Pathogen characteristics of aflatoxin in duck

(1) aflatoxin production aflatoxin, like other mycotoxins, is one of the metabolites of toxin-producing fungi in the process of growth and reproduction in the substrate. This toxin was found in the etiology of "turkey X disease" in England in 1960. In the second year, it was found that the peanut cake contaminated with Aspergillus flavus could induce liver cancer in rats and confirmed that aflatoxin was a carcinogenic mycotoxin. The main fungi that produce aflatoxin are Aspergillus flavus and parasitic Aspergillus flavus, while Aspergillus winterii and Penicillium molluscum can also produce a small amount. According to Eslaer, 80% of the first two fungal strains growing on substrates such as corn in the tropics can produce aflatoxins (Aspergillus flavus mainly produces B1, B2, while parasitic Aspergillus produces B1, B2 and G1, G2). Although the closely related strains growing on the same substrate in warm and cold regions, the detection rate of toxin-producing strains is also greatly reduced. Of course, in addition to the above regional differences, the most suitable conditions for toxin production are that the moisture content of the substrate should be more than 16%, the relative humidity should be between 80% and 90% (Aspergillus flavus is one of the mesophilic fungi), the temperature should be 25-30 ℃ and the oxygen content should not be less than 1%. At the same time, the substrate for its growth must be carbohydrate-rich agricultural products, in which rice, wheat, corn, peanuts, cottonseeds and other grain and oil crops are more ideal, easy to mildew and produce aflatoxin.

(2) aflatoxin is a kind of aflatoxin with similar structure and difuran ring-oxanaphtho ketone, that is, difuran ring-coumarin. According to the fluorescence color (B1, B2 is blue-purple, G1, G2 is yellowish green), RF value (that is, mobility on the thin plate) and chemical structure emitted on the thin layer plate at the wavelength of 365nm (nm), they are named as B1, B2, G1, G2, M1, M2, P1, Q1, toxol and GM1 respectively. Among them, except B1, B2 and G1, G24 are naturally produced, the rest are their derivatives.

Aflatoxin is resistant to high temperature and does little damage at the usual disinfection temperature. Pyrolysis damage can only occur at 280300 ℃. But it is easy to be destroyed by strong alkali or strong oxidant, and it can also be destroyed under ultraviolet light (for a long time).

Aflatoxin has low solubility in water and is easily soluble in some organic solvents, such as chloroform, methanol and ethanol, but insoluble in hexane, ether and petroleum ether. At present, thin layer chromatography (TLC) is used to detect Aspergillus flavus in all kinds of food, grain, oil, feed and forage in China.

(3) the toxicity of aflatoxins is different among aflatoxins, for example, the toxicity of B1 is 2 times higher than that of G1 and M1, 4 times of B2 and 8 times of G2. In addition to the fact that aflatoxin poisoning is more common in males than females in livestock and poultry, the sensitivity of young livestock is higher than that of adult livestock. The order of sensitivity of poultry to aflatoxin is duck chick > turkey chick > Japanese quail.

Through animal experiments, it is proved that the target organ of aflatoxin is liver, which belongs to liver toxin. Aflatoxin damage to the liver, if only a low dose, the liver lesions can be recovered; if high doses or repeated exposure to the toxin, the liver lesions often turn into a chronic pathological process.

(4) the carcinogenicity of aflatoxins aflatoxins and other chemical carcinogens are the same as those of other chemical carcinogens. after biological metabolism, aflatoxins form final carcinogens and combine with macromolecules such as DNA. Aflatoxins not only induce liver cancer in tested animals, but also induce cancer in other organs or sites, such as gastric adenocarcinoma, renal cancer, rectal cancer, breast cancer, ovarian tumor and small intestinal tumor. Tracheal squamous cell carcinoma can also be induced by endotracheal injection of aflatoxin.

Aflatoxin is also teratogenic. After intraperitoneal injection of aflatoxin in hamsters of 8-11 days of pregnancy, malformations such as anencephaly, small brain, ectopic heart and other defects can be induced.