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Samuel M. C. Njoroge
Eastern and Southern Africa Research Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Lilongwe P.O. Box 1096, Malawi

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Journal article
Published: 09 December 2019 in Toxins
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A knowledge, attitude and practice (KAP) study was conducted in three districts of Malawi to test whether the training had resulted in increased knowledge and adoption of recommended pre- and post-harvest crop management practices, and their contribution to reducing aflatoxin contamination in groundnut, maize and sorghum. The study was conducted with 900 farmers at the baseline and 624 farmers at the end-line, while 726 and 696 harvested crop samples were collected for aflatoxin testing at the baseline and end-line, respectively. Results show that the knowledge and practice of pre- and post-harvest crop management for mitigating aflatoxin were inadequate among the farmers at the baseline but somewhat improved after the training as shown at the end-line. As a result, despite unfavorable weather, the mean aflatoxin contamination level in their grain samples decreased from 83.6 to 55.8 ppb (p < 0.001). However, it was also noted that increased knowledge did not significantly change farmers’ attitude toward not consuming grade-outs because of economic incentive incompatibility, leaving potential for improving the practices further. This existing gap in the adoption of aflatoxin mitigation practices calls for approaches that take into account farmers’ needs and incentives to attain sustainable behavioral change.

ACS Style

Seetha Anitha; Takuji Tsusaka; Samuel Njoroge; Nelson Kumwenda; Lizzie Kachulu; Joseph Maruwo; Norah Machinjiri; Rosemary Botha; Harry Msere; Juma Masumba; Angela Tavares; Geoffrey Heinrich; Moses Siambi; Patrick Okori. Knowledge, Attitude and Practice of Malawian Farmers on Pre- and Post-Harvest Crop Management to Mitigate Aflatoxin Contamination in Groundnut, Maize and Sorghum—Implication for Behavioral Change. Toxins 2019, 11, 716 .

AMA Style

Seetha Anitha, Takuji Tsusaka, Samuel Njoroge, Nelson Kumwenda, Lizzie Kachulu, Joseph Maruwo, Norah Machinjiri, Rosemary Botha, Harry Msere, Juma Masumba, Angela Tavares, Geoffrey Heinrich, Moses Siambi, Patrick Okori. Knowledge, Attitude and Practice of Malawian Farmers on Pre- and Post-Harvest Crop Management to Mitigate Aflatoxin Contamination in Groundnut, Maize and Sorghum—Implication for Behavioral Change. Toxins. 2019; 11 (12):716.

Chicago/Turabian Style

Seetha Anitha; Takuji Tsusaka; Samuel Njoroge; Nelson Kumwenda; Lizzie Kachulu; Joseph Maruwo; Norah Machinjiri; Rosemary Botha; Harry Msere; Juma Masumba; Angela Tavares; Geoffrey Heinrich; Moses Siambi; Patrick Okori. 2019. "Knowledge, Attitude and Practice of Malawian Farmers on Pre- and Post-Harvest Crop Management to Mitigate Aflatoxin Contamination in Groundnut, Maize and Sorghum—Implication for Behavioral Change." Toxins 11, no. 12: 716.

Review
Published: 03 June 2019 in Toxins
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Aflatoxin is considered a “hidden poison” due to its slow and adverse effect on various biological pathways in humans, particularly among children, in whom it leads to delayed development, stunted growth, liver damage, and liver cancer. Unfortunately, the unpredictable behavior of the fungus as well as climatic conditions pose serious challenges in precise phenotyping, genetic prediction and genetic improvement, leaving the complete onus of preventing aflatoxin contamination in crops on post-harvest management. Equipping popular crop varieties with genetic resistance to aflatoxin is key to effective lowering of infection in farmer’s fields. A combination of genetic resistance for in vitro seed colonization (IVSC), pre-harvest aflatoxin contamination (PAC) and aflatoxin production together with pre- and post-harvest management may provide a sustainable solution to aflatoxin contamination. In this context, modern “omics” approaches, including next-generation genomics technologies, can provide improved and decisive information and genetic solutions. Preventing contamination will not only drastically boost the consumption and trade of the crops and products across nations/regions, but more importantly, stave off deleterious health problems among consumers across the globe.

