Aflatoxins contamination in processed cassava in Malawi and Zambia

Strains of the Aspergillus fungi, especially A. flavus and A. parasiticus, primarily produce aflatoxins which are a major health concern to man and livestock because of their acute and chronic health effects. Aflatoxins pose the greatest risk to health in tropical Africa because of their widespread prevalence and high toxicity; carcinogenic (cause liver and esophageal cancer) effect, immune system suppressing and anti-nutritional  contaminants in many food commodities and even cause death. Aflatoxins have also been reported to compromise vaccine efficacy in experimental animals. Due to the seriousness of aflatoxins, international agencies have restricted levels of aflatoxins to 20 ppb in food materials as the maximum permissible level in the United States and 4 ppb total aflatoxins and under 2 ppb aflatoxin B1 in Europe. These regulations directed at minimizing human exposure to aflatoxins results in severe economic loss to producers, processors and marketers of the contaminated crop. A study was conducted in Malawi and Zambia to assess the level of fungal and mycotoxins’ contamination in commonly processed cassava products. A total of 92 and 88 samples of processed cassava products comprising makaka, flour, kanyakaska, kadonoska, scrapes and grates were collected in the rainy season of 2008 and 2009 in Malawi, respectively. Further, 22 samples of processed cassava products comprising dried cassava chips and flour were collected in the rainy season of 2009 in Zambia. The samples were analyzed for fungal and aflatoxins B1, B2, G1 and G2 contamination using the Romer mini-column method and the VICAM AflaTest  immunoaffinity fluorometric method. None of the samples in 2008 were contaminated with aflatoxins. Similar results were obtained in 2009 with almost all the samples in Malawi and Zambia having aflatoxin levels much lower (<2.0 ìg/kg in Malawi and <4.2 ìg/kg in Zambia) than the Codex Alimentarius Commission (CAC) maximum permissible level of aflatoxins of 10.0 ìg/kg, implying that the cassava products analyzed were safe for human consumption. However, further studies are needed to cover a larger sample size over a period of a year to represent all seasons in the cassava producing and consuming areas and conclusively make certain the safety of these products for human consumption.Key words: Cassava, consumption, aflatoxin, food, safet

Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: a pooled analysis of four randomised trials.

