Aspergillus section Flavi community structure in Zambia influences aflatoxin contamination of maize and groundnut

Article purchased; Published online: 19 August 2017Aspergillus section Flavi have been implicated as causal agents of aflatoxin contamination in Africa. However, Aspergillus populations associated with aflatoxin contamination in Zambia have not been adequately detailed. Most of Zambia's arable land is non-cultivated and Aspergillus communities in crops may originate in non-cultivated soil. However, relationships between Aspergillus populations on crops and those resident in non-cultivated soils have not been explored. Because characterization of similar fungal populations outside of Zambia have resulted in strategies to prevent aflatoxins, the current study sought to improve understanding of fungal communities in cultivated and non-cultivated soils and in crops. Crops (n = 412) and soils from cultivated (n = 160) and non-cultivated land (n = 60) were assayed for Aspergillus section Flavi from 2012 to 2016. The L-strain morphotype of Aspergillus flavus and A. parasiticus were dominant on maize and groundnut (60% and 42% of Aspergillus section Flavi, respectively). Incidences of A. flavus L-morphotype were negatively correlated with aflatoxin in groundnut (log y = 2.4990935 − 0.09966x, R2 = 0.79, P = 0.001) but not in maize. Incidences of A. parasiticus partially explained groundnut aflatoxin concentrations in all agroecologies and maize aflatoxin in agroecology III (log y = 0.1956034 + 0.510379x, R2 = 0.57, P < 0.001) supporting A. parasiticus as the dominant etiologic agent of aflatoxin contamination in Zambia. Communities in both non-cultivated and cultivated soils were dominated by A. parasiticus (69% and 58%, respectively). Aspergillus parasiticus from cultivated and non-cultivated land produced statistically similar concentrations of aflatoxins. Aflatoxin-producers causing contamination of crops in Zambia may be native and, originate from non-cultivated areas, and not be introduced with non-native crops such as maize and groundnut. Non-cultivated land may be an important reservoir from which aflatoxin-producers are repeatedly introduced to cultivated areas. The potential of atoxigenic members of the A. flavus-L morphotype for management of aflatoxin in Zambia is also suggested. Characterization of the causal agents of aflatoxin contamination in agroecologies across Zambia gives support for modifying fungal community structure to reduce the aflatoxin-producing potential

Does exposure to aflatoxin constrain efforts to reduce stunting in Zambia?

On 8 June 2013, the Vice President of Zambia stated that his government ‘is fully committed to reducing chronic undernutrition by 50 per cent in the next ten years…’ What are the challenges to meeting this goal? Zambia has both a high consumption of groundnuts and high levels of aflatoxin contamination of this commodity. Recent studies indicate an association between stunting and aflatoxin exposure. If the association exists, then Zambia faces serious challenges to reaching its target of 50 per cent reduction in chronic undernutrition. Recent efforts to identify atoxigenic strains for biocontrol in maize and groundnuts give cause for cautious optimism. Nonetheless, the challenges ahead demand both a high level of political will to achieve effective multisectoral collaboration and the willingness of the agricultural and health sectors to undertake rigorous monitoring of aflatoxin contamination and growth of young children, as well as the agricultural sector’s commitment to reduce substantially levels of aflatoxin contamination and to promote agricultural diversification

