Market samples as a source of chronic aflatoxin exposure in Kenya

Surveillance of food and feed quality in Kenya has not reached effective level due to the expensive procedures of mycotoxin analysis and poor structures in quality control. Most foodstuffs and feeds sold in local markets do not go through any quality control measures. The outbreaks of aflatoxicoses every year since the major outbreak that occurred in 2004 (CDC, 2004; Muture and Ogana, 2005, Azziz-Baumgartner et al., 2005) suggests that the population is exposed to aflatoxins in their diet. Chronic exposure could be a more serious problem than the outbreaks of aflatoxicosis that attract attention at the time they occur. This paper analyses the extent to which market food and feed samples expose the residents of urban Nairobi Province to aflatoxins. Using TLC method of aflatoxins analysis, maize for food and feed samples collected randomly as part of routine surveillance between the years 2006-2009 were tested. Only 17% of the total maize sampled and 5% of feed were fit for human and animal consumption respectively. Maize Grain Grade 11 and maize milled products were significantly highly contaminated compared with Maize Grain Grade 1 throughout the period of sampling. There was no significant difference in level of contamination among the feeds tested

Curcumin-based photosensitization inactivates Aspergillus flavus and reduces aflatoxin B1 in maize kernels

Different methods have been applied in controlling contamination of foods and feeds by the carcinogenic fungal toxin, aflatoxin, but nevertheless the problem remains pervasive in developing countries. Curcumin is a natural polyphenolic compound from the spice turmeric (Curcuma longa L.) that has been identified as an efficient photosensitiser for inactivation of Aspergillus flavus conidia. Curcumin mediated photoinactivation of A. flavus has revealed the potential of this technology to be an effective method for reducing population density of the aflatoxin-producing fungus in foods. This study demonstrates the influence of pH and temperature on efficiency of photoinactivation of the fungus and how treating spore-contaminated maize kernels affects aflatoxin production. The results show the efficiency of curcumin mediated photoinactivation of fungal conidia and hyphae were not affected by temperatures between 15 and 35 °C or pH range of 1.5–9.0. The production of aflatoxin B was significantly lower (p < 0.05), with an average of 82.4 μg/kg as compared to up to 305.9 μg/kg observed in untreated maize kept under similar conditions. The results of this study indicate that curcumin mediated photosensitization can potentially be applied under simple environmental conditions to achieve significant reduction of post-harvest contamination of aflatoxin B in maize

Effects of Medicinal Plant Extracts and Photosensitization on Aflatoxin Producing Aspergillus flavus

This study was undertaken with an aim of exploring the effectiveness of medicinal plant extracts in the control of aflatoxin production. Antifungal properties, photosensitization, and phytochemical composition of aqueous and organic extracts of fruits from Solanum aculeastrum, bark from Syzygium cordatum, and leaves from Prunus africana, Ocimum lamiifolium, Lippia kituiensis, and Spinacia oleracea were tested. Spores from four-day-old cultures of previously identified toxigenic fungi, UONV017 and UONV003, were used. Disc diffusion and broth dilution methods were used to test the antifungal activity. The spores were suspended in 2 ml of each extract separately and treated with visible light (420 nm) for varying periods. Organic extracts displayed species and concentration dependent antifungal activity. Solanum aculeastrum had the highest zones of inhibition diameters in both strains: UONV017 (mean = 18.50±0.71 mm) and UONV003 (mean = 11.92±0.94 mm) at 600 mg/ml. Aqueous extracts had no antifungal activity because all diameters were below 8 mm. Solanum aculeastrum had the lowest minimum inhibitory concentration at 25 mg/ml against A. flavus UONV017. All the plant extracts in combination with light reduced the viability of fungal conidia compared with the controls without light, without extracts, and without both extracts and light. Six bioactive compounds were analyzed in the plant extracts. Medicinal plant extracts in this study can control conidia viability and hence with further development can control toxigenic fungal spread

Aflatoxin and the agriculture – nutrition nexus in Africa

Aflatoxins are a silent threat to health on the African continent. They are a group of mycotoxins – poisonous chemicals produced by fungi on crops that they colonise. Fatal in large amounts, in smaller concentrations aflatoxins harm humans, animals, birds and fish. The fungi that produce aflatoxins infect many of the cereals, legumes, oilseeds, roots, tubers, spices and nuts which are widely grown and eaten in Africa, placing aflatoxins at the very crux of the agriculture-nutrition nexus. This Technical Brief gives recommendations to fight against aflatoxins

Prospective Study of Plasmodium vivax Malaria Recurrence after Radical Treatment with a Chloroquine-Primaquine Standard Regimen in Turbo, Colombia.

