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Occurrence of Cryptosporidium spp. oocysts in low quality water and on vegetables irrigated with low quality water in Kumasi, Ghana

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Abstract

Protozoan parasites belonging to the genus Cryptosporidium are transmitted e.g. by food and water and may cause severe diarrhoea, dehydration, weight loss and malnutrition. Ingestion of 10 oocysts can lead to infection and pathogenic symptoms. Thus, to characterize Cryptosporidium spp. contamination level of river water, irrigation water and lettuce, 10L of water and 16 lettuce samples were collected four times in the period September – October 2013, with weekly intervals from six sample sites in and around Kumasi, Ghana. Oocysts were purified from water by sedimentation for 2 x 48 hours or pulsifying of lettuce followed by immunomagnetic separation and quantification by immunofluorescence microscopy, with sensitivities of 2 and 9%, respectively. Oocysts were stored approx. six weeks at 4C° before enumeration and approx. two weeks on slides at room temperature. Oocysts were subsequently washed off the slides and attempts to characterize Cryptosporidium spp. positive samples were done by PCR amplification and sequencing of the SSU rRNA, the HSP70 and the GP60 genes. Cryptosporidium oocysts were found in 75% of the water samples and on 43% of the lettuce with concentrations of 53 – 3,268 per 10L water and 11 – 118 oocysts per 15 g of lettuce. Positive water samples on one or more occasions were demonstrated in all water samples from both rivers and farm sites while all farms had positive lettuce samples on all occasions. Rainfall seemingly lowered the concentration of oocysts in water but not on lettuce. Molecular characterization of Cryptosporidium positive samples was unsuccessful, thus no conclusions can be drawn concerning sources of contamination. Nevertheless, the detection of high prevalence and concentration levels of Cryptosporidium oocysts on vegetables consumed raw and in water with direct contact to humans entails a potential risk of infection in humans. Implementation of preventive measures based on this study should be considered and actions taken accordingly.