Mycotoxins and their control: constraints and opportunities (NRI Bulletin 73)

The mycotoxins attract world-wide attention because of the significant economic losses associated with their impact on human health, animal productivity, and both domestic and international trade. It is likely that losses associated with human disease will be particularly significant in those developing countries where food staples, such as groundnuts and maize, are susceptible to contamination. In Mycotoxins and their Control: Constraints and Opportunities a systems approach to the occurrence and control of mycotoxins is adopted, which recognizes the interactions occurring within and between conceptual models of the commodity, spoilage, mycotoxin and control systems. Mycotoxins of 'world-wide', 'regional' and 'future' importance are discussed, together with the metabolic fate of selected mycotoxins, and its exploitation in the development of biomarkers of mycotoxin exposure. Control measures discussed include breeding for resistance, the biocontrol of moulds and the chemical detoxification of contaminated feeds. Future research needs are also identified. This Bulletin will be of special interest to policy makers and researchers and to those involved in the production and utilization of foods and feeds, in human and animal health, and in the international trade of commodities

Macroalgal meadow habitats support fish and fisheries in diverse tropical seascapes

Canopy-forming macroalgae can construct extensive meadow habitats in tropical seascapes occupied by fishes that span a diversity of taxa, life-history stages and ecological roles. Our synthesis assessed whether these tropical macroalgal habitats have unique fish assemblages, provide fish nurseries and support local fisheries. We also applied a meta-analysis of independent surveys across 23 tropical reef locations in 11 countries to examine how macroalgal canopy condition is related to the abundance of macroalgal-associated fishes. Over 627 fish species were documented in tropical macroalgal meadows, with 218 of these taxa exhibiting higher local abundance within this habitat (cf. nearby coral reef) during at least one life-history stage. Major overlap (40%–43%) in local fish species richness among macroalgal and seagrass or coral reef habitats suggest macroalgal meadows may provide an important habitat refuge. Moreover, the prominence of juvenile fishes suggests macroalgal meadows facilitate the triphasic life cycle of many fishes occupying diverse tropical seascapes. Correlations between macroalgal canopy structure and juvenile abundance suggests macroalgal habitat condition can influence levels of replenishment in tropical fish populations, including the majority of macroalgal-associated fishes that are targeted by commercial, subsistence or recreational fisheries. While many macroalgal-associated fishery species are of minor commercial value, their local importance for food and livelihood security can be substantial (e.g. up to 60% of landings in Kenyan reef fisheries). Given that macroalgal canopy condition can vary substantially with sea temperature, there is a high likelihood that climate change will impact macroalgal-associated fish and fisheries

ARCOBACTER BUTZLIERI STRAINS FROM POULTRY ABATTOIR EFFLUENT IN NIGERIA

ABSTRACTObjective:To investigate the prevalence, species distribution and genetic diversity of zoonoticArcobacter species.Design: Prospective study.Setting: Drainage system of a cosmopolitan chicken abattoir in Lagos, Nigeria.Methods : One hundred and fifity drainage water samples were enriched in a minimalantibiotics-containing medium at room temperature and bacteria then isolated by use of amembrane filtration method.Results: Twenty six (14%) of samples were positive for Arcobacter spp. Of these, 20 wereexamined by a comprehensive probabilistic identification scheme for Epsilobacteria and allstrains identified as A. butzleri. AFLP analysis of these strains revealed considerable geneticdiversity among the strains, with 12 genotypes defined at the 90% similarity level.Conclusion: The prevalence of A. butzleri in Nigerian poultry abattoir effluent indicates thisspecies may constitute a public health problem in this country. AFLP profiling could be auseful tool for molecular epidemiological and population genetic studies of this organism.This is the first known report of A. butzleri in Nigeria, and first application of AFLP analysisfor genotyping the species

Evaluation of the ability of different concentrations of aqueous acetone, aqueous methanol and aqueous acetone: Methanol (1∶1) to extract aflatoxin from naturally contaminated maize

A conventional TLC tank was compared with a specially designed continuous linear development chamber for the ether development phase of the quantitation of aflatoxins by bi-directional High Performance Thin Layer Chromatography (HPTLC). No significant difference was detected in the precision of the method. However, the continuous linear development chamber afforded greater accuracy in aflatoxin determination and required only half the development time and a small fraction of the solvent used in the conventional TLC tank. The ability of different concentrations of aqueous acetone, aqueous methanol and aqueous acetone: methanol (1∶1) to extract aflatoxin from naturally contaminated maize was assessed. With each system, the amount of aflatoxin extracted increased as the ratio of organic solvent: water progressed from 50∶50 to 80∶20 and then decreased or remained constant when the composition of the extraction solvent was altered to 90∶10. 80% aqueous acetone was found to extract 27% more aflatoxin than the corresponding aqueous methanol with the mixed solvent system extracting an intermediate amount of toxin. Clean-up of 80% aqueous acetone extracts of maize by elution through phenol (PH) bonded-phase cartridges resulted in poor aflatoxin retention when the proportion of acetone in 5 ml aliquots of extract was greater than 70%. This could be increased to 100% retention by the addition of an equal quantity of methanol prior to dilution with 1% aqueous acetic acid and elution through the cartridge

Absorption, distribution and excretion of aflatoxin-derived ammoniation products in lactating cows

