Aflatoxins in peanuts and the prevalence of aflatoxin induced hepatocellular carcinoma in Busia and Kisii Central Districts, Kenya
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Date
2015-12
Authors
Chengo, Nelson Menza
Journal Title
Journal ISSN
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Publisher
Kenyatta University
Abstract
Aflatoxin is a carcinogenic toxin produced mainly by Aspergillus jlavus and
contaminates foods including peanuts. Aflatoxin is associated with liver failure,
hepatocellular carcinoma (HCC) and death. Many people are exposed to chronic
levels of aflatoxins through consumption of contaminated foods. In Kenya, most
efforts have been focused on aflatoxin in maize while other highly predisposed
foods such as peanuts have received little attention. Also limited studies have been
done to link aflatoxin to HCC. This study identified aflatoxin producing
Aspergillus species and the type and levels of aflatoxin contamination of various
varieties of peanuts (Arachis hypogaea L.) in Busia and Kisii Central districts. It
also determined the peanut producers' exposure to aflatoxins and the prevalence of
aflatoxin induced HCC among patients from the study districts. Cross-sectional
and retrospective study designs with systematic random sampling technique were
adopted. One hundred and two (102) peanut and urine samples were collected
from peanut growers in each district and transported to Cooppers Labs, Nairobi for
analysis. Aspergillus species' were identified using plate technique of serially
diluted samples on modified Rose Bengal agar. Types and levels of aflatoxins
were analyzed using high performance liquid chromatography (HPLC) technique
while aflatoxin B (AFB) gual in urine was determined using fluorescence
Spectrophotometer. Analysis of records for patients from Busia and Kisii Central
districts who attended Moi Teaching and Referral Hospital in January 2010 to
December 2012 was done to determine the prevalence of HCC among the study
population. The diagnosis of HCC was confirmed by the presence of AFB 1
guanine adducts in urine or AFB 1 albumin adduct in blood. The levels of total
aflatoxin ranges were 0.1 to 2681lg/kg and 1.63 to 591.11lg/kg in peanuts from
Busia and Kisii Central respectively. Majority of peanuts samples had levels
within Kenya Bureau of Standards (KEBS) and European Union (EU) regulatory
limits for total aflatoxins. Aflatoxin type Bl was the most dominant (t = 12.4, df=
3, P = 0.034). Overall, the occurrence of Aspergillus jlavus L strain and A. flavus S
strain were significantly higher than other species identified (H = 15.55, df= 4, P
= 0.004) in peanuts from the two districts. However, A. jlavus S-strain was the
most dominant species (F=3.15, df=25, P=0.031) with an overall mean occurrence
of 45.1%. Oil content in peanuts decreased with an increase in aflatoxin levels (r =
-0.496, P = 0.031) except in peanuts of Uganda local red variety from Kisii
Central. Overall, males in both districts had slightly higher incidences (9.8%) of
exposure to urinary Aflatoxin B than females at 5.4%. The prevalence of aflatoxin
induced HCC among the patients was 19.73%. There is need for urgent awareness
through campaign among the peanuts producers on the aflatoxin levels and
promote sound practices when handling peanuts. Continuous screening of patients
with liver disorders should be done for early detection of HCC. The high levels of
aflatoxins in peanuts suggest the necessity to screen other foods consumed in the
study areas. The findings will form basis of policy development for aflatoxin
contamination control and management of aflatoxin induced HCC in Kenya.
Description
A thesis submitted in partial fulfillment of the requirement for the award of the Degree of Doctor of Philosophy (medical mycology) in the school of Medicine of Kenyatta University
December, 2015