ACS Style

Manish K. Pandey; Rakesh Kumar; Arun K. Pandey; Pooja Soni; Sunil S. Gangurde; Hari K. Sudini; Jake C. Fountain; Boshou Liao; Haile Desmae; Patrick Okori; Xiaoping Chen; Huifang Jiang; Venugopal Mendu; Hamidou Falalou; Samuel Njoroge; James Mwololo; Baozhu Guo; Weijian Zhuang; Xingjun Wang; Xuanqiang Liang; Rajeev K. Varshney. Mitigating Aflatoxin Contamination in Groundnut through A Combination of Genetic Resistance and Post-Harvest Management Practices. Toxins 2019, 11, 315 .

AMA Style

Manish K. Pandey, Rakesh Kumar, Arun K. Pandey, Pooja Soni, Sunil S. Gangurde, Hari K. Sudini, Jake C. Fountain, Boshou Liao, Haile Desmae, Patrick Okori, Xiaoping Chen, Huifang Jiang, Venugopal Mendu, Hamidou Falalou, Samuel Njoroge, James Mwololo, Baozhu Guo, Weijian Zhuang, Xingjun Wang, Xuanqiang Liang, Rajeev K. Varshney. Mitigating Aflatoxin Contamination in Groundnut through A Combination of Genetic Resistance and Post-Harvest Management Practices. Toxins. 2019; 11 (6):315.

Chicago/Turabian Style

Manish K. Pandey; Rakesh Kumar; Arun K. Pandey; Pooja Soni; Sunil S. Gangurde; Hari K. Sudini; Jake C. Fountain; Boshou Liao; Haile Desmae; Patrick Okori; Xiaoping Chen; Huifang Jiang; Venugopal Mendu; Hamidou Falalou; Samuel Njoroge; James Mwololo; Baozhu Guo; Weijian Zhuang; Xingjun Wang; Xuanqiang Liang; Rajeev K. Varshney. 2019. "Mitigating Aflatoxin Contamination in Groundnut through A Combination of Genetic Resistance and Post-Harvest Management Practices." Toxins 11, no. 6: 315.

Journal article
Published: 01 January 2019 in Plant Health Progress
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Finger millet blast, caused by Magnaporthe grisea, is the most important disease of finger millet in East Africa. Diseased plants are significantly less productive, and most cultivars grown by farmers are susceptible to the disease. Fungicide application is an option for disease management; however, smallholder farmers cannot afford the cost. Host plant resistance is therefore the most viable option for managing the disease. Eighty-one finger millet germplasm accessions from East Africa were evaluated for resistance to blast disease, in natural and inoculated trials. Three accessions (G18, G43, and G67) were identified as resistant to all the three progressive stages of blast: leaf, neck, and panicle. However, one (G3) and four (G15, G16, G60, and G70) accessions were only resistant to leaf and neck blast, respectively. Two resistant (G39 and G43) and 12 moderately resistant (G3, G7, G11, G20, G23, G27, G31, G33, G36, G66, G74, and G81) accessions to blast attained grain yields >2.0 t/ha. These accessions varied in time to maturity, plant height, and grain color, which will enable farmers to select accessions appropriate to their target agro-ecological zones and desired end uses. East African finger millet germplasm has high potential as a source of blast-resistant accessions that could be evaluated for direct production and/or for blast-resistance breeding.

ACS Style

Eric O. Manyasa; Pangirayi Tongoona; Paul Shanahan; Stephen Githiri; Henry Ojulong; Samuel M. C. Njoroge. Exploiting Genetic Diversity for Blast Disease Resistance Sources in Finger Millet (Eleusine coracana). Plant Health Progress 2019, 20, 180 -186.

AMA Style

Eric O. Manyasa, Pangirayi Tongoona, Paul Shanahan, Stephen Githiri, Henry Ojulong, Samuel M. C. Njoroge. Exploiting Genetic Diversity for Blast Disease Resistance Sources in Finger Millet (Eleusine coracana). Plant Health Progress. 2019; 20 (3):180-186.

