Research conducted in 2010 found that Listeria monocytogenes was not predominantly spread by water and chicken manure, two common farm inputs in Australian vegetable farming. It is however more prevalent in summer and in particular in Victoria.

Silage and baled hay produced high numbers of L. monocytogenes which are fed to and ingested by ruminants (cows, sheep, goats). This issue with this feed is that it passes through the animals usually without causing infection to them and becomes trapped within dust when the faeces becomes dry in hot weather.

The dust carrying the L. monocytogenes can then settle on and contaminate vegetables after being blown large distances by strong winds. Leafy vegetables (eg. curly parsley) can trap dust more effectively and show higher levels of detection than smooth leaf vegetables, such as cos lettuce.

A project recommendation is that intensive livestock operations (feedlots) and grazing cattle, sheep and goats should be kept as far from vegetable production as possible and particularly in the direction of prevailing summer winds.

To view the summary from the Fresh Produce Safety Centre please click here.