Assessment of aflatoxin b1 contamination in maize and awareness of aflatoxins in son la province

VIETNAM NATIONAL UNIVERSITY OF AGRICULTURE NGUYEN THI THANH XUAN ASSESSMENT OF AFLATOXIN B1 CONTAMINATION IN MAIZE AND AWARENESS OF AFLATOXINS IN SON LA PROVINCE Major : Food Science and Technology Code : 60540103 Supervisor : Dr Hu Suk Lee Dr Nguyen Thi Thanh Thuy AGRICULTURAL UNIVERSITY PRESS - 2017 DECLARATION This thesis contains no materials that have been accepted for the award of any other degrees or diploma in any educational institutions To the best of my knowledge, my paper includes no previously published work written by any person, except where indicated in references Hanoi, May 10th, 2017 Master candidate Nguyen Thi Thanh Xuan i ACKNOWLEDGEMENTS First of all, I am really grateful my supervisors Dr Hu Suk Lee from International Livestock Research Institute (ILRI) for his patience, enthusiasm, motivation and immense knowledge, and to Dr Nguyen Thi Thanh Thuy from Vietnam National University of Agriculture, who gave me the opportunity to carry out this thesis and always had a piece of advice ready regarding the practical aspect of my work Their guidance supported me during this research I wish to express my gratitude to Prof Nguyen Viet Hung, a Southeast Asia regional representative at ILRI in Vietnam, for giving me a profound insight into the research and sharing his valuable experience with me I always bear in mind the enthusiasm Prof Delia Grace and Dr Johanna Lindahl at ILRI in Nairobi I highly appreciate Ms Nguyen Le Thanh and Ms Le My Hanh for their help in the administrative aspect Eventually, I would like to thank to all the members at ILRI in Vietnam for giving me the opportunity to become temporarily a part of their team I owe my thanks to all staffs in Plant Protection Research Institute They helped me so much for conducting sampling, interview, data collection and laboratory analysis Many thanks particularly to the whole team, who went to Son La for their logistical support and suggestion I also express my admiration to all members in Son La who introduced me to the locals and supervised our team during sampling and interview process I am also very thankful to Son La residents who warmly welcomed our team in their homes and participated in the survey Last but not least, I want to convey my gratefulness to my family and friends for their unremitting support, patience and understanding Hanoi, May 10th, 2017 Master candidate Nguyen Thi Thanh Xuan ii LIST OF CONTENTS Declaration i Acknowledgements ii List of contents iii List of abbreviations v List of tables vii List of figures viii Thesis abstract ix Part Introduction 1.1 Introduction 1.2 Research objectives Part Literature review 2.1 Situation in the maize production in vietnam – case of Son La 2.1.1 Situation in the maize production in Vietnam 2.1.2 Study location - Son La province 2.2 Aflatoxins and their impacts on human and animal health 2.2.1 Aflatoxins 2.2.2 The impact of aflatoxins on human and animal health 2.3 Factors influencing aspergillus spp infection and aflatoxin development in maize 13 2.4 Situation in the aflatoxin contamination in maize 15 2.4.1 Situation in the aflatoxin contamination in the world 15 2.4.2 Situation in the aflatoxin contamination in Vietnam 16 2.5 Methods to detect aflatoxins 17 2.6 Regulations for aflatoxins in the world and Vietnam 18 2.6.1 Regulations for aflatoxins in the world 18 2.6.2 Regulations for aflatoxins in Vietnam 21 Part Materials and methods 24 3.1 Materials 24 3.1.1 Maize samples 24 3.1.2 The Sigma-Aldrich® Aflatoxin B1 Low Matrix ELISA kit 24 3.2 Methods 24 iii 3.2.1 Sample size calculation and selection 24 3.2.2 Sampling 25 3.2.3 Aflatoxin B1 analysis in Lab 25 3.2.4 Questionnaire survey 27 3.2.5 Survey data analysis 27 Part Results and discussions 30 4.1 Aflatoxin B1 contamination in maize in Son La 30 4.2 Awareness of aflatoxins in Son La 36 Part Conclusions and recommendations 46 5.1 Conclusions 46 5.2 Recommendations 46 References 47 Appendix 58 iv LIST OF ABBREVIATIONS Acronym Abbreviations A Aspergillus A flavus Aspergillus flavus A nomius Aspergillus nomius A parasiticus Aspergillus paraciticus AFB1 Aflatoxin B1 AFM1 Aflatoxin M1 AFs