2 Augu t 1980 SA MEDICAL JOURNAL 193

The animal which had been inoculated with Babesia6 week previously produced an extract which, wheninjected into the mice, resulted in the di appearance ofthe tran planted tumours in 75o.~ of cases. The tumour inthe remaining 25~ gre\v much more slowly than those inthe controls, which invariably died a week earlier thanthose treated mice in which the tumour failed to disappear.

The animal inoculated 8 weeks previously produced anextract which brought about a 71 % disappearance oftran planted tumour in the treated mice. Again, the re-maining tumours grew much more slowly than tho e inthe control .

The results of a typical experiment are illustrated IIIFigs 1 and 2.

The tumour di appeared in 9,4% of the mice injectedwith the Babesia-free extract and in the remaining miceit grew at the same rate as in the controls (Fig. 3). Thissurvival rate of 9,4% compares with the survival rate of

9.5~~ obtained in my previous experiments when u ingextract of bone marrow. Thi wa the survival rate of theuntreated control mice.

Histopathological examination of the fascia lata origi-nating from the Babesia-infected and similar examinationof the non-infected fascia lata revealed nothing abnormal.

DISCUSSIO

From the result obtained it appear that infection withBabesia is e ential for the production of an extract thatwill cause disappearance of mouse arcoma M(52)B inmice, since fa cia lata extract per se without the pre enceof Babesia ha no effect on mou e arcoma M(52)B.

The retardation of the rate of tumour growth ob ervedin tho e mice in which complete regre ion wa notobtained might be due to in ufficient amounts of thetumour-destroying principle. In future experiment theeffect of increa ing the Babesia content of the extract willbe studied.

I should like to expre s my gratitude to the taff of theVeterinary Research In titUle at Onderstepoort for (he valuableassistance they afforded me and particularly to Dr R. Bigalkefor advice and to Mr F. J. Schutle for his kilful assistancethroughout all the stages of the research.

REFERENCES

I. King, A. C. (1966): J. lrop. Med. Hyg., 69, 247.2. Idem (197): Onderslepoon J. vet. Res., 45, 141.

The Prevalence of Huntington's Chorea in South AfricaM. R. HAYDE , J. M. MacGREGOR, P. H. BEIGHTO T

SUMMARYThe results of a national investigation to determine theprevalence of Huntington's chorea in South Africa arepresented. A total of 481 persons who have died from

Department of Human Genetics, University of Cape Town,and Department of 'eurology, Groote Scbuur Hospital,Cape Town

M. R. HAYDE ,M.B. 01.8., PH. D., D.C.H.J. M. 1AcGREGOR, F.R.CP., F.R.C.P.E., D.P.M.P. H. BEIGHTO r. 1.0., PH.D., F.R.C.P., D.C.H.Dale received: 5 February IY~O.

or are presently suffering from ~he disorder have beenidentified.

The prevalence rate of 0,1 per million in the SouthAfrican Negro population is much less than the estimateof 22 per million in the White and Coloured groups. It isapparent that the great variation in the ethnic distributionof the disease is a reflection of the diverse origins of thedifferent population groups of South Africa.

S. A/r. med. J., 58 193 (19 0).

HlIntington' chorea is a lethal. genetically determinedncurop 'ychiatric di order which u ually appear in adlllt-

-2 August 1980 SA MEDICAL JOURNAL 195

TABLE I. PERSONS WITH HUNTINGTON'S CHOREA INSOUTH AFRICA

number of males and females recorded is almost equal,with a ratio of 1,004: 1,000, which is expected for adisease of autosomal dominant inheritance.

Even though the current investigation was carefullyundertaken in a large population with utilization of mul-tiple methods of collation of data, it is most likely thatthe figures presented are underestimates of the true fre-quency of Huntington's chorea in South Africa. Ignoranceof the disorder, its mode of inheritance and its implica-tions, among both the public and the medical profession,has resulted in a high proportion of initial misdiagnoses(approximately 40% in this survey). The current poorawareness of the disorder has added to the existing socialstigma and superstition attached to the disease, with sub-sequent reluctance of patients to voluntarily present them-selves for diagnosis. In addition, in the absence of anycurative drug, doctors themselves have sometimes encou-raged this attitude by discharging diagnosed patients bytelling them 'there is nothing we can do for Huntington'schorea'. Such pitfalls have prevented complete ascertain-ment of the prevalence of Huntington's chorea in thecurrent survey.

