Mycotoxins are still a significant challenge that silently affects animal health and, consequently, human health. Therefore, it is crucial to control feed contamination, since mycotoxins are present at the initial stage of the food chain. The European Union has established regulatory levels for aflatoxin B1 (AFB1) and provided recommendations for zearalenone (ZEN), ochratoxin A (OTA), deoxynivalenol (DON), fumonisin B1 and B2 (FB1 and FB2), the T-2 toxin and HT-2 for raw materials and feed. Exposure to these toxins (prevalent mycotoxins) can lead to various diseases, and the European Food Safety Authority (EFSA) has published different opinions on the risk to animal health related to the presence of different mycotoxins.
In the 1980s, it was observed that diseases caused by mycotoxins in animals were not directly related to the content of mycotoxins found in the diet, which suggested that prevalent mycotoxins were not the main source of exposure. This new discovery opened the doors to what we now call modified mycotoxins and emerging mycotoxins (Kovaslky et al., 2016).
Modified mycotoxins are metabolites from the most prevalent mycotoxins that can be classified according to whether the modification of the original mycotoxin has been through a chemical or biological reaction.
The main source of modified mycotoxins is related to the metabolism of plants and fungi. Plants can generate modified mycotoxins as a defense response to the fungus that produces the original mycotoxin. A second source of these compounds is related to the metabolism of animals and the processing of feed and food.
The most commonly detected mycotoxins belong to the fusariotoxins family (DON, ZEA, HT-2, Nivalenol (NIV) and fumonisins) bound to glucose or sulfate complexes (DON3G, NIV3Glc, HT2Glc, ZEA14G, ZEA14S, etc.). Furthermore, these bindings can be reversible, meaning that a prevalent mycotoxin can be modified, and a modified mycotoxin can break down and release the prevalent mycotoxin.
Due to the aforementioned factors, the modified mycotoxins present a great analytical challenge. They are not easily detectable due to their similarity in chemical structure with the prevalent mycotoxins and due to the lack of methodology for their determination in routine method.
The term “emerging mycotoxins” refers to a new group of chemically diverse toxins, which are not routinely determined and for which there is no regulation or legislative recommendation. Mainly, the emerging mycotoxins are metabolites of the mycotoxins produced by the fungus belonging to the genus Fusarium, such as enniatins (ENN), beauveracin (BEA), moniliformin (MON) and fusaproliferin (FUS).
The analytical complexity of emerging and modified mycotoxins makes their investigation difficult
Although more emerging and modified mycotoxins are being discovered today, studies dedicated to these types of mycotoxins are scarce, as the development of analytical methods for their quantification is restricted by the lack of standards and certified reference materials. Consequently, determining their presence is a complex challenge, considering their high occurrence in raw materials and feed.
In fact, climate change and the increase in cereal prices are factors that contribute to the production of these mycotoxins. On the one hand, fungi may alter their behavior and production to adapt to the new environmental conditions. On the other hand, the increased cost of cereals has led to the utilization of their by-products, which could increase the concentration of mycotoxins as they are not affected by the physical and/or chemical processes developed.
In this context, ongoing research is being conducted to investigate the toxicological properties of these mycotoxins, aiming to assess the risks they pose to animals (Berthiller, 2013; Nowak et al., 2021).
Regarding modified mycotoxins, their toxicity often coincides with the toxicity of their parent mycotoxin. However, it is important to consider that the digestion process in the gastrointestinal tract or the metabolization in the blood or organs, such as the liver, can contribute to a high level of unexpected toxicity. Therefore, the physiological properties of each animal species play a crucial role in determining the toxicity of modified mycotoxins. However, the available information on this topic is currently limited.
In the same way, in the case of emerging mycotoxins, in vitro induction of oxidative stress has been observed. However, more data is required to support the present in vivo studies that have reported immune dysfunction and damage to the intestinal barrier.
Therefore, it is necessary to be aware of the existence of modified and emerging mycotoxins since, although it has already been commented that there are not many available studies and the associated limitations, their global presence is considerable and should not be underestimated.
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