D. J. Van Schalkwyk

Hepatocellular carcinoma and dietary aflatoxin in Mozambique and Transkei

Estimations of the incidence of hepatocellular carcinoma (HCC) for the period 1968-74 in the Province of Inhambane, Mozambique, have been calculated and together with rates observed in South Africa among mineworkers from the same Province indicate very high levels of incidence in certain districts of Inhambane. Exceptionally high incidence levels in adolescents and young adults are not sustained at older ages and suggest the existence of a subgroup of highly susceptible individuals. A sharp decline in incidence occurred during the period of study. Concurrently with the studies of incidence, 2183 samples of prepared food were randomly collected from 6 districts of Inhambane as well as from Manhica-Magude, a region of lower HCC incidence to the south. A further 623 samples were taken during 1976-77 in Transkei, much further south, where an even lower incidence had been recorded. The mean aflatoxin dietary intake values for the regions studied were significantly related to HCC rates. Furthermore, data on aflatoxin B1 contamination of prepared food from 5 different countries showed overall a highly significant relationship with crude HCC rates. In view of the evidence that chronic hepatitis B virus (HBV) infection may be a prerequisite for the development of virtually all cases of HCC and given the merely moderate prevalence of carrier status that has been observed in some high incidence regions, it is likely that an interaction between HBV and aflatoxin is responsible for the exceptionally high rates evident in parts of Africa and Asia. Various indications from Mozambique suggest that aflatoxin may have a late stage effect on the development of HCC. This points to avenues for intervention that could be more rapidly implemented than with vaccination alone.

Mycotoxicological investigations on Zambian maize.

Abstract In Zambia there is a statutory requirement that visually diseased kernels should not constitute more than 2% of maize intended for human consumption. Four samples of Zambian maize containing 1·8, 5·4, 13·0 and 20·3% visually diseased kernels were subjected to mycological and chemical analyses and to toxicity trials in ducklings and rats. For all the samples the dominant fungi isolated from surface-sterilized kernels were Fusarium moniliforme Sheldon and Diplodia macrospora Earle, and the most prevalent fungus isolated from prepared maize meals was F. moniliforme . The level of fungal invasion of both kernels and meal was significantly lower for the 1·8%-diseased sample than for the other three. Protein and essential amino acid content tended to increase as the level of diseased kernels increased. None of the samples contained chemically detectable amounts of aflatoxins, ochratoxins, sterigmatocystin, cyclopiazonic acid or zearalenone. Although no samples were lethal to either ducklings or rats, body-weight gains were higher in male and female rats fed the 1·8%-diseased sample for 6 months than in those given the other test diets, the difference being statistically significant in the males. Of seven pure cultures of fungi isolated from the maize samples, five, including F. moniliforme and D. macrospora , were acutely toxic to ducklings and rats. In view of the indications that unidentified Fusarium and Diplodia toxins present in Zambian maize containing more than 1·8% visually diseased kernels reduce the growth rate of rats fed such samples for 6 months, it is recommended that the 2% maximum level of visually diseased kernels acceptable in Zambian maize for human consumption should be maintained.