BACKGROUND: The ChAdOx1 nCoV-19 (AZD1222) vaccine has been approved for emergency use by the UK regulatory authority, Medicines and Healthcare products Regulatory Agency, with a regimen of two standard doses given with an interval of 4-12 weeks. The planned roll-out in the UK will involve vaccinating people in high-risk categories with their first dose immediately, and delivering the second dose 12 weeks later. Here, we provide both a further prespecified pooled analysis of trials of ChAdOx1 nCoV-19 and exploratory analyses of the impact on immunogenicity and efficacy of extending the interval between priming and booster doses. In addition, we show the immunogenicity and protection afforded by the first dose, before a booster dose has been offered. METHODS: We present data from three single-blind randomised controlled trials-one phase 1/2 study in the UK (COV001), one phase 2/3 study in the UK (COV002), and a phase 3 study in Brazil (COV003)-and one double-blind phase 1/2 study in South Africa (COV005). As previously described, individuals 18 years and older were randomly assigned 1:1 to receive two standard doses of ChAdOx1 nCoV-19 (5 × 1010 viral particles) or a control vaccine or saline placebo. In the UK trial, a subset of participants received a lower dose (2·2 × 1010 viral particles) of the ChAdOx1 nCoV-19 for the first dose. The primary outcome was virologically confirmed symptomatic COVID-19 disease, defined as a nucleic acid amplification test (NAAT)-positive swab combined with at least one qualifying symptom (fever ≥37·8°C, cough, shortness of breath, or anosmia or ageusia) more than 14 days after the second dose. Secondary efficacy analyses included cases occuring at least 22 days after the first dose. Antibody responses measured by immunoassay and by pseudovirus neutralisation were exploratory outcomes. All cases of COVID-19 with a NAAT-positive swab were adjudicated for inclusion in the analysis by a masked independent endpoint review committee. The primary analysis included all participants who were SARS-CoV-2 N protein seronegative at baseline, had had at least 14 days of follow-up after the second dose, and had no evidence of previous SARS-CoV-2 infection from NAAT swabs. Safety was assessed in all participants who received at least one dose. The four trials are registered at ISRCTN89951424 (COV003) and ClinicalTrials.gov, NCT04324606 (COV001), NCT04400838 (COV002), and NCT04444674 (COV005). FINDINGS: Between April 23 and Dec 6, 2020, 24 422 participants were recruited and vaccinated across the four studies, of whom 17 178 were included in the primary analysis (8597 receiving ChAdOx1 nCoV-19 and 8581 receiving control vaccine). The data cutoff for these analyses was Dec 7, 2020. 332 NAAT-positive infections met the primary endpoint of symptomatic infection more than 14 days after the second dose. Overall vaccine efficacy more than 14 days after the second dose was 66·7% (95% CI 57·4-74·0), with 84 (1·0%) cases in the 8597 participants in the ChAdOx1 nCoV-19 group and 248 (2·9%) in the 8581 participants in the control group. There were no hospital admissions for COVID-19 in the ChAdOx1 nCoV-19 group after the initial 21-day exclusion period, and 15 in the control group. 108 (0·9%) of 12 282 participants in the ChAdOx1 nCoV-19 group and 127 (1·1%) of 11 962 participants in the control group had serious adverse events. There were seven deaths considered unrelated to vaccination (two in the ChAdOx1 nCov-19 group and five in the control group), including one COVID-19-related death in one participant in the control group. Exploratory analyses showed that vaccine efficacy after a single standard dose of vaccine from day 22 to day 90 after vaccination was 76·0% (59·3-85·9). Our modelling analysis indicated that protection did not wane during this initial 3-month period. Similarly, antibody levels were maintained during this period with minimal waning by day 90 (geometric mean ratio [GMR] 0·66 [95% CI 0·59-0·74]). In the participants who received two standard doses, after the second dose, efficacy was higher in those with a longer prime-boost interval (vaccine efficacy 81·3% [95% CI 60·3-91·2] at ≥12 weeks) than in those with a short interval (vaccine efficacy 55·1% [33·0-69·9] at <6 weeks). These observations are supported by immunogenicity data that showed binding antibody responses more than two-fold higher after an interval of 12 or more weeks compared with an interval of less than 6 weeks in those who were aged 18-55 years (GMR 2·32 [2·01-2·68]). INTERPRETATION: The results of this primary analysis of two doses of ChAdOx1 nCoV-19 were consistent with those seen in the interim analysis of the trials and confirm that the vaccine is efficacious, with results varying by dose interval in exploratory analyses. A 3-month dose interval might have advantages over a programme with a short dose interval for roll-out of a pandemic vaccine to protect the largest number of individuals in the population as early as possible when supplies are scarce, while also improving protection after receiving a second dose. FUNDING: UK Research and Innovation, National Institutes of Health Research (NIHR), The Coalition for Epidemic Preparedness Innovations, the Bill & Melinda Gates Foundation, the Lemann Foundation, Rede D'Or, the Brava and Telles Foundation, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and AstraZeneca

Cassava and sweetpotato yield assessment in Malawi

Cassava (Manihot esculenta Crantz) and sweetpotato (Ipomoea batatas Lam) are important food and cash crops in Malawi. However, key information regarding varieties grown, sources of planting materials, post-harvest handling, utilisation and tuber yields is lacking. A study was, therefore, conducted to source this information. Farmers grow mostly local varieties of cassava with own gardens as the main source of planting materials. Several varieties of sweetpotato are grown with Kenya (SPN/O, bred in Tanzania) as the most popular. Sprouts from previous season\'s gardens are the main source of planting materials. Cassava and sweetpotato are grown for food and cash. However, in some area cassava stems are used for fuel wood. Most farmers do not store fresh cassava roots but process them into makaka, kanyakaska and kadonoska, or sell them fresh. Processing for sweetpotato is limited to boiling and roasting. Most farmers store sweetpotato, but this is constrained by the sweetpotato weevil damage and rotting. Root yield ranged from 13.1 to 31.4 t ha-1 for cassava, and 10.2 to 14.0 t ha-1 for sweetpotato. Except for Nkhata Bay, the yields of both crops were much lower than from research stations. Unavailability of acceptable improved varieties, high incidence of pests and diseases, and poor cultural practices are the main causes of low yields in the targeted areas. Key words: Ipomoea batatas, Manihot esculenta, planting materials, weevil RÉSUMÉ Le manioc (Manihot esculenta Crantz) et la patate douce (Ipomoea batatas Lam) sont des importants aliments et plantes génératrices de ressources en Malawi. Cependant, l\'information clé concernant les variétés plantées, les sources de matériels de plantation, les manœuvres post-récoltes, l\'utilisation et les rendements de tubercules manque. Une étude était alors conduite pour approvisionner cette information. Les fermiers cultivent souvent les variétés locales de manioc avec comme source principale de matériels de plantation leurs propres champs. Plusieurs variétés de patate douce sont cultivées au Kenya (SPN/O, conditionnée en Tanzanie) comme le plus populaire. Les germes des champs de saison précédente sont la source principale de matériels de plantation. Le manioc et patate douce sont cultivés pour la nourriture et l\'argent. Cependant, dans certaines aires les tiges de manioc sont utilisées pour le bois de chauffe. La plus part des fermiers n\'entreposent pas les racines de manioc frais mais transforment les en makaka, kanyakaska et kadonoska, ou les vendent frais. La transformation de la patate douce est limitée à l\'ébullition et au rôtissage. La plus part des fermiers entreposent la patate douce, mais ceci est gêné par les dégâts et les avaries des charançons. Les rendements de racines ont variés de 13.1 a 13.4 t ha-1 pour la patate douce. A l\'exception de laurier Nkhata, les rendements des toutes les deux cultures étaient plus bas que ceux des stations de recherche. La non disponibilité des variétés améliorées acceptables, l\'incidence élevée des pestes et maladies, et les pauvres pratiques culturales sont les causes principales de faibles rendements dans les aires visées. Mots Cles: Ipomoea batatas, Manihot esculenta, matériels de plantation, charançon African Crop Science Journal Vol.12(3) 2004: 295-30

