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Wheat is a source of nutrients for around 40% world’s population and the second most important cereal crop in Kenya. However, Fusarium head blight (FHB) hinders sustainable sufficient production of the crop, causing both economic and health losses. With the emerging unfavorable climatic changes, effective disease management strategies and adequate seed system are necessary to meet the deficiency. Current information on prevalence of the causative pathogens in varieties of wheat genotypes is a critical prerequisite to such strategies. This study aimed at determining the prevalence of pathogenic Fusarium species in seeds of developed varieties of wheat genotypes in three major wheat-producing regions in Kenya. A total of 260 samples of 18 wheat genotypes from 123 farms were collected. Peptone pentachloronitrobenze agar was used for fungal isolation, while identification of Fusarium spp. was based on the gene encoding translation elongation factor 1-α (tef1-alpha) sequence analysis. Fusarium spp. isolated include Fusarium poae, F. tricinctum, F. heterosporum, F. culmorum, F. equiseti, Fusarium sp., F. verticillioides, and F. oxysporum. There was no significant difference in prevalence of Fusarium spp. pathogens among the three regions studied. Fusarium spp. diversity index for Nakuru was 2.008, Narok was 1.4603, and Uasin Gishu was 1.2337. Wheat produce from farm-saved seeds yielded 66.25% of the isolates, while the produce from certified commercial wheat seeds yielded 33.75% of the isolates. The significant finding of the study is that Fusarium spp. associated with mycotoxins that contaminate the wheat food chain seem to be flourishing in all the sampled wheat seed genotypes from the regions studied. Information on the prevalence and diversity of the pathogens on persistence of the disease in the crop is critical in advancing integrative FHB control measures.
Otieno P. Kheseli; Imbahale S. Susan; Okoth Sheila; Miriam Otipa; Wekesa V. Wafula. Prevalence and Phylogenetic Diversity of Pathogenic Fusarium Species in Genotypes of Wheat Seeds in Three Rift Valley Regions, Kenya. Advances in Agriculture 2021, 2021, 1 -13.
AMA StyleOtieno P. Kheseli, Imbahale S. Susan, Okoth Sheila, Miriam Otipa, Wekesa V. Wafula. Prevalence and Phylogenetic Diversity of Pathogenic Fusarium Species in Genotypes of Wheat Seeds in Three Rift Valley Regions, Kenya. Advances in Agriculture. 2021; 2021 ():1-13.
Chicago/Turabian StyleOtieno P. Kheseli; Imbahale S. Susan; Okoth Sheila; Miriam Otipa; Wekesa V. Wafula. 2021. "Prevalence and Phylogenetic Diversity of Pathogenic Fusarium Species in Genotypes of Wheat Seeds in Three Rift Valley Regions, Kenya." Advances in Agriculture 2021, no. : 1-13.
Mycotoxins are common in grains in sub-Saharan Africa and negatively impact human and animal health and production. This study assessed occurrences of mycotoxins, some plant, and bacterial metabolites in 16 dairy and 27 poultry feeds, and 24 feed ingredients from Machakos town, Kenya, in February and August 2019. We analyzed the samples using a validated multi-toxin liquid chromatography-tandem mass spectrometry method. A total of 153 mycotoxins, plant, and bacterial toxins, were detected in the samples. All the samples were co-contaminated with 21 to 116 different mycotoxins and/or metabolites. The commonly occurring and EU regulated mycotoxins reported were; aflatoxins (AFs) (70%; range 0.2–318.5 μg/kg), deoxynivalenol (82%; range 22.2–1037 μg/kg), ergot alkaloids (70%; range 0.4–285.7 μg/kg), fumonisins (90%; range 32.4–14,346 μg/kg), HT-2 toxin (3%; range 11.9–13.8 μg/kg), ochratoxin A (24%; range 1.1–24.3 μg/kg), T-2 toxin (4%; range 2.7–5.2 μg/kg) and zearalenone (94%; range 0.3–910.4 μg/kg). Other unregulated emerging mycotoxins and metabolites including Alternaria toxins, Aspergillus toxins, bacterial metabolites, cytochalasins, depsipeptides, Fusarium metabolites, metabolites from other fungi, Penicillium toxins, phytoestrogens, plant metabolites, and unspecific metabolites were also detected at varying levels. Except for total AFs, where the average contamination level was above the EU regulatory limit, all the other mycotoxins detected had average contamination levels below the limits. Ninety-six percent of all the samples were contaminated with more than one of the EU regulated mycotoxins. These co-occurrences may cause synergistic and additive health effects thereby hindering the growth of the Kenyan livestock sector.
David Chebutia Kemboi; Phillis E. Ochieng; Gunther Antonissen; Siska Croubels; Marie-Louise Scippo; Sheila Okoth; Erastus K. Kangethe; Johannes Faas; Barbara Doupovec; Johanna F. Lindahl; James K. Gathumbi. Multi-Mycotoxin Occurrence in Dairy Cattle and Poultry Feeds and Feed Ingredients from Machakos Town, Kenya. Toxins 2020, 12, 762 .
AMA StyleDavid Chebutia Kemboi, Phillis E. Ochieng, Gunther Antonissen, Siska Croubels, Marie-Louise Scippo, Sheila Okoth, Erastus K. Kangethe, Johannes Faas, Barbara Doupovec, Johanna F. Lindahl, James K. Gathumbi. Multi-Mycotoxin Occurrence in Dairy Cattle and Poultry Feeds and Feed Ingredients from Machakos Town, Kenya. Toxins. 2020; 12 (12):762.
Chicago/Turabian StyleDavid Chebutia Kemboi; Phillis E. Ochieng; Gunther Antonissen; Siska Croubels; Marie-Louise Scippo; Sheila Okoth; Erastus K. Kangethe; Johannes Faas; Barbara Doupovec; Johanna F. Lindahl; James K. Gathumbi. 2020. "Multi-Mycotoxin Occurrence in Dairy Cattle and Poultry Feeds and Feed Ingredients from Machakos Town, Kenya." Toxins 12, no. 12: 762.
