From the clinical and economic point of view, aflatoxins (AF) are the most important mycotoxins. The fungi which are mostly accountable for their production are Aspergillus flavus and Aspergillus parasiticus. Several compounds have been described as AF, but only AF B1 (the most prevalent), B2, G1 and G2 are proven natural contaminants of agricultural commodities and feeds.

The presence/magnitude of contamination with AF varies according to geographic/seasonal factors and conditions of cultivation, harvest, transport and storage, among others. Crops grown in tropical/subtropical regions are more prone to contamination, since the high humidity provides ideal conditions for toxins production. Toxigenic fungi may develop in a wide range of sources (e.g. cereals and seeds).

Clinical signs and severity of aflatoxicosis differ according to age (e.g. younger animals show increased sensitivity). Besides, the type and concentration of AF, diet composition, length of exposure and the animals’ nutritional status may also exert a decisive influence.

Aflatoxicosis may be acute or chronic, depending on the dose/length of exposure. Acute intoxication is recognized by hepatic injuries, clinically characterized by depression, anorexia, jaundice and hemorrhage. Severe cases of acute aflatoxicosis determine clinical signs within approximately 6 hours and rapidly progress to death. 

Swine and poultry are quite susceptible to the effects of AF. There may be a compromise of the immunologic system in pigs, but intoxication generally leads to a decline in performance. In birds, there are marked effects due to the prompt absorption of these mycotoxins through the gastrointestinal tract. Alterations in the size of internal organs (e.g. liver and spleen), reduced weight gain and productivity losses are usually observed.

Clinical signs caused by AF and species sensitivity: