Mycological Quality of Maize Flour from Aflatoxins “Hot” Zone Eastern Province – Kenya
Korir K.1 and Bii CC1.
1
Centre for Microbiology Research - Kenya Medical Research Institute P.O. Box 54840-00200, Nairobi, Kenya.
Corresponding author:Tel.: +254-2724264; Mobile + 254 – 710173815; Fax: +254202720030
E-mail address: [email protected]
SUMMARY
Background: Many agricultural commodities are vulnerable to attack by fungi that produce mycotoxins.
Among the mycotoxins, aflatoxins produced by Aspergillus flavus and Aspergillus parasiticus, have assumed
significance owing to their widespread occurrence. Aflatoxins are proven carcinogens. In developing
countries many individuals are chronically exposed to high levels of aflatoxins and other mycotoxins in their
diets. Tropical climate not only favour fungal infestation and toxins production but lack of monitoring may
lead to grave consequences.
Methods: Twenty sample of maize flour collected and confirmed to be mycotoxin positive from aflatoxin
“hot” zones in Eastern Province were subjected to mycological investigations. The samples were dissolved in
sterile distilled water and inoculated into Potato Dextrose Agar and incubated at 30oC. After 48 hours,
fungal colony forming units were determine and identified using conventional procedures.
Results/Discussion: Over 70% of the maize samples investigated were infested with toxigenic moulds. The
predominant species of fungi identified were; Aspergillus flavus. A. parasiticus, A. niger, Penicillium citrinum,
Fusarium moniliforme and Rhizomucor. Two Bacterial spp, Bacillus anthracoides and Streptomyces spp were
also isolated. This is an indication that other than aflatoxins produced by Aspergillus spp, there could be
other potentially carcinogenic mycotoxin such as fumonisins produced by Fusarium spp. which goes
undetected.
Conclusion: The results are of a particular public health importance given the long term consequences of
mycotoxins exposure to human and animal health and calls for detection of other non aflatoxin mycotoxins
and constant monitoring of mycotoxicological food contamination.
Key words: Fungi, Mycotoxins, Aflatoxines, Fumonisins, Tropical Climate, Public Health.
[Afr J Health Sci. 2012; 21:143-146]
Introduction
Mycotoxins are potent fungal metabolites that
frequently contaminates maize and other agricultural
products world wide (Peraica et al., 1999, Guo,
2000). Aflatoxin is a fungal toxin produced by
Aspergillus flavus and its related A. parasiticus.
Chronic exposure to aflatoxin contaminated foods is a
risk factor for liver cancer and over consumption
leads to acute hepatic failure known as aflatoxicosis
(Williams, 2004, Fung and Clark, 2004). It also leads
to impaired immune system and protein-nutrient
metabolism which may impact negatively on other
health parameters including HIV infection,
malnutrition and infectious disease (Fung and Clark,
2004).
Several outbreaks of acute aflatoxicosis have been
periodically reported in Kenya, with acute
aflatoxicoses reported in Machakos, Makueni and
Kitui Districts in 1982, 2004 and 2005 and now
known as the aflatoxin ‘hot’ zones (Lauren, 2004,
Ngindu et al., 1982). The zones catchments and
population consists of Kibwezi, Makindu, MtitoAndei, Mutha, Mutomo, Ikutha, Central and Kyuluni.
This catchment area comprises the region where the
majority of aflatoxicosis cases occurred in 2004 and
2005. It is a rural area where most of the local
population engages in small-scale, mixed farming
with maize being the primary dietary staple food
crop. Epidemiologic investigations determined that
the outbreak was as a result of aflatoxin poisoning
from ingestion of contaminated maize (corn). As of
20 July 2004, 317 cases and 125 deaths had occurred;
making this one of the largest and most severe
outbreaks of acute aflatoxicosis documented
worldwide (CDC 2004).
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143
Several control strategies including early detection
and replacement of contaminated food among
subsistence farmers has been attempted (AzzizBaumgartner, 2005, Sherphard, 2003), controlled
moisture level and adequate drying, proper storage
facilities and practices (Guo, 2000). Unfortunately, in
Kenya even if such guidelines exist, they are not fully
enforced However, in order to find a long term, cost
effective solution to mycotoxicoses given the remote
location of the high risk population, there is need for
educational, agricultural and medical intervention.
Given the favorable condition for fungal
contamination and proliferation, it is possible that the
population continue to be exposed to other fungal
metabolites other than aflatoxins which might lead to
long term adverse health consequences. Maize
replacement efforts by the Ministry of Health during
2004, 2005 aflatoxin outbreak served only the short
term effort of reducing morbidity and mortality
(Azziz-Baumgartner, 2005). In developed countries,
mycotoxin detection and control strategies have
eliminated aflatoxicosis (Guo, 2000). For long term
solutions to mycotoxin exposure in Kenya, strategies
at the subsistence farm level should target awareness,
storage practices, and control of storage pests, good
quality maize breeds and risk factors.
Materials and methods
The study catchments and population consists of three
divisions in Makueni (Kibwezi, Makindu, MtitoAndei) and five divisions within Kitui District
(Mutha, Mutomo, Ikutha, Central and Kyuluni).
According to the 1999 Kenya National Census data,
the total population of these six districts is 527,679.
