Mycotoxins in SE Asia aquaculture: A neglected threat?  

Mycotoxins, and their effect in aquaculture species, have been a recognized threat since 1960, where aflatoxin-contaminated cottonseed meal caused an outbreak of aflatoxicosis in hatchery-reared rainbow trout (Oncorhynchus mykiss). Concern about mycotoxins in aquaculture has been growing, partly due to the gradual replacement of animal-derived proteins, such as fish meal, by plant proteins. According to Tacon et al., (2011), plant-based feedstuffs represent the major dietary protein source used within feeds for lower trophic level fish species like tilapia, carp or catfish, and the second major source of dietary protein and lipids after fishmeal and fish oil for shrimp and European high trophic level fish species.

Over a period of three years (January 2014-December 2016), 68 samples of finished aquaculture feed (FF) for both shrimp and fish, were analyzed within the scope of the BIOMIN Mycotoxin Survey program. All samples were sourced in SE Asia. In 2014 and 2015 the samples were tested for aflatoxins (AF, sum of AFB1, AFB2, AFG1 and AFG2), zearalenone (ZEN), deoxynivalenol (DON), fumonisins (FB, sum of FB1 and FB2) and ochratoxin A. In 2016, beside the previous mycotoxins there were also analyzed metabolites and masked mycotoxins, in total 18 mycotoxins were analyzed (e.g. nivalenol; 3-acetyldeoxynivalenol; 15-acetyldeoxynivalenol and fusarenon X-glucosid).

DON and AF were the most prevalent mycotoxins for 2014, with 68% of the samples testing positive, followed by ZEN and FB (58% positive). In 2015 we saw a shift, with FB1 as the most prevalent mycotoxin followed by ZEN and DON. Concerning the average contamination levels, a decrease was observed for the 2015 samples. However when looking to the mycotoxin co-occurrence, the percentage of samples containing more than 1 mycotoxin increased from 84% to 90%, which raised the risk of synergistic effects of mycotoxins. In 2016 with the increased mycotoxin screen and differentiated analysis between fish and shrimp feeds, it was observed that fish and shrimp feeds present a different mycotoxin contamination pattern. Fish samples were mainly contaminated by FB1 while shrimp feeds were contaminated mainly by DON. The present study shows an increase in mycotoxin contamination from 2014 to 2016. Registered contamination values, especially for 2016 are within the sensitivity level of several important Asian Aquaculture species.