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The influence of a complex microflora residing in the gastrointestinal tract of cattle on the prion protein plays a crucial role with respect to early pathogenesis and the potential infectivity of faeces resulting in contamination of the environment. It is unknown whether infectious prion proteins, considered to be very stable, are inactivated by microbial processes in the gastrointestinal tract of animals during digestion. In our previous study it was shown that the scrapie-associated prion protein was degraded by ruminal and colonic microbiota of cattle, as indicated by a loss of anti-prion antibody 3F4 immunoreactivity in Western blot. Subsequently, in this study hamster bioassays with the pre-treated samples were performed. Although the PrPSc signal was reduced up to immunochemically undetectable levels within 40 h of pre-treatment, significant residual prion infectivity was retained after degradation of infected hamster brain through the gastrointestinal microflora of cattle. The data presented here show that the loss of anti-prion antibody 3F4 immunoreactivity is obviously not correlated with a biological inactivation of PrPSc. These results highlight the deficiency of using Western blot in transmissible spongiform encephalopathies inactivation assessment studies and, additionally, point to the possibility of environmental contamination with faeces containing PrPSc following an oral ingestion of prions. [ABSTRACT FROM AUTHOR]

Ochratoxin A in the food-chain During a period of more than 5 years, the natural occurrence of the mycotoxin ochratoxin A has been investigated in cereals and mixed feed. Furthermore, blood and kidneys of slaughter pigs and samples of human origin (blood, kidney, milk) have been analyzed for ochratoxin A residues. The presence of ochratoxin A could be shown in cereals and samples of animal origin, as well as in specimens obtained from man. Highest levels of ochratoxin A (up to 206 μg/kg) were found in cereals and mixed feed (n = 984), which were contaminated to an extent of 12.9%. Ochratoxin A was also found in 48.7% and 21.2% of blood sera (n = 191) and kidneys (n = 104) of pigs, respectively. The frequent contamination of human blood sera (56.6% positive out of 306 tested) and the detection of ochratoxin A residues in human kidneys and milk draw attention to a continuously exposure by food of plant and animal origin. These facts and the multiple toxic properties of ochratoxin A (nephrotoxic, hepatotoxic, teratogenic, immunosuppressive and carcinogenic effects) should give reason for establishing a monitoring concept and for considering ochratoxin A guidelines. Zusammenfassung In einer fünf Jahre dauernden Studie wurde das natürliche Vorkommen des Mykotoxins Ochratoxin A in Zerealien und Mischfuttermitteln untersucht. Des weiteren wurde geprüft, inwieweit Ochratoxin A-Rückstände in Schlachtschweinen (Blut, Nieren) und im Menschen (Blut, Nieren, Muttermilch) zu finden sind. Ochratoxin A konnte sowohl in den Proben pflanzlicher und tierischer Herkunft, als auch in dem vom Menschen stammenden Material nachgewiesen werden. Die höchsten Toxinkonzentrationen (bis zu 206 μg/kg) wurden in pflanzlichen Nahrungsmitteln (n = 984), die zu 12,9% kontaminiert waren, gemessen. 48,7% der untersuchten Schweineseren (n=191) und 21,2% der hierzulande gesammelten Schweinenieren (n = 104) wiesen Ochratoxin A auf. Der häufige Nachweis von Ochratoxin A in Blutseren vom Menschen (56,6% von 306 Proben) und die gefundenen Rückstände in Nieren und Muttermilch weisen auf eine kontinuierliche Aufnahme über Lebensmittel pflanzlicher und tierischer Herkunft hin. Dieser Sachverhalt und das multitoxische Wirkungsspektrum von Ochratoxin A (nephro- und hepatotoxische, teratogene, immunsuppressive, karzinogene Eigenschaften) geben hinreichend Anlaß, ein Monitoring-Konzept zu entwickeln und eine Höchstmengenbegrenzung in Erwägung zu ziehen. [ABSTRACT FROM AUTHOR]

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