Cryptosporidium SPP contamination and risk associated with the irrigation of lettuce with contaminated water in the Kumasi Metropolis of Ghana
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Date
2015-11-02
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Abstract
Cryptosporidium is a protozoan parasite which can be transmitted via food and water. Some
studies have shown irrigation water to be routes of transmission for Cryptosporidium into the
food chain, however, little information is known about Cryptosporidium levels in water used for
irrigation in the Kumasi Metropolis. The purpose of this study was to evaluate Cryptosporidium
contamination and risk associated with the irrigation of lettuce with contaminated water in the
Kumasi Metropolis of Ghana. The study considered Cryptosporidium detection and enumeration
in water and on lettuce samples using light microscopy, fluorescent microscopy and molecular
identification using nested polymerase chain reaction (PCR). A total of 54.10% of all water
samples tested positive by using microscopy or nested PCR (HSP70) approach. A comparative
assessment for microscopy and nested PCR (HSP70) showed that 37.5% of all water samples
were positive for Cryptosporidium using microscopy whilst 41.67% showed positive presence
using nested PCR approach. The study revealed that water samples from irrigation water
contaminated with hospital waste upstream had the highest number of oocyst with a total of
263.15±0.92 oocysts /10 L on all rounds of sampling. Water contaminated with effluent from a
waste stabilization pond had no detectable number of oocysts on all rounds of sampling. All
irrigation water with the exception of water contaminated with effluent from a waste stabilization
pond exceeded the recommendation of WHO/FAO for protozoan parasites (1 egg/L); however,
there was no statistical difference between oocysts counts from the various water samples from
the farms. Temperature had an inverse relationship with oocyst concentration from the farms
whilst pH and turbidity had no significant relationship with oocyst concentration. Molecular
detection of Cryptosporidium using nested PCR (HSP70) showed that 50.00% of all lettuce
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samples analysed were positive for Cryptosporidium. Risk analysis indicated that all water
sources for irrigation posed risk as possible sources of human infection through direct contact
with these water sources. The risk was higher than the WHO accepted threshold
of threshold. However, risk analysed using the E. coli conversion for
Cryptosporidium distribution resulted in an underestimation of risk. Based on the risk
assessment, measures should be put in place to reduce pathogen concentration in water sources
in order to reduce risk posed to farmers.
Description
A Thesis submitted to the Department of Biochemistry and Biotechnology,
College of Science,
in partial fulfilment of the requirements for Master of Philosophy degree in Biochemistry.