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A survey for haemoglobinopathies in Nepal
392 TRANSACTIONSOF THE ROYAL SOCIETYOF TROPICALMEDICINEAND HYGIENE.Vol. 68. No. 5. 1974. A S U R V E Y F O R H A E M O G L O B I N O P A T H I E S IN N E P A L
W. H. ADAMS The Johns Hopkins University Centrefor Medical Research and Training, Kathmandu, Nepal Introduction
Several surveys for abnormal haemoglobins and thalassaemia among the Nepalese have been reported. The varieties of disorders discovered have included haemoglobin H disease, beta thalassaemia, and haemoglobin E (BRAIN and VELLA, 1958; WEATr~RALL and VELLA, 1960; VELLA, 1962; CrUtTTERJEA, 1959). However, these studies were performed on Nepalese residing outside Nepal. Only one such survey performed within Nepal has been published, that being among the Sherpas living near Mt. Everest (JACKSON, LEmV~NN and SH~a~taH, 1960). During the period from March 1972 to March 1973, a survey was carried out by The Johns Hopkins University Centre for Medical Research and Training, in co-operation with His Majesty's Government of Nepal Directorate of Health Services, to define those areas in Nepal where genetic haemoglobin (Hb) abnormalities might exist. The present report gives the results of this survey. Subjects Specimens were collected from 2,473 unselected villagers or hospital in-patients and out-patients, mostly adults, from the areas indicated in Fig. 1. As there are 37 distinct ethnic groups in Nepal (BIsT^, 1972), and to avoid generalizations based on geographical distribution of haemoglobinopathies alone, a brief description of the people studied is indicated. \ '-'x.
,
/
i
TIBETAN
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CHINA
co%
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L
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FIG. 1. Study areas (Roman numerals) and distribution of haemoglobin E (% prevalence) in Nepal. Area I is populated by descendants of upper caste Hindus who centuries ago migrated from northern India into Nepal. Area II is very close to the Indian border, and the population phenotypically bears resemblance to that of the neighbouring Indian states of Bihar and West Bengal. Area III is Pokhara valley, where a mixture of Nepali ethnic groups resides. Area IV is Kathrnandu, the capital city. Virtually all Nepali ethnic groups are represented here, although the most common is Newari, whose people are I wish to thank Dr. B. R. Baidya, Director General, and Dr. N. K. Shah, Chief Epidemiologist, of His Majesty's Government of Nepal Directorate of Health Services, for their approval and assistance with this survey. Also, the most willing and helpful co-operation of numerous physicians througout Nepal is sincerely acknowledged. This project was financed by research Grant No. ROI--10048-12 from the National Institute of Allergy and Infectious Diseases, The National Institutes of Health, U.S. Public Health Service, Bethesda, Maryland.
W. H. ADAMS
393
considered to be descendants of the original inhabitants of Kathmandu valley. Area V, near the base of Nit. Everest, is inhabitated by the Khumbu Sherpas, and Area VI, near the mountain of Lang-Tang, is inhabited by people who are, as are the Sherpas, of Tibetan ancestry. Near Area vii, located in the inner terai, live the Tharus, a people of uncertain origin. As with most ethnic groups in Nepal, the Tharus are closely endogamous, and their villages are situated throughout most of southern Nepal. Another group studied was the Thamang. These people inhabit the hills around Kathmandu Valley, speak a TibetanBurmese dialect, and may have originally come from Tibet, although when this migration might have occurred is unknown. The Thamangs are listed herein as residing in Area VIII; i.e., around Kathmandu valley. Methods Haemoglobin electrophoresis was performed on whole blood using acrylamide gel, pH 8.9 (SMITH and