Mycotoxins are secondary metabolites of fungi that contaminate food and feed and have a significant negative impact on human and animal health and productivity. The tropical condition in Sub-Saharan Africa (SSA) together with poor storage of feed promotes fungal growth and subsequent mycotoxin production. Aflatoxins (AF) produced by Aspergillus species, fumonisins (FUM), zearalenone (ZEN), T-2 toxin (T-2), and deoxynivalenol (DON) produced by Fusarium species, and ochratoxin A (OTA) produced by Penicillium and Aspergillus species are well-known mycotoxins of agricultural importance. Consumption of feed contaminated with these toxins may cause mycotoxicoses in animals, characterized by a range of clinical signs depending on the toxin, and losses in the animal industry. In SSA, contamination of dairy feed with mycotoxins has been frequently reported, which poses a serious constraint to animal health and productivity, and is also a hazard to human health since some mycotoxins and their metabolites are excreted in milk, especially aflatoxin M1. This review describes the major mycotoxins, their occurrence, and impact in dairy cattle diets in SSA highlighting the problems related to animal health, productivity, and food safety and the up-to-date post-harvest mitigation strategies for the prevention and reduction of contamination of dairy feed.
David Chebutia Kemboi; Gunther Antonissen; Phillis E. Ochieng; Siska Croubels; Sheila Okoth; Erastus K. Kangethe; Johannes Faas; Johanna F. Lindahl; James K. Gathumbi. A Review of the Impact of Mycotoxins on Dairy Cattle Health: Challenges for Food Safety and Dairy Production in Sub-Saharan Africa. Toxins 2020, 12, 222 .
AMA StyleDavid Chebutia Kemboi, Gunther Antonissen, Phillis E. Ochieng, Siska Croubels, Sheila Okoth, Erastus K. Kangethe, Johannes Faas, Johanna F. Lindahl, James K. Gathumbi. A Review of the Impact of Mycotoxins on Dairy Cattle Health: Challenges for Food Safety and Dairy Production in Sub-Saharan Africa. Toxins. 2020; 12 (4):222.
Chicago/Turabian StyleDavid Chebutia Kemboi; Gunther Antonissen; Phillis E. Ochieng; Siska Croubels; Sheila Okoth; Erastus K. Kangethe; Johannes Faas; Johanna F. Lindahl; James K. Gathumbi. 2020. "A Review of the Impact of Mycotoxins on Dairy Cattle Health: Challenges for Food Safety and Dairy Production in Sub-Saharan Africa." Toxins 12, no. 4: 222.
Insect damage on trees can severely affect the quality of timber, reduce the fecundity of the host and render it susceptible to fungal infestation and disease. Such pathology weakens or eventually kills the host. Infestation by two insect woodborer species (a moth and a beetle) is causing mortality of Sonneratia alba, a wide-ranging pioneer mangrove species of the Indo-Pacific. Establishing the infestation mechanism of the two insect woodborer species is an initial and essential step towards understanding their ecological role in the mangroves and in determining sustainable management priorities and options. Our main objectives were to investigate the infestation mechanism employed by the two insect woodborers which infest S. alba trees, to establish the occurrence of secondary infestation by endophytic fungi in the infested S. alba branches, and to explore a control management option to the woodborer infestation. We conducted an external inspection of infested branches in two large embayments in Kenya, Gazi Bay and Mida Creek, and by splitting infested branches we determined the respective internal infestation mechanisms. Infested wood samples from Gazi Bay and Mida Creek were incubated at 28±1°C for 3-5 days to establish the presence of fungi. A survey was conducted in both Gazi Bay and Mida Creek to ascertain the presence of ants on S. alba. The infestation characteristics of the two insect woodborer species were different. It took 6-8 months for the beetle to kill a branch of 150 cm-200 cm long. For the moth to kill a branch, it depended upon several factors including the contribution by multiple species, other than the moth infestation alone. A total of 15 endophytic fungal species were identified. Two ant species Oecophylla longipoda and a Pheidole sp. inhabited 62% and 69% respectively of sampled S. alba trees in Gazi Bay whereas only Pheidole sp. inhabited 17% of the sampled S. alba trees in Mida Creek. In summary, we have documented the time it takes each woodborer species to kill a branch, the infestation mechanism of the two insect woodborers, and we hypothesized on the role of two ant species. The presence of several different fungal species was ascertained, and we discussed their possible role in the infested wood. Our results cannot unambiguously associate the woodborers and identified fungi. We recommend further studies to investigate the presence or absence, and if present, the nature of fungi in the gut of the woodborers.
Elisha Mrabu Jenoh; Etienne P. De Villiers; Santie M. De Villiers; Sheila Okoth; Joyce Jefwa; Esther Kioko; Davies Kaimenyi; Marijke Hendrickx; Farid Dahdouh-Guebas; Nico Koedam. Infestation mechanisms of two woodborer species in the mangrove Sonneratia alba J. Smith in Kenya and co-occurring endophytic fungi. PLOS ONE 2019, 14, e0221285 .
AMA StyleElisha Mrabu Jenoh, Etienne P. De Villiers, Santie M. De Villiers, Sheila Okoth, Joyce Jefwa, Esther Kioko, Davies Kaimenyi, Marijke Hendrickx, Farid Dahdouh-Guebas, Nico Koedam. Infestation mechanisms of two woodborer species in the mangrove Sonneratia alba J. Smith in Kenya and co-occurring endophytic fungi. PLOS ONE. 2019; 14 (10):e0221285.
Chicago/Turabian StyleElisha Mrabu Jenoh; Etienne P. De Villiers; Santie M. De Villiers; Sheila Okoth; Joyce Jefwa; Esther Kioko; Davies Kaimenyi; Marijke Hendrickx; Farid Dahdouh-Guebas; Nico Koedam. 2019. "Infestation mechanisms of two woodborer species in the mangrove Sonneratia alba J. Smith in Kenya and co-occurring endophytic fungi." PLOS ONE 14, no. 10: e0221285.