TABLE 11. NUMBER OF PERSONS WITH HUNTINGTON'SCHOREA IN SOUTH AFRICA (ACCORDING TO RACIAL

GROUP)Male Female Total

WhitesLive 46 51 97 } 355Dead 142 116 258

Coloureds(mixed ancestry)Live 21 32 53 } 115Dead 26 36 62

BlacksLive 2 1 3 } 11Dead 4 4 8

Total 241 240 481

TABLE Ill. PREVALENCE OF HUNTINGTON'S CHOREA INSOUTH AFRICA

Populatiop PrevalenceNo. (X 10') (/1 et)

1977Whites 97 4367 22,2Coloureds

(mixedancestry) 53 2432 21,7

Blacks 3 16647 0,1

able authorities in their areas for assistance. All informa-tion was treated confidentially and only persons directlyinvolved in the study were allowed access to patients'records.

The prevalence of Huntington's chorea was establishedfor 30 December 1977." This date was chosen because the1977 estimated population of South Africa was the latestavailable at the time of collating the data.

Di32Jlostic CriteriaA definitive diagnosis of Huntington's chorea was

accepted if each of the following features were present:(i) progressive motor disability, including chorea and/orrigidity with no other obvious cause; (ii) psychiatric distur-

banc~, usually comprising progressive dementia, with noother obvious cause; (iii) a positive family history of thedisorder with evidence of autosomal dominant inheritance.

Approximately 95'% of patients personally examined hadall three features. The remaining 5"% were diagnosed on thefollowing grounds: (a) the dia800sis was accepted in 5patients who had only features (i) and (iii); (h) the diagnosisof Huntington's chorea was made in the absence of afamily history if the disease conformed closely to theclinical features listed in (i) and (ii) and if no other causecould be found.

There were 8 patients in category (b) as definedabove. However, a negative family history did notnecessarily imply that .the affected person representeda mutation for the disorder. This may rather havereflected unreliable information about the health of theparents or their early accidental death before the diseasebecame manifest. The possibility that the patient wasnot the offspring of his alleged parents, but rather theillegitimate child of an unknown parent who carried thegene for Huntington's chorea, was also considered.

RESULTSThe total number of persons known to have died from,or presently suffering from, Huntington's chorea in SouthAfrica is shown in Table I. A total of 481 patients, ofwhom 153 are presently living, has been recorded. Abreakdown of this total according to different ethnicgroups is presented in Table Il. The prevalence of Hun-tington's chorea in South Africa according to the differentracial groups is shown in Table Ill. The regional distribu-tion of living persons suffering from Huntington's chorea,together with the respective prevalence rates, is tabulatedin Table IV.

DISCUSSIONThe prevalence of Huntington's chorea of 22,2 permillion in the White and 21,7 in the Coloured groups ismore than 200 times' greater than the calculated fre-quency of 0,1 in Blacks. The prevalence of the diseasein the White and Coloured populations of South Africa issimilar to the figures quoted in earlier reports from theUK; Canada (A. Barbeau - personal communication)and Australia: but lower than more recently ascertaineddata in these countries.- It is noteworthy that the total

UvingDeceased

Total

Male69

172

241

Female84

156

240

Total153328

481

196 SA MEDIESE TYDSKRIF 2 Augustus 1980

TABLE IV. PREVALENCE OF HUNTINGTON'S CHOREA INDIFFERENT PROVINCES OF SOUTH AFRICA

Population PrevalenceNo. eX 10') (/10')