EVATT, 1967) or on water-carbon tetrachloride haemolysates using cellulose acetate with trisborate buffer, pH 8.6. Haemoglobins C and E and haemoglobins D and S were differentiated by using agar gel electrophoresis, pH 6.0 (MARDER and CONLEY, 1959) wherein haemoglobins E and D move with Hb A but haemoglobins C and S retain their slower migration. The differentiation of Hb D from S was further confirmed by use of the sodium metabisulphate sickle test. Haemoglobin E migrated slightly slower than control samples of Hb C on acrylamide gel and cellulose acetate, as previously noted for paper electrophoresis with a tris buffer system (LEHMANNand HUNTSMAN,1968). Vertical starch gel electrophoresis using 0.004 M phosphate buffer, pH 7.0, was used for detection of Hb Barts in cord blood specimens. Haemoglobin Barts was quantitated by elution from cellulose acetate after electrophoresis in tris-borate buffer, pH 8.6, if present in large amounts. Foetal Hb was estimated by alkali denaturation (SINGER,CHERNOFFand SINGER,1951), with normal values being less than 1.0%, although occasional mild elevations were noted in apparently normal pregnant females. Haemoglobin A~ was quantitated by elution from cellulose acetate (WEATHERALLand CLEGG, 1972) with the upper limit of normal being 4.0%. Brilliant cresyl blue was used for the identification of Hb H inclusion bodies in erythrocytes, specimens being incubated at room temperature for 4 hours. The diagnosis of beta thalassaemia minor was made on the basis of a compatible blood smear and elevation of both foetal and A~ Hb. Subjects were judged homozygous if they had severe anaemia, splenomegaly, and foetal Hb levels above 10°/0. Alpha thalassaemia minor in adults was diagnosed if normal or low Hb A~ and foetal Hb values and characteristic Hb H inclusions of red cells were found, the latter being in the range of 1-2/1,000 red cells. Hb H disease was diagnosed if there was marked anaemia and if Hb H inclusions were present in 40% or more of red cells. Alpha thalassaemia in newborns was indicated by elevations of Hb Barts in cord blood, as judged by its characteristic mobility in the two electrophoretic systems used, and its quantity after elution from cellulose acetate. Results Abnormal haemoglobins : The number of subjects studied in the indicated areas of Nepal and the prevalence and types of abnormal haemoglobins encountered are presented in Table I, with Hb E distribution also shown in Fig. 1. Haemoglobin E was predominantly found in Areas II and VII of southeast Nepal, being 4.0 and 3"7%, respectively. It was present in 1.3% of Thamangs, 0.2°/0 of un-selected Kathmandu residents and 0.7% of those of Tibetan ancestry (i.e., Areas V and VI). Haemoglobin D was found in Areas I and IV, the prevalence being 1.0 and 0.3%, respectively. Two subjects that had a fast moving Hb, one a non-anaemic homozygote, were found in Kathmandu. Thalassaemia : The total number of cases and types of thalassaemia diagnosed are presented in Table II. However, only 3 populations were systematically screened for thalassaemia. These were, from south to north, Area II (50 subjects), Area IV (150 subjects) and Area VI (58 subjects). The prevalences were, respectively, 8~/o, 4~o and 0~o. The other cases were selected except for 105 newborns studied in Kathmandu. 2 of these had levels of Hb Barts of 6.4 and 5.8% in their cord blood, compatible with the diagnosis of alpha thalassaemia minor. The mother of one had Hb H disease. Because iron deficiency can lower Hb A~ values (WAsI et al., 1968) and can prevent Hb H inclusions from being recognized, the prevalence figures cited above must be considered approximate, especially in Area II, where hypochromia was extremely common.
394
A SURVEY FOR HAEMOGLOBINOPATHIES I N NEPAL
TABLE I. Abnormal haemoglobins in Nepal*. Number of subjects studied
Area
Number of abnormal Hbs
Percent and Type abnormal Hbs.
