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A survey of simian malaria in Japan
558 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL ~LEDICINE AND HYGIENE.
Vol. 62. No. 4.
1968.
A SURVEY OF SIMIAN MALARIA IN JAPAN MASAMITSU OTSURU aND HIROHO SEKIKAWA
Department of Medical Zoology, Niigata University School of Medicine,Japan Much work has been done on the distribution of simian malaria in Asia, and for several years a large amount of this has been done in Malaya. 5 or more species of simian malaria and their rough distribution are now known in South-east Asia, but none from China, Korea and Japan. Monkeys of Macaca species are widely distributed in Japan except Hokkaido, but their numbers are far less than other macaca monkeys in South-east Asia. As the demand for monkeys as laboratory animals grows, particularly for the production of poliomyelitis vaccine recently, they have been increasingly imported from other countries. This paper deals with results of the first blood survey of such monkeys, made during the past 3 years, and the possible significance of those findings in the field of simian malaria.
Materials and methods
Macacafuscatafuscata were captured in two districts (Mihara and Kyoto) of Honshu and a small island (Shodoshima) of Shikoku by the local hunters in charge of the Japan Monkey Centre, one of the activities of which is to supply monkeys for research; Macaca fuscata yakui were captured in Yakushima, a small island in the sea 70 kin. south of the southern end of Kyushu, in the same way. Some monkeys reared for a period after capture or born in the Centre were also included for this examination. All blood specimens were kindly taken by members of the Centre. Cercopithecus sp. were captured in Uganda and imported to Japan by the dealers, Macaca irus from the Philippines and Thailand, and Macaca mulatta from East Pakistan. Their blood specimens were taken by us about one month to two years after their arrival in this country, through the courtesy of National Institute of Health and of the vaccine producing institute. Thick or thin blood films, or both, were stained by Giemsa's method. In addition to the blood examination, liver merocysts of Hepatocystis were also looked for in Cercopithecus sp., and the livers of Macaca fuscata yakui which had been reserved after autopsy in the Japan Monkey Centre were also examined for this purpose. The white or translucent blebs about 2 ram. in diameter, visible on the surface of the liver, were sectioned and stained with haematoxylin-eosin in order to confirm the presence of merocysts. We are indebted to Professor P. C. C. Garnham, the late Professor G. Macdonald, Dr. R. S. Bray and Members of Japan Monkey Centre and National Institute of Health for their help and encouragement in this project.
559
MASAMITSU OTSURU AND HIROHO SEKIKAWA
Results The Japanese monkeys (Table I). No malaria parasites were found in 292 blood films of Macaca fuscata fuscata. examined, 202 of these were taken immediately after capture in Mihara (139), Shodoshima (42) and Kyoto (21); the remaining 90 were monkeys reared after capture or born in the Japan Monkey Centre. TABLE I.
The result of blood examination for simian malaria in Japanese monkeys, 1965-1967 No. examined
Species
Macaca fuscata fuscata
Positive
292
Macaca fuscata yakui
0
66*
Total
0
358
*Babesia sp. was found in 4 (6.1%) of 66 M. fi yakui. Likewise, no malaria parasites were found in 66 blood films of Macaca fuscata yakui, 26 captured in Yakushima and 40 reared after capture or born in the Centre. A most interesting finding, however, was that 4 of the 66 were infected with Babesia sp.; the infected monkeys had been all reared in the Centre for several years, consisting of 2 M and 2 F and ranging from 9 to 16 years old.
The monkeys imported from other countries (Table H). There were 65 Cercopithecus sp., 30 Macaca irus (Philippines and Thailand) and 22 Macaca mulatta (East Pakistan); Plasmodium inui was found in 5 (16.7%) Macaca irus in both countries. Hepatocystis kochi was found in 41 (63.1%) of the Cercopitkecus sp. from Uganda. TABLE II.
