Risks for animal health related to the presence of ochratoxin A (OTA) in feed

In 2004, the EFSA Panel on Contaminants in the Food Chain (CONTAM) adopted a Scientific Opinion on the risks to animal health and transfer from feed to food of animal origin related to the presence of ochratoxin A (OTA) in feed. The European Commission requested EFSA to assess newly available scientific information and to update the 2004 Scientific Opinion. OTA is produced by several fungi of the genera Aspergillus and Penicillium. In most animal species it is rapidly and extensively absorbed in the gastro-intestinal tract, binds strongly to plasma albumins and is mainly detoxified to ochratoxin alpha (OTalpha) by ruminal microbiota. In pigs, OTA has been found mainly in liver and kidney. Transfer of OTA from feed to milk in ruminants and donkeys as well as to eggs from poultry is confirmed but low. Overall, OTA impairs function and structure of kidneys and liver, causes immunosuppression and affects the zootechnical performance (e.g. body weight gain, feed/gain ratio, etc.), with monogastric species being more susceptible than ruminants because of limited detoxification to OTalpha. The CONTAM Panel considered as reference point (RP) for adverse animal health effects: for pigs and rabbits 0.01 mg OTA/kg feed, for chickens for fattening and hens 0.03 mg OTA/kg feed. A total of 9,184 analytical results on OTA in feed, expressed in dry matter, were available. Dietary exposure was assessed using different scenarios based on either model diets or compound feed (complete feed or complementary feed plus forage). Risk characterisation was made for the animals for which an RP could be identified. The CONTAM Panel considers that the risk related to OTA in feed for adverse health effects for pigs, chickens for fattening, hens and rabbits is low.

Toxicity and detoxification of T-2 toxin in poultry

This review summarizes the updated knowledge on the toxicity of T-2 on poultry, followed by potential strategies for detoxification of T-2 in poultry diet. The toxic effects of T-2 on poultry include cytotoxicity, genotoxicity, metabolism modulation, immunotoxicity, hepatotoxicity, gastrointestinal toxicity, skeletal toxicity, nephrotoxicity, reproductive toxicity, neurotoxicity, etc. Cytotoxicity is the primary toxicity of T-2, characterized by inhibiting protein and nucleic acid synthesis, altering the cell cycle, inducing oxidative stress, apoptosis and necrosis, which lead to damages of immune organs, liver, digestive tract, bone, kidney, etc., resulting in pathological changes and impaired physiological functions of these organs. Glutathione redox system, superoxide dismutase, catalase and autophagy are protective mechanisms against oxidative stress and apoptosis, and can compensate the pathological changes and physiological functions impaired by T-2 to some degree. T-2 detoxifying agents for poultry feeds include adsorbing agents (e.g., aluminosilicate-based clays and microbial cell wall), biotransforming agents (e.g., Eubacterium sp. BBSH 797 strain), and indirect detoxifying agents (e.g., plant-derived antioxidants). These T-2 detoxifying agents could alleviate different pathological changes to different degrees, and multi-component T-2 detoxifying agents can likely provide more comprehensive protection against the toxicity of T-2.

Exposure of Aspergillus fumigatus to T-2 toxin results in a stress response associated with exacerbation of aspergillosis in poultry

Aspergillus fumigatus is a ubiquitous airborne pathogen. Saprophytic growth in the presence of environmental mycotoxins might affect its fitness and virulence. T-2 toxin (T-2) is a trichothecene mycotoxin produced by Fusarium spp. in various substrates. This study aimed to evaluate the effects of T-2 on the fitness of A. fumigatus in vitro and its virulence in experimentally inoculated chickens. We cultured A. fumigatus on agar media containing T-2, and examined the changes in viability, morphology, growth rate, proteome expression, and susceptibility to antimycotics and oxidative stress of this fungus. Results showed that exposure to 1000 ng/ml T-2 in the substrate did not reduce the viability of A. fumigatus, but its growth was inhibited, with wrinkling and depigmentation of the colonies. Proteomic analysis revealed 21 upregulated proteins and 33 downregulated proteins, including those involved in stress response, pathogenesis, metabolism, transcription. The proteome seems to have shifted to enhance the glycolysis, catabolism of lipids, and amino acid conversion. Assays on fungal susceptibility to antimycotics and oxidative stress showed that T-2 exposure did not affect the minimal inhibitory concentrations of amphotericin B, itraconazole, voriconazole and terbinafine against A. fumigatus, but increased the susceptibility of A. fumigatus to H2O2 and menadione. Experimental inoculation of chickens with A. fumigatus showed that exposure of A. fumigatus to T-2 significantly exacerbated aspergillosis in chickens exposed to dietary T-2. In conclusion, A. fumigatus is capable of surviving and growing on substrates containing levels of T-2 up to 1000 ng/ml. Growth in presence of T-2 induces a stress response in A. fumigatus, which is associated with exacerbation of aspergillosis in vivo.