Towards microbial safety of fresh vegetables in Rwanda

Abstract

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 food borne 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 3.3 % (1/30) for Enteroinvasive E. coli (EIEC); 6.7% (2/30) for Enteroaggregative E. coli (EAEC); 13.3% (4/30) for Enterotoxigenic E. coli. (ETEC) and Vibrio cholera; 20.0% (6/30) for Yersinia pestis; 26.7% (8/30) for Francisella tularensis; 40% (12/30) for Cyclospora to 86.7% (26/30) for thermo-tolerant Campylobacter spp. DNA of the following pathogens was not detected 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 unprotected 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 to access of domestic and wild animals, while 50% of the farms used untreated manure. The high detection rate of foodborne pathogens in agricultural water in combination with the observed several risky farming practices forms a likely explanation for the observed prevalence of pathogens in farm vegetables as reported in this study and is of important public health concern if these vegetables are to be consumed raw.

Microbiological Risk Assessment – Guidelines for food

“…This study analysed the farm-to-fork microbial risk for the fresh vegetable supply chain in Rwanda (Ssemanda, 2018). One of the major data gaps identified by the authors was that they could not attribute the estimates of food related illnesses to any food vehicle based on the available data.…”

“…Risk estimates using probabilistic approach (Table 5 in CCFFP, 2011) Table 31. Number of illnesses per year and probability of illness per serving after 100 000 iterations of the baseline model and the what if scenarios (Table 6.4 in Ssemanda, 2018) Table 32. Dates used in the model for the baseline and alternative scenarios (Table 11 in EFSA, 2014b) Table 33.…”

“…Number of illnesses per year and probability of illness per serving after 100 000 iterations of the baseline model and the what if scenarios (Table6.4 inSsemanda, 2018) …”