Diseases: Quarterly Reports, 1953.