INSECT ANTAGONISTIC BIO-INOCULANTS FOR NATURAL CONTROL OF LEAF-MINING INSECT PESTS OF FRENCH BEANS

Fungal endophytes, specifically, Trichoderma asperellum , Beauveria bassiana and Metarhizium anisopliae ; strains M2RT4, S4SU1 and S4ST7, respectively, are known to deter aphid infestation and damage to leguminous crops, but no research exists on their biochemical profiles and effects on French bean ( Phaseolus vulgaris ) leaf miners. The objective of this study was to assess the ability of these endophytic bio-inoculants to produce extracellular enzymes, as well as determine their impact on French beans seedling emergence and growth, and leaf miner fecundity and pupation. Laboratory and greenhouse experiments were conduct at the International Centre of Insect Physiology and Ecology (ICIPE, Nairobi), and the University of Bonn (Germany). Bio-priming French bean seeds by soaking in fungal suspension containing 108 conidia/ ml for 4 hr positively impacted on seedling vigour. Six weeks after germination, all bio-inoculant treatments improved nodulation by 1.5-1.7 folds, while S4SU1 and M2TR4 improved shoot biomass by ~ 2g. In vitro, spore suspensions of these isolates were highly toxic to leaf miner larvae, often resulting in high mortalities and a suppression of pupation by over 70%. All tested isolates exhibited protease (Index=1.22), lipase (Index=1.32) and cellulase (Index=1.06) activities; with M. anisopliae being the best enzyme secretor when cultured under dark conditions on enzyme-specific substrate for 7-14 days. In vivo B. bassiana-primed seedlings deterred larval feeding and development, resulting in reduced number of larvae, pupae and adults, by 65.3, 43.2 and 54.0%, respectively. For the first time, this study showed that bio-priming French bean seeds with bio-inoculants can boost P. vulgaris growth and nodulation, consequently altering its interaction and response to leaf miner infestation, feeding and damage to treated seedlings. These bio-inoculants, thus, hold great potential as crop protection agents and could be safely used for priming seeds prior to planting, if leaf mining damages and associated yield losses in French beans are to be minimised in an environmentally sound manner. Further studies should be undertaken to elucidate the mechanisms involved in plant growth promotion, nodulation and insect feeding deterrence.Les endophytes fongiques, sp\ue9cialement, Trichoderma asperellum , Beauveria bassiana et Metarhizium anisopliae ; souches M2RT4, S4SU1 et S4ST7, respectivement, sont connues pour dissuader l\u2019infestation et le dommage des aphids sur les plantes l\ue9gumineuses, mais aucune recherche n\u2019a \ue9t\ue9 men\ue9e sur leurs profils biochmiques et leurs effets sur les insectes mineurs de feuilles du haricot vert ( Phaseolus vulgaris ). L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer la capacit\ue9 endophytique de ces bio-inoculants \ue0 produire des enzymes extra-cellulaires, ainsi que de d\ue9terminer leurs impacts sur l\u2019\ue9mergence et la croissance des plantules du haricot vert, sur la f\ue9condit\ue9 et la nymphose du mineur des feuilles. Des exp\ue9rimentations de laboratoire et sous serre on \ue9t\ue9 conduites au Centre International de Physiologie et d\u2019Ecologie d\u2019Insecte (ICIPE, Nairobi), et \ue0 l\u2019Universit\ue9 de Bonn (Allemagne). Le bio-amor\ue7age des graines du haricot vert par trempage dans une suspension fongique contenant 108 conidies/ml pendant 4heures a positivement imapct\ue9 la vigueur des plantules. Six semaines apr\ue8s la germination, tous les traitements de bio-inoculants ont augment\ue9 la nodulation par 1,5-1,7 fois, pendant que S4SU1 et M2TR4 ont augment\ue9 la biomasse des pousses d\u2019environ 2g. En conditions in vitro, les suspensions de spores de ces isolats \ue9taient fortement toxiques aux larves des mineurs de feuilles, r\ue9guli\ue8rement provoquant de grandes mortalit\ue9s et une suppression de la nymphose de plus de 70%. Tous les isolats test\ue9s ont produit des activit\ue9s protease (indice=1,22), lipase (indice=1,32) et cellulase (indice=1.06); avec M. anisopliae constiuant le meilleur s\ue9creteur d\u2019enzyme alors qu\u2019il est cultiv\ue9 dans le noir sur un substrat d\u2019enzyme sp\ue9cifique pendant 7-14 jours. En conditions in vitro, les plantules amorc\ue9es avec B. bassiana ont frein\ue9 l\u2019alimentation et le d\ue9veloppement des larves, r\ue9sultant en une r\ue9duction du nombre de larves, nymphes et adultes, par 65,3; 43,2; et 54,0%, respectivement. Pour une premi\ue8re fois, cette \ue9tude a montr\ue9 que le bio-amor\ue7age des graines du haricot vert avec des bio-inoculants peut augmenter la croissance et la nodulation de P. vulgaris, par cons\ue9quent alt\ue8re son interaction et sa r\ue9ponse \ue0 l\u2019infestation, \ue0 l\u2019alimentation de mineur de feuilles et les dommages sur les plantules trait\ue9es. Ces bio-inoculants, constituent ainsi de grands potentiels agents protecteurs de cultures et pourraient \ueatre utilis\ue9s de fa\ue7on s\ue9curisante pour l\u2019amor\ue7age des graines avant leur semis, si les dommages caus\ue9s sur les feuilles et la perte de rendement associ\ue9e sur le haricot vert sont \ue0 r\ue9duire sans danger pour l\u2019environnement. Des \ue9tudes suppl\ue9mentaires devraient \ueatre men\ue9es pour \ue9lucider les m\ue9canismes impliqu\ue9s dans la promotion de la croissance v\ue9g\ue9tale, la nodulation et la dissuasion de l\u2019alimentation de l\u2019insecte