Highly toxigenic strains of Aspergillus flavus have been reported to frequently contaminate maize, causing fatal aflatoxin poisoning in Kenya. To gain insights into the environmental and genetic factors that influence toxigenicity, fungi (n = 218) that were culturally identified as A. flavus were isolated from maize grains samples (n = 120) from three regions of Kenya. The fungi were further characterized to confirm their identities using a PCR-sequence analysis of the internal transcribed spacer (ITS) region of rDNA which also revealed all of them to be A. flavus. A subset of 72 isolates representing ITS sequence-based phylogeny cluster and the agroecological origin of maize samples was constituted for subsequent analysis. The analysis of partial calmodulin gene sequences showed that the subset consisted of A. flavus (87%) and Aspergillus minisclerotigenes (13%). No obvious association was detected between the presence of seven aflatoxin biosynthesis genes and fungal species or region. However, the presence of the aflD and aflS genes showed some association with aflatoxin production. The assessment of toxigenicity showed higher aflatoxin production potential in A. minisclerotigenes isolates. Given that A. minisclerotigenes were mainly observed in maize samples from Eastern Kenya, a known aflatoxin hotspot, we speculate that production of copious aflatoxin is an adaptative trait of this recently discovered species in the region.
Richard Dooso Oloo; Sheila Okoth; Peter Wachira; Samuel Mutiga; Phillis Ochieng; Leah Kago; Fredrick Nganga; Jean-Baka Domelevo Entfellner; Sita Ghimire. Genetic Profiling of Aspergillus Isolates with Varying Aflatoxin Production Potential from Different Maize-Growing Regions of Kenya. Toxins 2019, 11, 467 .
AMA StyleRichard Dooso Oloo, Sheila Okoth, Peter Wachira, Samuel Mutiga, Phillis Ochieng, Leah Kago, Fredrick Nganga, Jean-Baka Domelevo Entfellner, Sita Ghimire. Genetic Profiling of Aspergillus Isolates with Varying Aflatoxin Production Potential from Different Maize-Growing Regions of Kenya. Toxins. 2019; 11 (8):467.
Chicago/Turabian StyleRichard Dooso Oloo; Sheila Okoth; Peter Wachira; Samuel Mutiga; Phillis Ochieng; Leah Kago; Fredrick Nganga; Jean-Baka Domelevo Entfellner; Sita Ghimire. 2019. "Genetic Profiling of Aspergillus Isolates with Varying Aflatoxin Production Potential from Different Maize-Growing Regions of Kenya." Toxins 11, no. 8: 467.
Aflatoxins continue to be a food safety problem globally, especially in developing regions. A significant amount of effort and resources have been invested in an attempt to control aflatoxins. However, these efforts have not substantially decreased the prevalence nor the dietary exposure to aflatoxins in developing countries. One approach to aflatoxin control is the use of binding agents in foods, and lactic acid bacteria (LAB) have been studied extensively for this purpose. However, when assessing the results comprehensively and reviewing the practicality and ethics of use, risks are evident, and concerns arise. In conclusion, our review suggests that there are too many issues with using LAB for aflatoxin binding for it to be safely promoted. Arguably, using binders in human food might even worsen food safety in the longer term.
Sara Ahlberg; Delia Randolph; Sheila Okoth; Johanna Lindahl. Aflatoxin Binders in Foods for Human Consumption—Can This be Promoted Safely and Ethically? Toxins 2019, 11, 410 .
AMA StyleSara Ahlberg, Delia Randolph, Sheila Okoth, Johanna Lindahl. Aflatoxin Binders in Foods for Human Consumption—Can This be Promoted Safely and Ethically? Toxins. 2019; 11 (7):410.
Chicago/Turabian StyleSara Ahlberg; Delia Randolph; Sheila Okoth; Johanna Lindahl. 2019. "Aflatoxin Binders in Foods for Human Consumption—Can This be Promoted Safely and Ethically?" Toxins 11, no. 7: 410.
The authors wish to make the following correction to their paper [...].
Alfred Mitema; Sheila Okoth; Suhail M. Rafudeen. Correction: Mitema, A. et al. The Development of a qPCR Assay to Measure Aspergillus flavus Biomass in Maize and the Use of a Biocontrol Strategy to Limit Aflatoxin Production. Toxins 2019, 11, 179. Toxins 2019, 11, 384 .
AMA StyleAlfred Mitema, Sheila Okoth, Suhail M. Rafudeen. Correction: Mitema, A. et al. The Development of a qPCR Assay to Measure Aspergillus flavus Biomass in Maize and the Use of a Biocontrol Strategy to Limit Aflatoxin Production. Toxins 2019, 11, 179. Toxins. 2019; 11 (7):384.
Chicago/Turabian StyleAlfred Mitema; Sheila Okoth; Suhail M. Rafudeen. 2019. "Correction: Mitema, A. et al. The Development of a qPCR Assay to Measure Aspergillus flavus Biomass in Maize and the Use of a Biocontrol Strategy to Limit Aflatoxin Production. Toxins 2019, 11, 179." Toxins 11, no. 7: 384.
Aspergillus flavus colonisation of maize can produce mycotoxins that are detrimental to both human and animal health. Screening of maize lines, resistant to A. flavus infection, together with a biocontrol strategy, could help minimize subsequent aflatoxin contamination. We developed a qPCR assay to measure A. flavus biomass and showed that two African maize lines, GAF4 and KDV1, had different fungal loads for the aflatoxigenic isolate (KSM014), fourteen days after infection. The qPCR assay revealed no significant variation in A. flavus biomass between diseased and non-diseased maize tissues for GAF4, while KDV1 had a significantly higher A. flavus biomass (p < 0.05) in infected shoots and roots compared to the control. The biocontrol strategy using an atoxigenic isolate (KSM012) against the toxigenic isolate (KSM014), showed aflatoxin production inhibition at the co-infection ratio, 50:50 for both maize lines (KDV1 > 99.7% and GAF ≥ 69.4%), as confirmed by bioanalytical techniques. As far as we are aware, this is the first report in Kenya where the biomass of A. flavus from maize tissue was detected and quantified using a qPCR assay. Our results suggest that maize lines, which have adequate resistance to A. flavus, together with the appropriate biocontrol strategy, could limit outbreaks of aflatoxicoses.
Alfred Mitema; Sheila Okoth; Suhail M. Rafudeen. The Development of a qPCR Assay to Measure Aspergillus flavus Biomass in Maize and the Use of a Biocontrol Strategy to Limit Aflatoxin Production. Toxins 2019, 11, 179 .
