Foodborne pathogens and their risk exposure factors associated with farm vegetables in Rwanda

In this study, we tested farm vegetables and agricultural water for the presence of foodborne pathogens, and evaluated farming practices of vegetable farms in Rwanda. Farm vegetable samples were found to be contaminated with foodborne pathogens at considerably high rate (overall 15/99 = 15%). Specifically, the prevalence of pathogens in farm vegetables varied from 1.0% (1/99) for Listeria monocytogenes, 3.0% (3/99) for thermo-tolerant Campylobacter spp., 5.1% (5/99) for Salmonella spp. to 6.1% (6/99) pathogenic Escherichia coli. In agricultural water from rivers, lakes, lagoons, ground and marshlands, prevalence of DNA from pathogens varied from 3% (1/30) for Enteroinvasive E. coli (EIEC); 7% (2/30) for Enteroaggregative E. coli (EAEC); 13% (4/30) for Enterotoxigenic E. coli. (ETEC) and Vibrio cholera; 20% (6/30) for Yersinia pestis; 27% (8/30) for Francisella tularensis; 40% (12/30) for Cyclospora to 87% (26/30) for thermo-tolerant Campylobacter spp. DNA of the following pathogens was not detected (0/30) in water: entero pathogenic E. coli (EPEC), shiga toxin producing E. coli (STEC), Salmonella spp., L. monocytogenes, Burkholderia, Rickettsia, Toxoplasma gondii, Giardia lamblia, Cryptosporidium, Entamoeba histolytica and Hepatitis E. About farming practices, 60% of the visited vegetable farms practiced irrigation and all the water used was from un-protected sources (from marshlands [70% ], rivers [18% ], lakes [7% ], runoff lagoons [5% ]). Over 80% of the farms applied overhead irrigation methods and none of the farms had implemented measures to restrict the access of domestic and wild animals, while 50% of the farms used untreated manure. The reported high detection rate of foodborne pathogens DNA in agricultural water and the observed risky farming practices, provides a likely explanation of the reported prevalence of pathogens in farm vegetables and presents an important public health concern if these vegetables are to be consumed raw.