Cape ProvinceWhites 32 1207 26,5Coloureds 48 2094 22,9Blacks 2 1674 0,5

Total 82

NatalWhiles 16 530 30,1Coloureds 90Blacks 1238

Total 16

TransvaalWhiles 30 2294 13,1Coloureds 3 199 15,1Blacks 5131

Total 33

Orange Free StateWhiles 4 328 12,1Coloureds 1 44 22,7Blacks 1 1582 0,6

Total 6

Unknown locationWhites 15Coloureds 1Blacks

Total 16Grand total 153

The very low prevalence rate of 0,1 in the AfricanNegro is the lowest reported figure in the world, anddeserves .s.ome comment. Only 11 patients, three of whomare living, are known to have the gene for Huntington'schorea. (Glass and SafIer' have recently reported anotheraffected Black family.) Even considering that there mayhave been incomplete ascertainment of data in this popu-lation group, it can be stated with confidence that Hun-tington's chorea is exceedingly rare in the African Negro.The most likely explanation for this finding is that thegene for Huntington's chorea in South Africa has itsorigins in north-western Europe. In view of the fact thatthere has been little genetic drift between those of Euro-pean descent and the African Negro group, one wouldexpect the gene to be uncommon in the latter population.

Huntington's chorea is thought to have one of thelowest mutation rates of any known genetic disease. Therarity of Huntington's chorea in the African Negro wouldseem to confirm this hypothesis.

These results are consistent with reports of a muchlower prevalence in American Negroes (15) compared

with US Whites (41,2): However, the frequency of thiseJisorder in the American Negroes is still much higherthani.in African Negroes. One explanation may be thatthe American Negro has a much larger White geneticadmixtun~) than his African counterpart, who has fewCaucasian 'genes. "

The overall prevalence rate in South African Whitesand Coloureds is similar ( 22). This is not an unexpectedfinding, owing to the large White contribution to thegenetic constitution of the Coloured people. By contrast,the prevalence rate of Huntington's chorea in the CapeColoured population within the boundaries of the Divi-sional Council of the Cape (not including the rest of theCape Province) has initially been reported as being 35 permillion. This calculation was based on 26 living affectedpersons, but a further 7 patients have now been identified,thus raising the prevalence to 45 per million, which isthe highest frequency of the disorder in South Africa. Itis clear that this finding is the result of more completeascertainment of data in greater Cape Town, due to thefact that the project was centred in this area.

The relatively high prevalence rate in Natal (30,1)reflects 16 patients in a population of 530 000 (Table IV).Assigning significance to the different prevalence rates inthe various provinces of South Africa must be done withcircumspection, as a few affected individuals in a smallsurvey population can artificially raise the prevalence.Thus, in spite of a lower number of patients, the preva-lence rate of Huntington's chorea in atal is higher thanthat of other provinces because of the relatively small sizeof the population being investigated.

With increased awareness of the disorder, it is to beanticipated that the prevalence of Huntington's chorea inSouth Africa will increase, owing to more accuratediagnosis and identification of patients. The prevalencefigures quoted are therefore minimum estimates of thetrue frequency of the disease in this country.

At the present time, there is no cure or reliable methodfor recognizing the asymptomatic carrier heterozygote forthe gene of Huntington's chorea. However, it is possiblethat a combination of careful ascertainment of affectedindividuals and their families, together with appropriategenetic counselling, will play some part in reducing theprevalence of the disease.

We are grateful to numerous colleagues, especially ProfessorF. Ames and Dr T. Zabow, who have provided access to theirfacilities and patients and who have contributed enormouslyto this project, and to Miss L. Solomon for typing the manu-script.

This investigation was supported by the Mauerberger Foun-dation Fund, the Baron HartleY-SCliolarship, the South Afri-can Medical Research Counci~ "l!P.d the University of CapeTown Staff Research Fund.

REFERENCES

1. Hayden, M. R. and Beighton, P. (1977): S. AIr. med. J., 52, 886.2. Heathfield, K. W. G. (1967): Brain, 90, 203.3. Parker, N. (1958): Med. J. Aust., 1, 251.4. Stevens, D. (1977): M.D. thesis, University of London.5. Caro, A. (1977): J. ray. Coli. gen. Practil., 27, 4l.6. Shokeir, M. H. (1975): Clin. Genet.. 7, 354.7. Glass, J. and Saffer, D. S. (1979): S. Afr. med. J., 56, 685.8. Wallace, D. C. (1972): Med. J. Aust., 2, 1275.