Contribution of SARRNET to food security in the SADC region

The Southern Africa Root Crops Research Netwrok (SARRNET), in collaboration with national research programmes in Southern Africa Development Community (SADC ) have made considerable impact in the SADC region in terms of promoting cassava (Manihot esculenta) and sweetpotato (Ipomea batatus) production and commercialization. Area under cassava and sweetpotato production has increased tremendously in some SADC countries since mid 1990s. This is attributable to research work on germplasm development where about 51 improved cassava and sweetpotato varieties have been released and made available to farmers through the accelerated plant material multiplication and distribution programmes that took place in at least 10 of the 14 SADC countries. SARRNET has also made great impacts in skill development and knowledge in root crops research for development in the SADC region through funding post graduate/graduate studies, short-term training courses, workshops and symposia. In its second phase which started in 1999, SARRNET shifted its strategy with more emphasis on market oriented research for development by promoting cassava and sweetpotato commercialization in the region. This has made these crops to play a significant role in the economic growth of the SADC countries. This paper presents the contribution of SARRNET on cassava and sweetpotato germplasm development, seed multiplication and distribution, cassava commercialisation, post harvest technologies, training, information and technology exchange. Key words: Cassava, germplasm, Ipomea batatus, Manihot esculenta, sweetpotato RÉSUMÉ Le réseau de recherche du sud de l'Afrique en racines des plantes (SARRNET), en collaboration avec les programmes de recherche national des communautés de développement du sud de l'Afrique (SADC) ont rapporté des impacts considérables dans la région du SADC en termes de promotion de production de manioc (Manihot esculenta) et de patate douce (Ipomea batatus) et de commercialisation. Les aires sous production de manioc et patate douce ont énormément augmenté dans certains pays de SADC depuis mi 1990. Ceci est attribué au travail de recherche sur le développement du germplasme ou environ 51 variétés de manioc et patate douce améliorées ont été larguées et disponibilisées aux fermiers a travers les programmes accélérées de l'usine de distribution et de multiplication des matériels qui se sont tenu dans au moins 10 de 14 pays de SADC. SARRNET a aussi fait des grands impacts dans le développement d'habileté et de connaissance dans la recherche en racines des plantes pour le développement dans la région de SADC a travers des fonds d'études post graduat et de graduat, des cours de formation à court terme, séminaires et symposiums. Dans sa seconde phase qui a commencé en 1999, SARRNET a orienté sa stratégie avec plus d'insistance sur la recherche orientée au marché pour le développement par la promotion de la commercialisation du manioc et de la patate douce dans la région. Ceci a amené ces cultures à jouer un rôle significatif dans la croissance économique des pays de SADC. Cet article présente la contribution de SARRNET sur le développement de germplasme du manioc et de la patate douce, la multiplication et distribution des semences, la commercialisation du manioc, les technologies de post culture, la formation, l'échange de l'information et de la technologie. Mots clés: Manioc, germplasme, Ipomea batatus, Manihot esculenta, patate douce African Crop Science Journal Vol.12(3) 2004:311-31