Aspergilli and aflatoxin B in finished feed for farmed Nile tilapia

In aquaculture, Aflatoxins are the most recorded between all mycotoxins. It seems to be particularly prone to deposition in several fish tissues representing a risk for human consumption. Aspergillus flavus is the major producer of aflatoxin that commonly contaminates food and feed all over the world. A total of 57 finished fish feed samples were collected from feed factories in Cairo, Dakahlia and Kafr El Sheikh governorates, Egypt. Twenty nine fungal isolates belonging to four species were recovered from the collected feedstock. A. flavus was the most frequently isolated species (29.82%) compared with the other fungal species which include: A. parasiticus (12.28%), F. oxysporum (7.01%) and F. sporotrichioides (1.75%).Mycotoxin profile was determined using high performance liquid chromatography, Aflatoxins were detected in the culture filtrate of only 4 isolates of A. flavus out of the 17 examined these four isolates were deposited under the strain codes: AUMC 13909, AUMC 13910, AUMC 13911 and AUMC 13917. A. flavus strain AUMC13917 can produce both aflatoxins B1 (1.016 µg /L) and B2 (0.314 µg /L). while, the remaining three isolates AUMC13909, AUMC 13910 & AUMC 13911 were able to produce only aflatoxin B1 (8.082 µg/L, 1.617 µg/L & 0.141µg/L, respectively). Naturally occurring aflatoxin B1 was also detected in 4 samples of fish feed and a single sample was contaminated with aflatoxin B2. Aflatoxin B1 was the prevalent mycotoxin within the collected feed samples, which is the most toxic aflatoxin chemotype. Yield of this aflatoxin differed between A. flavus strains and concentrations ranged from 0.106 to 11.546 mg/kg. The levels of aflatoxin detected in this study point to possible potential risks to fish health, performance and to aquaculture future investment.