Peanut meal naturally contaminated with 3.5mg/kg aflatoxin B1 (AFB1) was spiked with radiolabelled AFB1 (meal14C-I0) and decontaminated by a smallscale copy of an industrial ammoniation process (meal 14C-I1). During the process 15␘f the radioactivity was lost, whereas 90␘f the remaining radiolabel could not be extracted from the meal. In the extractable part, AFB1 accounted for 10␘f the radiolabel, consistent with a total AFB1 reduction of more than 99ÐNo degradation products were observed in the extracts. Four lactating cows were fed with a diet containing 15␘f either meal 14C-I0 or 14C-I1 for 10 days. On day 9 of this treatment, respectively 23 and 67␘f the radiolabel was excreted in the urine and faeces of cows fed meal 14C-I0, as compared with 2 and 101␒n the case of cows fed meal 14C-I1. Milk contained respectively 1.35 (meal 14C-I0) and 0.25ømeal 14C-I1) of the radiolabel. Milk samples taken during the equilibrium stage contained respectively 5 and 0.5 ng/ml of AFB1-derived compounds. Aflatoxin M1 (AFM1) accounted for 50-80␘f these compounds in the case of milk from cows fed 14C-I0, as compared with 6-20␒n the case of 14C-I1. AFB1 to AFM1 carry-over rates for 14C-I0 or 14C-I1 were estimated to be respectively 0.5 and 5.9ÐOnly liver and kidney samples contained detectable levels of the radiolabel, being respectively 260 and 37 w g/kg for cows fed meal 14C-I0, and 10 and 3 w g/kg for those fed meal 14C-I1. In the latter case, more than 55␘f the radiolabel in the liver could not be extracted, as compared with 90␒n the group fed meal 14C-I1. A small part of the extractable radiolabel in the livers of 14C-I0 could be attributed to AFB1 and cows fed meal AFM1 (less than 1␘f total radioactivity). In the case of the animals fed 14C-I1 there were indications for the presence of AFB1 and AFM1 (6␘f total radioactivity). Decontamination of the highly contaminated (non-radiolabelled) peanut meal by two different industrial ammoniation processes, resulted in a similar reduction of the initial AFB1 levels of 3.5mg/kg to 15 mu g/kg. Feeding of diets containing 15␘f the nontreated and two treated peanut meals to cows for a period of 10 days, resulted in AFM1 levels in milk of respectively 2.1, 0.04 and 0.07 ng/ml. AFB1 to AFM1 carry-over rates were calculated to be respectively 0.5, 2.0, and 3.6ÐIt is concluded that the efficient reduction of aflatoxin levels by ammoniation of contaminated peanut meal results in a strong reduction of aflatoxin-related residues in milk and meat of cows, most likely caused by a decreased bioavailability of the degradation product

Differences detected in vivo between samples of aflatoxin-contaminated peanut meal, following decontamination by two ammonia-based processes

A sample of peanut meal, highly contaminated with aflatoxins, has been subjected to decontamination by two commercial ammonia-based processes. The original contaminated and the two decontaminated meals were fed to rats for 90 days. No lesions associated with aflatoxin-induced hepatocarcinogenesis were detected histologically following feeding with the two detoxified meals. There were, however, clear differences between the two meals in respect of growth rates of the rats. In addition, feeding one of the detoxified meals resulted in hepatic abnormalities detected using novel immunohistochemical reagents. Differences between the two detoxified meals were also indicated by the results of studies using meals 'spiked' with [14C]-aflatoxin B1 prior to being subjected to the detoxification processes. The meals differed in the bioavailability of the label. It was concluded that peanut meal where an initial, unacceptable level of contamination with aflatoxins had been reduced by two ammonia-based processes to comparable, acceptable levels, may still have different effects in vivo when incorporated into animal diets

Genotoxicity testing of extracts from aflatoxin-contaminated peanut meal, following chemical decontamination

One of the most important concerns in the decontamination of aflatoxin-containing feed commodities is the safety of the products for food-producing animals and for human consumption of products derived from these animals. A new method, based on the use of florisil and C18 solid phase extraction columns, was developed for the preparation of extracts from decontaminated peanut meal, which allowed testing with in vitro genotoxicity assays without interference of the residual aflatoxin B1. Recovery of degradation products in the extracts was evaluated by the use of radiolabelled \\[14C]-aflatoxin B1 (AFB1) added to naturallycontaminated peanut meal (3.5mg AFB1/kg). The meal was treated by a small-scale version of an industrial decontamination process based on ammoniation. Following decontamination, more than 90␘f the label could not be extracted from the meal. AFB1 accounted for about 10␘f the radiolabel present in the extractable fraction, indicating a total AFB reduction of more than 99ÐDecontamination of the meal by a number of other small- and industrial-scale ammonia-based processes resulted in similar efficiencies. Application of the extraction procedure resulted in AFB1-rich and AFB1-poor fractions, the latter containing half of the extractable decontamination products but less than 1␘f the residual AFB1. Testing in the Salmonella /microsome mutagenicity assay (TA 100, with S9-mix) of the original crude extracts and AFB1 rich fractions prepared from non-treated and decontaminated meal, showed the positive results expected from the AFB1 contents as determined by HPLC analysis. Analysis and testing of the AFB1-poor fractions showed that the various decontamination processes not only resulted in a successful degradation of AFB1 but also did not produce other potent mutagenic compounds. Slight positive results obtained with these extracts were similar for the untreated and treated meals and may be due to unknown compounds originally present in the meal. Results obtained with an unscheduled DNA synthesis (UDS) and Comet assay with rat hepatocytes supported this conclusion. Positive results obtained with the micronucleus assay, using immortalized mouse hepatocytes (GKB), did not clearly reflect the mycotoxin levels and require further examination. It is concluded that the newly developed extraction procedure yields highly reproducible fractions and hence is very suitable for examining the possible formation of less potent degradation products of aflatoxins in short-term genotoxicity tests