I
Jumla
99
1
1.0°/~-Hb D
II
Biratnagar
99
4
4-0%-Hb E
III
Pokhara
102
0
--
IV
Kathmandu
1695
10
V
Khumbu (Tibetan ancestry)
80
1
Lang-Tang (Tibetan ancestry)
58
0
VI
0-6~o-Hb E (3) Hb D (5) fast Hb, type unknown (2) 1.3%-Hb E
VII
Tharu Tribe
190
7
3.7%-Hb E
VIII
Thamang Tribe
150
2
1.3°/o-Hb E
2,473
25
Total
Overall % abnormal Hbs = 1.0%
*Areas by Roman numeral correspond to those in Fig. 1. TABLE II. Thalassaemias in Nepal. Area IV
II
No. of Cases
(Kathmandu) Beta thalassaemia major
3
Beta thalassaemia minor
9
Beta thalassaemia-Hb E disease
1
Haemoglobin H disease
1
Alpha thalassaemia minor (adult)
4
Alpha thalassaemia minor (newborn)
2
(Biratnagar) Beta thalassaemia major
1
Beta thalassaemia minor
2
Haemoglobin H disease
1
Discussion
This paper presents data on the regional and ethnic distribution of haemoglobinopathies in Nepal. With regard to Hb E, 3-9% of unselected Bengalese have been estimated to have this abnormality (CHATTm~IEA et al., 1957), similar to the prevalence found in this survey in southeast Nepal near the Indian (West Bengal and Bihar) border. Haemoglobin E is reportedly rare west of Bengal (CHATTERJEA, 1966), and was not found in the more western parts of Nepal. No area had the extremely high incidence of Hb E found in Thailand (WASI et al., 1969), Burma (AUNG-THAU-BATUet al., 1971) and Cambodia (GouE~ON and DUSASSAY, 1969), where it has been found in 25 to 50% of some populations. As reviewed by LEHMANN and HUNTSMAN(1968), H b E appears to be associated with the earlier mongoloid (Indo-Chinese) populations of southeast Asia. T h e relatively low prevalence of Hb E in southeast Nepal and its decrease as one
w. H. ADAMS
395
goes further north and west, similar to the situation in India, may indicate the loss of a selective genetic factor at work primarily in southeast Asia. However, the problems involved in such an interpretation have been reviewed (L:E-IlqJO, 1969). The very low prevalence of Hb E among people of definite Tibetan and Nepali ancestry was quite different from subjects living adjacent to the Indian border, suggesting racial or migrational influences on Hb E distribution. On the other hand, the Tharus of south Nepal have been variously deemed to be of mongoloid or south Indian ancestry (BISTA, 1972), and yet the prevalence of Hb E was similar to that of the Bengalese. Southeast Nepal was the only area studied that previously had a high incidence of malaria. But the prevalence of Hb E, while the highest encountered in Nepal, was still quite low when compared with that of southeast Asia and to sickle Hb in many areas of Africa. There is no previously published information regarding haemoglobinopathies among Tibetans or subjects of pure Tibetan ancestry except for that obtained during the British Khumbu Expedition in 1959, where no abnormal haemoglobins were reported in 129 subjects (JACKSON,LF.HMANNand Sr~RrAH, 1960). This area corresponds to Area V of the present survey. I f those data are combined with the present data, only one Hb E heterozygote was found among 267 subjects examined (0"4~/o). Similarly, Hb E is not commonly found among "modern" Chinese (LEnM~qN and HUNTSMAN, 1968; BLACKWELLet al., 1968). The genetic segregation of subjects of Tibetan ancestry from the Indo-Chinese and from the Nepalese residing further to the south is also suggested by the absence of thalassaemia in Area VI and only one case of beta thalassaemia found in the earlier Khumbu study. Haemoglobin D has been reported in 2°~ of the population of the Punjab of North India (B:RD and LEHMAI'a~q, 1956) as well as among Bengalese (CHATTERJEA, 1966). Thus its presence in Nepal is not surprising. Sickle Hb was not found in this survey, despite its presence in certain tribes such as the aboriginal Veddoids of South India. It was noted that the Tharus, who purportedly can live with relative impunity in malarious areas* (although there is no scientific corroboration of this observation), had no sickle Hb in 3 villages studied, despite the fact that this area until about 12 years ago was highly endemic for falciparum malaria. Beta thalassaemia major and minor and beta thalassaemia-Hb E disease were encountered in Kathmandu and southeast Nepal. Two forms of alpha thalassaemia were diagnosed in adults; Hb H disease and alpha thalassaemia minor. These correspond to alpha thalassaemial/alpha thalassaemia~ and alpha thalassaemial trait, respectively, of W^sI et al. (1969). Two of the 105 newborns in Kathmandu had levels of Hb Barts compatible with the presence of alpha thalassaemia minor (NA-NAKORN et al., 1969), the values being higher than those associated with Hb Constant Spring (LIF-INJO, 1973). The decreasing prevalence of thalassaemia from south to north among 3 populations studied in Nepal is similar to the fading out of Hb E, except that the latter did so much more abruptly. However the ethnic differences of these populations make interpretation of this decrease difficult to ascribe to the geographic factors alone. Surveys of this sort may be exhausting, but are rarely exhaustive. Many other areas and ethnic groups in Nepal, often very isolated, remain to be studied before an accurate idea of how much race, environment and migration are involved in determining the distribution of haemoglobinopathies and thalassaemia in Nepal. Moreover, the identification of the haemoglobins was by electrophoresis and the final and definite identification would have to be done on the basis of "fingerprinting".