Chicago/Turabian Style

Eric O. Manyasa; Pangirayi Tongoona; Paul Shanahan; Stephen Githiri; Henry Ojulong; Samuel M. C. Njoroge. 2019. "Exploiting Genetic Diversity for Blast Disease Resistance Sources in Finger Millet (Eleusine coracana)." Plant Health Progress 20, no. 3: 180-186.

Review
Published: 01 December 2018 in Plant Disease
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Peanut (Arachis hypogaea L.) is an important crop in Malawi and Zambia. The crop is valued for soil improvement in cereal-based cropping systems, for improving the livelihoods of farming households who consume it and also sell it for cash, and for earning foreign exchange when exported. Research and development efforts have resulted in an increase in both peanut production area and productivity. However, a key challenge that still needs to be solved in these countries is how to produce peanuts with acceptable levels of aflatoxin contamination. Data continues to show that aflatoxin continues to be a problem in both formal and informal trade. As a result, unlike 30 years ago, most of the peanut trade has now shifted to domestic and regional markets that do not restrict the sale of aflatoxin-contaminated peanuts. Impacts of aflatoxin contamination on health and also on the full cost burden of control are not well documented. Technologies are available for mitigating against aflatoxin contamination. The advantages, disadvantages, and gaps associated with these technologies are discussed. Considerable money and effort continues to be invested in Malawi and Zambia into mitigating aflatoxin contamination, but evidence of long-term success is limited. Based on past and current initiatives, the prospects of eliminating aflatoxin in the near future at the household level and in trade are not promising.

ACS Style

Samuel M. C. Njoroge. A Critical Review of Aflatoxin Contamination of Peanuts in Malawi and Zambia: The Past, Present, and Future. Plant Disease 2018, 102, 2394 -2406.

AMA Style

Samuel M. C. Njoroge. A Critical Review of Aflatoxin Contamination of Peanuts in Malawi and Zambia: The Past, Present, and Future. Plant Disease. 2018; 102 (12):2394-2406.

Chicago/Turabian Style

Samuel M. C. Njoroge. 2018. "A Critical Review of Aflatoxin Contamination of Peanuts in Malawi and Zambia: The Past, Present, and Future." Plant Disease 102, no. 12: 2394-2406.

Research article
Published: 01 January 2018 in Plant Health Progress
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A survey was conducted in 2014 to determine the prevalence of fungal diseases on sorghum across different agroecological zones in Tanzania and Uganda. In Tanzania, 37 sorghum fields were sampled in Dodoma and Singida Provinces, representing the central drier areas, and in Simiyu, Shinyanga, Mwanza, and Mara Provinces, representing the lake-zone region. In Uganda, 134 fields were sampled across four agroecological zones of Teso, Western, Northern, and West Nile. Farmers were purposively selected, and at least 30 plants per field along two diagonal transects were visually assessed for disease. Ten and 14 diseases were identified in Tanzania and Uganda, respectively. Among the major diseases identified, those more prevalent in Tanzania than in Uganda were leaf blight caused by Setosphaeria turcica (P = 0.0031) and rust caused by Puccinia purpurea (P < 0.0001). Major diseases more prevalent in Uganda than in Tanzania were anthracnose caused by Colletotrichum sublineola (P = 0.0207) and zonate leaf spot caused by Gloeocercospora sorghi (P = 0.0312). We report for the first time the occurrence of ladder leaf spot caused by Cercospora fusimaculans in Uganda and confirm its occurrence in Tanzania. This is the first comprehensive sorghum disease survey report in over 15 years in both countries.

ACS Style

Samuel M. C. Njoroge; John Peter Takan; Elias A. Letayo; Patrick S. Okoth; Daniel O. Ajaku; Anil Kumar; Abhishek Rathore; Henry Ojulong; Eric Manyasa. Survey of Fungal Foliar and Panicle Diseases of Sorghum in Important Agroecological Zones of Tanzania and Uganda. Plant Health Progress 2018, 19, 265 -271.

AMA Style

Samuel M. C. Njoroge, John Peter Takan, Elias A. Letayo, Patrick S. Okoth, Daniel O. Ajaku, Anil Kumar, Abhishek Rathore, Henry Ojulong, Eric Manyasa. Survey of Fungal Foliar and Panicle Diseases of Sorghum in Important Agroecological Zones of Tanzania and Uganda. Plant Health Progress. 2018; 19 (3):265-271.