AMA StyleAlfred Mitema, Sheila Okoth, Suhail M. Rafudeen. The Development of a qPCR Assay to Measure Aspergillus flavus Biomass in Maize and the Use of a Biocontrol Strategy to Limit Aflatoxin Production. Toxins. 2019; 11 (3):179.
Chicago/Turabian StyleAlfred Mitema; Sheila Okoth; Suhail M. Rafudeen. 2019. "The Development of a qPCR Assay to Measure Aspergillus flavus Biomass in Maize and the Use of a Biocontrol Strategy to Limit Aflatoxin Production." Toxins 11, no. 3: 179.
Fungal contamination and the consequent mycotoxin production is a hindrance to food and feed safety, international trade and human and animal health. In Africa, fungal contamination by Fusarium and Aspergillus is heightened by tropical climatic conditions that create a suitable environment for pre- and postharvest mycotoxin production. The biocontrol of Fusarium and its associated fusariotoxins has stagnated at laboratory and experimental levels with species of Trichoderma, Bacillus and atoxigenic Fusarium being tested as the most promising candidates. Hitherto, there is no impetus to upscale for field use owing to the inconsistent results of these agents. Non-aflatoxigenic strains of Aspergillus have been developed to create biocontrol formulations by outcompeting the aflatoxigenic strains, thus thwarting aflatoxins on the target produce by 70% to 90%. Questions have been raised on their ability to produce other mycotoxins like cyclopiazonic acid, to potentially exchange genetic material and to become aflatoxigenic with consequent deleterious effects on other organisms and environments. Other biocontrol approaches to mitigate aflatoxins include the use of lactic acid bacteria and yeast species which have demonstrated the ability to prevent the growth of Aspergillus flavus and consequent toxin production under laboratory conditions. Nevertheless, these strategies seem to be ineffective under field conditions. The efficacy of biological agents is normally dependent on environmental factors, formulations’ safety to non-target hosts and the ecological impact. Biocontrol agents can only be effectively evaluated after long-term use, causing a never-ending debate on the use of live organisms as a remedy to pests and diseases over the use of chemicals. Biocontrol should be used in conjunction with good agricultural practices coupled with good postharvest management to significantly reduce mycotoxins in the African continent.
Victor Kagot; Sheila Okoth; Marthe De Boevre; Sarah De Saeger. Biocontrol of Aspergillus and Fusarium Mycotoxins in Africa: Benefits and Limitations. Toxins 2019, 11, 109 .
AMA StyleVictor Kagot, Sheila Okoth, Marthe De Boevre, Sarah De Saeger. Biocontrol of Aspergillus and Fusarium Mycotoxins in Africa: Benefits and Limitations. Toxins. 2019; 11 (2):109.
Chicago/Turabian StyleVictor Kagot; Sheila Okoth; Marthe De Boevre; Sarah De Saeger. 2019. "Biocontrol of Aspergillus and Fusarium Mycotoxins in Africa: Benefits and Limitations." Toxins 11, no. 2: 109.
Fungal species recovered from fermented foods and beverage from Nigeria and South Africa were studied to establish their toxigenic potential in producing an array of secondary metabolites including mycotoxins (n = 49) that could compromise human and animal safety. In total, 385 fungal isolates were grown on solidified yeast extract sucrose agar. Their metabolites were extracted and analyzed via ultra-performance liquid chromatography tandem mass spectrometry. To examine the grouping of isolates and co-occurrence of metabolites, hierarchal clustering and pairwise association analysis was performed. Of the 385 fungal strains tested, over 41% were toxigenic producing different mycotoxins. A. flavus and A. parasiticus strains were the principal producers of aflatoxin B1 (27–7406 µg/kg). Aflatoxin B1 and cyclopiazonic acid had a positive association. Ochratoxin A was produced by 67% of the A. niger strains in the range of 28–1302 µg/kg. The sterigmatocystin producers found were A. versicolor (n = 12), A. amstelodami (n = 4), and A. sydowii (n = 6). Apart from P. chrysogenum, none of the Penicillium spp. produced roquefortine C. Amongst the Fusarium strains tested, F. verticillioides produced fumonisin B1 (range: 77–218 µg/kg) meanwhile low levels of deoxynivalenol were observed. The production of multiple metabolites by single fungal species was also evident.
Ifeoluwa Adekoya; Patrick Njobeh; Adewale Obadina; Sofie Landschoot; Kris Audenaert; Sheila Okoth; Marthe De Boevre; Sarah De Saeger. Investigation of the Metabolic Profile and Toxigenic Variability of Fungal Species Occurring in Fermented Foods and Beverage from Nigeria and South Africa Using UPLC-MS/MS. Toxins 2019, 11, 85 .
AMA StyleIfeoluwa Adekoya, Patrick Njobeh, Adewale Obadina, Sofie Landschoot, Kris Audenaert, Sheila Okoth, Marthe De Boevre, Sarah De Saeger. Investigation of the Metabolic Profile and Toxigenic Variability of Fungal Species Occurring in Fermented Foods and Beverage from Nigeria and South Africa Using UPLC-MS/MS. Toxins. 2019; 11 (2):85.
Chicago/Turabian StyleIfeoluwa Adekoya; Patrick Njobeh; Adewale Obadina; Sofie Landschoot; Kris Audenaert; Sheila Okoth; Marthe De Boevre; Sarah De Saeger. 2019. "Investigation of the Metabolic Profile and Toxigenic Variability of Fungal Species Occurring in Fermented Foods and Beverage from Nigeria and South Africa Using UPLC-MS/MS." Toxins 11, no. 2: 85.
This study evaluated the effect of dietary aflatoxin B1 (AFB1) on growth, milt and egg quality in matured Nile tilapia (Oreochromis niloticus). Triplicate groups of Nile tilapia (initial body weight 24.1 ± 2.6 g) were fed with either of four diets (Diets 1 to 4) designed to contain 0, 20, 200 and 2000 μg AFB1 kg−1 diets for 24 weeks. After 24 weeks of AFB1 exposure, growth was significantly (P <0.05) different between the control and the AFB1 exposed treatments in both sexes. No significant differences were observed in 17β-oestradiol, absolute fecundity, oocytes volume and diameters between AFB1 exposure groups and the control group. However, we observed a significant reduction in relative fecundity and gonad somatic index (GSI) in females fed 2000 μg AFB1 kg−1 diet. On the other hand, we observed significant differences (P <0.05) in gonadosomatic index (GSI), testosterone, milt count and motility between males in the control group and AFB1 treatments. We conclude that rearing Nile tilapia with aflatoxin-contaminated diets for a prolonged period affects milt quality, fecundity (at higher doses) and growth performance. This implies that for optimal seed production, provision of aflatoxin free diets should be part of the management practices in Nile tilapia hatcheries.