Aflatoxins CIT Citrinin DON Deoxynivalenol EC European Commission EFTA European Free Trade Association ELISA Enzyme Linked Immunosorbent Assay EU European Union F moniliforme Fusarium moniliforme FAO Food and Agriculture Organization of the United Nations FB1 Fumonisin B1 FDA Food and Drug Administration FUM Fumonisins GAPs Good agricultural practices GPS Global positioning system HBV Hepatitis B virus HCC Hepatocellular Carcinoma HPLC High-performance liquid chromatography IARC International Agency for Research on Cancer LOD Limit of detection v OD Optical density OTA Ochratoxin A PBS Phosphate-buffered saline PE Polyethylene ppb Part per billion TLC Thin-layer chromatography USA United States of America ZEA Zearalenone µg/kg Microgram per kilogram vi LIST OF TABLES Table 2.1 Area under maize, maize production and yield of districts in Son La in 2013 Table 2.2 The property of aflatoxins Table 2.3 Limits of aflatoxin growth and production by A flavus and A parasiticus 14 Table 2.4 The FDA action levels for aflatoxins in human food and livestock feed 20 Table 2.5 Vietnamese limits for aflatoxins in human food 22 Table 4.1 Awareness of moldy contamination in maize in Son La 30 Table 4.2 Prevalence of AFB1 contamination in maize in Son La 32 Table 4.3 Awareness of molds among 107 respondents in each category corresponding questions with answers 39 Table 4.5 Practices associated with consumption of maize, meat and milk 42 Table 4.6 Practices related to the medical examination 45 vii LIST OF FIGURES Figure 2.1 Agro-ecological regions in Vietnam Figure 2.2 The administrative map in Son La province Figure 2.3 Area under maize, maize production and yield in Son La province Figure 2.4 Chemical structure of aflatoxins Figure 3.1 The map shows sampling sites in Son La province 25 Figure 4.1 Difference in the prevalence of AFB1 contamination in maize 33 Figure 4.2 Socio- demographic characteristics of respondents 37 viii THESIS ABSTRACT Master candidate: Nguyen Thi Thanh Xuan Thesis title: Assessment of aflatoxin B1 contamination in maize and awareness of aflatoxins in Son La province Major:Food Technology Code: 60540103 Educational organization: Vietnam National University of Agriculture (VNUA) Research Objectives This research was conducted to evaluate the prevalence of aflatoxin B1 contamination in maize and residents’ awareness of aflatoxins in Son La province Materials and Methods Materials included maize samples and the Sigma-Aldrich® Aflatoxin B1 Low Matrix ELISA kit Maize samples were randomly collected at the end of the rainy season from 25 communes in districts in Son La with recording GPS location All maize samples were analysed for AFB1 contamination in Lab, using the Sigma-Aldrich® Aflatoxin B1 Low Matrix ELISA kit Besides, questionnaire survey was simultaneously carried out with maize collection using face-to-face interviews Eventually, all data were imported into Microsoft Excel 2010 and analyzed using STATA (version 14.0, StataCorp, College Station, TX, USA) ArcGIS version 10.4.1 ArcMap (ESRI, Redlands, CA, USA) was used to create the map Main findings and conclusions The prevalence of AFB1 contamination in maize in Son La was lower when harvested in the field; however, this prevalence was higher in the rainy season Noticeably, most people had adequate awareness of molds and their impacts on human and animal health, but they lack insight of aflatoxins and the impacts of aflatoxins, particularly ethnic minority groups In conclusion, the findings can conclude that maize in Son La is exposed to AFB1 to varying degree, and there may be a risk that maize production could contain AFB1 Therefore, we believe that this study produces evidence on potential risk to humans and animals in Son La and will inform science-based messages for reducing risk Addtionally, the findings underline the need to enhance public's awareness about aflatoxins and health risks associated with aflatoxins on human beings and animals ix Table 4.6 Practices related to the medical examination Characteristic Definition Porportion (%) Mean ($/year) Do you have a medical examination? Yes 55.1 No 44.9 How many times per year you have a medical examination? Rarely (2-3x/year) 88.7 77.8 Sometimes (1x/month) 