Summary 2,473 Hb electrophoreses performed on specimens collected from various parts of Nepal showed the most common abnormal Hb to be Hb E. The highest prevalence of Hb E (4%) was found in southeast Nepal. Haemoglobin D was occasionally found in central Nepal. Both alpha and beta thalassaemias were diagnosed, and thalassaemia was likewise more frequent in southeast Nepal. The diverse ethnic background on which the significance of the distribution of Hb E and thalassaemia must be considered is presented, and this challenges attempts to attribute their distribution to environmental factors alone. REFERENCES ALrNG-THAu-BATO,U-HLA-PE, KHII~-KYI-NYUNT & TIN-U (1971). Parts I-IV. Trop. geogr. Med., 27,, 15. BIRD, G. W. G. & LEHMANN,H. (1956). Br. med. J., 1, 514. *As mentioned in A Preliminary Report on a Malarial Survey carried out in the Valley between the Churri and Mahabaret Ranges of Hills, by Jas. Phillips Major, I.M.S., Assistant Director of Public Health, Malariology Branch, United Provinces, 1925.
396
A SURVEYFOR HAEMOGLOBINOPATHIESIN NEPAL
BLACKWELL,R. Q., YANG, H. J., LIU, C. S. & WANG,C. C. (1968). Trop. geogr. Med., 90, 257. BRAIN, M. C. & VELLA,F. (1958). Lancet, 1, 192. CHATTERJEA,J. B., SWARUP, S., GHOSH, S. K. • RAY, R. N. (1957). Bull. Calcutta Sch. trop. Med., 5, 159. (1959). Haemoglobinopathy in India. In: Jonxis, J. H. P. & DelaPresnaye, J. F., ed., Abnormal Haemoglobins, Oxford: Blackwell Scientific Publications, p. 322. - (1966). IVld Hlth Org. Tech. Rept. Series, 35, 837. GOUEFFON, S. & DuSASSAY, C. (1969). Bull. Soc. Path. exot., 62, 1118. JACKSON, F. S., LEHMANN, H. & SHARIAH,A. (1960). Nature (Lond.), 188, 1121. LEHMANN, H. & HUNTSMAN,R. G. (1968). In Man's Haemoglobins, Amsterdam: North-Holland Publishing Company. LIE-INIo, L. E. (1969). Trans. R. Soc. trop. Med. Hyg., 63, 664. - (1973). Acta Haem., 49, 25. MARDER, V. J. & CONLEY, C. L. (1959). Bull. Johns Hopkins Hosp., 105, 77. NA-NAKORN, S., WASI, P., PORNPATKUL,M. & POOTRAKUL,S. N. (1969). Nature (Lond.), 223, 59. SINGER, K., CHERNOFF, A. I. & SINGER, L. (1951). Blood, 6, 413. SMITH, E. W. & EVATT, B. L. (1967). J. Lab. clin. Med., 59, 1018. VELLA, F. (1962). Oceania, 32, 219. WASI, P., DISTHASONGCHAN,P. & NA-NAKORN, S. (1968). J. Lab. din. Med., 71, 85. NA-NAKORN, S., POOTRAKUL,S., SOOKANEK,M., DISTHASONGCHAN,P., PORNPATKUL,M. & PANICK, V. (1969). Ann. N . Y . Acad. Sci., 185, 50. WEATHERALL,D. J. & VELLA, F. (1960). Br. reed. J., 1, 1711. & CLEGG, J. B. (1972). In The Thalassaemia Syndromes, Oxford: Blackwell Scientific Publishers, p. 311. -
-
,
W. H. ADAMS The Johns Hopkins University Centrefor Medical Research and Training, Kathmandu, Nepal Introduction
Several surveys for abnormal haemoglobins and thalassaemia among the Nepalese have been reported. The varieties of disorders discovered have included haemoglobin H disease, beta thalassaemia, and haemoglobin E (BRAIN and VELLA, 1958; WEATr~RALL and VELLA, 1960; VELLA, 1962; CrUtTTERJEA, 1959). However, these studies were performed on Nepalese residing outside Nepal. Only one such survey performed within Nepal has been published, that being among the Sherpas living near Mt. Everest (JACKSON, LEmV~NN and SH~a~taH, 1960). During the period from March 1972 to March 1973, a survey was carried out by The Johns Hopkins University Centre for Medical Research and Training, in co-operation with His Majesty's