Results from a prospective sero-epidemiological study initiated in Uganda in 1971 indicate that children with high antibody titres to Epstein-Barr virus structural antigens are at high risk of developing Burkitt's lymphoma. These findings strongly support a causal relationship between the Epstein-Barr virus and Burkitt's lymphoma but suggest that the oncogenic potential of the virus is realised only in exceptional circumstances.
From 1977 to 1982, the authors attempted a malaria suppression trial in North Mara District, Tanzania, to see whether the incidence of Burkitt's lymphoma (BL) could be lowered by reducing the level of malarial infection in a child population below 10 years of age. Immediately after initiation of the suppression trial, the prevalence of malaria fell drastically in the Mara children; however, soon after, the rate of malarial infection rose again in the trial area in spite of continued chloroquine distribution, and by 1981 the prevalence of malarial infection again reached the high levels that had prevailed in the North Mara lowlands before 1977. However, during the period of chloroquine distribution in North Mara, the level of malarial infection there was constantly lower than that observed in a comparison area in South Mara, although the two areas had been similar with respect to malaria endemicity prior to the intervention. During the years of chloroquine distribution in North Mara, the incidence rate of BL there fell considerably, from about 4 per 100,000 population to about 1 per 100,000 population, and it rose again to pretrial levels in 1984, that is, about two years after the chloroquine distribution had been terminated. This apparent association between malaria suppression and decline in BL incidence at first seemed to indicate that malaria is a causal factor in BL production. A close scrutiny of the survey data revealed, however, that the decline in BL incidence might have started several years before the chloroquine distribution began; thus it appears that the malaria suppression could not have been the sole cause of the BL decline.
A prospective epidemiological study was carried out in the West Nile District of Uganda from 1972 to 1979 in order to investigate the aetiological role of the Epstein-Barr virus (EBV) in Burkitt's lymphoma (BL). By 1976, fourteen BL cases had been detected among the 42,000 children originally bled in the study area. Testing of sera from BL candidates and neighbourhood controls showed that children who develop BL later have EBV/VCA titres several dilutions higher than their age- and sex-matched neighbours. This appearance of a strong EBV activity long before BL development was taken as evidence of a causal role of EBV in BL. In order to add to the unique material of pre-bled BL cases, BL detection was continued up to March 1979 when field work became impossible in Uganda. Two additional pre-bled BL cases were found during this extension of the study. The serological and virological evaluation of these additional cases showed that the EBV/VCA titres, but not the EA and EBNA titres, were about two dilutions higher in the BL candidates than in the controls. Hybridization assays showed that both lymphomas contained EBV/DNA in the tumour cells. These additional results thus confirm the findings in the first 14 cases and strengthen the epidemiological evidence for a causal role of the EBV in endemic BL.
Thirty-four males and 45 females who participated in household surveys 15 or 25 years earlier in rural Denmark were interviewed in 1982 about present and past food habits. Comparison of the information from the survey and the two interviews indicates that recall of past diet is strongly influenced by present dietary habits. As the relative classification of individuals according to their food habits appears to have changed little over time, information on current diet, perhaps supplemented by information on particular changes, can provide useful classification of individuals for epidemiologic purposes.
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