When food or feed crops are stored in hot, humid conditions, fungi that live on them can produce mycotoxins that threaten human and animal health. Even minute quantities of mycotoxins can cause disease. For example, aflatoxins are potent carcinogens, ochratoxin has been implicated in kidney disease, and zearalenone is an estrogen mimic that can cause infertility or miscarriage. Deoxynivalenol is a threat to livestock because when it is present in feed, the livestock fail to gain weight.
The European Commission sets strict maximum limits on mycotoxin concentrations in crops used for food or feed in Europe. However, the regulations never mention insects or insect feed. Edible insects are a promising emerging crop because they produce protein more efficiently and with less pollution than larger livestock animals. The European legal limit of mycotoxins in edible insects is not clear.
Recently, Camenzuli et al. set out to clarify the safety of mycotoxin exposure in edible insects. They studied two promising food insect species, the lesser mealworm (Alphitobius diaperinus) and the black soldier fly (Hermetia illucens). The researchers spiked larvae feed with aflatoxin B1, deoxynivalenol, ochratoxin A and zearalenone at 1, 10 and 25 times the limit allowed for livestock feed. They found no effect on the survival or weight gain for either species, except for lesser mealworms given the highest level of ochratoxin A, which gained less weight.
Camenzuli et al. also tested for accumulation of the mycotoxins in the larvae. They could not detect any of the mycotoxins in the lesser mealworms, even when given the highest doses. In the black soldier fly, they could not detect mycotoxins when larvae were given low doses, and found only minute quantities of deoxynivalenol, zearalenone, and ochratoxin at the highest doses.
The metabolites of mycotoxins might also pose a threat to human or livestock health. For example, the zearalenone metabolite α-zearalenol is a more potent estrogen mimic than zearalenone itself. To account for this, the researchers tested for the accumulation of aflatoxicol, aflatoxin P1, aflatoxin Q1, aflatoxin M1, 3-acetyl-DON, 15-acetyl-DON, DON-3-glycoside, and α- and β-zearalenol in the larvae. None of the mycotoxin metabolites were detectable in the lesser mealworms. In the black soldier fly larvae, aflatoxin and deoxynivalenol metabolites were undetectable. Low concentrations of α- and β-zearalenol were found in the black soldier fly larvae at all doses.
Camenzuli et al. concluded that food source insects might be able to tolerate higher concentrations of mycotoxins in their feed than other livestock, but more research is needed.
Full list of available mycotoxins
Camenzuli L, Van Dam R, Rijk T, Andriessen R, Van Schelt J, Van der Fels-Klerx HJ. Tolerance and Excretion of the Mycotoxins Aflatoxin B1, Zearalenone, Deoxynivalenol, and Ochratoxin A by Alphitobius diaperinus and Hermetia illucens from Contaminated Substrates. Toxins 2018, 10, 91; doi:10.3390/toxins10020091