The result of blood examination for simian malaria in monkeys imported from other countries, 1966-1967 Species (Origins)
No. examined
Plasmodium inui Hepatocystis Vos. (%) kochi Pos. (%)
41
Cercopithecus sp. (Uganda)
65
0
Macaca irus (Philippines)
22
3
(13.6)
0
8
2
(25.0)
0
22
0
117
5
Macaca irus (Thailand) Macaca mulatta (East Pakistan) Total
(63.1)
0 (4.3)
41
(35.0)
The liver examination The typical merocysts of H. kochi were found in the 41 Cercopithecus sp. in which the same parasite was present in blood films. No merocysts were seen in 12 Macaca fuscata yakui examined.
560
A S~RWY OF SIMIAN MALARIAIN I~AN
Discussion The Japanese monkeys are distributed in 3 of the 4 islands of Japan, namely Kyushu, Shikoku, Honshu, but not in Hokkaido, the northernmost island. They are classified into two subspecies, Macaca fuscata fuscata distributed in Kyushu, Shikoku and the main island Honshu, and Macaca fuscata yakui only in Yakushima, one of the small islands located between Kyushu and the Loochoo Islands. Aomori, the northernmost prefecture of Honshu, represents the northernmost distribution of monkeys in the world. The number of the wild Japanese monkeys was estimated at 16,000 by KISHIDA (1953) and 26,000 by TAKESHIT/~(1963), but that their population has probably increased since their designation as protected animals in 1947. They have many points of advantage as laboratory animals, because they are easily cared for and managed according to a high degree of adaptability to Japanese environment. However, as mentioned above, their absolute number is far less than that of other macaca monkeys in Asia. Plasmodium cynomolgi cyclopis, P. inui, Hepatocystis taiwanensis and other species of simian malaria parasites were recorded in Macaca cyclopis, the only species of monkey ever reported from Taiwan, which is crossed by the Tropic of Cancer in the middle; there are no reports of simian malaria in China, Korea and Japan. According to this first survey, no malaria parasites were found in the 358 Japanese monkeys examined. However, it is of deep interest that 4 of 66 Macaca fuscata yakui were infected with Babesia sp. There was at first some doubt whether a babesia or its related genus or a plasmodium was involved. But since no segmenters and no evidence of pigment were found, even in the larger parasites, we concluded that we were dealing with Babesia, excluding Theileria because of the presence of dividing forms. These parasites were all minute and the ring forms were most numerous. Amoeboid forms and pyriform bodies were also seen. Two or more species of Babesia have been found in monkeys, and that of the Japanese monkeys seems to resemble Entopolypoides macad M. Mayer, 1934, which was described from Macaca irus in Java. However, some differences between the two species have been observed, particularly in the presence of pyriform bodies (2 to 4) in the former. We believe that this is an apparently new species, considering that a new host record of Babesia, especially in new region, means a new species. We shall describe that of the simian Babesia in another paper. Plasmodium inui was found in 1 3 . 6 ~ of Macaca irus from the Philippines and in 25"0~o of Macaca irus from Thailand. Plasmodium inui appears to be the widestranging species of simian malaria parasites, most likely as a result of the high chronicity of infection, and it has been already recorded in Philippines and Thailand. On the other hand, Hepatocystis kochi was found in high proportion (63.1%) of Cercopithecus sp. imported from Uganda. In tropical Africa 1-1.kochi is extremely common and has been seen in practically every country, and the blue monkey (Cercopithecus mitis albogularis) of the Kenya Highlands is reported to be very heavily infected with H. kochi, neatly to the extent of 100 ~ . Malaria was one of the diseases with which a great number of the Japanese troops were afflicted on the Chinese mainland and in South-east Asia duringWorldWar II. After the war, especially during the period 1945-46, when troops and civilians, estimated at about 600,000 in all, came home with malaria parasites, the Japanese people were exposed to an unprecedented danger of malaria. Fortunately, however, the imported malaria was almost exterminated in about 5 years, as was the case in Britain after World War I, while there broke out new infections of malignant tertian malaria as a epidemiological warning. On the other hand, indigenous benign tertian malaria 'began to show a decreasing tendency'in the early part of the present century. The patients with indigenous
MASAMITSU OTSURU AND HIROHO SEKIKAWA
561
malaria continued to decrease in number despite the war, and no cases infected naturally have been reported by physicians from any part of the country during the past several years, although cases due to transfusion of fresh or stored blood occasionally occurred. 7 species of anophelines are recognized in Japan, and Anopheles sinensis is considered to be one of the most important vectors in Japan. Though based on a limited survey, the results shown in this paper may be of some value in the field of malaria epidemiology of Japan. However, this report suggests at present that those simian reservoirs of malaria are probably of very limited significance for the Japanese monkeys and the human population. For reference, in Japan there are distributed 40 or more species of Culicoides, which are considered to be responsible for the transmission of Hepatocystis.
