PROF. OKOTH SHEILA

A 24-week feeding experiment was conducted to assess whether males and females of Oreochromis niloticus exhibit differences in
their hematological responses and organosomatic indices to dietary AFB1 contamination. Triplicate groups of O. niloticus (initial
body weight: 24.1 ± 0.6 g) were fed with four diets (Diets 1 to 4) containing 0, 20, 200, and 2,000

Fusarium verticillioides and Aspergillus
flavus cause Fusarium ear rot (FER) and Aspergillus
ear rot (AER) of maize, respectively. Both pathogens
are of concern to producers as they reduce grain yield
and affect quality. F. verticillioides and A. flavus also
contaminate maize grain with the mycotoxins fumonisins
and aflatoxins, respectively, which has been
associated with mycotoxicosis in humans and animals.
The occurrence of common resistance mechanisms to
FER and AER has been reported. Hence, ten Kenyan
inbred lines resistant to AER and aflatoxin accumulation
were evaluated for resistance to FER, F.
verticillioides colonisation and fumonisin accumulation;
and compared to nine South African lines
resistant to FER and fumonisin accumulation. Field
trials were conducted at three localities in South Africa
and two localities in Kenya. FER severity was
determined by visual assessment, while F. verticillioides
colonisation and fumonisin content were
quantified by real-time PCR and liquid chromatography
tandem mass spectrometry, respectively. Significant
genotype x environment interactions was
determined at each location (P B 0.05). Kenyan
inbred CML495 was most resistant to FER and F.
verticillioides colonisation, and accumulated the lowest
concentration of fumonisins across localities. It
was, however, not significantly more resistant than
Kenyan lines CML264 and CKL05015, and the South
African line RO549 W, which also exhibited low FER
severity (B5%), fungal target DNA (B0.025 ng lL-1
)
and fumonisin levels (B2.5 mg kg-1
). Inbred lines
resistant to AER and aflatoxin accumulation appear to
be promising sources of resistance to F. verticillioides
and fumonisin contamination.
Keywords Fusarium ear rot Aspergillus ear rot
Resistance Mycotoxins Maize inbred lines
In

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
fromSolanumaculeastrum, bark fromSyzygium 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 2ml 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 600mg/ml. Aqueous extracts
had no antifungal activity because all diameters were below 8 mm. Solanum aculeastrum had the lowest minimum inhibitory
concentration at 25mg/ml against A. flavusUONV017.All the plant extracts in combinationwith 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.

Groundnut is one of the staple foods in many parts of the world. Due to its high nutrient content, the nuts are liable to colonization by aflatoxigenic fungi and subsequent aflatoxin accumulation. This study was aimed at determining susceptibility of locally grown groundnut varieties to Aspergillus flavus in Homa Bay County, Western Kenya. A pretested questionnaire was used to survey agronomic practices on groundnut cultivation in 75 randomly selected households in the study site. From each household farm, 100 g soil samples and 500 g of groundnuts were collected at harvest and A. flavus isolated on Modified Rose-Bengal Agar and identified. Aflatoxin was then extracted from each of the groundnut samples and quantified using direct competitive enzyme linked immunosorbent assay (ELISA). Red Valencia was the most cultivated among the 8 varieties identified. Farmers (66%) obtained the planting seeds from the local market and most (92%) did not use fertilizers with majority (94%) having no knowledge of aflatoxins. There was no significant inter-variety difference in aflatoxin accumulation (p=0.744, F=0.581, Df=6, 61). A highly significant association (t = 2.652; P = 0.010) was found between storage state of the groundnuts and aflatoxin levels, with 94% of the samples stored unshelled having aflatoxin levels below 10 ppb. Overall, only 6.7% of kernels sampled from all the divisions did not meet the EC aflatoxin limit of ≤4 ppb while 4% did not meet the KEBS limit of ≤10 ppb. Though the agronomic practices were poor, aflatoxin levels were predominantly low in the region suggesting that the aflatoxin accumulation is likely influenced by agro-ecological zoning as other studies have also been indicated.

Key words: Groundnuts, Aflatoxins, Aspergillus flavus.

n November 2013, a Plasmodium falciparum malaria outbreak of 11 cases occurred in Cusco, southern Peru, where falciparum malaria had not been reported since 1946. Although initial microscopic diagnosis reported only Plasmodium vivax infection in each of the specimens, subsequent examination by the national reference laboratory confirmed P. falciparum infection in all samples. Molecular typing of four available isolates revealed identity as the B-variant (BV1) strain that was responsible for a malaria outbreak in Tumbes, northern Peru, between 2010 and 2012. The P. falciparum BV1 strain is multidrug resistant, can escape detection by PfHRP2-based rapid diagnostic tests, and has contributed to two malaria outbreaks in Peru. This investigation highlights the importance of accurate species diagnosis given the potential for P. falciparum to be reintroduced to regions where it may have been absent. Similar molecular epidemiological investigations can track the probable source(s) of outbreak parasite strains for malaria surveillance and control purposes.