10.4 98.8 Usually (1x/week) 0.9 12.5 Everyday 0.00 Has any member of your family been diagnosed with hepatitis? Yes 4.7 No 95.3 Has any member of your family been diagnosed with liver cancer? Yes 5.6 No 94.4 Consequently, aflatoxins contamination, particularly AFB1 not only pose serious health risks but also cause significant economic lost to farmers whether their maize might be refused or agreed for consumption Otherwise, AFB1 contamination in maize and awareness of aflatoxin are serious challenges to people in Son La as well as general public 45 PART CONCLUSIONS AND RECOMMENDATIONS 5.1 CONCLUSIONS The findings in this research can conclude that maize in Son La is exposed to AFB1 to varying degrees, and there may be a risk that maize production could contain AFB1 In addition, we found that the level of AFB1 is relatively high during the rainy season Thus, it is important to undertake control strategies and to distinguish the maize samples whether it is suitable for human consumptions and animal feed or not We believe that this study produces evidence on potential risk to humans and animals in Son La and will inform science-based messages for reducing risk People in Son La had adequately awareness of molds and their impacts on human and animal health, but they have lack of information and impacts of aflatoxins, particularly ethnic minority groups Therefore, the findings highlight the need to raise public's awareness about aflatoxins as well as conducting further investigation of health risks on humams and animals 5.2 RECOMMENDATIONS It is necessary to evaluate the association between AFB1 contamination and environmental risk factors (such as temperatures, relative humidity, cropping, agronomic practices or other potential risk factors) Additionally, the intervention programs may include timing of planting, avoiding drought and rodent/insect control for field management, washing, rapid and proper drying and cleaning for post-harvest (Hell, 1997) It is recommended that ethnic minority groups should be targeted for raising the public awareness of aflatoxin risks as well as introduction of control and prevention strategies Besides, a further dietary research is needed to evaluate the impact of aflatoxin on human and animal health through risk assessments A further investigation is needed into the possible health impacts as well as to aid in establishing regulations for animal feed in order to reduce the direct or indirect health impacts in human beings and animals 46 REFERENCES Ahmad, S.K., 1993 Mycoflora changes and aflatoxin production in stored blackgram seeds Journal of stored products research 29, 33-36 Akşit, S., Çaǧlayan, S., Yaprak, I., Kansoy, S., 1997 Aflatoxin: Is it a neglected threat for formula fed infants Pediatrics International 39, 34-36 Alborch, L., Bragulat, M., Castellá, G., Abarca, M., Cabañes, F., 2012 Mycobiota and mycotoxin contamination of maize flours and popcorn kernels for human consumption commercialized in Spain Food microbiology 32, 97103 Bacaloni, A., Cavaliere, C., Cucci, F., Foglia, P., Samperi, R., Laganà, A., 2008 Determination of aflatoxins in hazelnuts by various sample preparation methods and liquid chromatography-tandem mass spectrometry Journal of Chromatography A 1179, 182-189 Bandara, J.S., Cai, Y., 2014 The impact of climate change on food crop productivity, food prices and food security in South Asia Economic Analysis and Policy 44, 451-465 Bankole, S.A., A, 2003 Mycotoxins in food in West Africa: current situation and possibilities of controlling it African Journal of Biotechnology 2, 254-263 Battilani, P., Toscano, P., Van der Fels-Klerx, H., Moretti, A., Leggieri, M.C., Brera, C., Rortais, A., Goumperis, T., Robinson, T., 2016 Aflatoxin B1 contamination in maize in Europe increases due to climate change Scientific reports Bilgrami, K., Sinha, K., 1987 Aflatoxin in India: I, US Universities-CIMMYT Maize Aflatoxin Workshop, El Batan, Mexico (Mexico), 7-11 Apr 1986 CIMMYT Binder, E., Tan, L., Chin, L., Handl, J., Richard, J., 2007 Worldwide occurrence of mycotoxins in commodities, feeds and feed ingredients Animal feed science and technology 137, 265-282 10 Biswas, A., Kondaiah, N., Anjaneyulu, A., Mandal, P., 2010 Food safety