Joseph Atehnkeng

Distribution and toxigenicity of Aspergillus species isolated from maize kernels from three agro-ecological zones in Nigeria

Maize samples were collected during a survey in three agro-ecological zones in Nigeria to determine the distribution and aflatoxin-producing potential of members of Aspergillus section Flavi. The three agro-ecological zones were, Derived Savannah (DS) and Southern Guinea Savannah (SGS) in the humid south and North Guinea Savannah (NGS) in the drier north. Across agro-ecological zones, Aspergillus was the most predominant fungal genera identified followed by Fusarium with mean incidences of 70 and 24%, respectively. Among Aspergillus, A. flavus was the most predominant and L-strains constituted >90% of the species identified, while the frequency of the unnamed taxon S(BG) was <3%. The incidence of atoxigenic strains of A. flavus was higher in all the districts surveyed except in the Ogbomosho and Mokwa districts in DS and SGS zones, respectively, where frequency of toxigenic strains were significantly (P<0.05) higher than that of atoxigenic strains. The highest and lowest incidence of aflatoxin positive samples was recorded in the SGS (72%) and NGS (20%), respectively. Aflatoxin contamination in grain also followed a similar trend and the highest mean levels of B-aflatoxins were detected in maize samples obtained from Bida (612 ng g(-1)) and Mokwa (169 ng g(-1)) districts, respectively, in the SGS. Similarly, the highest concentrations of G-aflatoxins were detected in samples from Akwanga district in the SGS with a mean of 193 and 60 ng g(-1), respectively. When agro-ecological zones were compared, B-aflatoxins were significantly (P<0.05) higher in SGS than in NGS, and intermediate in maize samples from the DS agro-ecological zone.

Quantitation of Mycotoxins in Food and Feed from Burkina Faso and Mozambique Using a Modern LC-MS/MS Multitoxin Method

In this study an LC-MS/MS multitoxin method covering a total of 247 fungal and bacterial metabolites was applied to the analysis of different foods and feedstuffs from Burkina Faso and Mozambique. Overall, 63 metabolites were determined in 122 samples of mainly maize and groundnuts and a few samples of sorghum, millet, rice, wheat, soy, dried fruits, other processed foods and animal feeds. Aflatoxin B(1) was observed more frequently in maize (Burkina Faso, 50% incidence, median = 23.6 μg/kg; Mozambique, 46% incidence, median = 69.9 μg/kg) than in groundnuts (Burkina Faso, 22% incidence, median = 10.5 μg/kg; Mozambique, 14% incidence, median = 3.4 μg/kg). Fumonisin B(1) concentrations in maize were higher in Mozambique (92% incidence, median = 869 μg/kg) than in Burkina Faso (81% incidence, median = 269 μg/kg). In addition, ochratoxin A, zearalenone, deoxynivalenol, nivalenol, and other less reported mycotoxins such as citrinin, alternariol, cyclopiazonic acid, sterigmatocystin, moniliformin, beauvericin, and enniatins were detected. Up to 28 toxic fungal metabolites were quantitated in a single sample, emphasizing the great variety of mycotoxin coexposure. Most mycotoxins have not been reported before in either country.

Evaluation of atoxigenic isolates of Aspergillus flavus as potential biocontrol agents for aflatoxin in maize

Aflatoxin contamination resulting from maize infection by Aspergillus flavus is both an economic and a public health concern. Therefore, strategies for controlling aflatoxin contamination in maize are being investigated. The abilities of eleven naturally occurring atoxigenic isolates in Nigeria to reduce aflatoxin contamination in maize were evaluated in grain competition experiments and in field studies during the 2005 and 2006 growing seasons. Treatments consisted of inoculation of either grains in vials or ears at mid-silking stage in field plots, with the toxigenic isolate (La3228) or atoxigenic isolate alone and co-inoculation of each atoxigenic isolate and La3328. Aflatoxin B1 + B2 concentrations were significantly (p < 0.05) lower in the co-inoculation treatments compared with the treatment in which the aflatoxin-producing isolate La3228 was inoculated alone. Relative levels of aflatoxin B1 + B2 reduction ranged from 70.1% to 99.9%. Among the atoxigenics, two isolates from Lafia, La3279 and La3303, were most effective at reducing aflatoxin B1 + B2 concentrations in both laboratory and field trials. These two isolates have potential value as agents for the biocontrol of aflatoxin contamination in maize. Because these isolates are endemic to West Africa, they are both more likely than introduced isolates to be well adapted to West African environments and to meet regulatory concerns over their use throughout that region.

Mycotoxin exposure in rural residents in northern Nigeria: a pilot study using multi-urinary biomarkers.

A pilot, cross-sectional, correlational study was conducted in eight rural communities in northern Nigeria to investigate mycotoxin exposures in 120 volunteers (19 children, 20 adolescents and 81 adults) using a modern LC-MS/MS based multi-biomarker approach. First morning urine samples were analyzed and urinary biomarker levels correlated with mycotoxin levels in foods consumed the day before urine collection. A total of eight analytes were detected in 61/120 (50.8%) of studied urine samples, with ochratoxin A, aflatoxin M1 and fumonisin B1 being the most frequently occurring biomarkers of exposure. These mycotoxin biomarkers were present in samples from all age categories, suggestive of chronic (lifetime) exposures. Rough estimates of mycotoxin intake suggested some exposures were higher than the tolerable daily intake. Overall, rural consumer populations from Nasarawa were more exposed to several mixtures of mycotoxins in their diets relative to those from Kaduna as shown by food and urine biomarker data. This study has shown that mycotoxin co-exposure may be a major public health challenge in rural Nigeria; this calls for urgent intervention.