Summary The first survey of simian malaria in Japan showed that no Japanese monkeys (Macaca fuscata fuscata and Macaca fuscata yakui) were infected with malaria parasites, but most interestingly, Babesia sp. was found in 4 (6.1%) of 66 Macaca fuscata yakui. As for the monkeys imported from other countries, Plasmodium inui was found in 3 (13.6%) of 22 Macaca irus (Philippines) and in 2 (25.0%) of 8 Macaca irus (Thailand), and Hepatocystis kochi was seen in 41 (63.1%) of 65 Cercopithecus sp. (Uganda). Although based on a limited survey, this report suggests at present that those simian reservoirs of malaria are probably of very limited significance for the Japanese monkeys and the human population. REFERENCES BRAY, R. S. (1963). Malaria Infections in Primates and their Importance to Man. Berlin, G6ttingen, Heidelberg: Springer-Verleg. EYLES, D. E. (1963). 37. Parasit., 49, 866. GARNHAM, P. C. C. (1966). Malaria Parasites and other HaemospoHdia. Oxford: Blackwell Scientific Publications. HOWARD, L. M. & CABRERA,B. D. (1961). Science, 134, 555. HSlEH, H. (1960). Formosan Sci., 14, 477. KOTERA, S. (1961). Primates, 3, 47. MAYER, M. (1934). Zentbl. Bakt. ParasitKde., 131, 132. OTSURU,M. (1960). 37ap.37. exp. Med., 30, 23. & OHMORI, Y. (1960). Ibid., 30, 33.
Vol. 62. No. 4.
1968.
A SURVEY OF SIMIAN MALARIA IN JAPAN MASAMITSU OTSURU aND HIROHO SEKIKAWA
Department of Medical Zoology, Niigata University School of Medicine,Japan Much work has been done on the distribution of simian malaria in Asia, and for several years a large amount of this has been done in Malaya. 5 or more species of simian malaria and their rough distribution are now known in South-east Asia, but none from China, Korea and Japan. Monkeys of Macaca species are widely distributed in Japan except Hokkaido, but their numbers are far less than other macaca monkeys in South-east Asia. As the demand for monkeys as laboratory animals grows, particularly for the production of poliomyelitis vaccine recently, they have been increasingly imported from other countries. This paper deals with results of the first blood survey of such monkeys, made during the past 3 years, and the possible significance of those findings in the field of simian malaria.
Materials and methods
Macacafuscatafuscata were captured in two districts (Mihara and Kyoto) of Honshu and a small island (Shodoshima) of Shikoku by the local hunters in charge of the Japan Monkey Centre, one of the activities of which is to supply monkeys for research; Macaca fuscata yakui were captured in Yakushima, a small island in the sea 70 kin. south of the southern end of Kyushu, in the same way. Some monkeys reared for a period after capture or born in the Centre were also included for this examination. All blood specimens were kindly taken by members of the Centre. Cercopithecus sp. were captured in Uganda and imported to Japan by the dealers, Macaca irus from the Philippines and Thailand, and Macaca mulatta from East Pakistan. Their blood specimens were taken by us about one month to two years after their arrival in this country, through the courtesy of National Institute of Health and of the vaccine producing institute. Thick or thin blood films, or both, were stained by Giemsa's method. In addition to the blood examination, liver merocysts of Hepatocystis were also looked for in Cercopithecus sp., and the livers of Macaca fuscata yakui which had been reserved after autopsy in the Japan Monkey Centre were also examined for this purpose. The white or translucent blebs about 2 ram. in diameter, visible on the surface of the liver, were sectioned and stained with haematoxylin-eosin in order to confirm the presence of merocysts. We are indebted to Professor P. C. C. Garnham, the late Professor G. Macdonald, Dr. R. S. Bray and Members of Japan Monkey Centre and National Institute of Health for their help and encouragement in this project.
