Ochratoxin A

Overview
Ochratoxin A, a toxin produced by Aspergillus ochraceus and Penicillium verrucosum, is one of the most abundant food-contaminating mycotoxins in the world. Human exposure occurs mainly through consumption of improperly stored food products, particularly contaminated grain and pork products, as well as coffee, wine grapes and dried grapes. The toxin has been found in the tissues and organs of animals, including human blood and breast milk. Ochratoxin A toxicity has large species- and sex-specific differences.

Synonyms:
 * (R)-N-[(5-Chloro-3,4-dihydro-8-hydroxy-3-methyl-1-oxo-1H-2-benzopyran-7-yl)-carbonyl]- L-phenylalanine
 * (-)-N-[(5-Chloro-8-hydroxy-3-methyl-1-oxo-7-isochromanyl)carbonyl]-3-phenylalanine

Carcinogenicity
Ochratoxin A is potentially carcinogenic to humans (Group 2B). Ochratoxin A has been shown to be weakly mutagenic, possibly by induction of oxidative DNA damage.

There is sufficient evidence in experimental animals for the carcinogenicity of ochratoxin A. Ochratoxin A was tested for carcinogenicity by oral administration in mice and rats. It increased the incidence of hepato-cellular tumours in mice of each sex and produced renal-cell adenomas and carcinomas in male mice and in rats of each sex.

Immuno suppression and immunotoxicity
Ochratoxin A can cause immunosuppression and immunotoxicity in animals. The toxin's immunosuppressant activity in animals may include depressed antibody responses, reduced size of immune organs (such as the thymus, spleen, and lymph nodes), changes in immune cell number and function, and altered cytokine production. Immunotoxicity probably results from cell death following apoptosis and necrosis, in combination with slow replacement of affected immune cells due to inhibition of protein synthesis.

Potential link to Balkan endemic nephropathy
A number of descriptive studies have suggested a correlation between exposure to ochratoxin A and Balkan endemic nephropathy, and have found a correlation between the geographical distribution of Balkan endemic nephropathy and a high incidence of, and mortality from, urothelial urinary tract tumours. However, there is currently insufficient information to conclusively link ochratoxin A to Balkan endemic nephropathy. The toxin may require synergistic interactions with predisposing genotypes or other environmental toxicants to induce Balkan endemic nephropathy.

Food animal industry impact
Ochratoxin-contaminated feed has its major economic impact on the poultry industry. Chickens, turkeys and ducklings are susceptible to this toxin. Clinical signs of avian ochratoxicosis are similar to other toxins and generally involve reduction in weight gains, poor feed conversion, reduced egg production, poor egg shell quality and kidney poisoning.

Acute toxicity does not seem to constitute a problem in cattle.