This catchment area comprises the region within
Makueni and Kitui Districts where the majority of
aflatoxicosis cases occurred in 2004 and 2005. It is a
rural area where most of the local population engages
in small-scale, mixed farming with maize being the
primary dietary staple crop. Villages were randomly
selected from the catchment area where the majority
of reported acute aflatoxicosis cases occurred. Out of
147 samples initially collected for detection of
aflatoxin, we randomly selected twenty samples for
mycological investigations. The maize flour samples
were prepared for colony forming units culture by
weighing five grams in 10ml of sterile distilled water
and the mixture was vortex for 1 min. One hundred
microlitres of the sample was inoculated onto potato
dextrose agar using micro pipette and uniformly
spread using sterile spreaders. The plates were
incubated for 48 hours after which the colony
forming units were counted. The procedure was done
in triplicates and the average result was recorded.
Fungal identification was done using cultural and
morphological characteristics (Campbell, 1996,
Marassas et al, 1994). Plates inoculated with sterile
distilled water were included as controls.
Results
The results revealed that 15/20 (75%) of the samples
were infested with potential mycotoxin producing
fungi. Three samples had >1000 colony forming unit
(CFU) per ml of sample tested. In the positive
samples 12/15(80%) were infested with A. flavus and
A. parasiticu, 6/15 (40%) were A. niger infested.
There were five samples infested with Fusarium
moniliforme and three with Penicillium citrinum. The
results are as shown in table I below.
Table I: Colony Forming Unit Counts of Fungal Contaminants after 48 Hours
Reference No.
Colony forming Units
Contaminants
M141
M035
Fusarium
moniliforme,
Rhizomucor,
Bacillus
>1000
anthracoides
M073
2
Fusarium miniliforme
M071
3
Penicillium citrinum, A. flavus, A. parasiticus
M083
3
Aspergillus niger, A. flavus, A. parasiticus
M023
2
A. flavus, A. parasiticus
M062
21
A. flavus, A. parasiticus, A. niger, Fusarium
moniliforme
M084
37
Bacillus anthracoides, Streptomyces spp.
M088
20
A. flavus, A. parasiticus, Penicillium citrinum,
Fusarium moniliforme
M144
85
A.flavus, A. niger, A. parasiticus
M074
5
A. niger, A. flavus, A. parasiticus, Penicillium
citrinum
M134
A. niger, A. flavus, A. parasiticus
>1000
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144
M086
M087
M082
M081
M135
M091
M134
M077
18
5
>1000
16
A. flavus, A. niger, A. parasiticus, A. tereus
F. moniliforme
A. niger, A. flavus, A. parasiticus
A. flavus, A. parasiticus
The following are sample photographs of culture plates with heavy infestation with toxigenic fungi.
Figure I: Plates of Flour Samples Showing Heavy Infestation by Toxigenic Fungi
a. Fusarium moniliforme and
A. parasiticus
c. Aspergillus flavus and
A. niger
Discussion
Other contaminants encountered were bacterial strain;
Bacillus anthracoides and Streptomyces spp. The
presence of environmental bacterial contaminants
such as Bacillus anthracoides and Streptomyces spp
is an indication of poor hygienic condition during
handling, transportation and storage of maize product
which is a further predisposing factor to fungal
contamination. Rhizomucor is a saprophyte found in
the environment and although it has not been reported
to produce any harmful mycotoxins, such fungal
infestation leads to caking and poor quality of maize
(Hesseltine, 1976). Several practices have been
suggested to reduce fungal infestations and includes;
Sanitation practices, destroying and discarding hairs,
shattered kernels and shelled cobs which can harbour
insects (especially maize weevil) and A. flavus.
Fumigation for insects (especially maize weevil) at
the earliest practical time after shelling can also
reduce fungal infestation. Build-up of fungal during
temporary storage (prior to transport to the silo) may
be a major contributor to A. flavus and A. Parasiticus
b. Penicillium citrinum
d. Bacillus anthrocoides
leading to aflatoxin build-up. Aflatoxin out break in
Kenya with certainty and is attributed to drought and
food shortages (USAID, 2004). However, before a
long lasting mycotoxin control can be achieved, apart
from enforcing the recommended guidelines, first,
there is need to determine whether we are dealing
with only aflatoxin exposure or there are other fungal
metabolites of public health concerns and why are
certain areas of the country prone to aflatoxicoses
outbreaks. There is a possibility that the maize seed
variety grown in the Aflatoxin ‘hot’ zones could be
more susceptible to fungal infestations and
subsequent mycotoxin contamination with possible
‘super’ aflatoxin producing Aspergillus flavus. There
could also be cultural practices among the population
that makes the grains more susceptible to fungal
infestations and subsequent toxin production while
the population may not understand the long term
consequences of mycotoxin exposure. There is also a
possibility that the rising cases of cancers may be
attributed to mycotoxin exposure. There is also need
to investigate the role of insect pest such as weevil in
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145
fungal infestation of maize from the field to the
granary.
Conclusion
The maize samples from ‘aflatoxin hot zones’ had a
high percentage of potential mycotoxin producing
fungal contaminants. There is a possibility that the
population is exposed to other toxic fungal
metabolites such as fumonisins. The results are of a
particular public health importance given the long
term health consequences of mycotoxins exposure in
both human and animal. In order to reduce morbidity
and mortality associated with aflatoxin exposure in
high risk population, there is need for long term
intervention measures. Apart from identifying simple
cost effective method of detecting fungal
contamination, on-farm mycotoxin management
approach and educational campaigns would be useful
in finding long term solution to mycotoxin exposure
in peasant farmers.
Acknowledgement
The authors would like to sincerely acknowledge the
Director KEMRI for providing a conducive
environment for this work to be accomplished.
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