host homeostasis by contributing to optimal digestion and absorption, regulation of energy metabolism, prevention of mucosal infections and modulation of the immune system. Disturbances in the gut microbial ecosystems during the rear- ing of livestock animals can dramatically increase risk of dis- ease. Few studies have demonstrated an impact of mycotoxin exposure on the gut microbiota composition and diversity in humans and different animal species. It has been observed that the abundance of different bacterial families / genera such as Lachnospiraceae, Ruminococcaceae, Lactospiraceae, Faecalibacterium, Clostridiaceae Enterobacteriaceae, and Rose- buria can be affected by mycotoxin exposure. These shifts in the intestinal microbiota composition might be associated with the impact of the mycotoxins on the digestive physiolo- gy, enterocyte viability, and mucus production.
such as deoxynivalenol (DON) and fumonisins (FUM) are able to increase the permeability of the intestinal epithelial layer of humans and animals e.g. pigs and poultry. Also, the viability and proliferation of animal and human intestinal epithelial cells can be negatively affected by mycotoxins. Besides the negative impact of mycotoxins on the intestinal epithelial cells, these toxins have also an impact on the other elements of the intestinal barrier, such as the mucus layer, secretion of antimicrobial peptides, chemokines and cytokines, and oxidative stress. Exposure to the mycotoxins DON and/or zearalenone (ZEN) decreased the number of goblet cells in the small and large intestine of pigs, which are of major importance for the mucus secretion. Besides, sub- toxic doses of DON were found to reduce intestinal mucin production through a specific decrease in levels of mRNA encoding for the membrane-associated mucins in pigs and poultry. Several mycotoxins are also able to modulate the production of intestinal inflammatory cytokines. For example, intestinal exposure to DON induced a pro-inflammatory response with an increased expression of interleukin (IL)-1α, IL-1β, IL-8, and tumour necrosis factor (TNF)-α.
Interaction between mycotoxins and gut microbiota The gastro-intestinal tract hosts a dynamic microbial popula- tion that forms a complex ecosystem and has a symbiotic re- lationship with the animal host. The intestinal microbiota contributes to several physiological functions such as protec- tive, structural and metabolic functions, regulation of the
Enhanced susceptibility for infectious diseases The negative impact of mycotoxins on the gastro-intestinal physiology and immune system might also enhance the ani- mal susceptibility to common infectious diseases in animal production, such as increasing Salmonella Typhimurium issues in pigs by promoting bacterial invasion, trans-intestinal epi- thelial passage, and the uptake by alveolar macrophages. Ad- ditionally, feeding pigeons a DON contaminated diet resulted in an increased percentage of pigeons shedding Salmonella compared to birds fed control diet, 87% versus 74 %, respec- tively. Furthermore, it was demonstrated that feeding a DON or FUM contaminated diet is a predisposing factor for the de- velopment of Clostridium perfringens induced necrotic enteri- tis in broiler chickens. This coincides with the above-men- tioned negative effects on selected components of the intestinal barrier of the chicken host, i.e. villus height, tight junctions, mucus, oxidative stress, and microbiota homeosta- sis. Recently, it was also demonstrated that DON also influ- ences the infection profile of Campylobacter jejuni in broiler chickens. The co-exposure of DON in poultry feed and C. jejuni resulted in an enhanced C. jejuni colonisation in the gut as well as an increase in gut permeability.
Susceptibility to diseases In conclusion, the omnipresence of mycotoxins in feed represents an important threat for animal health. Even low to moderate amounts of mycotoxins have a negative impact on gut health by inducing leaky gut, intestinal inflammation, and influencing the intestinal microbiota composition. Consequently, the mycotoxin-induced intestinal metabolic, physiologic and immunologic disturbances mean animals are more susceptible to infectious diseases.
References are available on request. ▶ MYCOTOXINS | NOVEMBER 2021 75
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