Biomedical subjects
Publications and source records attributed to M C Botha.
Two sisters in a Hei//om family of the southern African Khoisan race in Namibia were found to have Wd(a+) red blood cells. Wda is a low-frequency antigen identified so far only in a European family in Canada and a family in Holland. The Wda gene may have had an independent origin in the Khoisan. Alternatively, the Hei//om population may have acquired it through miscegenation.
Serological evidence for HTLV-I infection in the South African population has now been confirmed by the isolation of the virus from the peripheral blood lymphocytes of an adult Tsonga male. The subject was an indigenous black man from the south-eastern Transvaal who had suffered from Kaposi's sarcoma for a decade and in whom serum antibodies against HTLV-I were demonstrated. T-lymphocyte cell lines were established from his peripheral blood lymphocytes and shown to be productively infected with HTLV-I as evidenced by: the characteristic cell morphology; the typical viral morphogenesis on ultra-thin section electron microscopy; the viral genome in DNA extracted from the cell lines; characteristic reverse transcriptase activity and viral specific proteins in the cell culture supernatant fluids. Spread of infection occurs through sexual intercourse, from mother to child, and by blood transfusion. Donated blood should be screened to contain the spread of HTLV-I infection.
Huntington chorea is rare in ethnically pure blacks; 8 South African black patients, 6 adults and 2 children, from 4 families are described. The symptoms do not appear to differ materially from Huntington chorea in other races. Increased awareness of the disease in this population group is warranted.
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Inherited disorders transmitted by simple genetic mechanisms are documented, with discussion of those notable for their unusually high or low prevalence.
Genetic, geographic and socio-economic diversity has resulted in disparity in the relative prevalence of many inherited disorders and congenital conditions in the populations of southern Africa. In the first section of a 3-part article an account is given of the historical and demographic background in relation to factors which influence the presence and frequency of faulty genes in the black community. In addition, inherited haematological conditions--in particular haemoglobinopathies, red-cell enzyme and membrane defects--are discussed in terms of their clinical, genetic and anthropological significance. The conditions transmitted by simple genetic mechanisms are documented in Part II, with discussion of those notable for their unusually high or low prevalence. In the final section multifactorial, chromosomal and non-genetic congenital disorders are reviewed and a number of unusual conditions of obscure aetiology are mentioned. In this 3-part overview an attempt has been made to document present knowledge and to provide a bibliography for inherited and congenital disorders in the black population.
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Antibodies which probably indicate infection with human T-cell leukaemia virus type I (HTLV-I) were determined in three species of non-human primates from several localities. A significant prevalence among chacma baboons and vervet monkeys was confirmed. According to sero-epidemiological evidence that HTLV-I infection is predominantly sexually transmitted between adult animals; comparison of prevalence rates between localities or species should therefore take sexual maturity into account. It appears unlikely that transmission from non-human primates to humans is frequent.
The prevalence of serum antibodies which probably indicate infection with a human T-cell leukaemia virus type I was determined among random population samples of more than 100 healthy black individuals in several localities in Transvaal. The percentage of seropositive subjects increases northwards and eastwards, where geoclimatic conditions are similar to those of endemic areas elsewhere in the world. The comparatively higher prevalence among females in the Kruger National Park suggests that this is predominantly a sexually transmitted disease.
The cord blood of 1,207 randomly selected neonates from the Cape Coloured population of South Africa was analysed for the presence of Hb Barts. 40 individuals (3.3%) had detectable Hb Barts levels with values ranging from 1.1 to 7.3%. Restriction enzyme analysis of DNA from subjects with Hb Barts showed that 85% of the cases studied had the genotypes -alpha 3.7/alpha alpha or -alpha 3.7/-alpha 3.7. The observed frequency of the -alpha/alpha alpha genotype was much lower than the expected frequency which suggests that this genotype is often not associated with detectable levels of Hb Barts. Mapping of the sigma-globin locus in three subjects with HbH disease revealed the presence of the--SEA/alpha-thalassaemia determinant in this population.
In addition to the genetic conditions reviewed in Part I of this article, sclerosteosis, spondyloepimetaphyseal dysplasia, lipoid proteinosis, keratolytic winter erythema and various haematological disorders also occur in high frequency in the Afrikaner community. The recognition of the presence of these serious inherited disorders is important in differential diagnosis and is fundamental to the establishment of public health programmes for amelioration and prevention.
Certain genetic disorders occur with unusually high frequency in the Afrikaner population of southern Africa. Conditions of this type (reviewed in Part I of this article) include familial hypercholesterolaemia, progressive familial heart block, Huntington's chorea, porphyria variegata, Gaucher's disease, cystic fibrosis and familial colonic polyposis. This genetic situation is explicable to some extent on the basis of the demographic development of the Afrikaner population during the 14 generations since the arrival of the first immigrants from Holland more than 330 years ago.
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Measles antibody titres and HLA antigens were determined in 71 White and 11 Coloured multiple sclerosis (MS) patients and 71 White and 11 Coloured age and sex-matched controls. Measles antibody titres were determined by the hemagglutination inhibition test and HLA antigens were determined serologically by a micro-lymphocytotoxicity test. Measles antibody titres were significantly higher in MS than in control cases and this was true for both female and male patients. No association was observed between the HLA antigens, especially HLA-A3 or HLA-B7 and measles antibody titres in the sera of MS patients or controls.
Cape Town has a Greek community of about 5000, of whom approximately 75% originate from the island of Lesbos. In a survey of inherited haematological conditions in this population, 250 unrelated volunteers were investigated. The prevalence of heterozygous beta-thalassaemia was found to be 6.4%, with a gene frequency of 0.033. G6PD deficiency was detected in 10 males and it can be estimated that the prevalence in the male members of this population is 6.7%, with a gene frequency of 0.067. Hereditary spherocytosis was found in three respondents and this represents a prevalence of 1.2%, with a gene frequency of 0.006. One subject was heterozygous for the sickle cell trait (HbS) and another volunteer had haemoglobin Lepore, which had already been diagnosed in Greece. Our findings with respect to beta-thalassaemia and G6PD deficiency are similar to those reported from regions in Greece where malaria is not highly endemic.
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