concerns of pesticides, veterinary drug residues and mycotoxins in meat and meat products Asian Journal of Animal Sciences 4, 46-55 11 Bullerman, L.B., Bianchini, A., 2007 Stability of mycotoxins during food processing International Journal of Food Microbiology 119, 140-146 47 12 Busby, W., Wogan, G., 1984 Aflatoxins Chemical carcinogens 2, 945-1136 13 Calvo A.M., Wilson R A., Bok J.W and Keller N.P 2002 Relationship between secondary metabolism and fungal development Microbiology and Molecular Biology 66: 447-459 14 CAST, 2003 Mycotoxins—Risks in Plant, Animal and Human Systems CAST Report, 139, 4-29 15 Chang, H., Markakis, P., 1981 Effect of moisture content on aflatoxin production in barley Cereal Chemistry 58, 89-91 16 Chen, S.-Y., Chen, C.-J., Chou, S.-R., Hsieh, L.-L., Wang, L.-Y., Tsai, W.-Y., Ahsan, H., Santella, R.M., 2001 Association of aflatoxin B1-albumin adduct levels with hepatitis B surface antigen status among adolescents in Taiwan Cancer Epidemiology and Prevention Biomarkers 10, 1223-1226 17 Chulze, S., 2010 Strategies to reduce mycotoxin levels in maize during storage: a review Food Additives and Contaminants 27, 651-657 18 Cole, R., Cox, R., 1981 The trichothecenes Handbook of toxic fungal metabolites, 152-263 19 Cotty, P., 1994 Influence of field application of an atoxigenic strain of Aspergillus flavus on the populations of A flavus infecting cotton bolls and on the aflatoxin content of cottonseed Plant Diseases 20 Cullen, J.M., Newberne, P.M., 1994 Acute hepatoxicity of aflatoxins In: Eaton DL, Groopman JD (eds) The toxicology of aflatoxins Academic Press, San Diego, pp 3–26 21 Dang, H.-A., 2012 Vietnam: A widening poverty gap for ethnic minorities 22 De Campos, M., 1987 Mycotoxins and food in developing countries, Joint FAO/WHO/UNEP International Conference on Mycotoxins 2, Bangkok (Thailand), 28 Sep-3 Oct 1987 23 Denli, M., Pérez, J.F., 2006 Contaminación por micotoxinas en los piensos: efectos, tratamiento y prevención XXII Curso de Especialización FEDNA, 118 24 Denning, D.W., Allen, R., Wilkinson, A.P., Morgan, M.R., 1990 Transplacental transfer of aflatoxin in humans Carcinogenesis 11, 1033-1035 25 Dennis P., Hsieh H., 1981 International Symposium and Workshop on Mycotoxins, Cairo, Dokki, Egypt, Proceedings International Symposium on Mycotoxins, p.151-165 48 26 Diener, U.L., Cole, R.J., Sanders, T., Payne, G.A., Lee, L.S., Klich, M.A., 1987 Epidemiology of aflatoxin formation by Aspergillus flavus Annual review of phytopathology 25, 249-270 27 Dosman, D.M., Adamowicz, W.L., Hrudey, S.E., 2001 Socioeconomic determinants of health and food safety related risk perceptions Risk analysis 21, 307-318 28 Dubale, B., Solomon, A., Geremew, B., Sethumadhava, R., Waktole, S., 2014 Mycoflora of grain maize (Zea mays L.) stored in traditional storage containers (Gombisa and sacks) in selected woredas of Jimma zone, Ethiopia African Journal of Food, Agriculture, Nutrition and Development 14 29 EFSA, 2004 Opinion of the Scientific Panel on Contaminants in the Food Chain on a request from the Commission related to Aflatoxin B1 as undesirable substance in animal feed The EFSA Journal, 39, 31-27 30 FAO, 1979 Prevention of mycotoxins FAO Food and Nutrition Paper, No 10 31 FAO., IFIF., 2010 Good practices for industry-Implementing the codex Alimentarius Code of Practice on Good Animal Feeding FAO Animal Production and Health Manual Rome, 32 FSI, F.S.I.V., 2011 National technical regulation on the limits of mycotoxins contamination in food Available at: http://tinyurl.com/za2j2b9 33 Gbodi, T., Nwude, N., Aliu, Y., Ikediobi, C., 1986 The mycoflora and some mycotoxins found in maize (Zea mays) in the Plateau State of Nigeria Veterinary and Human toxicology 28, 1-5 34 Ghiasian, S., Shephard, G., Yazdanpanah, H., 2011 Natural occurrence of aflatoxins from maize in Iran Mycopathologia 172, 153-160 35 Gimeno, A., 2004 Aflatoxina M1 no leite Riscos para a saúde pública, prevenỗóo e controlo Alimentaỗóo Animal (Revista de la Associaỗóo Portuguesa dos Industriais de Alimentos Compostos para Animais (IACA)) 49, 32-44 36 Gonỗalez, E., Pinto, M.M., Manginelli, S., Felicio, J., 2004 Dairy cows poisoned with cottonseed meal naturally contaminated with aflatoxins Ciência