High prevalence of Haemoglobin E in three population of the Malda District,West Bengal, India

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High Prevalence of Haemoglobin E in Three Populations of the Malda District, West Bengal, India

M .K . Das, B. Dey, M. Roy, B.N. Mukherjee

A n thropom etry and Human G en etics U n it, Indian Statistical Institute, Calcutta, India

Key Words. H aem oglobin E • P opulation study • In d ia

Abstract. High frequencies o f haem oglobin (H b) E were reported earlier from Assam in northeast India. In the presen t study one o f the three populations of the Malda dis­

trict of W est Bengal, called the D eshi, was found to show one of the highest incidences o f the H b E gene (0.61) recorded so far. A fo u n d er effect a n d /o r local inbreeding may possibly explain this observation.


Some populations o f the Tibeto-B ur- m an-speaking Bodo ethnic g ro u p residing in Assam have shown the highest fre­

quency (0.64) o f the haem oglobin E (H b E ) gene [Deka et al., 1988], so far, in the w orld. There are alternative h y p o ­ theses regarding the origin, spread and m aintenance o f the gene in sou th east Asia and in northeast India. U ntil recently, the hypothesis o f the single Hb A -*■ H b E m u­

tation an d its spread from southeast Asia was generally accepted. It was believed to be m aintained through an ad ap tiv e ad ­ vantage in the m alarious environm ent [Flatz, 1967; Flatz et al., 1972; K ruatra- chue et al., 1969], but a higher incidence o f the gene (0.4-0.6) am ong the Bodo populations th an am ong th e p o p u latio n s

speaking A ustroasiatic or Thai languages - the K hasi a n d the Ahom (0.3-0.4), who could have carried the gene from Thai­

lan d o r from Shahn in Burma - could noi be ex p la in ed by this hypothesis. T h e de­

m o g rap h ic analyses of some Bodo popu­

latio n s have suggested different selective m echanism s in Assam and in Thailand [D eka, 1981; Das and Deka, 1985; Deka et al., 1988]. O n the other hand, th e re ate rep o rts on two different mutations of H b E w ith tw o different DNA frame- w orks [A ntonarakis et al., 1982; Hun- drieser et al., 1988]. In this re p o rt the re­

sults o f a study of the Hb E gene fre­

quency in three endogam ous p o p u lations o f the n o rth e rn part of West Bengal, who are offshoots o f the Bodo group, are dis­

cussed in the light o f this background know ledge.


Fig. 1. Map o f West Bengal, showing the distribution o f the populations under study.

Material and Methods

The Poliya, Deshi and Tiyor p op u lation s h a v e originated from the Koch ethnic group o f the n o rth ­ ern part of the present West Bengal (fig. 1) and A s ­ sam states who are described as one o f the m ost an- cient peoples of India [D alton, 1872]. The P oliya and the Deshi are Bengali-speaking pop u lation s and f o l­

low village exogamy. The Tiyors speak ‘K hotta or mixed Hindi dialect’. There are two su b d iv isio n s o f the Poliya, known as Sadhu Poliya and Babu P o liy a ,

an d the D esh i are o n e o f the subcastes o f Sadhu P o­

liya. The Sadhu P oliya are traditionally horticultur­

ists, and the D esh i are settled agriculturists who claim a superior status. The Tiyor form a subcaste o f the R ajbanshi - a n e w n am e adopted by the K och [R isley, 1891; S an yal, 1965]. Their traditional occu ­ p a tio n s are fishin g and p lyin g o f boats, though som e o f them are n ow en gaged as agricultural labourers.

B lood sam p les from 85 unrelated Sadhu Poliya, 103 D esh i and 95 T iyor, i.e. a total o f 283 apparently h ealthy in d ivid u als b elon gin g to both sexes, were


collected in E D T A by finger pricks from M arch to June 1987. The haem oglobin types w ere screened by electrophoresis on starch gel and o n cellu lo se acetate strips in parallel alon g with k n ow n co n tro l sam ples.

The differentiation betw een Hb E a n d H b A 2 w as ver­

ified by th e an alysis o f glob in ch ain s in cellu lo se ace­

tate paper using T ris-E D T A -borate w ith citrate-urea buffer at p H 6.0.