Transmission intensity, movement of human and vector hosts, biogeographical features, and malaria control measures are some of the important factors that determine Plasmodium falciparum parasite genetic variability and population structure. Kenya has different malaria ecologies which might require different disease intervention methods. Refined parasite population genetic studies are critical for informing malaria control and elimination strategies. This study describes the genetic diversity and population structure of P. falciparum parasites from the different malaria ecological zones in Kenya. Twelve multi-locus microsatellite (MS) loci previously described were genotyped in 225 P. falciparum isolates collected between 2012 and 2013 from five sites; three in lowland endemic regions (Kisumu, Kombewa, and Malindi) and two in highland, epidemic regions (Kisii and Kericho). Parasites from the lowland endemic and highland epidemic regions of western Kenya had high genetic diversity compared to coastal lowland endemic region of Kenya [Malindi]. The Kenyan parasites had a mean genetic differentiation index (FST) of 0.072 (p = 0.011). The multi-locus genetic analysis of the 12 MS revealed all the parasites had unique haplotypes. Significant linkage disequilibrium (LD) was observed in all the five parasite populations. Kisumu had the most significant index of association values (0.16; p < 0.0001) whereas Kisii had the least significant index of association values (0.03; p < 0.0001). Our data suggest high genetic diversity in Kenyan parasite population with the exception of parasite from Malindi where malaria has been on the decline. The presence of significant LD suggests that there is occurrence of inbreeding in the parasite population. Parasite populations from Kisii showed the strongest evidence for epidemic population structure whereas the rest of the regions showed panmixia. Defining the genetic diversity of the parasites in different ecological regions of Kenya after introduction of the artemether–lumefantrine is important in refining the spread of drug resistant strains and malaria transmission for more effective control and eventual elimination of malaria in Kenya.

Most Plasmodium falciparum-detecting rapid diagnostic tests (RDTs) target histidine-rich
protein 2 (PfHRP2). However, P. falciparumisolates with deletion of the pfhrp2 gene and its
homolog gene, pfhrp3, have been detected. We carried out an extensive investigation on
365 P. falciparumdried blood samples collected from seven P. falciparumendemic sites in
Colombia between 2003 and 2012 to genetically characterise and geographically map
pfhrp2- and/or pfhrp3-negative P. falciparumparasites in the country. We found a high proportion
of pfhrp2-negative parasites only in Amazonas (15/39; 38.5%), and these parasites
were also pfhrp3-negative. These parasites were collected between 2008 and 2009 in
Amazonas, while pfhrp3-negative parasites (157/365, 43%) were found in all the sites and
from each of the sample collection years evaluated (2003 to 2012). We also found that all
pfhrp2- and/or pfhrp3-negative parasites were also negative for one or both flanking genes.
Six sub-population clusters were established with 93.3% (14/15) of the pfhrp2-negative
parasites grouped in the same cluster and sharing the same haplotype. This haplotype
corresponded with the genetic lineage BV1, a multidrug resistant strain that caused two outbreaks
reportedin Peru between 2010 and 2013. We found this BV1 lineage in the Colombian
Amazon as early as 2006. Two new clonal lineages were identified in these parasites
from Colombia: the genetic lineages EV1 and F. PfHRP2 sequence analysis revealed high
genetic diversity at the amino acid level, with 17 unique sequences identified among 53
PfHRP2 sequences analysed. The use of PfHRP2-based RDTs is not recommended in
Amazonas because of the high proportionof parasites with pfhrp2 deletion (38.5%), and
implementation of new strategies for malaria diagnosis and control in Amazonas must be
prioritised.Moreover, studies to monitor and genetically characterise pfhrp2-negative P. falciparumparasites in the Americas are warranted, given the extensive human migration
occurring in the region.