Rural 34, 171-174 37 GSO, 2017 General Statistics Office of Viet Nam., p Available at: https://gso.gov.vn/default.aspx?tabid=713 49 38 Ha, D.T., Thao, T.D., Khiem, N.T., Trieu, M.X., Gerpacio, R.V., Pingali, P.L., 2004 Maize in Vietnam: Production Systems, Constraints, and Research Priorities CIMMYT: International Maize and Wheat Improvement Center 39 Hall, A.J., Wild, C.P., 1994 Epidemiology of Aflatoxin The toxicology of aflatoxins: Human health, veterinary, and agricultural significance 40 Hell, K., 1997 Factors contributing to the distribution and incidence of aflatoxin producing fungi in stored maize in Benin 41 Hell, K., Mutegi, C., 2011 Aflatoxin control and prevention strategies in key crops of Sub-Saharan Africa 42 Hendrickse, R., 1999 Of sick turkeys, kwashiorkor, malaria, perinatal mortality, heroin addicts and food poisoning: research on the influence of aflatoxins on child health in the tropics Annals of tropical paediatrics 19, 229-235 43 Henry , M.H 2006 Mycotoxins in Feeds: CVM’s Perspective, Presentation for Risk Management Agency Division of Animal Feeds, Center for Veterinary Medicine, Food and Drug Administration, August 23, 2006, in Austin, Texas http://www.fda.gov/cvm/ fdaaustintx823.htm 44 Henry, S.H., Bosch, F.X., Bowers, J., 2002 Aflatoxin, hepatitis and worldwide liver cancer risks, Mycotoxins and food safety Springer, pp 229-233 45 Hesseltine, C.W., 1976 Conditions leading to mycotoxin contamination of foods and feeds ACS Publications 46 Hipgrave, D.B., Van, N.T., Huong, V.M., Long, H.T., Tuan, D.D., Trung, T.N., Jolley, D., Maynard, J.E., Biggs, B.-A., 2003 Hepatitis B infection in rural Vietnam and the implications for a national program of infant immunization The American journal of tropical medicine and hygiene 69, 288-294 47 Horn, B.W., 2003 Ecology and population biology of aflatoxigenic fungi in soil Journal of Toxicology: Toxin Reviews 22, 351-379 48 Hosmer, D.W., Hosmer, T., Le Cessie, S., Lemeshow, S., 1997 A comparison of goodness-of-fit tests for the logistic regression model Statistics in medicine 16, 965-980 49 Huong, B.T.M., Do, T.T., Madsen, H., Brimer, L., Dalsgaard, A., 2016 Aflatoxins and fumonisins in rice and maize staple cereals in Northern Vietnam and dietary exposure in different ethnic groups Food Control 70, 191-200 50 ICMSF 1996 Intestinally pathogenic Escherichia Coli In: Micro-Organisms in Foods, 5, Microbiological Specifications of Food Pathogens, 127 140 London: Blackie Academic & Professional 50 51 Ilangantileke, S., 1987 Application of chemicals at farm levels in the control of aflatoxin in stored maize cobs Unpublished report to Rural Investment Overseas Ltd 52 Jinap, S., De Rijk, T., Arzandeh, S., Kleijnen, H., Zomer, P., Van der Weg, G., Mol, J., 2012 Aflatoxin determination using in-line immunoaffinity chromatography in foods Food Control 26, 42-48 53 Jones, R., Duncan, H., 1981 Effect of nitrogen fertilizer, planting date, and harvest date on aflatoxin production in corn inoculated with Aspergillus flavus [North Carolina; USA] (USA) 54 Karimov A A., Thinh T N., Cadilhon J J., Tung T H., Hai T D., Doan V V., and Duan Q B 2016 Value chain assessment report for maize, pig, plum and tea in son la province of northwest Vietnam International Livestock Research Institute 1-2 55 Kawasugi, S., SIRIACHA, P., TONBOON-EK, P., 1988 Experimental studies on the field-dried Thai maize inoculated with Aspergillus flavus JSM Mycotoxins 1988, 17-22 56 Khlangwiset, P., Shephard, G.S., Wu, F., 2011 Aflatoxins and growth impairment: a review Critical reviews in toxicology 41, 740-755 57 Lawley, R., 2013 Aflatoxins Food Safety Watch, http://www foodsafetywatch org/factsheets/aflatoxins 58 Lee, H., Chuang, T., 1993 Comparison of Aspergillus flavus and aflatoxin contamination among various types of peanut harvest at Penghu Plant Pathol Bull 2, 88-97 59 Lee, H.S., Nguyen-Viet, H., Lindahl, J., Thanh, H.M., Khanh, T.N., Hien, L., Grace, D., 2017 A survey of aflatoxin B1 in maize and awareness of aflatoxins in Vietnam World Mycotoxin Journal, 1-8 60 Lee, N.A., Wang, S., Allan, R.D., Kennedy, I.R., 2004 A rapid aflatoxin B1 ELISA: development and validation with reduced matrix effects for peanuts, corn, pistachio, and soybeans Journal