Henry Njapau - Academia.edu (original) (raw)
Papers by Henry Njapau
a International Institute of Tropical Agriculture (IITA-Zambia), Lusaka, Zambia b IITA-Ibadan, Oy... more a International Institute of Tropical Agriculture (IITA-Zambia), Lusaka, Zambia b IITA-Ibadan, Oyo Road, Ibadan, Nigeria c Zambia Agriculture Research Institute, Mount Makulu Central Research Station, Zambia. d National Institute for Scientific and Industrial Research (NISIR), Lusaka, Zambia e The World Vegetable Center (AVRDC) Eastern and Southern Africa , Duluti, Arusha, Tanzania f USDA-ARS, School of Plant Sciences, University of Arizona, Tucson, USA.
Journal of Chromatography B: Biomedical Sciences and Applications, 1982
Applied and Environmental Microbiology, May 31, 2023
Fungi contaminate various crops worldwide. Maize, an important human staple and livestock cereal,... more Fungi contaminate various crops worldwide. Maize, an important human staple and livestock cereal, is susceptible to contamination with fungi in the field.
Mycotoxins, 2006
Acute aflatoxicosis outbreaks sporadically occur among subsistence farmers in Makueni and Kitui d... more Acute aflatoxicosis outbreaks sporadically occur among subsistence farmers in Makueni and Kitui districts, Eastern Province, Kenya. Over the past 25 years, four documented outbreaks of acute aflatoxicosis affecting 467 individuals and resulting in 178 deaths have occurred in the same region. The outbreaks occurred in the southeastern part of Eastern Province between the months of April and July.
Journal of Fungi
Aflatoxins (AFs) are considered to play important functions in species of Aspergillus section Fla... more Aflatoxins (AFs) are considered to play important functions in species of Aspergillus section Flavi including an antioxidative role, as a deterrent against fungivorous insects, and in antibiosis. Atoxigenic Flavi are known to degrade AF-B1 (B1). To better understand the purpose of AF degradation, we investigated the degradation of B1 and AF-G1 (G1) in an antioxidative role in Flavi. Atoxigenic and toxigenic Flavi were treated with artificial B1 and G1 with or without the antioxidant selenium (Se), which is expected to affect levels of AF. After incubations, AF levels were measured by HPLC. To estimate which population would likely be favoured between toxigenic and atoxigenic Flavi under Se, we investigated the fitness, by spore count, of the Flavi as a result of exposure to 0, 0.40, and 0.86 µg/g Se in 3%-sucrose cornmeal agar (3gCMA). Results showed that levels B1 in medium without Se were reduced in all isolates, while G1 did not significantly change. When the medium was treated w...
<b>Copyright information:</b>Taken from "Aflatoxin Contamination of Commercial M... more <b>Copyright information:</b>Taken from "Aflatoxin Contamination of Commercial Maize Products during an Outbreak of Acute Aflatoxicosis in Eastern and Central Kenya"Environmental Health Perspectives 2005;113(12):1763-1767.Published online 10 Aug 2005PMCID:PMC1314917.This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI. Each dot represents the rate of aflatoxicosis by division, and dots are in the center of each division (divisions are not shown).
<b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxi... more <b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxicosis Outbreak, Kenya, 2004"Environmental Health Perspectives 2005;113(12):1779-1783.Published online 9 Aug 2005PMCID:PMC1314920.This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.
See next page for additional authors
See next page for additional authors
aflatoxicosis outbreak in eastern Kenya resulted in 317 cases and 125 deaths. We conducted a case... more aflatoxicosis outbreak in eastern Kenya resulted in 317 cases and 125 deaths. We conducted a case-control study to identify risk factors for contamination of implicated maize and, for the first time, quantitated biomarkers associated with acute aflatoxicosis. DESIGN: We administered questionnaires regarding maize storage and consumption and obtained maize and blood samples from participants. PARTICIPANTS: We recruited 40 case-patients with aflatoxicosis and 80 randomly selected controls to participate in this study. EVALUATIONS/MEASUREMENTS: We analyzed maize for total aflatoxins and serum for aflatoxin B 1 -lysine albumin adducts and hepatitis B surface antigen. We used regression and survival analyses to explore the relationship between aflatoxins, maize consumption, hepatitis B surface antigen, and case status. RESULTS: Homegrown (not commercial) maize kernels from case households had higher concentrations of aflatoxins than did kernels from control households [ To select 40 pati...
