Choice of coronary heart disease risk factor variables in a cross-sectional study of white South Africans

This report explores the possibility of redefining risk factors so as to improve their observed associations with prevalent coronary heart disease (CHD). A large cross-sectional community study of 5,895 white males and females aged 25-64 years yielded 240 cases of confirmed angina pectoris and 361 of confirmed myocardial infarction. Odds ratios for CHD end-points by level of risk factors when risk factors were expressed in the conventional manner (e.g. total cholesterol, systolic and diastolic blood pressure or current smoking) were often low and not statistically significant. Redefinition of risk factor variables in a manner that improved their specificity or compensated to some extent for the decreased risk factor exposure as a result of a CHD event (e.g. stopping smoking after a myocardial infarct) improved the strength of association. In this study, the most useful cholesterol variable was total cholesterol minus high-density lipoprotein cholesterol; for blood pressure the most useful variable was a blood pressure of 160/95 mmHg or above and/or being on anti-hypertensive treatment; and for smoking the most useful variable was the total duration of smoking (previous and current). Strong associations with CHD end-points were also found for conventionally expressed serum uric acid, diabetes prevalence (females) and family history of CHD. The study suggests that appropriate redefinition of risk factor variables and CHD end-points in cross-sectional studies yields associations similar in strength and direction to those found in prospective studies.     

Effect of breast feeding on the plasma cholesterol and growth of infants

The effect of breast-feeding on plasma cholesterol, body weight, and body length was studied longitudinally in a large free-living cohort of infants (n = 512) from birth until the age of 1 year. Of the cohort, 21.4% were exclusively breast-fed for at least 3 months, 39.3% received bottle-feeding, and 39.3% received a combination of breast- and bottle-feeding. At birth the plasma cholesterol was similar in the three groups. After 3 months the mean plasma cholesterol and proportion of hypercholesterolemic infants in the breast-fed group were significantly (p less than 0.001) higher than that of the other two groups. These differences had disappeared at the age of 1 year. Breast-fed infants weighed less at 3 and 12 months, but body length was similar to those of the other groups. These results suggest that breast-feeding elevates plasma cholesterol by a direct mechanism and that the effect persists only as long as the breast-feeding is continued.     

Serodiagnosis of Crimean-Congo haemorrhagic fever.

Several methods for demonstrating antibody to Crimean-Congo haemorrhagic fever virus were compared on serum samples taken from 101 patients during the acute stage of illness and at intervals for up to 59 months thereafter, with emphasis on early detection of the immune response. The deaths of 23 patients on days 5-14 of illness were ascribed to the effects of the disease; two patients died later from other causes. Very few of the patients who died from the acute illness mounted an antibody response detectable by the methods tested. Four patients who died and 18 who recovered were treated with immune plasma collected from recovered patients. Treated patients acquired IgG antibody from the plasma, but it was possible to discern the onset of an endogenous IgM response in those individuals who survived the disease by all of the methods tested. Indirect immunofluorescence (IF) tests detected IgM and/or IgG antibodies at the earliest on day 4 of illness in about 10% of patients who survived the disease, and by day 9 all survivors had antibodies demonstrable by IF. A biotin-streptavidin IF technique offered no advantage over the standard IF test for the early detection of IgG antibody, but demonstrated higher antibody titres and detected IgM antibody earlier in about a quarter of the patients tested. An IgM-capture enzyme-linked immunoassay (ELISA) and an IgG sandwich ELISA demonstrated higher antibody titres than did IF tests, and detected antibody responses at an earlier stage of infection than did IF tests in about one-fifth of patients, but the reverse was true in a similar proportion of instances. A competition ELISA, which detected total antibody activity, produced lower titres than did the IgM and IgG ELISAs, but yielded results which were in close agreement with the findings in IF tests. It was concluded that the IF tests were most convenient for use in making a rapid serodiagnosis of the disease.     