of agricultural and food chemistry 52, 2746-2755 61 Lewis, L., Onsongo, M., Njapau, H., Schurz-Rogers, H., Luber, G., Kieszak, S., Nyamongo, J., Backer, L., Dahiye, A.M., Misore, A., 2005 Aflatoxin contamination of commercial maize products during an outbreak of acute aflatoxicosis in eastern and central Kenya Environmental health perspectives, 1763-1767 51 62 Lillehoj, E.B., 1983 Effect of environmental and cultural factors on aflatoxin contamination of developing corn kernels Southern cooperative series bulletin (USA) 63 López, C., Ramos, L., Ramadan, S., Bulacio, L., 2003 Presence of aflatoxin M1 in milk for human consumption in Argentina Food control 14, 31-34 64 Lynch, R.E., Wilson, D.M., 1991 Enhanced Infection of Peanut, Arachis hypogaea L., Seeds With Aspergillus flavus Group Fungi Due to External Scarification of Peanut Pods by the Lesser Cornstalk Borer, Elasmopalpus lignosellus (Zeller) Peanut Science 18, 110-116 65 Magan, N., Lacey, J., 1988 Ecological determinants of mold growth in stored grain International Journal of Food Microbiology 7, 245-256 66 Masoero, F., Gallo, A., Moschini, M., Piva, G., Diaz, D., 2007 Carryover of aflatoxin from feed to milk in dairy cows with low or high somatic cell counts 67 Matumba, L., Van Poucke, C., Njumbe Ediage, E., Jacobs, B., De Saeger, S., 2015 Effectiveness of hand sorting, flotation/washing, dehulling and combinations thereof on the decontamination of mycotoxin-contaminated white maize Food Additives & Contaminants: Part A 32, 960-969 68 McMillan, J., 1990 Managing suppliers: Incentive systems in Japanese and US industry California Management Review 32, 38-55 69 Mehan, V., McDonald, D., Haravu, L., Jayanthi, S., 1991 The groundnut aflatoxin problem review and literature database International Crops Research Institute for the Semi-Arid Tropics 70 Miller D.M., Wilson D.M., 1994 Veterinary Diseases Related to Aflatoxins In: The Toxicology of Aflatoxins: Human Health, Veterinary, and Agricultural Significance DL Eaton and JD Groopman (eds) San Diego, CA, Academic Press, Inc.: 347-364 71 Muscarella, M., Magro, S.L., Palermo, C., Centonze, D., 2007 Validation according to European Commission Decision 2002/657/EC of a confirmatory method for aflatoxin M1 in milk based on immunoaffinity columns and high performance liquid chromatography with fluorescence detection 72 Murugavel, K., Naranatt, P., Shankar, E., Mathews, S., Raghuram, K., Rajasambandam, P., Jayanthi, V., Surendran, R., Murali, A., Srinivas, U., 2007 Prevalence of aflatoxin B1 in liver biopsies of proven hepatocellular carcinoma in India determined by an in-house immunoperoxidase test Journal of medical microbiology 56, 1455-1459 52 73 Navas, S., Sabino, M., Rodriguez-Amaya, D., 2005 Aflatoxin M1 and ochratoxin A in a human milk bank in the city of Sao Paulo, Brazil Food additives and contaminants 22, 457-462 74 Njapau, H., 2008 Sampling village corn for aflatoxin analysis: practical aspects Mycotoxin Contamination and Control (Njapau H, Trujillo S, Pohland AE, Park DL, eds) Bloomington, IN: Authorhouse, 113-132 75 Nguyen, M.T., Tozlovanu, M., Tran, T.L., Pfohl-Leszkowicz, A., 2007 Occurrence of aflatoxin B1, citrinin and ochratoxin A in rice in five provinces of the central region of Vietnam Food chemistry 105, 42-47 76 Odoemelam, S., Osu, C., 2009 Aflatoxin B1Contamination of Some Edible Grains Marketed in Nigeria Journal of Chemistry 6, 308-314 77 Omer, R.E., Kuijsten, A., Kadaru, A.M., Kok, F.J., Idris, M.O., El Khidir, I.M., van't Veer, P., 2004 Population-attributable risk of dietary aflatoxins and hepatitis B virus infection with respect to hepatocellular carcinoma Nutrition and cancer 48, 15-21 78 Parkin, D.M., Bray, F., Ferlay, J., Pisani, P., 2005 Global cancer statistics, 2002 CA: a cancer journal for clinicians 55, 74-108 79 Phuong, N.H., Thieu, N.Q., Ogle, B., Pettersson, H., 2015 Aflatoxins, Fumonisins and Zearalenone Contamination of Maize in the Southeastern and Central Highlands Provinces of Vietnam Agriculture 5, 1195-1203 80 Pier, A., 1992 Major biological consequences of aflatoxicosis in animal production Journal of Animal Science 70, 3964-3967 81 Pingali, P.L., 2001 CIMMYT 1999/2000 World maize facts and trends Meeting world maize needs: Technological opportunities and priorities for the public sector 82 Qian, G.