Molecular characterization of atoxigenic strains for biological control of aflatoxins in Nigeria

Aflatoxins are highly toxic carcinogens produced by several species in Aspergillus section Flavi. Strains of A. flavus that do not produce aflatoxins, called atoxigenic strains, have been used commercially in North America as tools for limiting aflatoxin contamination. A similar aflatoxin management strategy is being pursued in Nigeria. In the current study, loci across the 68 kb aflatoxin biosynthesis gene cluster were compared among 18 atoxigenic and two aflatoxin-producing vegetative compatibility groups (VCGs) from Nigeria and an atoxigenic VCG used commercially in North America. Five of the atoxigenic VCGs had large deletions (37–65 kb) extending from the teleomeric side of the aflatoxin biosynthesis cluster. In one VCG (AV0222) the deletion extended through the cluster to the adjacent sugar cluster. The remaining twelve atoxigenic VCGs, including the VCG used for aflatoxin management in North America, contained all the aflatoxin pathway genes, but with defects. Two observations support the long-term persistence of atoxigenicity within A. flavus: first, a comparison of pathway genes revealed more changes in atoxigenic than in aflatoxin-producing isolates relative to the aflatoxin-producing strain NRRL 3357; and second, several non-synonymous changes are unique to atoxigenics. Atoxigenic VCG diversity was assessed with phylogenetic analyses. Although some atoxigenics share relatively recent ancestry, several are more closely related to aflatoxin producers than to other atoxigenics. The current study demonstrates VCGs of A. flavus in West Africa with diverse mechanisms of atoxigenicity and potential value in aflatoxin management programmes.

Biological control of aflatoxins in Africa: current status and potential challenges in the face of climate change

Bill & Melinda Gates Foundation (BMGF); United States Agency for International Development (USAID); Bundesministerium fur wirtschaftliche Zusammenarbeit und Entwicklung (BMZ, German Federal Ministry for Economic Cooperation and Development); AgResults; MycoRed; CGIAR A4NH Research Program; CGIAR MAIZE Research Program; Meridian Institute on behalf of the Partnership for Aflatoxin Control in Africa (PACA); United States Department of Agriculture - Foreign Agricultural Service; Austrian Development Cooperation; Commercial Agriculture Development Program of the Government of Nigeria

Distribution of aflatoxigenic Aspergillus section Flavi in commercial poultry feed in Nigeria.

The distribution and aflatoxigenicity of Aspergillus section Flavi isolates in 58 commercial poultry feed samples obtained from 17 states in five agro-ecological zones (AEZs) in Nigeria were determined in order to assess the safety of the feeds with respect to aflatoxin-producing fungi. Correlation was also performed for incidence of species, aflatoxin-producing ability of isolates in vitro, and aflatoxin (AFB1) concentrations in the feed. A total of 1006 Aspergillus section Flavi isolates were obtained from 87.9% of the feed samples and identified as Aspergillus flavus, unnamed taxon SBG, Aspergillus parasiticus and Aspergillus tamarii. A. flavus was the most prevalent (91.8%) of the isolates obtained from the feed in the AEZs while A. parasiticus had the lowest incidence (0.1%) and was isolated only from a layer mash sample collected from the DS zone. About 29% of the Aspergillus isolates produced aflatoxins in maize grains at concentrations up to 440,500μg/kg B and 341,000μg/kgG aflatoxins. The incidence of toxigenic isolates was highest (44.4%) in chick mash and lowest (19.9%) in grower mash. The population of A. flavus in the feed had positive (r=0.50) but non significant (p>0.05) correlations with proportion of toxigenic isolates obtained from the feed while SBG had significant (p<0.001) positive (r=0.99) influence on AFB1 concentrations in the feed. Poultry feed in Nigerian markets are therefore highly contaminated with aflatoxigenic Aspergillus species and consequently, aflatoxins. This is a potential threat to the poultry industry and requires urgent intervention.

An Assessment of Willingness To Pay by Maize and Groundnut Farmers for Aflatoxin Biocontrol Product in Northern Nigeria

In Nigeria, Aflasafe is a registered biological product for reducing aflatoxin infestation of crops from the field to storage, making the crops safer for consumption. The important questions are whether farmers will purchase and apply this product to reduce aflatoxin contamination of crops, and if so under what conditions. A study was carried out to address these questions and assess determinants of willingness to pay (WTP) for the product among maize and groundnut farmers in Kano and Kaduna states in Nigeria. A multistage sampling technique was used to collect primary data from 492 farmers. The majority of farmers who had direct experience with Aflasafe (experienced farmers) in Kano (80.7%) and Kaduna (84.3%) had a WTP bid value equal to or greater than the threshold price (

Technical innovations for small-scale producers and households to process wet cassava peels into high quality animal feed ingredients and aflasafe™ substrate

10) at which Aflasafe was to be sold. The mean WTP estimates for Aflasafe for experienced farmers in Kano and Kaduna were statistically the same. However, values of

Seasonal and geographical differences in aflatoxin exposures in Senegal

3.56 and