Risk of Waterborne Parasitic Infection among Vegetables Producers in the City of Ouagadougou, Burkina Faso: An Attempt to Quantify Them Using the Quantitative Microbiological Risk Assessment Method

The use of wastewater in urban agriculture has been promoted as an alternative to water scarcity and as a means to increase soil fertilizer. However, the use of wastewater in urban agriculture raises major public health concerns, mainly due to the often high concentration of pathogenic micro-organisms. Waterborne parasites are a major health concern in this regard, especially in endemic areas, mainly due to the high environmental resistance of eggs/cysts combined with a low infectious dose. In this study, the parasitological risk to vegetables producers in Ouagadougou using polluted water was evaluated through the quantitative microbiological risk analysis method. For this purpose, the search for and quantification of viable parasite eggs and cysts in irrigation water was coupled with epidemiological surveillance of vegetables producers in Ouagadougou. Protozoa and helminths belonging to 9 species were recorded and samples analyzed. These include Ancylostoma sp., Ascaris lumbricoides, tapeworm’s sp, Strongyloides stercoralis, Entamoeba histolytica, Giardia lamblia. Despite the variability of isolated parasitic species, Ancylostoma sp. eggs were common and severe to all types of water. Moreover, epidemiological approach showed that there were more parasitic species found in irrigation water and also other parasitic species circulating among vegetable farmers. In addition, there is no statistical significant association between the type of water used for irrigation and the carried parasites by vegetable gardeners. However, contamination of the groups using the raw wastewater is once higher than those using well water. When one is interested in the groups using treated wastewater as a source of irrigation, these risks of contaminations are halved. These contaminations are halved when one looks at groups using treated wastewater as a source of irrigation water. Still, whatever the type of water used by the gardeners, they have a probability of infection with Ancylostoma sp. of around 9.83 × 10−1 pppy.

Foodborne Pathogens in Retail Oysters in South China

Objective To investigate the occurrence of important foodbome pathogens in shellstock Pacific oysters in the food markets in South China. Methods From July 2007 to June 2008, retail oysters were collected in different seasons from South China and analyzed for the prevalence and levels of Listeria monocytogenes, Vibrio vulnificus and Vibrio parahaemolyticus. Results None of L. monocytogenes could be detected in any of the 202 oyster samples tested, while E vulnificus and E parahaemolyticus could be detected in 67 （54.9%） and 109 （89.3%） of the 122 oyster samples analyzed, respectively, with an MPN （most probable number） value greater than or equal to 3. V. wdnificus and Eparahaemolyticus with a more than 102 MPN/g were found in 36 （29.5%） and 59 （48.4%） of the 122 oyster samples, respectively. The tdh and trh genes were detected in 4 （0.3%） and 8 （0.6%） of the 1 349 V. parahaemolyticus isolates, respectively. Of the 122 samples, 4 （3.3%） was positive for either tdh or trh. The levels of E vulnificus and total V. parahaemolyticus in oysters in South China varied in different seasons. Conclusion V. vulnificus and pathogenic V. parahaemolyticus are frequently found in oysters in south China, which may pose a potential threat to public health. Data presented here will be useful for the microbiological risk assessment in oysters in China.