-S., Ross, R.K., Yu, M.C., Yuan, J.-M., Gao, Y.-T., Henderson, B.E., Wogan, G.N., Groopman, J.D., 1994 A follow-up study of urinary markers of aflatoxin exposure and liver cancer risk in Shanghai, People's Republic of China Cancer Epidemiology and Prevention Biomarkers 3, 3-10 83 Quyet, T.Q., 2013 Ecosystems classification mapping in Vietnam, BCA, WWF, Stockholm University 84 Ramakrishna, N., Lacey, J., Smith, J., 1993 Effects of water activity and temperature on the growth of fungi interacting on barley grain Mycological research 97, 1393-1402 53 85 Ranum, P., Peña?Rosas, J.P., Garcia Casal, M.N., 2014 Global maize production, utilization, and consumption Annals of the New York Academy of Sciences 1312, 105-112 86 Raters, M., Matissek, R., 2008 Thermal stability of aflatoxin B1 and ochratoxin A Mycotoxin research 24, 130-134 87 Reddy, K., Abbas, H., Abel, C., Shier, W.T., Oliveira, C., Raghavender, C., 2009 Mycotoxin contamination of commercially important agricultural commodities Toxin Reviews 28, 154-168 88 Richard, J.L., 2007 Some major mycotoxins and their mycotoxicoses—An overview International journal of food microbiology 119, 3-10 89 Rodrigues, I., Nahrer, K., 2008 Biomin Mycotoxin Survey Program 2008 Biomin Newsletter 90 Ross, I., Loewer, O., White, G., 1979 Potential for aflatoxin development in low temperature drying systems Transactions of the ASAE 22, 1439-1443 91 Rustom, I.Y., 1997 Aflatoxin in food and feed: occurrence, legislation and inactivation by physical methods Food chemistry 59, 57-67 92 Saad, A., Abdelgadirt, A., Moss, M., 1995 Exposure of infants to aflatoxin M1 from mothers’ breast milk in Abu Dhabi, UAE Food Additives & Contaminants 12, 255-261 93 Sandra, V., McNeel, D V M., Richard, A., Kreutzer, M D., 1996 Fungi and indoor air quality Health Environ Digest 10:6–12 94 Scott, G.E., Zummo, N., 1994 Kernel Infection and Aflatoxin Production in Maize by Aspergillus flavus Plant disease 78, 123 95 Setamou, M., CardwelL, K.F., Schulthess, F., Hell, K., 1997 Aspergillus flavus infection and aflatoxin contamination of preharvest maize in Benin Plant Disease 81, 1323-1327 96 Shephard, G., 2008 Impact of mycotoxins on human health in developing countries Food Additives and contaminants 25, 146-151 97 Shephard, R.J., 2003 Limits to the measurement of habitual physical activity by questionnaires British journal of sports medicine 37, 197-206 98 Siegrist, M., Cvetkovich, G., 2000 Perception of hazards: The role of social trust and knowledge Risk analysis 20, 713-720 54 99 Sobolev, V.S., 2007 Simple, rapid, and inexpensive cleanup method for quantitation of aflatoxins in important agricultural products by HPLC Journal of agricultural and food chemistry 55, 2136-2141 100 Stroka, J., Anklam, E., Jörissen, U., Gilbert, J., 2000 Immunoaffinity column cleanup with liquid chromatography using post-column bromination for determination of aflatoxins in peanut butter, pistachio paste, fig paste, and paprika powder: collaborative study Journal of AOAC International 83, 320340 101 Strosnider, H., Azziz-Baumgartner, E., Banziger, M., Bhat, R.V., Breiman, R., Brune, M.-N., DeCock, K., Dilley, A., Groopman, J., Hell, K., 2006 Workgroup report: public health strategies for reducing aflatoxin exposure in developing countries Environmental health perspectives, 1898-1903 102 Tedesco, D., Barbieri, C., Lugano, S., Garavaglia, L., 2008 Aflatoxin contamination risk: bioactive natural compounds for animal health and healthy food, Impact of pollution on Animal Products Springer, pp 177-184 103 Thieu, N.Q., Ogle, B., Pettersson, H., 2008 Screening of Aflatoxins and Zearalenone in feedstuffs and complete feeds for pigs in Southern Vietnam Tropical Animal Health and Production 40, 77-83 104 Thompson, D., Lillehoj, E., Leonard, K., Kwolek, W., Zuber, M., 1980 Aflatoxin concentration in corn as influenced by kernel development stage and postinoculation temperature in controlled environments Crop Science 20, 609612 105 Thompson, C., Henke, S.E., 2000 Effect of climate and type of storage container on aflatoxin production in corn and its associated risks to wildlife species Journal of Wildlife Diseases 36, 