Chicago/Turabian Style

Samuel M. C. Njoroge; John Peter Takan; Elias A. Letayo; Patrick S. Okoth; Daniel O. Ajaku; Anil Kumar; Abhishek Rathore; Henry Ojulong; Eric Manyasa. 2018. "Survey of Fungal Foliar and Panicle Diseases of Sorghum in Important Agroecological Zones of Tanzania and Uganda." Plant Health Progress 19, no. 3: 265-271.

Research article
Published: 18 September 2017 in Journal of Consumer Protection and Food Safety
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This study was performed as a follow-up to a study from 2013, to assess the impact of management interventions on aflatoxin incidence and levels in commercial groundnut products in Malawi. Sixty-seven samples of commercial groundnut products were analyzed for aflatoxin using a fluorometric method. Total aflatoxin levels ranged from 1.5 to 1200 μg/kg in raw groundnuts and 83–820 μg/kg in groundnut flour from vendors. In branded groundnut flour and peanut butter from supermarkets, aflatoxin levels ranged from 13 to 670 μg/kg and 1.3 to 180 μg/kg, respectively. About 93, 88, 78 and 72% of the samples analyzed contained aflatoxin levels above regulatory limit used in Malawi (3 μg/kg), EU (4 μg/kg), most developing countries (10 μg/kg), and the USA (20 μg/kg), respectively. Despite much effort, aflatoxin levels remain persistently high in commercial groundnut. Considering the difficulty of achieving an efficient government regulation system due to resource constraint, the authors recommend the promotion of a socially responsible groundnut processing industry that has consumer welfare as its central feature.

ACS Style

Kennedy Magamba; Limbikani Matumba; Grey Matita; Aggrey Gama; Lazarus Singano; Maurice Monjerezi; Samuel M. C. Njoroge. Aflatoxin risk management in commercial groundnut products in Malawi (Sub-Saharan Africa): a call for a more socially responsible industry. Journal of Consumer Protection and Food Safety 2017, 12, 309 -316.

AMA Style

Kennedy Magamba, Limbikani Matumba, Grey Matita, Aggrey Gama, Lazarus Singano, Maurice Monjerezi, Samuel M. C. Njoroge. Aflatoxin risk management in commercial groundnut products in Malawi (Sub-Saharan Africa): a call for a more socially responsible industry. Journal of Consumer Protection and Food Safety. 2017; 12 (4):309-316.

Chicago/Turabian Style

Kennedy Magamba; Limbikani Matumba; Grey Matita; Aggrey Gama; Lazarus Singano; Maurice Monjerezi; Samuel M. C. Njoroge. 2017. "Aflatoxin risk management in commercial groundnut products in Malawi (Sub-Saharan Africa): a call for a more socially responsible industry." Journal of Consumer Protection and Food Safety 12, no. 4: 309-316.

Original article
Published: 26 January 2017 in Mycotoxin Research
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In Zambia, groundnut products (milled groundnut powder, groundnut kernels) are mostly sold in under-regulated markets. Coupled with the lack of quality enforcement in such markets, consumers may be at risk to aflatoxin exposure. However, the level of aflatoxin contamination in these products is not known. Compared to groundnut kernels, milled groundnut powder obscures visual indicators of aflatoxin contamination in groundnuts such as moldiness, discoloration, insect damage or kernel damage. A survey was therefore conducted from 2012 to 2014, to estimate and compare aflatoxin levels in these products (n = 202), purchased from markets in important groundnut growing districts and in urban areas. Samples of whole groundnut kernels (n = 163) and milled groundnut powder (n = 39) were analysed for aflatoxin B1 (AFB1) by competitive enzyme-linked immunosorbent assay (cELISA). Results showed substantial AFB1 contamination levels in both types of groundnut products with maximum AFB1 levels of 11,100 μg/kg (groundnut kernels) and 3000 μg/kg (milled groundnut powder). However, paired t test analysis showed that AFB1 contamination levels in milled groundnut powder were not always significantly higher (P > 0.05) than those in groundnut kernels. Even for products from the same vendor, AFB1 levels were not consistently higher in milled groundnut powder than in whole groundnut kernels. This suggests that vendors do not systematically sort out whole groundnut kernels of visually poor quality for milling. However, the overall contamination levels of groundnut products with AFB1 were found to be alarmingly high in all years and locations. Therefore, solutions are needed to reduce aflatoxin levels in such under-regulated markets.