Esther Marijani; Harrison Charo-Karisa; Gbemenou Joselin Benoit Gnonlonfin; Emmanuel Kigadye; Sheila Okoth. Effects of aflatoxin B1on reproductive performance of farmed Nile tilapia. International Journal of Veterinary Science and Medicine 2019, 7, 35 -42.
AMA StyleEsther Marijani, Harrison Charo-Karisa, Gbemenou Joselin Benoit Gnonlonfin, Emmanuel Kigadye, Sheila Okoth. Effects of aflatoxin B1on reproductive performance of farmed Nile tilapia. International Journal of Veterinary Science and Medicine. 2019; 7 (1):35-42.
Chicago/Turabian StyleEsther Marijani; Harrison Charo-Karisa; Gbemenou Joselin Benoit Gnonlonfin; Emmanuel Kigadye; Sheila Okoth. 2019. "Effects of aflatoxin B1on reproductive performance of farmed Nile tilapia." International Journal of Veterinary Science and Medicine 7, no. 1: 35-42.
In this study, the possibility of sexual reproduction in sampled Aspergillus flavus strains was evaluated by assessing the distribution of mating type (MAT) genes, which are known to control sexual character among fungi, for two counties in Kenya. Forty-four isolates from Nandi and Makueni counties were genotyped by MAT using a multiplex polymerase chain reaction assay. The primer pair for the MAT1-1 amplified a 396 base pair (bp) fragment containing an α-box motif, and MAT1-2 primers targeted a 270 bp segment with a high mobility group protein. The MAT1-2 genes dominated in both regions although the frequency was higher in Nandi (75%) than in Makueni (54.17%). There were no MAT1-1 genes sampled in Nandi, and in Makueni their proportion was 15.91%. The percentage of isolates that amplified for both MAT genes in Makueni was 9.09%, while in Nandi it was 11.36%. Currently, use of aggressive aflatoxin non-producing A. flavus strains as biocontrol is the most promising preharvest aflatoxin control strategy in Kenya. However, we address the possibility of introduced biocontrol strains to breed with existing aflatoxin producing strains in nature, which could lead to the generation of A. flavus offspring capable of aflatoxin production while also being aggressive colonizers and possibly increasing the burden of aflatoxin exposure in food.
Ouko Abigael; Okoth Sheila; Amugune Nelson; Vesa Joutsjoki. Characterization of Mating Type Genes in Aspergillus flavus Populations from Two Locations in Kenya. Advances in Agriculture 2018, 2018, 1 -6.
AMA StyleOuko Abigael, Okoth Sheila, Amugune Nelson, Vesa Joutsjoki. Characterization of Mating Type Genes in Aspergillus flavus Populations from Two Locations in Kenya. Advances in Agriculture. 2018; 2018 ():1-6.
Chicago/Turabian StyleOuko Abigael; Okoth Sheila; Amugune Nelson; Vesa Joutsjoki. 2018. "Characterization of Mating Type Genes in Aspergillus flavus Populations from Two Locations in Kenya." Advances in Agriculture 2018, no. : 1-6.
Beer, a beverage consumed throughout the world, is mainly derived from cereals. In this study, fungal and mycotoxin contamination, as well as the physicochemical properties of maize-based opaque beer (umqombothi) obtained from the Gauteng province of South Africa, was investigated. The mean water activity, pH and total titratable acidity of the analysed beer samples were 0.91, 3.76 and 1.20% lactic acid, respectively. The investigation revealed Aspergillus, Penicillium, Phoma and Saccharomyces as the predominant fungal genera with a mean fungal load of 3.66 × 105 CFU/mL. Among the mycotoxigenic fungal species recovered, Aspergillus flavus had the highest incidence of 26%. Previously unreported strains such as P. chrysogenum strain AD25, A. sydowii strain AD 22 and A. tritici strain AD 11 were found. Furthermore, mycotoxin quantitative analysis via liquid chromatography-tandem mass spectrophotometry showed that deoxynivalenol was the dominant mycotoxin occurring in 84% of the samples. This was followed by enniatin B that occurred in 75% of samples ranging from 12 to 44 μg/L and fumonisin B1 (FB1) (incidence of 53% at a maximum level of 182 μg/L). Generally, there was low occurrence aflatoxins, whereas T-2, HT-2, nivalenol, zearalenone, 3- and 15-acetyl-deoxynivalenol were not detected. All the samples analysed had safe levels of mycotoxins tested but were contaminated by at least two mycotoxins that could pose some additive or synergistic health effects among consumers. On average: a 60 kg adult consuming 1–6 L/day of the beer was exposed to FB1 + FB2 at an estimated 2.20–13.20 μg/kg body weight/day. These values were far above the maximum tolerable daily intake of 2 μg/kg bw/day established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The study demonstrates that consumption of umqombothi can significantly enhance dietary exposure to multiple mycotoxins among consumers, and therefore accentuates the need for strategies aimed at reducing toxigenic fungal colonization and mycotoxin contamination in the beer processing chain.
Ifeoluwa Adekoya; Adewale Obadina; Cynthia Chilaka Adaku; Marthe De Boevre; Sheila Okoth; Sarah De Saeger; Patrick Njobeh. Mycobiota and co-occurrence of mycotoxins in South African maize-based opaque beer. International Journal of Food Microbiology 2018, 270, 22 -30.
AMA StyleIfeoluwa Adekoya, Adewale Obadina, Cynthia Chilaka Adaku, Marthe De Boevre, Sheila Okoth, Sarah De Saeger, Patrick Njobeh. Mycobiota and co-occurrence of mycotoxins in South African maize-based opaque beer. International Journal of Food Microbiology. 2018; 270 ():22-30.