172-179 106 Tran, D., 2005 Maize production and selling maize in Son La Tran, DV et al, 212-227 107 Trung, T., Tabuc, C., Bailly, S., Querin, A., Guerre, P., Bailly, J., 2008 Fungal mycoflora and contamination of maize from Vietnam with aflatoxin B1 and fumonisin B1 World Mycotoxin Journal 1, 87-94 108 United Nations., 2011 Climate change fact sheet: The effects of climate change in Vietnam and the UN's responses Version of 11 April 2011 109 Van Egmond, H., Jonker, M., 2004 Worldwide regulations for mycotoxins in food and feed: the situation in 2003 Draft FAO Food and Nutrition Paper National Institute for Public Health & the Environment, Bilthoven 55 110 Vargas, E., Preis, R., Castro, L., Silva, C., 2001 Co-occurrence of aflatoxins B 1, B 2, G 1, G 2, zearalenone and fumonisin B1 in Brazilian corn Food Additives & Contaminants 18, 981-986 111 Wagacha, J., Muthomi, J., 2008 Mycotoxin problem in Africa: current status, implications to food safety and health and possible management strategies International journal of food microbiology 124, 1-12 112 Walderhaug, M., 1992 Ciguatera Foodborne Pathogenic Microorganisms and Natural Toxins Handbook Food and Drug Administration, US 113 Walke, M., Mtimet, N., Baker, D., Lindahl, J., Hartmann, M., Grace, D., 2014 Kenyan perceptions of aflatoxin: An analysis of raw milk consumption 114 Wang, D.S., Liang, Y.X., Nguyen, T.C., Le, D.D., Tanaka, T., Ueno, Y., 1995 Natural co-occurrence of Fusarium toxins and aflatoxin B1 in corn for feed in north Vietnam Natural Toxins 3, 445-449 115 Wang, J., Liu, X., 2006 Surveillance on contamination of total aflatoxins in corn, peanut, rice, walnut and pine nut in several areas in China Zhonghua yu fang yi xue za zhi [Chinese journal of preventive medicine] 40, 33-37 116 Wang, L.Y., Hatch, M., Chen, C.J., Levin, B., You, S.L., Lu, S.N., Wu, M.H., Wu, W.P., Wang, L.W., Wang, Q., 1996 Aflatoxin exposure and risk of hepatocellular carcinoma in Taiwan International journal of cancer 67, 620625 117 WHO, 1998 Safety evaluation of certain food additives and contaminant pp 359 - 468 Geneve: WHO 118 Wicklow, D., Hesseltine, C., Shotwell, O., Adams, G., 1980 Interference competition and aflatoxin levels in corn Phytopathology 70, 761-764 119 Wild, C.P., Gong, Y.Y., 2010 Mycotoxins and human disease: a largely ignored global health issue Carcinogenesis 31, 71-82 120 Williams, J.H., Phillips, T.D., Jolly, P.E., Stiles, J.K., Jolly, C.M., Aggarwal, D., 2004 Human aflatoxicosis in developing countries: a review of toxicology, exposure, potential health consequences, and interventions The American journal of clinical nutrition 80, 1106-1122 121 Wilson, D.M., Payne, G.A., 1994 Factors affecting The Toxicology of Aflatoxins: Human Health, Veterinary, and Agricultural Significance 122 Yard, E.E., Daniel, J.H., Lewis, L.S., Rybak, M.E., Paliakov, E.M., Kim, A.A., Montgomery, J.M., Bunnell, R., Abudo, M.U., Akhwale, W., 2013 Human 56 aflatoxin exposure in Kenya, 2007: a cross-sectional study Food Additives & Contaminants: Part A 30, 1322-1331 123 Zinedine, A., Juan, C., Soriano, J., Molto, J., Idrissi, L., Manes, J., 2007 Limited survey for the occurrence of aflatoxins in cereals and poultry feeds from Rabat, Morocco International Journal of Food Microbiology 115, 124-127 124 Zohova, T., 2011 Improving sustainability of rural livelihoods in Son La province, Northwest Vietnam: Potential of use of biogas digesters 57 APPENDIX APPENDIX 2.1: Areas under maize, maize production and yields in Son La (2004 2014) Production Area (thousand (thousand tons) ha) Year Yield (tons/ha) 2004 3.19 217.8 68.2 2005 2.82 228 80.9 2006 3.26 269 82.4 2007 3.77 444 117.8 2008 3.81 503.5 132.3 2009 3.89 514.2 132.1 2010 3.15 417.4 132.7 2011 3.97 506.7 127.5 2012 3.96 667.3 168.7 2013 4.02 654.7 162.8 2014 4.06 659.1 162.5 APPENDIX 2.2: Perciptation every month in 2015 in Son La Months Jan Feb Mar Apr May Percipitation (mm) 76.3 1.6 61.3 Jun Jul Agu Sept 75.1 42.6 359.8 429.5 258.9 266.2 Oct Nov 86 (Source: GSO, 2017) 58 Dec 44.9 101.2 APPENDIX 4: Prevalence and levels of AFB1 in maize in Son La in March, 2016 Districts (No sample) AFB1 level > ug/kg Prevalence (%) 95% CI AFB1 level > 20 ug/kg Prevalence (%) Mean 95% CI * Media n* Range (