Application of Fungi for effective removal of hydrocarbon contamination from soil is being considered as the better option when it comes to biodegradation. Other method like physical and chemical bioremediation leads to production of toxic compounds and these methods are not cost effective. In the present study, soil samples from four different oil contaminated soils were assessed for any recovery of fungi present. Cultural characterization was used as preliminary identification using keys. Initial isolation from the oil contaminated soil was done using potato dextrose agar. Colonies were observed and characterized morphologically. The isolates were grown at varied temperatures and pH. Eight fungal isolates were recovered from polluted soils namely, Trichoderma viride, Trichoderma spirale, Neosartorya pseudofischeri, Neosartorya aureola, Aspergillus flavus, Aspergillus terreus, Penicillium griseofulvum and Trichoderma longibrachiatum. The optimum growth temperature range for the eight fungi was 30 o C and 40 o C. There was no growth at 50 o C for all isolates except some slight growth by Aspergillus flavus. Optimum growth at pH 7 and pH 9 and poor growth at pH 5 was noted. This study will contribute to the database on locally available fungal diversity and their ecology.

The aim of this study was to identify Aspergillus species isolated from maize kernels and soils of
maize fields of Nandi County using macro and micro morphological characteristics. A cross sectional
research design was used in the study and purposive sampling was employed to determine
districts of Nandi County and sub locations where sampling was done. This study was part of a
larger project whose aim was to survey aflatoxin exposure in the maize value chain. Aspergillus
species were isolated from maize and soil samples using quarter strength potato dextrose agar
and modified Rose Bengal agar respectively. Pure cultures of the isolates were sub cultured and
transferred onto differential media; malt extract agar, czapek yeast extract agar and czapek dox
agar for species identification using macro morphological characteristics. Fungal slides were prepared
from pure cultures on potato dextrose agar media after three days to identify micro morphological
characteristics. Based on morphological characteristics, seven sections of Aspergillus
namely: Flavi, Fumigati, Nigri, Circumdati, Clavati, Nidulantes and Candidi were identified. Aspergillus
section Flavi was the most predominant with 57% followed by section Nigri with 27% from
maize and 58% of section Flavi followed by 26% of section Nigri from the soil across the three locations.
Aspergillus sections Nidulantes and Candidi were rare and only recovered from the soil
samples of Kaptumo location. All the Aspergillius flavus that formed sclerotia both from the soils
or maize kernels were of the L strains. In conclusion Aspergillus section Flavi was most frequent
during the isolation process and dominated with Aspergillus flavus from both the maize and soil.
Morphological characteristics remain the primary tool for detection and identification of Aspergillus
species. The significance for high incidence of Aspergillus section Flavi is in regard to their
aflatoxin production profiles that poses a health threat to the community and it is of public health
concern. Morphological characteristics as a primary tool for Aspergillus identification should be
embraced and more personnel with the knowledge are required since modern and faster techniques
are scarce and expensive.

The recent emergence of artemisinin resistance in the Greater Mekong Subregion poses a major threat to the global effort to control malaria. Tracking the spread and evolution of artemisinin-resistant parasites is critical in aiding efforts to contain the spread of resistance. A total of 417 patient samples from the year 2007, collected during malaria surveillance studies across ten provinces in Thailand, were genotyped for the candidate Plasmodium falciparum molecular marker of artemisinin resistance K13. Parasite genotypes were examined for K13 propeller mutations associated with artemisinin resistance, signatures of positive selection, and for evidence of whether artemisinin-resistant alleles arose independently across Thailand. A total of seven K13 mutant alleles were found (N458Y, R539T, E556D, P574L, R575K, C580Y, S621F). Notably, the R575K and S621F mutations have previously not been reported in Thailand. The most prevalent artemisinin resistance-associated K13 mutation, C580Y, carried two distinct haplotype profiles that were separated based on geography, along the Thai-Cambodia and Thai-Myanmar borders. It appears these two haplotypes may have independent evolutionary origins. In summary, parasites with K13 propeller mutations associated with artemisinin resistance were widely present along the Thai-Cambodia and Thai-Myanmar borders prior to the implementation of the artemisinin resistance containment project in the region.

During 2010–2012, an outbreak of 210 cases of malaria occurred in Tumbes, in the northern coast of Peru, where no Plasmodium falciparum malaria case had been reported since 2006. To identify the source of the parasite causing this outbreak, we conducted a molecular epidemiology investigation. Microsatellite typing showed an identical genotype in all 54 available isolates. This genotype was also identical to that of parasites isolated in 2010 in the Loreto region of the Peruvian Amazon and closely related to clonet B, a parasite lineage previously reported in the Amazon during 1998–2000. These findings are consistent with travel history of index case-patients. DNA sequencing revealed mutations in the Pfdhfr, Pfdhps, Pfcrt, and Pfmdr1 loci, which are strongly associated with resistance to chloroquine and sulfadoxine/pyrimethamine, and deletion of the Pfhrp2 gene. These results highlight the need for timely molecular epidemiology investigations to trace the parasite source during malaria reintroduction events.

