Effect of groundnut meal containing aflatoxin on Cynomolgus monkeys

1. Both male and female Cynomolgus (Macaca irus) monkeys survived for 3 years without apparent ill health when fed on diets containing groundnut meal to provide up to 0·36 μg aflatoxin B1per g diet and thus supplying a mean daily consumption of up to 2 μg aflatoxin B1per kg body-weight. No histological changes attributable to aflatoxicosis were discovered in any of the organs from the monkeys receiving these quantities of aflatoxin. 2. Few monkeys survived for more than a month or two when given a diet containing 1·8 μg aflatoxin B1per g, which provided about 50 μg aflatoxin B1per kg body-weight per day. 3. No depression in growth rate nor effect on health was noted in those monkeys which survived on diets containing 1·8 μg aflatoxin B1, nor in any of the other monkeys. 4. Histological changes were observed in the livers of all monkeys receiving the diet containing 1·8 μg aflatoxin B1per g for more than a month or two, but no abnormalities related to aflatoxicosis could be detected in any of the other organs, except for minor changes in the kidneys of two monkeys. 5. No tumours were seen in any of the monkeys, even in those surviving for 3 years on diets providing 1·8 μg aflatoxin B1/g. Thus, no conclusions can be drawn from this work as to the carcinogenicity of aflatoxin in monkeys (still less in man), because the animals were young and little is known of the duration of exposure required to demonstrate carcinogenicity in this species.