Aflatoxin is a potent carcinogen. The fungus, genus Aspergillus, that secretes aflatoxin enters the plant usually through the wounds left by an insect pest, since most plants have a hard outer layer that acts as a barrier to fungi. Once inside the plant, the fungus can reach all parts of the plant, including its seeds. Aflatoxin is a serious cause of illness and death in developing countries which have fewer food safety regulations. Some plant scientists are trying to develop transgenic corn with a gene for an enzyme which breaks down aflatoxin. |Aflatoxin is listed as a possible carcinogen, and has been shown to cause liver damage, some of which may be cumulative,  in many mammals that ingest sufficient quantities of it, though tolerance seems to vary by species.  In most species, aflatoxin cannot be detected in the liver 14 days after it has been withdrawn from the animals diet, though some of its effects may still be present.  Animals affected by aflatoxicosis show reduced feed intake, and even mortality, if sufficient amounts of aflatoxin are ingested for a sufficient period of time.  Sensitivity, however, seems to vary not only by species, but also by individual animals.