Plasmodium vivax recurrences help maintain malaria transmission. They are caused by recrudescence, reinfection, or relapse, which are not easily differentiated. A longitudinal observational study took place in Turbo municipality, Colombia. Participants with uncomplicated P. vivax infection received supervised treatment concomitantly with 25 mg/kg chloroquine and 0.25 mg/kg/day primaquine for 14 days. Incidence of recurrence was assessed over 180 days. Samples were genotyped, and origins of recurrences were established. A total of 134 participants were enrolled between February 2012 and July 2013, and 87 were followed for 180 days, during which 29 recurrences were detected. The cumulative incidence of first recurrence was 24.1% (21/87) (95% confidence interval [CI], 14.6 to 33.7%), and 86% (18/21) of these events occurred between days 51 and 110. High genetic diversity of P. vivax strains was found, and 12.5% (16/128) of the infections were polyclonal. Among detected recurrences, 93.1% (27/29) of strains were genotyped as genetically identical to the strain from the previous infection episode, and 65.5% (19/29) of infections were classified as relapses. Our results indicate that there is a high incidence of P. vivax malaria recurrence after treatment in Turbo municipality, Colombia, and that a large majority of these episodes are likely relapses from the previous infection. We attribute this to the primaquine regimen currently used in Colombia, which may be insufficient to eliminate hypnozoites

INFLUENCE OF SOIL CHEMICAL AND PHYSICAL PROPERTIES ON OCURRENCE OF TRICHODERMA SPP. IN EMBU, KENYA

Soil samples were collected from 8 land use types in Embu to study the effects of land use on soil chemical and physical parameters and on the occurrence of Trichoderma spp. The fungus was recovered from the soil using the dilution plate and soil washing technique. The remaining soil samples were used to measure the following characters of the soil; pH was determined in 1:1 (w/v) soil – water suspension with pH meter, total nitrogen was determined by the Kjeldahl method, available nutrients P, K, Na, Ca and Mg were determined using Mehlich method while total organic carbon was determined by calorimetric method. Land use type (LUT), plant cover, and soil physical and chemical properties influenced Trichoderma occurrence. The frequency of isolation of Trichoderma spp. was highest in napier LUT followed by indigenous forests. Carbon, N, Mg and Fe loaded with forest land use type suggesting their influence on fungal diversity in this LUT. The forests had clay loam soils with higher porosity and water retention capacity compared with the cultivated LUTs which were characterized with clay soils and bulk density. Napier together with other cultivated LUTs which had low records of the fungus loaded positively with Mn and Cu. This implied that plant type was the major determining factor for the high population of Trichoderma recorded in napier LUT. The diversity of soil factors observed in the fallow lands explained the influence of land management on soil physical and chemical characteristics which in turn determined the fungal distribution. Soil depth (0-20cm) did not influence soil factors though fungal diversity, abundance and evenness varied with depth suggesting the influence of other drivers.This study explains the fact that many factors interact in determining the occurrence of Trichoderma spp. and that in some situations it is the soil that is the key factor determining fungal occurrence and diversity while in others it is the plant type

Influence of soil chemical and physical properties on occurrence of Trichoderma spp. in Embu, Kenya = Influencia de las propiedades químicas y físicas del suelo sobre la ocurrencia de Trichoderma spp. en Embu, Kenia

