The risk of Listeria monocytogenes infection in beef cattle operations

To determine the prevalence of Listeria monocytogenes and associated risk factors among beef operations (cow-calf and feedlot) in central and southern California.

A repeated cross-sectional study where faecal and environmental samples were collected from 50 operations three times a year at different seasons was carried out. Samples were tested for presence of L. monocytogenes using a combination of enrichment and polymerase chain reaction tests. Data on putative risk factors were also collected. Listeria monocytogenes was detected in faecal samples from cows, calves and other animals on calf-cow operations at proportions of 3.1%, 3.75% and 2.5%, respectively. The organism was detected in 5.3% of cut-grass, 5.3% of soil, 14.3% of irrigation ditches, 3.1% of the ponds and 6.5% of water troughs samples. Listeria monocytogenes was less common in faecal (0.3%) and soil (0.75%) samples collected from feedlots.

Listeria monocytogenes was present at a higher proportion among cow-calf operations than feedlots. There was no significant seasonal variation in the occurrence of this pathogen within the two types of operations.

If risk mitigation strategies were implemented to reduce the public health risk these should focus in cow-calf operations.