ACS Style

Samuel M. C. Njoroge; Limbikani Matumba; Kennedy Kanenga; Moses Siambi; Farid Waliyar; Joseph Maruwo; Norah Machinjiri; Emmanuel S. Monyo. Aflatoxin B1 levels in groundnut products from local markets in Zambia. Mycotoxin Research 2017, 33, 113 -119.

AMA Style

Samuel M. C. Njoroge, Limbikani Matumba, Kennedy Kanenga, Moses Siambi, Farid Waliyar, Joseph Maruwo, Norah Machinjiri, Emmanuel S. Monyo. Aflatoxin B1 levels in groundnut products from local markets in Zambia. Mycotoxin Research. 2017; 33 (2):113-119.

Chicago/Turabian Style

Samuel M. C. Njoroge; Limbikani Matumba; Kennedy Kanenga; Moses Siambi; Farid Waliyar; Joseph Maruwo; Norah Machinjiri; Emmanuel S. Monyo. 2017. "Aflatoxin B1 levels in groundnut products from local markets in Zambia." Mycotoxin Research 33, no. 2: 113-119.

Journal article
Published: 01 May 2016 in Journal of Food Protection
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A 3-year comprehensive analysis of aflatoxin contamination in peanut butter was conducted in Zambia, sub-Saharan Africa. The study analyzed 954 containers of 24 local and imported peanut butter brands collected from shops in Chipata, Mambwe, Petauke, Katete, and Nyimba districts and also in Lusaka from 2012 to 2014. For analysis, a sample included six containers of a single brand, from the same processing batch number and the same shop. Each container was quantitatively analyzed for aflatoxin B1 (AFB1) in six replicates by using competitive enzyme-linked immunosorbent assay; thus, aflatoxin contamination level of a given sample was derived from an average of 36 test values. Results showed that 73% of the brands tested in 2012 were contaminated with AFB1 levels >20 μg/kg and ranged up to 130 μg/kg. In 2013, 80% of the brands were contaminated with AFB1 levels >20 μg/kg and ranged up to 10,740 μg/kg. Compared with brand data from 2012 and 2013, fewer brands in 2014, i.e., 53%, had aflatoxin B1 levels >20 μg/kg and ranged up to 1,000 μg/kg. Of the eight brands tested repeatedly across the 3-year period, none consistently averaged ≤20 μg/kg. Our survey clearly demonstrates the regular occurrence of high levels of AF B1 in peanut butter in Zambia. Considering that some of the brands tested originated from neighboring countries such as Malawi, Zimbabwe, and South Africa, the current findings provide a sub-Saharan regional perspective regarding the safety of peanut butter.

ACS Style

Samuel M. C. Njoroge; Limbikani Matumba; Kennedy Kanenga; Moses Siambi; Farid Waliyar; Joseph Maruwo; Emmanuel S. Monyo. A Case for Regular Aflatoxin Monitoring in Peanut Butter in Sub-Saharan Africa: Lessons from a 3-Year Survey in Zambia. Journal of Food Protection 2016, 79, 795 -800.

AMA Style

Samuel M. C. Njoroge, Limbikani Matumba, Kennedy Kanenga, Moses Siambi, Farid Waliyar, Joseph Maruwo, Emmanuel S. Monyo. A Case for Regular Aflatoxin Monitoring in Peanut Butter in Sub-Saharan Africa: Lessons from a 3-Year Survey in Zambia. Journal of Food Protection. 2016; 79 (5):795-800.

Chicago/Turabian Style

Samuel M. C. Njoroge; Limbikani Matumba; Kennedy Kanenga; Moses Siambi; Farid Waliyar; Joseph Maruwo; Emmanuel S. Monyo. 2016. "A Case for Regular Aflatoxin Monitoring in Peanut Butter in Sub-Saharan Africa: Lessons from a 3-Year Survey in Zambia." Journal of Food Protection 79, no. 5: 795-800.