Aflatoxin contamination of dried insects and fish in Zambia

Open Access Article; Published online: 17 Aug 2018Dried insects and fish are important sources of income and dietary protein in Zambia. Some aflatoxin-producing fungi are entomopathogenic and also colonize insects and fish after harvest and processing. Aflatoxins are carcinogenic, immune-suppressing mycotoxins that are frequent food contaminants worldwide. Several species within Aspergillus section Flavi have been implicated as causal agents of aflatoxin contamination of crops in Africa. However, aflatoxin producers associated with dried fish and edible insects in Zambia remain unknown, and aflatoxin concentrations in these foods have been inadequately evaluated. The current study sought to address these data gaps to assess potential human vulnerability through the dried fish and edible insect routes of aflatoxin exposure. Caterpillars (n = 97), termites (n = 4), and dried fish (n = 66) sampled in 2016 and 2017 were assayed for aflatoxin by using lateral flow immunochromatography. Average aflatoxin concentrations exceeded regulatory limits for Zambia (10 μg/kg) in the moth Gynanisa maja (11 μg/kg), the moth Gonimbrasia zambesina (Walker) (12 μg/kg), and the termite Macrotermes falciger (Gerstacker) (24 μg/kg). When samples were subjected to simulated poor storage, aflatoxins increased (P < 0.001) to unsafe levels in caterpillars (mean, 4,800 μg/kg) and fish (Oreochromis) (mean, 23 μg/kg). The L strain morphotype of A. flavus was the most common aflatoxin producer on dried fish (88% of Aspergillus section Flavi), termites (68%), and caterpillars (61%), with the exception of Gynanisa maja, for which A. parasiticus was the most common (44%). Dried fish and insects supported growth (mean, 1.3 × 109 CFU/g) and aflatoxin production (mean, 63,620 μg/kg) by previously characterized toxigenic Aspergillus section Flavi species, although the extent of growth and aflatoxigenicity depended on specific fungus-host combinations. The current study shows the need for proper storage and testing of dried insects and fish before consumption as measures to mitigate human exposure to aflatoxins through consumption in Zambia

Preparedness needs research: How fundamental science and international collaboration accelerated the response to COVID-19

The first cluster of patients suffering from coronavirus disease 2019 (COVID-19) was identified on December 21, 2019, and as of July 29, 2020, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have been linked with 664,333 deaths and number at least 16,932,996 worldwide. Unprecedented in global societal impact, the COVID-19 pandemic has tested local, national, and international preparedness for viral outbreaks to the limits. Just as it will be vital to identify missed opportunities and improve contingency planning for future outbreaks, we must also highlight key successes and build on them. Concomitant to the emergence of a novel viral disease, there is a ‘research and development gap’ that poses a threat to the overall pace and quality of outbreak response during its most crucial early phase. Here, we outline key components of an adequate research response to novel viral outbreaks using the example of SARS-CoV-2. We highlight the exceptional recent progress made in fundamental science, resulting in the fastest scientific response to a major infectious disease outbreak or pandemic. We underline the vital role of the international research community, from the implementation of diagnostics and contact tracing procedures to the collective search for vaccines and antiviral therapies, sustained by unique information sharing efforts

Mapping the molecular surface of the analgesic NaV1.7-selective peptide Pn3a reveals residues essential for membrane and channel interactions

Compelling human genetic studies have identified the voltage-gated sodium channel NaV1.7 as a promising therapeutic target for the treatment of pain. The analgesic spider venom-derived peptide µtheraphotoxin-Pn3a is an exceptionally potent and selective inhibitor of NaV1.7, however, little is known about the structure-activity relationships or channel interactions that define this activity. We rationally designed seventeen Pn3a analogues and determined their activity at hNaV1.7 using patchclamp electrophysiology. The positively charged amino acids K22 and K24 were identified as crucial for Pn3a activity, with molecular modeling identifying interactions of these residues with the S3-S4 loop of domain II of hNaV1.7. Removal of hydrophobic residues Y4, Y27 and W30 led to a loss of potency (>250-fold), while replacement of negatively charged D1 and D8 residues with a positively charged lysine led to increased potencies (>13-fold), likely through alterations in membrane lipid interactions. Mutating D8 to an asparagine led to the greatest improvement in Pn3a potency at NaV1.7 (20-fold), whilst maintaining >100-fold selectivity over the major off-targets NaV1.4, NaV1.5 and NaV1.6. The Pn3a[D8N] mutant retained analgesic activity in vivo, significantly attenuating mechanical allodynia in a clinically relevant mouse model of post-surgical pain at doses 3-fold lower than wild-type Pn3a, without causing motor adverse effects. Results from this study will facilitate future rational design of potent and selective peptidic NaV1.7 inhibitors for the development of more efficacious and safer analgesics but also to further investigate the involvement of NaV1.7 in pain