Government of Nepal Directorate of Health Services, to define those areas in Nepal where genetic haemoglobin (Hb) abnormalities might exist. The present report gives the results of this survey. Subjects Specimens were collected from 2,473 unselected villagers or hospital in-patients and out-patients, mostly adults, from the areas indicated in Fig. 1. As there are 37 distinct ethnic groups in Nepal (BIsT^, 1972), and to avoid generalizations based on geographical distribution of haemoglobinopathies alone, a brief description of the people studied is indicated. \ '-'x.
,
/
i
TIBETAN
REGION
OF
CHINA
co%
~.xr\ N
E
P
A
L
•,.~.,.~.
C'"x"J3 '-'~. "k. ~ v,-L,,,G,,,,G ~V-KHUMBU -~. . t.~l . • ~ '~ ""-'x~..-,~-...,-f "7
• oo/.
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FIG. 1. Study areas (Roman numerals) and distribution of haemoglobin E (% prevalence) in Nepal. Area I is populated by descendants of upper caste Hindus who centuries ago migrated from northern India into Nepal. Area II is very close to the Indian border, and the population phenotypically bears resemblance to that of the neighbouring Indian states of Bihar and West Bengal. Area III is Pokhara valley, where a mixture of Nepali ethnic groups resides. Area IV is Kathrnandu, the capital city. Virtually all Nepali ethnic groups are represented here, although the most common is Newari, whose people are I wish to thank Dr. B. R. Baidya, Director General, and Dr. N. K. Shah, Chief Epidemiologist, of His Majesty's Government of Nepal Directorate of Health Services, for their approval and assistance with this survey. Also, the most willing and helpful co-operation of numerous physicians througout Nepal is sincerely acknowledged. This project was financed by research Grant No. ROI--10048-12 from the National Institute of Allergy and Infectious Diseases, The National Institutes of Health, U.S. Public Health Service, Bethesda, Maryland.
W. H. ADAMS
393
considered to be descendants of the original inhabitants of Kathmandu valley. Area V, near the base of Nit. Everest, is inhabitated by the Khumbu Sherpas, and Area VI, near the mountain of Lang-Tang, is inhabited by people who are, as are the Sherpas, of Tibetan ancestry. Near Area vii, located in the inner terai, live the Tharus, a people of uncertain origin. As with most ethnic groups in Nepal, the Tharus are closely endogamous, and their villages are situated throughout most of southern Nepal. Another group studied was the Thamang. These people inhabit the hills around Kathmandu Valley, speak a TibetanBurmese dialect, and may have originally come from Tibet, although when this migration might have occurred is unknown. The Thamangs are listed herein as residing in Area VIII; i.e., around Kathmandu valley. Methods Haemoglobin electrophoresis was performed on whole blood using acrylamide gel, pH 8.9 (SMITH and EVATT, 1967) or on water-carbon tetrachloride haemolysates using cellulose acetate with trisborate buffer, pH 8.6. Haemoglobins C and E and haemoglobins D and S were differentiated by using agar gel electrophoresis, pH 6.0 (MARDER and CONLEY, 1959) wherein haemoglobins E and D move with Hb A but haemoglobins C and S retain their slower migration. The differentiation of Hb D from S was further confirmed by use of the sodium metabisulphate sickle test. Haemoglobin E migrated slightly slower than control samples of Hb C on