559
MASAMITSU OTSURU AND HIROHO SEKIKAWA
Results The Japanese monkeys (Table I). No malaria parasites were found in 292 blood films of Macaca fuscata fuscata. examined, 202 of these were taken immediately after capture in Mihara (139), Shodoshima (42) and Kyoto (21); the remaining 90 were monkeys reared after capture or born in the Japan Monkey Centre. TABLE I.
The result of blood examination for simian malaria in Japanese monkeys, 1965-1967 No. examined
Species
Macaca fuscata fuscata
Positive
292
Macaca fuscata yakui
0
66*
Total
0
358
*Babesia sp. was found in 4 (6.1%) of 66 M. fi yakui. Likewise, no malaria parasites were found in 66 blood films of Macaca fuscata yakui, 26 captured in Yakushima and 40 reared after capture or born in the Centre. A most interesting finding, however, was that 4 of the 66 were infected with Babesia sp.; the infected monkeys had been all reared in the Centre for several years, consisting of 2 M and 2 F and ranging from 9 to 16 years old.
The monkeys imported from other countries (Table H). There were 65 Cercopithecus sp., 30 Macaca irus (Philippines and Thailand) and 22 Macaca mulatta (East Pakistan); Plasmodium inui was found in 5 (16.7%) Macaca irus in both countries. Hepatocystis kochi was found in 41 (63.1%) of the Cercopitkecus sp. from Uganda. TABLE II.
The result of blood examination for simian malaria in monkeys imported from other countries, 1966-1967 Species (Origins)
No. examined
Plasmodium inui Hepatocystis Vos. (%) kochi Pos. (%)
41
Cercopithecus sp. (Uganda)
65
0
Macaca irus (Philippines)
22
3
(13.6)
0
8
2
(25.0)
0
22
0
117
5
Macaca irus (Thailand) Macaca mulatta (East Pakistan) Total
(63.1)
0 (4.3)
41
(35.0)
The liver examination The typical merocysts of H. kochi were found in the 41 Cercopithecus sp. in which the same parasite was present in blood films. No merocysts were seen in 12 Macaca fuscata yakui examined.
560
A S~RWY OF SIMIAN MALARIAIN I~AN
Discussion The Japanese monkeys are distributed in 3 of the 4 islands of Japan, namely Kyushu, Shikoku, Honshu, but not in Hokkaido, the northernmost island. They are classified into two subspecies, Macaca fuscata fuscata distributed in Kyushu, Shikoku and the main island Honshu, and Macaca fuscata yakui only in Yakushima, one of the small islands located between Kyushu and the Loochoo Islands. Aomori, the northernmost prefecture of Honshu, represents the northernmost distribution of monkeys in the world. The number of the wild Japanese monkeys was estimated at 16,000 by KISHIDA (1953) and 26,000 by TAKESHIT/~(1963), but that their population has probably increased since their designation as protected animals in 1947. They have many points of advantage as laboratory animals, because they are easily cared for and managed according to a high degree of adaptability to Japanese environment. However, as mentioned above, their absolute number is far less than that of other macaca monkeys in Asia. Plasmodium cynomolgi cyclopis, P. inui, Hepatocystis taiwanensis and other species of simian malaria parasites were recorded in Macaca cyclopis, the only species of monkey ever reported from Taiwan, which is crossed by the Tropic of Cancer in the middle; there are no reports of simian malaria in China, Korea and Japan. According to this first survey, no malaria parasites were found in the 358 Japanese monkeys examined. However, it is of deep interest that 4 of 66 Macaca fuscata yakui were infected with Babesia sp. There was at first some doubt whether a babesia or its related genus or a plasmodium was involved. But since no segmenters and no evidence of pigment were found, even in the larger parasites, we concluded that we were dealing with Babesia, excluding Theileria because of the presence of dividing forms. These parasites were all minute and the ring forms were most numerous. Amoeboid forms and pyriform bodies were also seen. Two or more species of Babesia have been found in monkeys, and that of the Japanese monkeys seems to resemble Entopolypoides macad M. Mayer, 1934, which was described from Macaca irus in Java. However, some differences between the two species have been observed, particularly in the presence of pyriform bodies (2 to 4) in the former. We believe that this is an apparently new species, considering that a new host record of Babesia, especially in new region, means a new species. We shall describe that of the simian Babesia in another paper. Plasmodium inui was found in 1 3 . 