Understanding the management practices of animal manure and associated risks of transference of bacterial pathogens to crop vegetables

Abstract

Manure is commonly used in agricultural production in Mauritius, but little is documented on the local management practices. Animal manure, in particular, is a livestock waste that harbors enteric microorganisms which are potentially pathogenic to humans. The objectives of the study were therefore (i) to shed light on the management practices of manure among cattle and poultry farmers  (manure producers) and carrot and lettuce growers (manure end-users) and any associated health risks and (ii) to determine the prevalence of human pathogens (diarrheagenic Escherichia coli, Salmonella, Listeria monocytogenes and Clostridium perfringens) in manure collected from farmers, vegetable crops fertilized with manure as well as manure-amended soil (MAS) used in crop cultivation. A survey was conducted through in-depth interviews with 16 producers and 36 end-users to gather data on their MMP and their  perception of the health risks associated with manure handling. Samples of manure, MAS and vegetables were also microbiologically analyzed to enumerate and/or detect pathogens. Findings revealed that cattle and poultry manure was an important resource for many small-holder vegetable farmers in Mauritius. The manure distributors or end users had no negative perception of the use of untreated manure for vegetable cultivation and were generally unaware of any biosecurity risks arising from the improper handling or subsequent use of untreated manure. Microbiological analyses however showed that 100% of manure samples collected from cattle farms and 58% of the poultry litter samples tested positive for pathogenic E. coli with population ranging from 3.3 to 6.5 Log CFU/g. Manure-borne pathogens were generally undetectable in the analyzed vegetables hence indicating a low risk of foodborne infections. However, the systematic presence of pathogenic E. coli in cattle manure and frequent occurrence in poultry litter clearly point to a need for creating greater awareness amongst farmers on the occupational health risks associated with handling of raw or inadequately decomposed manure. This study therefore points to the health risks associated with enteric pathogens present in raw or untreated raw manure in Mauritius.

Key words: Manure Management, Pathogens, E. coli, Salmonella, Cattle, Poultry, Carrot, Lettuce, Mauritius