Applied and environmental …, 2007
a Deutsche Gesellschaft für Internationale Zusammenar beit (GIZ), Germany b International Institu... more a Deutsche Gesellschaft für Internationale Zusammenar beit (GIZ), Germany b International Institute of Tropical Agriculture (II TA-Zambia), Lusaka, Zambia c IITA-Ibadan, Oyo Road, Ibadan, Nigeria d Zambia Agriculture Research Institute, Mount Makul u Central Research Station, Zambia. e National Institute for Scientific and Industrial Re search (NISIR), Lusaka, Zambia f The World Vegetable Center (AVRDC) Eastern and Sou thern Africa , Duluti, Arusha, Tanzania g USDA-ARS, School of Plant Sciences, University of Arizona, Tucson, USA.
<b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxi... more <b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxicosis Outbreak, Kenya, 2004"Environmental Health Perspectives 2005;113(12):1779-1783.Published online 9 Aug 2005PMCID:PMC1314920.This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.
Journal of AOAC International
The number of elevator facilities with laboratories to test shelled corn for aflatoxin on site is... more The number of elevator facilities with laboratories to test shelled corn for aflatoxin on site is increasing. The inherent difficulty in accurately determining the true aflatoxin concentration of a lot of corn may have serious implications. Deviations from the true value are of even greater significance at busy locations where a high throughput is desired. This study was instituted to measure (1) the differences in aflatoxin test results between elevator laboratories and the Louisiana Agricultural Chemistry (LAC) laboratory and (2) the variability in aflatoxin test results associated with sampling, sample preparation, and analysis of shelled corn at such locations. One hundred lots of shelled corn from 10 elevators in Louisiana were analyzed for aflatoxin using the Aflatest method (at elevators and at the LAC laboratory) and high-performance column liquid chromatography (HPLC; LAC laboratory only). Mean aflatoxin levels determined at elevator laboratories were significantly (P < ...
Maize contaminated with aflatoxins has been implicated in deadly epidemics in Kenya three times s... more Maize contaminated with aflatoxins has been implicated in deadly epidemics in Kenya three times since 1981, but the fungi contaminating the maize with aflatoxins have not been characterized. Here we associate the S strain of Aspergillus flavus with lethal aflatoxicoses that took more than 125 lives in 2004. The 2004 outbreak of acute aflatoxicosis in Kenya was one of the most severe episodes of human aflatoxin poisoning in history. A total of 317 cases were reported by 20 July 2004, with a case fatality rate of 39 % (1, 26). This epidemic resulted from ingestion of contaminated maize (22). However, identities of the fungi causing the contamination remain unclear. Aflatoxins are carcinogenic metabolites produced by several Aspergillus species (4, 28). Aflatoxin-producing fungi vary widely in many characteristics, including virulence for crops and aflatoxin-producing capacity (10). A. flavus and A. parasiticus are most commonly implicated as causal agents of aflatoxin contamination. A...
In April 2004, one of the largest aflatoxicosis outbreaks occurred in rural Kenya, resulting in 3... more In April 2004, one of the largest aflatoxicosis outbreaks occurred in rural Kenya, resulting in 317 cases and 125 deaths. Aflatoxin-contaminated homegrown maize was the source of the outbreak, but the extent of regional contamination and status of maize in commercial markets (market maize) were unknown. We conducted a cross-sectional survey to assess the extent of market maize contamination and evaluate the relationship between market maize aflatoxin and the aflatoxicosis outbreak. We surveyed 65 markets and 243 maize vendors and collected 350 maize products in the most affected districts. Fifty-five percent of maize products had aflatoxin levels greater than the Kenyan regulatory limit of 20 ppb, 35 % had levels> 100 ppb, and 7 % had levels> 1,000 ppb. Makueni, the district with the most aflatoxicosis case-patients, had significantly higher market maize aflatoxin than did Thika, the study district with fewest case-patients (geometric mean aflatoxin = 52.91 ppb vs. 7.52 ppb, p...
OBJECTIVES: During January–June 2004, an aflatoxicosis outbreak in eastern Kenya resulted in 317 ... more OBJECTIVES: During January–June 2004, an aflatoxicosis outbreak in eastern Kenya resulted in 317 cases and 125 deaths. We conducted a case–control study to identify risk factors for contamination of implicated maize and, for the first time, quantitated biomarkers associated with acute aflatoxicosis. DESIGN: We administered questionnaires regarding maize storage and consumption and obtained maize and blood samples from participants. PARTICIPANTS: We recruited 40 case-patients with aflatoxicosis and 80 randomly selected controls to participate in this study. EVALUATIONS/MEASUREMENTS: We analyzed maize for total aflatoxins and serum for aflatoxin B1–lysine albumin adducts and hepatitis B surface antigen. We used regression and survival analyses to explore the relationship between aflatoxins, maize consumption, hepatitis B surface antigen, and case status. RESULTS: Homegrown (not commercial) maize kernels from case households had higher concentrations of aflatoxins than did kernels from...
a International Institute of Tropical Agriculture (IITA-Zambia), Lusaka, Zambia b IITA-Ibadan, Oy... more a International Institute of Tropical Agriculture (IITA-Zambia), Lusaka, Zambia b IITA-Ibadan, Oyo Road, Ibadan, Nigeria c Zambia Agriculture Research Institute, Mount Makulu Central Research Station, Zambia. d National Institute for Scientific and Industrial Research (NISIR), Lusaka, Zambia e The World Vegetable Center (AVRDC) Eastern and Southern Africa , Duluti, Arusha, Tanzania f USDA-ARS, School of Plant Sciences, University of Arizona, Tucson, USA.
