The aim of our survey was to assess the effect of irrigation water of
the microbiological quality on the production chain of lettuce in the
Dakar area. Microbiological analysis showed that 35% of irrigation
water was contaminated by Salmonella spp. between the two water-types
used for irrigation (groundwater and wastewater), no significant
difference (p>0.05) in their degree of contamination was found. The
incidence of different types of irrigation water on the contamination
rate of lettuces from the farm (Pikine and Patte d'Oie) was not
different either (p>0.05). However, the contamination rate of lettuce
from markets of Dalifort and Grand-Yoff that were supplied by the area
of Patte d'Oie was greater than those of Sham and Zinc supplied by
Pikine (p<0.05). Comparison of serotypes of Salmonella isolated from
irrigation water and lettuce showed that irrigation water may affect the
microbiological quality of lettuce. Manures, frequently used as organic
amendment in cultivating lettuce are another potential source of
contamination. These results showed that lettuce may constitute
effective vectors for the transmission of pathogens to consumers.
Extensive treatment of the used wastewater and/or composting of manure
could considerably reduce these risks.