acrylamide gel and cellulose acetate, as previously noted for paper electrophoresis with a tris buffer system (LEHMANNand HUNTSMAN,1968). Vertical starch gel electrophoresis using 0.004 M phosphate buffer, pH 7.0, was used for detection of Hb Barts in cord blood specimens. Haemoglobin Barts was quantitated by elution from cellulose acetate after electrophoresis in tris-borate buffer, pH 8.6, if present in large amounts. Foetal Hb was estimated by alkali denaturation (SINGER,CHERNOFFand SINGER,1951), with normal values being less than 1.0%, although occasional mild elevations were noted in apparently normal pregnant females. Haemoglobin A~ was quantitated by elution from cellulose acetate (WEATHERALLand CLEGG, 1972) with the upper limit of normal being 4.0%. Brilliant cresyl blue was used for the identification of Hb H inclusion bodies in erythrocytes, specimens being incubated at room temperature for 4 hours. The diagnosis of beta thalassaemia minor was made on the basis of a compatible blood smear and elevation of both foetal and A~ Hb. Subjects were judged homozygous if they had severe anaemia, splenomegaly, and foetal Hb levels above 10°/0. Alpha thalassaemia minor in adults was diagnosed if normal or low Hb A~ and foetal Hb values and characteristic Hb H inclusions of red cells were found, the latter being in the range of 1-2/1,000 red cells. Hb H disease was diagnosed if there was marked anaemia and if Hb H inclusions were present in 40% or more of red cells. Alpha thalassaemia in newborns was indicated by elevations of Hb Barts in cord blood, as judged by its characteristic mobility in the two electrophoretic systems used, and its quantity after elution from cellulose acetate. Results Abnormal haemoglobins : The number of subjects studied in the indicated areas of Nepal and the prevalence and types of abnormal haemoglobins encountered are presented in Table I, with Hb E distribution also shown in Fig. 1. Haemoglobin E was predominantly found in Areas II and VII of southeast Nepal, being 4.0 and 3"7%, respectively. It was present in 1.3% of Thamangs, 0.2°/0 of un-selected Kathmandu residents and 0.7% of those of Tibetan ancestry (i.e., Areas V and VI). Haemoglobin D was found in Areas I and IV, the prevalence being 1.0 and 0.3%, respectively. Two subjects that had a fast moving Hb, one a non-anaemic homozygote, were found in Kathmandu. Thalassaemia : The total number of cases and types of thalassaemia diagnosed are presented in Table II. However, only 3 populations were systematically screened for thalassaemia. These were, from south to north, Area II (50 subjects), Area IV (150 subjects) and Area VI (58 subjects). The prevalences were, respectively, 8~/o, 4~o and 0~o. The other cases were selected except for 105 newborns studied in Kathmandu. 2 of these had levels of Hb Barts of 6.4 and 5.8% in their cord blood, compatible with the diagnosis of alpha thalassaemia minor. The mother of one had Hb H disease. Because iron deficiency can lower Hb A~ values (WAsI et al., 1968) and can prevent Hb H inclusions from being recognized, the prevalence figures cited above must be considered approximate, especially in Area II, where hypochromia was extremely common.
394
A SURVEY FOR HAEMOGLOBINOPATHIES I N NEPAL
TABLE I. Abnormal haemoglobins in Nepal*. Number of subjects studied
Area
Number of abnormal Hbs
Percent and Type abnormal Hbs.