Chicago/Turabian StyleIfeoluwa Adekoya; Adewale Obadina; Cynthia Chilaka Adaku; Marthe De Boevre; Sheila Okoth; Sarah De Saeger; Patrick Njobeh. 2018. "Mycobiota and co-occurrence of mycotoxins in South African maize-based opaque beer." International Journal of Food Microbiology 270, no. : 22-30.
Aspergillus flavus is the main producer of carcinogenic aflatoxins in agricultural commodities such as maize. This fungus occurs naturally on crops, and produces aflatoxins when environmental conditions are favorable. The aim of this study is to analyse the genetic variability among 109 A. flavus isolates previously recovered from maize sampled from a known aflatoxin-hotspot (Eastern region, Kenya) and the major maize-growing area in the Rift Valley (Kenya), and to determine their toxigenic potential. DNA analyses of internal transcribed spacer (ITS) regions of ribosomal DNA, partial β-tubulin gene (benA) and calmodulin gene (CaM) sequences were used. The strains were further analyzed for the presence of four aflatoxin-biosynthesis genes in relation to their capability to produce aflatoxins and other metabolites, targeting the regulatory gene aflR and the structural genes aflP, aflD, and aflQ. In addition, the metabolic profile of the fungal strains was unraveled using state-of-the-art LC-MS/MS instrumentation. The three gene-sequence data grouped the isolates into two major clades, A. minisclerotigenes and A. flavus. A. minisclerotigenes was most prevalent in Eastern Kenya, while A. flavus was common in both regions. A. parasiticus was represented by a single isolate collected from Rift Valley. Diversity existed within the A. flavus population, which formed several subclades. An inconsistency in identification of some isolates using the three markers was observed. The calmodulin gene sequences showed wider variation of polymorphisms. The aflatoxin production pattern was not consistent with the presence of aflatoxigenic genes, suggesting an inability of the primers to always detect the genes or presence of genetic mutations. Significant variation was observed in toxin profiles of the isolates. This is the first time that a profound metabolic profiling of A. flavus isolates was done in Kenya. Positive associations were evident for some metabolites, while for others no associations were found and for a few metabolite-pairs negative associations were seen. Additionally, the growth medium influenced the mycotoxin metabolite production. These results confirm the wide variation that exists among the group A. flavus and the need for more insight in clustering the group.
Sheila Okoth; Marthe De Boevre; Arnau Vidal; José Diana Di Mavungu; Sofie Landschoot; Martina Kyallo; Joyce Njuguna; Jagger Harvey; Sarah De Saeger. Genetic and Toxigenic Variability within Aspergillus flavus Population Isolated from Maize in Two Diverse Environments in Kenya. Frontiers in Microbiology 2018, 9, 57 .
AMA StyleSheila Okoth, Marthe De Boevre, Arnau Vidal, José Diana Di Mavungu, Sofie Landschoot, Martina Kyallo, Joyce Njuguna, Jagger Harvey, Sarah De Saeger. Genetic and Toxigenic Variability within Aspergillus flavus Population Isolated from Maize in Two Diverse Environments in Kenya. Frontiers in Microbiology. 2018; 9 ():57.
Chicago/Turabian StyleSheila Okoth; Marthe De Boevre; Arnau Vidal; José Diana Di Mavungu; Sofie Landschoot; Martina Kyallo; Joyce Njuguna; Jagger Harvey; Sarah De Saeger. 2018. "Genetic and Toxigenic Variability within Aspergillus flavus Population Isolated from Maize in Two Diverse Environments in Kenya." Frontiers in Microbiology 9, no. : 57.
Ouko Abigael; Okoth Sheila; Amugune Nelson; Vesa Joutsjoki. Field Assessment of Agronomic Performance, Resistance to Aflatoxin, and Fumonisin Accumulation in Selected Maize Inbred Lines in Kenya. Agriculture, Forestry and Fisheries 2018, 7, 94 .
AMA StyleOuko Abigael, Okoth Sheila, Amugune Nelson, Vesa Joutsjoki. Field Assessment of Agronomic Performance, Resistance to Aflatoxin, and Fumonisin Accumulation in Selected Maize Inbred Lines in Kenya. Agriculture, Forestry and Fisheries. 2018; 7 (4):94.
Chicago/Turabian StyleOuko Abigael; Okoth Sheila; Amugune Nelson; Vesa Joutsjoki. 2018. "Field Assessment of Agronomic Performance, Resistance to Aflatoxin, and Fumonisin Accumulation in Selected Maize Inbred Lines in Kenya." Agriculture, Forestry and Fisheries 7, no. 4: 94.
Aspergillus flavus, causal agent of the Aspergillus ear rot (AER) of maize, also produces aflatoxins that cause aflatoxicosis in humans and livestock. Ten maize inbred lines were evaluated in replicated trials in two aflatoxicosis outbreak hot spots in Kenya and in three maize-growing areas in South Africa for resistance to AER, A. flavus colonization, and pre-harvest aflatoxin accumulation during the 2012/13 growing season. AER severity was measured by visual assessment, while A. flavus colonization and aflatoxin content were quantified by real-time polymerase chain reaction (PCR) and liquid chromatography tandem mass spectrometry, respectively. Genotype by environment interaction (GEI) was determined using analysis of variance (ANOVA), additive main effects and multiplicative models (AMMI), and genotype plus by environment (GGE) biplot analyses. Stability of genotypes was evaluated using AMMI analysis. AER severity and fungal colonization significantly (p < 0.001) varied between genotypes. GEI influenced the severity of AER symptoms and aflatoxin accumulation significantly (p < 0.001), while fungal colonization was not affected. The inbred lines response was consistent for this trait in the test environments and was thus considered a desirable measure to indicate maize lines with a high risk of aflatoxin accumulation. CML495, CKL05019, LaPosta, and MIRTC5 were the least diseased lines, with the lowest aflatoxin contamination and a stable phenotypic response across the environments. Kiboko was determined as the ideal representative test environment, with discriminative ability of the genotypes for selection of the desired stable responses of the three traits.
Sheila Okoth; Lindy J. Rose; Abigael Ouko; Nakisani E. I. Netshifhefhe; Henry Sila; Altus Viljoen. Assessing Genotype-By-Environment Interactions in Aspergillus Ear Rot and Pre-Harvest Aflatoxin Accumulation in Maize Inbred Lines. Agronomy 2017, 7, 86 .