Journal of Chromatography B: Biomedical Sciences and Applications, 1982
Applied and Environmental Microbiology, May 31, 2023
Fungi contaminate various crops worldwide. Maize, an important human staple and livestock cereal,... more Fungi contaminate various crops worldwide. Maize, an important human staple and livestock cereal, is susceptible to contamination with fungi in the field.
Mycotoxins, 2006
Acute aflatoxicosis outbreaks sporadically occur among subsistence farmers in Makueni and Kitui d... more Acute aflatoxicosis outbreaks sporadically occur among subsistence farmers in Makueni and Kitui districts, Eastern Province, Kenya. Over the past 25 years, four documented outbreaks of acute aflatoxicosis affecting 467 individuals and resulting in 178 deaths have occurred in the same region. The outbreaks occurred in the southeastern part of Eastern Province between the months of April and July.
Journal of Fungi
Aflatoxins (AFs) are considered to play important functions in species of Aspergillus section Fla... more Aflatoxins (AFs) are considered to play important functions in species of Aspergillus section Flavi including an antioxidative role, as a deterrent against fungivorous insects, and in antibiosis. Atoxigenic Flavi are known to degrade AF-B1 (B1). To better understand the purpose of AF degradation, we investigated the degradation of B1 and AF-G1 (G1) in an antioxidative role in Flavi. Atoxigenic and toxigenic Flavi were treated with artificial B1 and G1 with or without the antioxidant selenium (Se), which is expected to affect levels of AF. After incubations, AF levels were measured by HPLC. To estimate which population would likely be favoured between toxigenic and atoxigenic Flavi under Se, we investigated the fitness, by spore count, of the Flavi as a result of exposure to 0, 0.40, and 0.86 µg/g Se in 3%-sucrose cornmeal agar (3gCMA). Results showed that levels B1 in medium without Se were reduced in all isolates, while G1 did not significantly change. When the medium was treated w...
<b>Copyright information:</b>Taken from "Aflatoxin Contamination of Commercial M... more <b>Copyright information:</b>Taken from "Aflatoxin Contamination of Commercial Maize Products during an Outbreak of Acute Aflatoxicosis in Eastern and Central Kenya"Environmental Health Perspectives 2005;113(12):1763-1767.Published online 10 Aug 2005PMCID:PMC1314917.This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI. Each dot represents the rate of aflatoxicosis by division, and dots are in the center of each division (divisions are not shown).
<b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxi... more <b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxicosis Outbreak, Kenya, 2004"Environmental Health Perspectives 2005;113(12):1779-1783.Published online 9 Aug 2005PMCID:PMC1314920.This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.
See next page for additional authors
See next page for additional authors
aflatoxicosis outbreak in eastern Kenya resulted in 317 cases and 125 deaths. We conducted a case... more aflatoxicosis outbreak in eastern Kenya resulted in 317 cases and 125 deaths. We conducted a case-control study to identify risk factors for contamination of implicated maize and, for the first time, quantitated biomarkers associated with acute aflatoxicosis. DESIGN: We administered questionnaires regarding maize storage and consumption and obtained maize and blood samples from participants. PARTICIPANTS: We recruited 40 case-patients with aflatoxicosis and 80 randomly selected controls to participate in this study. EVALUATIONS/MEASUREMENTS: We analyzed maize for total aflatoxins and serum for aflatoxin B 1 -lysine albumin adducts and hepatitis B surface antigen. We used regression and survival analyses to explore the relationship between aflatoxins, maize consumption, hepatitis B surface antigen, and case status. RESULTS: Homegrown (not commercial) maize kernels from case households had higher concentrations of aflatoxins than did kernels from control households [ To select 40 pati...
