Impact of Aspergillus section Flavi community structure on the development of lethal levels of aflatoxins in Kenyan maize (Zea mays)

Aims: To evaluate the potential role of fungal community structure in predisposing Kenyan maize to severe aflatoxin contamination by contrasting aflatoxin‐producing fungi resident in the region with repeated outbreaks of lethal aflatoxicosis to those in regions without a history of aflatoxicosis. Methods and Results: Fungi belonging to Aspergillus section Flavi were isolated from maize samples from three Kenyan provinces between 2004 and 2006. Frequencies of identified strains and aflatoxin‐producing abilities were assessed, and the data were analysed by statistical means. Most aflatoxin‐producing fungi belonged to Aspergillus flavus. The two major morphotypes of A. flavus varied greatly between provinces, with the S strain dominant in both soil and maize within aflatoxicosis outbreak regions and the L strain dominant in nonoutbreak regions. Conclusions: Aspergillus community structure is an important factor in the development of aflatoxins in maize in Kenya and, as such, is a major contributor to the development of aflatoxicosis in the Eastern Province. Significance and Impact of the Study: Since 1982, deaths caused by aflatoxin‐contaminated maize have repeatedly occurred in the Eastern Province of Kenya. The current study characterized an unusual fungal community structure associated with the lethal contamination events. The results will be helpful in developing aflatoxin management practices to prevent future outbreaks in Kenya.     

Aflatoxins in aquatic species: metabolism,toxicity and perspectives

Among all known mycotoxins, aflatoxins represent the most investigated, widespread and worrisome source of contamination of foods and feed worldwide. In the early 1960s, soon after the finding of aflatoxin B₁ (AFB₁) in the feedstuffs of aquacultured rainbow trout that had died in an epizootic of hepatomas, great scientific discoveries were made in several areas by a number of researchers under the direction of scientists like J. Halver, R. 0. Sinnhuber, G. S. Bailey, J. D. Hendricks and colleagues. Since that time, several studies have focused on the identification of new isoenzymes involved in AFB₁ metabolism and on the discovery of new modulators in AFB₁-induced cancer initiation and progression. However, metabolic and toxicological studies on aflatoxins in marine aquacultured species are fragmented and restricted to a limited number of fish species. Aflatoxins exert a substantial impact on the fish farming production, causing disease with high mortality and a gradual decline of reared fish stock quality, thus representing a significant problem in aquaculture systems. Based on these considerations, the goals of this review article are: (1) to gather the currently available scientific information, summarising existing data on aflatoxin contamination on feeds and fishmeals, and toxicological effects induced in reared aquatic species; (2) to make a comparative analysis of AFB₁ metabolism in the most representative species studied; (3) to gain new insights on the risk of DNA damage caused by aflatoxins on fish genomes and their role in cancer development.     

Acute effect of aflatoxin B1 on different inbred mouse strains II

The acute effects of Aflatoxin B₁(AFB₁) were evaluated on C57B1/6, CBA/J, B10A and Balb/c mice challenged with a single intraperitoneal dose of the mycotoxin (60 mg/Kg animal weight). 90 mice per strain were divided into three groups of 30 animals each: the intoxicated group and control groups I and II. Intoxicated mice were injected intraperitonealy with AFB₁ dissolved in corn oil, while control I mice received corn oil only (0.01 ml/g) by the same route. Lots of 10 animals from the intoxicated and control groups were sacrificed 24, 72 and 168 hours after challenge. Control mice II remained untreated and were used as standards of normality for biochemical (hepatic and renal function) and hematological evaluation. AFB₁ was detected in the liver of C57B1/6 and CBA/J mice 24 hours (1.46 and 0.75 ng/g, respectively), 72 hours (2.30 and 0.08 ng/g, respectively), and 168 hours (2.18 and 0.25 ng/g, respectively) after challenge. The mycotoxin was also observed in the liver of B10A mice (6.20 ng/g) 72 hours post-injection. The most evident histological lesions were observed 168 hours after treatment in C57B1/6 and B10A mice. Serum levels of alkaline phosphatase in intoxicated C57B1/6 and B10A mice were significantly higher than those of control I and II animals. The histopathologic lesions and biochemical changes were very discrete in Balb/c and CBA/J mice. It is included that strains C57B1/6 and B10A are more susceptible than strains CBA/J and Balb/c to the acute effects of AFB₁. Such difference probably reflects each strains's ability to biotransform and eliminate AFB₁ and its metabolites.     

Genotypic variability in maize for aflatoxin contamination

A total of 60 maize genotype samples from different agroclimatic regions of India were collected. Fresh harvest of these maize samples comprising some commercial maize genotypes and some land races were kept under ambient storage conditions for 9 months duration at grain moisture ranges from 14% to 10.5% with a view to identifying the least contaminated maize genotype with aflatoxin. The purpose of this study was to identify the maize genotypes which can survive in ambient storage conditions with minimum spoilage. The response of various maize genotypes for AFB₁ accumulation was variable in similar storage conditions. Promising genotypes which showed lower accumulation of AFB₁ were identified: Shaktiman-1 (A QPM variety) by showing the lowest concentration of AFB₁ (0.30 ppb) followed by KMH-1701 (0.40 ppb); HQPM-1 (0.50 ppb); and QPM-2-136 (0.60 ppb), whereas the most highly toxic sample was Mon - 4 (62.42 ppb) at grain moisture ranges from 12.6 to 11.1%. During the study it has been observed that Shaktiman-1 and other QPM genotypes showed minimum levels of AFB₁. Further, it was confirmed by western blot analysis by comparing the resistant and susceptible genotype under artificially inoculated grains with Aspergillus flavus and uninoculated maize grains. It was observed that more chitinase activity was found in shaktiman-1, when the grains were artificially inoculated with A. flavus. The thickness of the seed coat and Aleuron layer was maximum in (90–100 μm) in Shaktiman compared to that of Pro-311 (80–85 μm). It was observed that the thickness of seed coat may act as a barrier for mold contamination and as a result the storage spoilage is minimised.