Keywords: Falciparum malaria, Plasmodium, Peru, microsatellite markers, parasites, malaria, Peru

Plant-parasitic nematodes cause severe damage to a wide range of economic crops, causing upto 5% yield losses
globally. In Kenya, vegetables are affected, among other pests, by parasitic nematodes, causing upto 80% loss in yield.
Nematode control is very difficult and relies heavily on use of chemical nematicides. Use of these chemical nematicides
leads to biological magnification, and elimination of natural enemies of other pathogens, thus creating a need for
greater application of pesticides, increased production costs, and development of insecticide-resistance. These factors
have led to a growing interest in search for alternate management strategies. The objective of this study was, therefore,
to document nematode-destroying fungi in selected, major vegetable-growing areas in Kenya as a step towards
developing a self-sustaining system for management of plant-parasitic nematodes. Soil samples were collected from
five vegetable-production zones, viz., Kinare, Kabete, Athi-river, Machakos and Kibwezi, and transported to the laboratory
for extraction of nematode-destroying fungi. The soil-sprinkle technique described by Jaffee et al (1996) was used for
isolating the nematode-destroying fungi from soil, while, their identification was done using identification keys
described by Soto Barrientos et al (2001). From this study, a total of 171 fungal isolates were identified as nematodedestroying.
The highest population was recorded in Kabete, at 33.9% of the total, followed by Machakos, Kibwezi,
Athi-river, with the least in Kinare, at 24.6, 22.2, 11.7 and 7.6% of the total population, in that order. Arthrobotrys was
the most frequent genus, with mean occurrence of 7.3, followed by Monacrosporium with 6 and Stylophage with 5.2.
A. dactyloides was significantly (P=0.002) affected by the agro-ecological zone, with the highest occurrence recorded
in Kabete, and the least in Athi-river. Kibwezi recorded highest diversity index, with a mean of 1.017, while, Athi-river
recorded the least, with a mean of 0.333. Kibwezi had the highest species richness, recording a mean of 3.4, while, the
least mean of 1.6 was recorded in Athi-river. Mean species richness of 2.2 was recorded for both Kabete and Machakos,
and 1.8 for Kinare. From the three genera recorded, Arthrobotrys was more effective at trapping nematodes compared
to Monocrosporium and Stylopage. The genus Arthrobotrys had the highest number of trapped nematodes, with a
total population of 57, followed by Monacrosporium, the least being Stylopage, with 45 and 36, respectively, in a period
of 104 hours. From the study, it is evident that agricultural practices affect occurrence and diversity of nematodedestroying
fungi, and, Arthrobotrys can be used as a bio-control agent for managing plant-parasitic nematodes.
Key words: Artabotrys, biological control, plant-parasitic nematodes

Background: Recent studies have demonstrated the deletion of the histidine-rich protein 2 (PfHRP2) gene (pfhrp2)
in field isolates of Plasmodium falciparum, which could result in false negative test results when PfHRP2-based rapid
diagnostic tests (RDTs) are used for malaria diagnosis. Although primary diagnosis of malaria in Honduras is
determined based on microscopy, RDTs may be useful in remote areas. In this study, it was investigated whether
there are deletions of the pfhrp2, pfhrp3 and their respective flanking genes in 68 P. falciparum parasite isolates
collected from the city of Puerto Lempira, Honduras. In addition, further investigation considered the possible
correlation between parasite population structure and the distribution of these gene deletions by genotyping
seven neutral microsatellites.
Methods: Sixty-eight samples used in this study, which were obtained from a previous chloroquine efficacy
study, were utilized in the analysis. All samples were genotyped for pfhrp2, pfhrp3 and flanking genes by PCR.
The samples were then genotyped for seven neutral microsatellites in order to determine the parasite
population structure in Puerto Lempira at the time of sample collection.
Results: It was found that all samples were positive for pfhrp2 and its flanking genes on chromosome 8.
However, only 50% of the samples were positive for pfhrp3 and its neighboring genes while the rest were either
pfhrp3-negative only or had deleted a combination of pfhrp3 and its neighbouring genes on chromosome 13.
Population structure analysis predicted that there are at least two distinct parasite population clusters in this
sample population. It was also determined that a greater proportion of parasites with pfhrp3-(and flanking gene)
deletions belonged to one cluster compared to the other.
Conclusion: The findings indicate that the P. falciparum parasite population in the municipality of Puerto Lempira
maintains the pfhrp2 gene and that PfHRP2-based RDTs could be considered for use in this region; however continued
monitoring of parasite population will be useful to detect any parasites with deletions of pfhrp2.
Keywords: Plasmodium falciparum, Histidine-rich protein, Rapid diagnostic tests, Microsatellites, Honduras