The results of this analysis in the three populations (table 1) show ed a very high incidence o f Hb E allele am ong the Deshi and the Poliya. A significant deviation

Table 1. Distribution o f Hb E in three p o p u la ­ tions o f the M alda district, W est B engal

Population H aem oglobin type H b E gene frequency

X2 value N A A A E EE

Poliya 85 17 52 16 0.494 5.86

D eshi 103 17 46 40 0.612 0.47

Tiyor 95 73 20 2 0.126 0.44

from the genetic equilibrium was observed' in the Poliya sample (p = 0.15) with ar.

excess o f heterozygotes. In the Deshi sam­

ple a very high frequency of the E gene was observed, but in the Tiyor sample the E frequency was low.

T he th ree populations show significant differences in their distribution of Hbf frequencies ( p < 0.001). Even the Deshi and the Poliya, who have close ethnic affinities, differ significantly (p < 0.03).

W hen the present data are compared witl those from some M ongoloid populations o f A ssam and West Bengal (table 2), the D eshi p o p u latio n does not differ signifi­

cantly from the Bodo-Kachari and Rabat o f A ssam b u t the Poliya show a signifi­

cantly low er Hb E gene frequency that th a t o f the Bodo-K achari population. The D eshi po p u latio n shows significant!) h igher H b E frequencies than that of tie A hom . O n the other hand, the Tiyor do n o t d iffer significantly from the Rajbanshi a n d M ech populations of northern Wesi B engal, possibly due to their admixture w ith the neighbouring caste populations

T ab le 2. %2 values o f c om p arison betw een P oliya, D esh i a n d T iyor with som e M ongoloid populations ci A ssam and W est Bengal (in parentheses H b E gene freq uencies)

P opulation P resent study

P oliya (0.494)

D esh i (0.612)

T iyor (0.126)


B odo-K achari (0.645) 9.062 0.528 _ Deka etal., 1988

A hom (0.403) 3 .312 19.158 40.221 Deka et al., 1988

Rabah (0.535) 2.728 2.732 _ Das and Deka, 1980

R ajbanshi (0.230) - - 7.222 Deka et al., 1988

R ajbanshi (0.103) - - 0.402 Mukherjeeetal.,1®

M ech (0.173) - - 0.759 Mukherjeeetal., W



The Deshi population of the M alda d is­

trict, though living far away from the high frequency area for Hb E in Assam [D as and Deka, 1985; Deka et al., 1988], e x h ib ­ its one of the highest know n incidences o f the Hb E gene in the world along with the Bodo-Kachari [Deka et al., 1988], w ith whom it has ancestral affinities. T here is, however, no evidence of a recent a d m ix ­ ture between these populations. T he re­

sults of the present study do not co n fo rm to the hypothesis of adaptation to m ala ria [Flatz, 1967; K ruatrachue et al., 1969] in view of the following facts: (1) a signifi­

cant increase in Hb E am ong the D eshi compared to the ancestral p o p u latio n o f i the Poliya, who have lived in a sim ilar en-

^ tironment for a long time; (2) the fre­

quency distributions of Hb E in successive age groups do not indicate any change, a l­

though a malaria control program m e has been operating successfully since the 1950s, and (3) the Tiyor show a very low frequency of Hb E despite their com m on ancestry and similar geographical e n v ir­

onment. Ethnohistorical inform ation a n d cultural comparisons indicate th at b o th the Poliya (including the Deshi) a n d the Tiyor populations are offshoots o f the Koch tribe, which again is a branch o f the Bodo group of population spread over the plains of Assam and the northern p a rt o f West Bengal.

The genotypic frequencies in the a g ri­

cultural Deshi population which displays the highest E gene incidence do not a p p e a r to deviate from genetic equilibrium . T here is no suggestion that the Hb E p o ly m o r­

phism is transitional in the Deshi a n d there is no clear-cut indication o f any se­

lection m echanism operating in this p o p u ­ lation. The caste endogam y in a lim ited area and a fo u n d er effect might have led to a greater increase in the Hb E frequency am ong the D eshi p o p u lation th an in the Poliya, who are widely dispersed in the adjacent districts o f M alda and West D inajpur.


This work is partly supported by the award o f a Research A sso cia tesh ip o f U G C to M .K .D .


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Prof. B .N . M ukherjee

A n thropom etry and Human Genetics Unit In d ian Statistical Institute

203 B.T. R oad

C a lcu tta -7 0 0 035 (India)




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