I
Jumla
99
1
1.0°/~-Hb D
II
Biratnagar
99
4
4-0%-Hb E
III
Pokhara
102
0
--
IV
Kathmandu
1695
10
V
Khumbu (Tibetan ancestry)
80
1
Lang-Tang (Tibetan ancestry)
58
0
VI
0-6~o-Hb E (3) Hb D (5) fast Hb, type unknown (2) 1.3%-Hb E
VII
Tharu Tribe
190
7
3.7%-Hb E
VIII
Thamang Tribe
150
2
1.3°/o-Hb E
2,473
25
Total
Overall % abnormal Hbs = 1.0%
*Areas by Roman numeral correspond to those in Fig. 1. TABLE II. Thalassaemias in Nepal. Area IV
II
No. of Cases
(Kathmandu) Beta thalassaemia major
3
Beta thalassaemia minor
9
Beta thalassaemia-Hb E disease
1
Haemoglobin H disease
1
Alpha thalassaemia minor (adult)
4
Alpha thalassaemia minor (newborn)
2
(Biratnagar) Beta thalassaemia major
1
Beta thalassaemia minor
2
Haemoglobin H disease
1
Discussion
This paper presents data on the regional and ethnic distribution of haemoglobinopathies in Nepal. With regard to Hb E, 3-9% of unselected Bengalese have been estimated to have this abnormality (CHATTm~IEA et al., 1957), similar to the prevalence found in this survey in southeast Nepal near the Indian (West Bengal and Bihar) border. Haemoglobin E is reportedly rare west of Bengal (CHATTERJEA, 1966), and was not found in the more western parts of Nepal. No area had the extremely high incidence of Hb E found in Thailand (WASI et al., 1969), Burma (AUNG-THAU-BATUet al., 1971) and Cambodia (GouE~ON and DUSASSAY, 1969), where it has been found in 25 to 50% of some populations. As reviewed by LEHMANN and HUNTSMAN(1968), H b E appears to be associated with the earlier mongoloid (Indo-Chinese) populations of southeast Asia. T h e relatively low prevalence of Hb E in southeast Nepal and its decrease as one
w. H. ADAMS
395
goes further north and west, similar to the situation in India, may indicate the loss of a selective genetic factor at work primarily in southeast Asia. However, the problems involved in such an interpretation have been reviewed (L:E-IlqJO, 1969). The very low prevalence of Hb E among people of definite Tibetan and Nepali ancestry was quite different from subjects living adjacent to the Indian border, suggesting racial or migrational influences on Hb E distribution. On the other hand, the Tharus of south Nepal have been variously deemed to be of mongoloid or south Indian ancestry (BISTA, 1972), and yet the prevalence of Hb E was similar to that of the Bengalese. Southeast Nepal was the only area studied that previously had a high incidence of malaria. But the prevalence of Hb E, while the highest encountered in Nepal, was still quite low when compared with that of southeast Asia and to sickle Hb in many areas of Africa. There is no previously published information regarding haemoglobinopathies among Tibetans or subjects of pure Tibetan ancestry except for that obtained during the British Khumbu Expedition in 1959, where no abnormal haemoglobins were reported in 129 subjects (JACKSON,LF.HMANNand Sr~RrAH, 1960). This area corresponds to Area V of the present survey. I f those data are combined with the present data, only one Hb E heterozygote was found among 267 subjects examined (0"4~/o). Similarly, Hb E is not commonly found among "modern" Chinese (LEnM~qN and HUNTSMAN, 1968; BLACKWELLet al., 1968). The genetic segregation of subjects of Tibetan ancestry from the Indo-Chinese and from the Nepalese residing further to the south is also suggested by the absence of thalassaemia in Area VI and only one case of beta thalassaemia found in the earlier Khumbu study. Haemoglobin D has been reported in 2°~ of the population of the Punjab of North India (B:RD and LEHMAI'a~q, 1956) as well as among Bengalese (CHATTERJEA, 1966). Thus its presence in Nepal is not surprising. Sickle Hb was not found in this survey, despite its presence in certain tribes such as the aboriginal Veddoids of South India. It was noted that the Tharus, who purportedly can live with relative impunity in malarious areas* (although there is no scientific corroboration of this observation), had no sickle Hb in 3 villages studied, despite the fact that this area until about 12 years ago was highly endemic for falciparum malaria. Beta thalassaemia major and minor and beta thalassaemia-Hb E disease were encountered in Kathmandu and southeast Nepal. Two forms of alpha thalassaemia were diagnosed in adults; Hb H disease and alpha thalassaemia minor. These correspond to alpha thalassaemial/alpha thalassaemia~ and alpha thalassaemial trait, respectively, of W^sI et al. (1969). Two of the 105 newborns in Kathmandu had levels of Hb Barts compatible with the presence of alpha thalassaemia minor (NA-NAKORN et al., 1969), the values being higher than those associated with Hb Constant Spring (LIF-INJO, 1973). The decreasing prevalence of thalassaemia from south to north among 3 populations studied in Nepal is similar to the fading out of Hb E, except that the latter did so much more abruptly. However the ethnic differences of these populations make interpretation of this decrease difficult to ascribe to the geographic factors alone. Surveys of this sort may be exhausting, but are rarely exhaustive. Many other areas and ethnic groups in Nepal, often very isolated, remain to be studied before an accurate idea of how much race, environment and migration are involved in determining the distribution of haemoglobinopathies and thalassaemia in Nepal. Moreover, the identification of the haemoglobins was by electrophoresis and the final and definite identification would have to be done on the basis of "fingerprinting".
