Water availability and temperature are considered the main factors influencing fungal growth and hence mycotoxins formation. A rise in CO2 levels and high variability in weather conditions have also been shown to affect mycotoxin production.
According to the Emerging Risks Unit of the European Food Safety Authority (EFSA), the impact of climate change on food production is considered an emerging hazard for food and feed security worldwide. One key aspect in food and feed safety is the changing pattern of mycotoxin contamination in cereals such as wheat, maize and rice due to climate change. The 2014 Intergovernmental Panel on Climate Change (IPCC) report predicts that global temperatures may increase by up to 4.8°C in the year 2100. The distribution of species around the world is expected to undergo an overall shift polewards. For instance, plant pathogens and pests are moving at a rate of about 2.7 km/year towards the poles.
Shifts in mycotoxin profiles
Aspergillus flavus and A. parasiticus, the main aflatoxin producers, favour high temperatures and low rainfall. During the hot and dry episodes in northern Italy in 2003, A. flavus actively colonised the ripening maize by outcompeting the more common Fusarium species, which resulted in an uncommon increase in aflatoxin B1 contamination in Europe. Fumonisin occurrence is generally correlated with drought stress and even grains that appear to be of very good quality can contain high levels of this toxin. The role of fumonsins is much lower in northern temperate zones with cooler climates. High temperatures favour the growth of the main fumonisin producer Fusarium verticillioides. Consequently, a warming trend may lead to greater domination of the fungus compared to other maize-borne Fusarium species.
The displacement of the formerly predominant species, F. culmorum and Microdochium nivale, by the more virulent plant pathogen F. graminearum has been observed as a result of warmer European summers. M. nivale is non-toxigenic and F. culmorum generally produces a lower number of mycotoxins than F. graminearum. This means that the concentrations of mycotoxins may increase accordingly. Such shifts in mycotoxigenic fungi may also lead to changes in the mycotoxin chemical profile.
Factors for fungal colonisation
Climate change is projected to increase the biomass of crops. Also, alternative host plants may further increase inoculum production. An increase in atmospheric CO2 concentration has been shown to directly increase the amounts of Fusarium Head Blight (FHB) and Crown Rot (CR) inoculum. A deterioration of grain quality may occur as a direct effect of increasing temperature and CO2 which may favour mold growth. Water availability is expected to be altered by climate change as some areas experience drought and others, greater precipitation. The effects of humidity on mycotoxin production in crops are less clear than those for temperature. In a post-harvest setting, an increase in condensation can lead to spoilage which may increase contamination with mycotoxins such as ochratoxin A, aflatoxins and perhaps trichothecenes in damp grain. The distributions and types of mycotoxins post-harvest might change significantly, giving way to new, emerging mycotoxins.
Trends in multi-mycotoxin occurrence
As part of its mycotoxin risk management programme, Biomin has been conducting a yearly Mycotoxin Survey since 2004 which provides insight into the risks caused by the main mycotoxins found in agricultural commodities such as corn, wheat, barley and silage, as well as finished feed and others. From January to September 2014, more than 3000 samples from different countries around the world were evaluated for the presence of aflatoxins (Afla), zearalenone (ZEN), deoxynivalenol (DON), fumonisins (FUM) and ochratoxin A (OTA). The Biomin Mycotoxin Survey summarises the importance of the co-occurrence of various mycotoxins in the different samples. The Mycotoxin Survey has now expanded its horizons with the implementation of the Spectrum 380®, a method based on Liquid Chromatography coupled with tandem Mass Spectrometry (LC-MS/MS). This state-of-the-art technique, developed at the hot-spot for mycotoxins research at the Department of Agrobiotechnology (IFA), Austria, enables the detection of more than 380 mycotoxins and other secondary metabolites at one go, providing the most comprehensive results on global mycotoxin contamination (Malachová et al., 2014).
This unique method not only includes the most commonly found mycotoxins but also allows the detection of other lesser known metabolites to provide a full picture of the toxic load in a sample. Part of the Mycotoxin Survey, a total of 537 samples (raw materials like corn and wheat, as well as finished feed) were collected worldwide from the current harvest season and screened for the presence of multiple mycotoxins and other secondary metabolites using the Spectrum 380®.
Figure 1 shows the number of samples found to be co-contaminated with two to 24 different mycotoxins. On average, 30 different metabolites were detected per sample. These results clearly indicate that mycotoxins are a topic of concern in animal feed.
Most common mycotoxins
Emodin, beauvericin and enniatins were the most common groups of mycotoxins found in over 80% of all samples (Table 1). The European Food Safety Authority (EFSA) evaluated the occurrence data of enniatins and beauvericin and recently published a scientific opinion on these toxins as a concern for food and feed (EFSA, 2014). ZEN was found in 74% (average 50 ppb; max. 3,800ppb) of all samples. Another emerging mycotoxin present in a large number of soy samples (68%) was moniliformin. Data on the effects of this substance on mammalian species is still scarce. However, the European Mycotoxin Awareness Network (EMAN) has described the natural occurrence of moniliformin in various products such as wheat, rye, rice and corn. 60% of the analysed samples tested positive for DON and 75% of samples for total B-trichothecenes (Table 2). The masked mycotoxin DON-3-glucoside was detected in 47% of all samples. Fumonisins were detected in 44% of the samples at an average of 1,286 µg/kg, a level that poses a high risk to piglets, sows and horses, which show the highest sensitivity to this substance. Although aflatoxins were present in only 9% of all samples, the average of these samples was 37 µg/kg, a level that may pose a threat to several livestock animals. Mixtures of different Fusarium mycotoxins were the most frequently detected and constitute 48% of all metabolites detected in total. Similar results were shown by Streit et al. (2013) who surveyed multi-mycotoxin occurrences in more than 80 different samples from all over the world. Aspergillus toxins (including aflatoxins) and Penicillium toxins were detected in 12% of all samples respectively.
Food safety is indisputably linked to a complex net of different factors and would be incomplete without taking into account the effects caused by climate changes. Shifts in mycotoxin profiles are being observed and it seems that environmental changes are giving way to new, emerging mycotoxins. An important advantage of multi-mycotoxin analysis is the detection of normally undetected masked mycotoxins. Performing multi-mycotoxin analysis also allows the evaluation of the occurrence of emerging mycotoxins which are not commonly measured such as beauvericin and enniatins. The effects of such mycotoxins on health and performance of humans and animals still need to be elucidated. Constant monitoring and continual research on the prevention and mitigation of mycotoxin contamination are therefore necessary. The first steps towards preventing the negative effects of these harmful substances are the implementation of good agricultural practices and proper storage conditions.
References are available upon request.
[Source: Managing mycotoxins, 2014]