6 ~ of Macaca irus from the Philippines and in 25"0~o of Macaca irus from Thailand. Plasmodium inui appears to be the widestranging species of simian malaria parasites, most likely as a result of the high chronicity of infection, and it has been already recorded in Philippines and Thailand. On the other hand, Hepatocystis kochi was found in high proportion (63.1%) of Cercopithecus sp. imported from Uganda. In tropical Africa 1-1.kochi is extremely common and has been seen in practically every country, and the blue monkey (Cercopithecus mitis albogularis) of the Kenya Highlands is reported to be very heavily infected with H. kochi, neatly to the extent of 100 ~ . Malaria was one of the diseases with which a great number of the Japanese troops were afflicted on the Chinese mainland and in South-east Asia duringWorldWar II. After the war, especially during the period 1945-46, when troops and civilians, estimated at about 600,000 in all, came home with malaria parasites, the Japanese people were exposed to an unprecedented danger of malaria. Fortunately, however, the imported malaria was almost exterminated in about 5 years, as was the case in Britain after World War I, while there broke out new infections of malignant tertian malaria as a epidemiological warning. On the other hand, indigenous benign tertian malaria 'began to show a decreasing tendency'in the early part of the present century. The patients with indigenous
MASAMITSU OTSURU AND HIROHO SEKIKAWA
561
malaria continued to decrease in number despite the war, and no cases infected naturally have been reported by physicians from any part of the country during the past several years, although cases due to transfusion of fresh or stored blood occasionally occurred. 7 species of anophelines are recognized in Japan, and Anopheles sinensis is considered to be one of the most important vectors in Japan. Though based on a limited survey, the results shown in this paper may be of some value in the field of malaria epidemiology of Japan. However, this report suggests at present that those simian reservoirs of malaria are probably of very limited significance for the Japanese monkeys and the human population. For reference, in Japan there are distributed 40 or more species of Culicoides, which are considered to be responsible for the transmission of Hepatocystis.
Summary The first survey of simian malaria in Japan showed that no Japanese monkeys (Macaca fuscata fuscata and Macaca fuscata yakui) were infected with malaria parasites, but most interestingly, Babesia sp. was found in 4 (6.1%) of 66 Macaca fuscata yakui. As for the monkeys imported from other countries, Plasmodium inui was found in 3 (13.6%) of 22 Macaca irus (Philippines) and in 2 (25.0%) of 8 Macaca irus (Thailand), and Hepatocystis kochi was seen in 41 (63.1%) of 65 Cercopithecus sp. (Uganda). Although based on a limited survey, this report suggests at present that those simian reservoirs of malaria are probably of very limited significance for the Japanese monkeys and the human population. REFERENCES BRAY, R. S. (1963). Malaria Infections in Primates and their Importance to Man. Berlin, G6ttingen, Heidelberg: Springer-Verleg. EYLES, D. E. (1963). 37. Parasit., 49, 866. GARNHAM, P. C. C. (1966). Malaria Parasites and other HaemospoHdia. Oxford: Blackwell Scientific Publications. HOWARD, L. M. & CABRERA,B. D. (1961). Science, 134, 555. HSlEH, H. (1960). Formosan Sci., 14, 477. KOTERA, S. (1961). Primates, 3, 47. MAYER, M. (1934). Zentbl. Bakt. ParasitKde., 131, 132. OTSURU,M. (1960). 37ap.37. exp. Med., 30, 23. & OHMORI, Y. (1960). Ibid., 30, 33.