AMA StyleSheila Okoth, Lindy J. Rose, Abigael Ouko, Nakisani E. I. Netshifhefhe, Henry Sila, Altus Viljoen. Assessing Genotype-By-Environment Interactions in Aspergillus Ear Rot and Pre-Harvest Aflatoxin Accumulation in Maize Inbred Lines. Agronomy. 2017; 7 (4):86.
Chicago/Turabian StyleSheila Okoth; Lindy J. Rose; Abigael Ouko; Nakisani E. I. Netshifhefhe; Henry Sila; Altus Viljoen. 2017. "Assessing Genotype-By-Environment Interactions in Aspergillus Ear Rot and Pre-Harvest Aflatoxin Accumulation in Maize Inbred Lines." Agronomy 7, no. 4: 86.
Fermented food samples (n = 191) including maize gruel (ogi), sorghum gruel (ogi-baba), melon seed (ogiri), locust bean (iru) and African oil bean seed (ugba) from Southwest Nigeria were quantified for 23 mycotoxins, including aflatoxin B1 (AFB1), fumonisin B1 (FB1), and sterigmatocystin (STE) using liquid chromatography-tandem mass spectrometry. The practices, perceived understanding and health risks related to fungal and mycotoxin contamination amongst fermented food sellers was also established. Data obtained revealed that 82% of the samples had mycotoxins occurring singly or in combination. FB1 was present in 83% of ogi-baba samples, whereas 20% of ugba samples contained AFB1 (range: 3 to 36 µg/kg) and STE was present in 29% of the ogi samples. In terms of multi-mycotoxin contamination, FB1 + FB2 + FB3 + STE + AFB1 + alternariol + HT-2 co-occurred within one sample. The awareness study revealed that 98% of respondents were unaware of mycotoxin contamination, and their education level slightly correlated with their level of awareness (p < 0.01, r = 0.308). The extent to which the analyzed mycotoxins contaminated these food commodities, coupled with the poor perception of the population under study on fungi and mycotoxins, justifies the need to enact fungal and mycotoxin mitigation strategies along the food chain.
Ifeoluwa Adekoya; Patrick Njobeh; Adewale Obadina; Cynthia Chilaka; Sheila Okoth; Marthe De Boevre; Sarah De Saeger. Awareness and Prevalence of Mycotoxin Contamination in Selected Nigerian Fermented Foods. Toxins 2017, 9, 363 .
AMA StyleIfeoluwa Adekoya, Patrick Njobeh, Adewale Obadina, Cynthia Chilaka, Sheila Okoth, Marthe De Boevre, Sarah De Saeger. Awareness and Prevalence of Mycotoxin Contamination in Selected Nigerian Fermented Foods. Toxins. 2017; 9 (11):363.
Chicago/Turabian StyleIfeoluwa Adekoya; Patrick Njobeh; Adewale Obadina; Cynthia Chilaka; Sheila Okoth; Marthe De Boevre; Sarah De Saeger. 2017. "Awareness and Prevalence of Mycotoxin Contamination in Selected Nigerian Fermented Foods." Toxins 9, no. 11: 363.
Aflatoxin, a carcinogenic toxin, is produced mainly by Aspergillus flavus and Aspergillus parasiticus. Contamination of maize (Zea mays L.) grain by these fungi occurs before harvest, and the easiest strategy to prevent this is to develop/use maize varieties resistant to Aspergillus spp. and aflatoxin accumulation. The objective of this investigation was to identify potential sources of resistance among 23 maize inbred lines (13 obtained from the MAIZE Competitive Grants Initiative, International Maize and Wheat Improvement Centre and 10 from Agricultural Research Council, South Africa). The inbred lines were planted in a randomized complete-block design at two locations each in Kenya and South Africa. Maize ears were inoculated at silking with three toxigenic strains of A. flavus. The inoculated ears in each plot were harvested at 12–18% moisture, dried, and visually assessed for Aspergillus ear rot (AER). Aflatoxin concentration in the kernels was determined using liquid chromatography–tandem mass spectrometry. Significant variation for both AER and aflatoxin concentration existed among the inbred lines at both locations in Kenya and one location in South Africa. Combined analysis revealed a significant (p < 0.001) lines × locations interaction for both AER and aflatoxin concentration. Higher incidences of AER (0–86.0%) and aflatoxin concentration (0.21–6.51 µg/kg) were recorded at Kiboko in Kenya than at the other three locations. A stronger genetic correlation (rG = 0.936, p < 0.0001) between the AER and aflatoxin concentration was recorded in Potchefstroom than at the other three locations. Repeatability of aflatoxin concentration was high at Kiboko (0.87) and Potchefstroom in South Africa (0.74). Three inbred lines, CML247, CML444, and CML495, emerged as potentially useful sources of resistance to AER and aflatoxin accumulation as they showed low levels of aflatoxin contamination in both localities in Kenya and in South Africa.
Sheila Okoth; Lindy Joy Rose; Abigael Ouko; Ilze Beukes; Henry Sila; Marili Mouton; Bradley Charles Flett; Dan Makumbi; Altus Viljoen. Field evaluation of resistance to aflatoxin accumulation in maize inbred lines in Kenya and South Africa. Journal of Crop Improvement 2017, 31, 862 -878.
AMA StyleSheila Okoth, Lindy Joy Rose, Abigael Ouko, Ilze Beukes, Henry Sila, Marili Mouton, Bradley Charles Flett, Dan Makumbi, Altus Viljoen. Field evaluation of resistance to aflatoxin accumulation in maize inbred lines in Kenya and South Africa. Journal of Crop Improvement. 2017; 31 (6):862-878.
Chicago/Turabian StyleSheila Okoth; Lindy Joy Rose; Abigael Ouko; Ilze Beukes; Henry Sila; Marili Mouton; Bradley Charles Flett; Dan Makumbi; Altus Viljoen. 2017. "Field evaluation of resistance to aflatoxin accumulation in maize inbred lines in Kenya and South Africa." Journal of Crop Improvement 31, no. 6: 862-878.