An inhibition enzyme-linked immunosorbent assay for the detection of antibody to Rift Valley fever virus in humans, domestic and wild ruminants

This paper describes the development and validation of an inhibition ELISA based on gamma-irradiated tissue culture-derived antigen for the detection of antibody to Rift Valley fever virus (RVFV) in humans, domestic and wild ruminants. Validation data sets derived from field-collected sera in Africa (humans=1367, cattle=649, goats=806, sheep=493, buffalo=258, camels=156) were categorized according to the results of a virus neutralisation test. In addition, individual sera from 93 laboratory workers immunized with inactivated RVF vaccine, 136 serial bleeds from eight sheep experimentally infected with wild-type of RVFV, and 200 serial bleeds from 10 sheep vaccinated with the live-attenuated strain of the virus, were used to study the kinetics of RVFV antibody production under controlled conditions. At cut-off values selected at 95% accuracy level by the two-graph receiver operating characteristic analysis the ELISA sensitivity ranged from 99.47% (humans) to 100% (sheep, buffalo, camels). The specificity ranged from 99.29% (sheep) to 100% (camels). Compared to virus neutralisation and haemagglutination-inhibition tests, the ELISA was more sensitive in detection of the earliest immunological responses in experimentally infected and vaccinated sheep. Our results demonstrate that the ELISA format reported here can be used as a safe, robust and highly accurate diagnostic tool in disease-surveillance and control programmes, import/export veterinary certification, and for monitoring of the immune response in vaccinees.     

Antibody to Crimean-Congo hemorrhagic fever virus in wild mammals from southern Africa

Crimean-Congo hemorrhagic fever (CCHF) virus is becoming increasingly recognized as an important human pathogen in southern Africa. In order to determine the role of wild mammals in the natural ecology of the virus, sera from 3,772 wild mammals of 87 species and from 1,978 domestic dogs collected in South Africa and Zimbabwe between 1964 and 1985 were tested for antibody to CCHF virus by reversed passive hemagglutination inhibition (RPHI) and by indirect immunofluorescence (IF). Antibody was found to be highly prevalent in large mammals in the Orders Artiodactyla and Perissodactyla such as giraffe, Giraffa camelopardalis (3/3 positive), rhinoceros, Ceratotherium simium and Diceros bicornis (7/13), eland, Taurotragus oryx (59/127), buffalo, Syncerus caffer (56/287), kudu, Tragelaphus strepsiceros (17/78), and zebra, Equus burchelli (16/93). In small mammals antibody was found in the sera of 40/293 hares, 22/1,305 rodents, and 1/74 wild carnivores, but not in 522 primates, 176 insectivores, or 19 hyrax. Antibody was also found in the sera of 118/1,978 domestic dogs. The species of wild mammal in which antibody was distributed (with highest antibody prevalence in hares and large herbivores) reflects the feeding preference of immature and adult ticks of the genus Hyalomma, suggesting that Hyalomma sp. are the principal CCHF vectors in the wild.     

Auditory pathology in cri-du-chat (5p-) syndrome: phenotypic evidence for auditory neuropathy

5p-(cri-du-chat syndrome) is a well-defined clinical entity presenting with phenotypic and cytogenetic variability. Despite recognition that abnormalities in audition are common, limited reports on auditory functioning in affected individuals are available. The current study presents a case illustrating the auditory functioning in a 22-month-old patient diagnosed with 5p- syndrome, karyotype 46,XX,del(5)(p13). Auditory neuropathy was diagnosed based on abnormal auditory evoked potentials with neural components suggesting severe to profound hearing loss in the presence of cochlear microphonic responses and behavioral reactions to sound at mild to moderate hearing levels. The current case and a review of available reports indicate that auditory neuropathy or neural dys-synchrony may be another phenotype of the condition possibly related to abnormal expression of the protein beta-catenin mapped to 5p. Implications are for routine and diagnostic specific assessments of auditory functioning and for employment of non-verbal communication methods in early intervention.     

Phylogenetic relationships of southern African West Nile virus isolates

Phylogenetic relationships were examined for 29 southern African West Nile virus (formal name West Nile virus [WNV]) isolates from various sources in four countries from 1958 to 2001. In addition, sequence data were retrieved from GenBank for another 23 WNV isolates and Kunjin and Japanese encephalitis viruses. All isolates belonged to two lineages. Lineage 1 isolates were from central and North Africa, Europe, Israel, and North America; lineage 2 isolates were from central and southern Africa and Madagascar. No strict correlation existed between grouping and source of virus isolate, pathogenicity, geographic distribution, or year of isolation. Some southern African isolates have been associated with encephalitis in a human, a horse, and a dog and with fatal hepatitis in a human and death of an ostrich chick.