Applied and environmental …, 2007
a Deutsche Gesellschaft für Internationale Zusammenar beit (GIZ), Germany b International Institu... more a Deutsche Gesellschaft für Internationale Zusammenar beit (GIZ), Germany b International Institute of Tropical Agriculture (II TA-Zambia), Lusaka, Zambia c IITA-Ibadan, Oyo Road, Ibadan, Nigeria d Zambia Agriculture Research Institute, Mount Makul u Central Research Station, Zambia. e National Institute for Scientific and Industrial Re search (NISIR), Lusaka, Zambia f The World Vegetable Center (AVRDC) Eastern and Sou thern Africa , Duluti, Arusha, Tanzania g USDA-ARS, School of Plant Sciences, University of Arizona, Tucson, USA.
<b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxi... more <b>Copyright information:</b>Taken from "Case–Control Study of an Acute Aflatoxicosis Outbreak, Kenya, 2004"Environmental Health Perspectives 2005;113(12):1779-1783.Published online 9 Aug 2005PMCID:PMC1314920.This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.
Journal of AOAC International
The number of elevator facilities with laboratories to test shelled corn for aflatoxin on site is... more The number of elevator facilities with laboratories to test shelled corn for aflatoxin on site is increasing. The inherent difficulty in accurately determining the true aflatoxin concentration of a lot of corn may have serious implications. Deviations from the true value are of even greater significance at busy locations where a high throughput is desired. This study was instituted to measure (1) the differences in aflatoxin test results between elevator laboratories and the Louisiana Agricultural Chemistry (LAC) laboratory and (2) the variability in aflatoxin test results associated with sampling, sample preparation, and analysis of shelled corn at such locations. One hundred lots of shelled corn from 10 elevators in Louisiana were analyzed for aflatoxin using the Aflatest method (at elevators and at the LAC laboratory) and high-performance column liquid chromatography (HPLC; LAC laboratory only). Mean aflatoxin levels determined at elevator laboratories were significantly (P < ...
Maize contaminated with aflatoxins has been implicated in deadly epidemics in Kenya three times s... more Maize contaminated with aflatoxins has been implicated in deadly epidemics in Kenya three times since 1981, but the fungi contaminating the maize with aflatoxins have not been characterized. Here we associate the S strain of Aspergillus flavus with lethal aflatoxicoses that took more than 125 lives in 2004. The 2004 outbreak of acute aflatoxicosis in Kenya was one of the most severe episodes of human aflatoxin poisoning in history. A total of 317 cases were reported by 20 July 2004, with a case fatality rate of 39 % (1, 26). This epidemic resulted from ingestion of contaminated maize (22). However, identities of the fungi causing the contamination remain unclear. Aflatoxins are carcinogenic metabolites produced by several Aspergillus species (4, 28). Aflatoxin-producing fungi vary widely in many characteristics, including virulence for crops and aflatoxin-producing capacity (10). A. flavus and A. parasiticus are most commonly implicated as causal agents of aflatoxin contamination. A...
In April 2004, one of the largest aflatoxicosis outbreaks occurred in rural Kenya, resulting in 3... more In April 2004, one of the largest aflatoxicosis outbreaks occurred in rural Kenya, resulting in 317 cases and 125 deaths. Aflatoxin-contaminated homegrown maize was the source of the outbreak, but the extent of regional contamination and status of maize in commercial markets (market maize) were unknown. We conducted a cross-sectional survey to assess the extent of market maize contamination and evaluate the relationship between market maize aflatoxin and the aflatoxicosis outbreak. We surveyed 65 markets and 243 maize vendors and collected 350 maize products in the most affected districts. Fifty-five percent of maize products had aflatoxin levels greater than the Kenyan regulatory limit of 20 ppb, 35 % had levels> 100 ppb, and 7 % had levels> 1,000 ppb. Makueni, the district with the most aflatoxicosis case-patients, had significantly higher market maize aflatoxin than did Thika, the study district with fewest case-patients (geometric mean aflatoxin = 52.91 ppb vs. 7.52 ppb, p...
OBJECTIVES: During January–June 2004, an aflatoxicosis outbreak in eastern Kenya resulted in 317 ... more OBJECTIVES: During January–June 2004, an aflatoxicosis outbreak in eastern Kenya resulted in 317 cases and 125 deaths. We conducted a case–control study to identify risk factors for contamination of implicated maize and, for the first time, quantitated biomarkers associated with acute aflatoxicosis. DESIGN: We administered questionnaires regarding maize storage and consumption and obtained maize and blood samples from participants. PARTICIPANTS: We recruited 40 case-patients with aflatoxicosis and 80 randomly selected controls to participate in this study. EVALUATIONS/MEASUREMENTS: We analyzed maize for total aflatoxins and serum for aflatoxin B1–lysine albumin adducts and hepatitis B surface antigen. We used regression and survival analyses to explore the relationship between aflatoxins, maize consumption, hepatitis B surface antigen, and case status. RESULTS: Homegrown (not commercial) maize kernels from case households had higher concentrations of aflatoxins than did kernels from...