Groundnut is one of the staple foods in many parts of the world. Due to its high nutrient content, the nuts are liable to colonization by aflatoxigenic fungi and subsequent aflatoxin accumulation. This study was aimed at determining susceptibility of locally grown groundnut varieties to Aspergillus flavus in Homa Bay County, Western Kenya. A pretested questionnaire was used to survey agronomic practices on groundnut cultivation in 75 randomly selected households in the study site. From each household farm, 100 g soil samples and 500 g of groundnuts were collected at harvest and A. flavus isolated on Modified Rose-Bengal Agar and identified. Aflatoxin was then extracted from each of the groundnut samples and quantified using direct competitive enzyme linked immunosorbent assay (ELISA). Red Valencia was the most cultivated among the 8 varieties identified. Farmers (66%) obtained the planting seeds from the local market and most (92%) did not use fertilizers with majority (94%) having no knowledge of aflatoxins. There was no significant inter-variety difference in aflatoxin accumulation (p=0.744, F=0.581, Df=6, 61). A highly significant association (t = 2.652; P = 0.010) was found between storage state of the groundnuts and aflatoxin levels, with 94% of the samples stored unshelled having aflatoxin levels below 10 ppb. Overall, only 6.7% of kernels sampled from all the divisions did not meet the EC aflatoxin limit of ≤4 ppb while 4% did not meet the KEBS limit of ≤10 ppb. Though the agronomic practices were poor, aflatoxin levels were predominantly low in the region suggesting that the aflatoxin accumulation is likely influenced by agro-ecological zoning as other studies have also been indicated. Key words: Groundnuts, Aflatoxins, Aspergillus flavus.
Boaz Ndisio; Wachira Peter; Kagot Victor; Okoth Sheila; Ndisio Boaz; Peter Wachira; Victor Kagot; Sheila Okoth. Susceptibility of locally cultivated groundnut (Arachis hypogaea) varieties to aflatoxin accumulation in Homa Bay County, Kenya. African Journal of Microbiology Research 2017, 11, 1329 -1337.
AMA StyleBoaz Ndisio, Wachira Peter, Kagot Victor, Okoth Sheila, Ndisio Boaz, Peter Wachira, Victor Kagot, Sheila Okoth. Susceptibility of locally cultivated groundnut (Arachis hypogaea) varieties to aflatoxin accumulation in Homa Bay County, Kenya. African Journal of Microbiology Research. 2017; 11 (33):1329-1337.
Chicago/Turabian StyleBoaz Ndisio; Wachira Peter; Kagot Victor; Okoth Sheila; Ndisio Boaz; Peter Wachira; Victor Kagot; Sheila Okoth. 2017. "Susceptibility of locally cultivated groundnut (Arachis hypogaea) varieties to aflatoxin accumulation in Homa Bay County, Kenya." African Journal of Microbiology Research 11, no. 33: 1329-1337.
Several interrelated and site-specific agronomic factors ranging from agroecological conditions to systems management practices have been shown to variably affect arbuscular mycorrhizal fungi (AMF) diversity in the soil. Also, there have been various attempts in the past to evaluate the potential of AMF field inoculation but a majority focussed on the use of exotic strains, disregarding the potential of the existing naturally occurring strains. In an attempt to address these problems, our study aimed to develop ‘best-bet practice’ based on soil fertility amendment practice (SFAP) that encourages occurrence and diversity of AMF in the soil. Control treatment (no application) was compared with three (3) SFAP used singly or in combination with AMF or two other soil nutrients enhancing organisms (Bacillus and Trichoderma) which included the following: (1) Mavuno (macro- and micronutrients and secondary nutrients) fertilizer, (2) calcium ammonium nitrate (CAN) plus triple super phosphate (TSP) and (3) cattle manure. Maize (Zea mays L.) and common bean (Phaseoli vulgaris L.) were planted at on-station and on-farm plots for two consecutive cropping seasons with the experiment replicated in two benchmark sites of Embu and Taita-Taveta Districts. Embu site recorded a lower soil pH and also very low phosphorus levels compared to Taita site. The number of AMF spores per kg of soil was very low, ranging from 30 to 100, at Embu in the first season and application of SFAP resulted in no significant difference. However, in the second season, use of Trichoderma + CAN plus TSP was shown to significantly stimulate AMF species in the soil, with a 250 % increase in species density compared to use of Bacillus + Manure. At Taita, after the first cropping season, significant change in spore density was only recorded from AMF applied singly with a 66.1 % increase in spore density compared to Control treatment. In comparison, after the second cropping season, use of AMF applied singly, AMF + CAN plus TSP and AMF + Manure increased spore density by 135.4, 109.6 and 100 % respectively compared to Control treatment. Use of AMF applied singly increased species density in the soil by 100 and 81.1 % compared to CAN plus TSP and Trichoderma treatments respectively after first season at Taita site: while after the second cropping season, application of AMF + CAN plus TSP, AMF + Manure and AMF + Mavuno increased AMF species density in the soil by 60.3, 51.5 and 55.9 % respectively compared to Control treatment. These findings provide evidence that it is possible to increase the number of AMF spores in the soil through inoculation with native species and also possibly stimulate dormant species through other SFAP treatments.
John Nyaga; Joyce M. Jefwa; Catherine W. Muthuri; Viviene N. Matiru; Peter M. Wachira; Sheila A. Okoth. Arbuscular mycorrhizal fungi with different soil fertility amendment practices in agricultural landscapes of Kenyan highlands. Nutrient Cycling in Agroecosystems 2015, 103, 229 -240.
AMA StyleJohn Nyaga, Joyce M. Jefwa, Catherine W. Muthuri, Viviene N. Matiru, Peter M. Wachira, Sheila A. Okoth. Arbuscular mycorrhizal fungi with different soil fertility amendment practices in agricultural landscapes of Kenyan highlands. Nutrient Cycling in Agroecosystems. 2015; 103 (2):229-240.
Chicago/Turabian StyleJohn Nyaga; Joyce M. Jefwa; Catherine W. Muthuri; Viviene N. Matiru; Peter M. Wachira; Sheila A. Okoth. 2015. "Arbuscular mycorrhizal fungi with different soil fertility amendment practices in agricultural landscapes of Kenyan highlands." Nutrient Cycling in Agroecosystems 103, no. 2: 229-240.