Summary 2,473 Hb electrophoreses performed on specimens collected from various parts of Nepal showed the most common abnormal Hb to be Hb E. The highest prevalence of Hb E (4%) was found in southeast Nepal. Haemoglobin D was occasionally found in central Nepal. Both alpha and beta thalassaemias were diagnosed, and thalassaemia was likewise more frequent in southeast Nepal. The diverse ethnic background on which the significance of the distribution of Hb E and thalassaemia must be considered is presented, and this challenges attempts to attribute their distribution to environmental factors alone. REFERENCES ALrNG-THAu-BATO,U-HLA-PE, KHII~-KYI-NYUNT & TIN-U (1971). Parts I-IV. Trop. geogr. Med., 27,, 15. BIRD, G. W. G. & LEHMANN,H. (1956). Br. med. J., 1, 514. *As mentioned in A Preliminary Report on a Malarial Survey carried out in the Valley between the Churri and Mahabaret Ranges of Hills, by Jas. Phillips Major, I.M.S., Assistant Director of Public Health, Malariology Branch, United Provinces, 1925.
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BLACKWELL,R. Q., YANG, H. J., LIU, C. S. & WANG,C. C. (1968). Trop. geogr. Med., 90, 257. BRAIN, M. C. & VELLA,F. (1958). Lancet, 1, 192. CHATTERJEA,J. B., SWARUP, S., GHOSH, S. K. • RAY, R. N. (1957). Bull. Calcutta Sch. trop. Med., 5, 159. (1959). Haemoglobinopathy in India. In: Jonxis, J. H. P. & DelaPresnaye, J. F., ed., Abnormal Haemoglobins, Oxford: Blackwell Scientific Publications, p. 322. - (1966). IVld Hlth Org. Tech. Rept. Series, 35, 837. GOUEFFON, S. & DuSASSAY, C. (1969). Bull. Soc. Path. exot., 62, 1118. JACKSON, F. S., LEHMANN, H. & SHARIAH,A. (1960). Nature (Lond.), 188, 1121. LEHMANN, H. & HUNTSMAN,R. G. (1968). In Man's Haemoglobins, Amsterdam: North-Holland Publishing Company. LIE-INIo, L. E. (1969). Trans. R. Soc. trop. Med. Hyg., 63, 664. - (1973). Acta Haem., 49, 25. MARDER, V. J. & CONLEY, C. L. (1959). Bull. Johns Hopkins Hosp., 105, 77. NA-NAKORN, S., WASI, P., PORNPATKUL,M. & POOTRAKUL,S. N. (1969). Nature (Lond.), 223, 59. SINGER, K., CHERNOFF, A. I. & SINGER, L. (1951). Blood, 6, 413. SMITH, E. W. & EVATT, B. L. (1967). J. Lab. clin. Med., 59, 1018. VELLA, F. (1962). Oceania, 32, 219. WASI, P., DISTHASONGCHAN,P. & NA-NAKORN, S. (1968). J. Lab. din. Med., 71, 85. NA-NAKORN, S., POOTRAKUL,S., SOOKANEK,M., DISTHASONGCHAN,P., PORNPATKUL,M. & PANICK, V. (1969). Ann. N . Y . Acad. Sci., 185, 50. WEATHERALL,D. J. & VELLA, F. (1960). Br. reed. J., 1, 1711. & CLEGG, J. B. (1972). In The Thalassaemia Syndromes, Oxford: Blackwell Scientific Publishers, p. 311. -
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