Soil samples were collected from 8 land use types in Embu to study the effects of land use on soil chemical and physical parameters and on the occurrence of Trichoderma spp. The fungus was recovered from the soil using the dilution plate and soil washing technique. The remaining soil samples were used to measure the following characters of the soil; pH was determined in 1:1 (w/v) soil – water suspension with pH meter, total nitrogen was determined by the Kjeldahl method, available nutrients P, K, Na, Ca and Mg were determined using Mehlich method while total organic carbon was determined by calorimetric method. Land use type (LUT), plant cover, and soil physical and chemical properties influenced Trichoderma occurrence. The frequency of isolation of Trichoderma spp. was highest in napier LUT followed by indigenous forests. Carbon, N, Mg and Fe loaded with forest land use type suggesting their influence on fungal diversity in this LUT. The forests had clay loam soils with higher porosity and water retention capacity compared with the cultivated LUTs which were characterized with clay soils and bulk density. Napier together with other cultivated LUTs which had low records of the fungus loaded positively with Mn and Cu. This implied that plant type was the major determining factor for the high population of Trichoderma recorded in napier LUT. The diversity of soil factors observed in the fallow lands explained the influence of land management on soil physical and chemical characteristics which in turn determined the fungal distribution. Soil depth (0-20cm) did not influence soil factors though fungal diversity, abundance and evenness varied with depth suggesting the influence of other drivers.This study explains the fact that many factors interact in determining the occurrence of Trichoderma spp. and that in some situations it is the soil that is the key factor determining fungal occurrence and diversity while in others it is the plant type

Evaluation of selected soil fertility management interventions for suppression of fusarium spp. in a maize and beans intercrop

Fusarium root rot of maize and beans is a common problem in Taita District, Kenya causing reduction in yields to the small scale farmers. The pathogen attacks maize and beans at all growth stages causing rot at the seedling stage, yellowing of the leaves, stunted growth, and death if severe. Potentially effective crop rotations to maintain the pathogen at low levels are not currently practical due to the small size of farms while fungicides are out of reach to the small scale farmer due to high prices. This study aimed at assessing alternatives to fungicides in controlling root infection by Fusarium sp. in maize and beans. Field trials were done in Taita District where agriculture contributes to 95% of household income with very little or no soil fertility ameliorating inputs in farms. The following were tested in the trials; three types of inorganic fertilizers, cow manure, and Trichoderma seed coating. Planting was done during the long and short rains. Soil and roots were collected from the rhizosphere during harvesting and assessed for inoculum density while the roots were evaluated for incidence of infection by Fusarium spp. The most common species in both soil and roots were F. oxysporum (Schlecht) Snyd.et Hans. and F. sporotrichoides Sherb. Addition of soil ammandments had a positive effect of reducing root infection and in some cases lowering inoculum density in the soil. Of the four integrated soil fertility interventions, Mavuno had the highest yield and was the most effective in suppressing root colonisation by Fusarium spp

SPATIAL DISTRIBUTION OF TRICHODERMA SP. IN EMBU AND TAITA REGIONS, KENYA

The distribution of Trichoderma species in soils of Embu and Taita regions in Kenya with relation to land use practices was investigated. The study areas were chosen because of their significant land use intensification and for being biodiversity hot spots. Soil washing and dilution plate techniques were used to recover Trichoderma spp from the soil samples collected from different land use types. The fungal isolates were identified and assigned to nine species from Embu soils and eleven species from the Taita soils. Greater populations were however observed in Embu than in Taita. Geographic differences between the regions mostly explain the differences in ecological niches of the two regions that result to different soil assemblages and plant types in the regions and therefore variation in available substrate for the fungus. Land use at each site affected the distribution, richness and abundance of Trichoderma with Napier grass having the highest abundance in both Embu and Taita while coffee had the lowest richness and abundance. Trichoderma favoured plants with shallow and widely spreading rooting systems, compared to the deeply rooted perennial coffee and tea trees. This underpins the importance of plant type and in effect land use system in the abundance of Trichoderma. The unevenness in the distribution of Trichoderma within the LUTs suggests yet another factor influencing the distribution of Trichoderma apart from the LUTs. Unevenness was greater in Embu than in Taita. The differences could mostly be attributed to soil management practices employed by different farmers while managing their land and crops differently. Trichoderma harziunum was the most frequently isolated species and the most abundant in both Embu and Taita. The presence of Trichoderma species in some land use types and the absence in others, provides a clue on the most preferred habitats, plants and/or crops. Considering the beneficial aspects of Trichoderma such as being antagonistic to the pathogenic fungi, crops or plants such as napier grass that induce high abundance and richness of Trichoderma can be used in crop rotations or in combinations with other crops to maintain high levels of the fungus in the soil