Produced by : several species

Introduction and structure

Trichothecene toxins belong to a group of closely related chemical compounds produced by several species of Fusarium, Cephalosporium, Myrothecium, Trichoderma, and Stachybotrys. Four trichothecenes (T-2 toxin, nivalenol, deoxynivalenol (DON), and diacetoxyscirpenol) have been detected as natural contaminants in a small number of food samples. deoxynivalenol is the most common but least toxic of these. Trichothecenes are strong inhibitors of protein synthesis in mammalian cells. However, deoxynivalenol received its common name, vomitoxin, from the vomiting that generally accompanies trichothecene poisoning.

Occurrence

DON is probably the most frequently detected trichothecene and the toxin is mainly produced by F. graminearum and F. culmorum . The two Fusarium species are plant pathogens and cause outbreaks of fusarium head blight (also called wheat scab). The most serious outbreaks of the disease occur in years with heavy rainfall during the flowering season. In an world-wide average, DON has been found in 57% of the wheat samples, 40% of the maize samples, 68% of the oats samples, 59% of barley samples, 49% of rye samples and 27% of the rice samples analysed. DON was also found in wheat and maize products, for example flour, bread and breakfast cereals. The concentrations of DON in random cereal samples showed a large annual variation, concentrations ranging from below the detection limits (5-50 µg/kg) to more than 30 mg/kg.

Nivalenol is more common in Europe, Australia and Asia than in America. Both mean levels and incidence of positive samples of nivalenol are lower than for DON.

T2 toxin has been found in many different products, but often in very low amounts.

Effects on human health

A possible role of trichothecenes in the human disease Alimentary Toxic Aleukia (ATA) in Russia was reported. The disease has been reported since the 19 th century,and a severe outbreak occurred in the Orenburg district during 1942-1947 where 100 000 people died. The disease was attributed to the consumption of Fusarium infected wheat kept outdoors. The disease was characterized by spots on the skin, necrotic angina, extreme leukopenia and multiple haemorrhages and exhaustion of the bone marrow. Isolates of Fusarium sporotrichioides and F. poae from the wheat were later shown to produce T-2 toxin and related trichothecenes (Yagen & Joffe, 1976). Symptoms similar to those reported from patients suffering from ATA have later been observed in animals exposed to acute toxic doses of T-2 toxin. Trichothecenes have also been associated with outbreaks of human gastrointestinal disorders in Japan.