A longitudinal study of environmental salmonella contamination in caged and free-range layer flocks

Abstract

The environmental contamination by salmonella was examined over a 12-month period in 74 commercial layer flocks from eight farms in the UK, which previously had been identified as being contaminated with salmonella. Samples of faeces, dust, litter, egg belt spillage and wildlife vectors were taken, plus swabs of cages, feeders, drinkers, floors, egg belts and boots. Some sampling was performed in each month of the year. Numerous serovars were detected but Salmonella enterica serotype Enteritidis was the only persistent serotype found among single-age flocks. There was a significant correlation between qualitative environmental samples and semi-quantitative faeces samples. The level of environmental contamination increased significantly over time. There were significant temperature and seasonal effects upon contamination. Wildlife vectors proved to be sensitive samples for the detection of salmonella. The efficacy of cleaning and disinfection upon residual salmonella contamination, and upon subsequent flock contamination, was highly variable between and within premises. The variability between detected prevalences over time and between flocks indicates a need for regular, sensitive monitoring of flocks for salmonella to permit targeting of control measures aimed at eliminating contamination of the layer environment by salmonella. There is substantial scope for improvement of cleaning and disinfection procedures.

Dynamics of Salmonella Shedding and Welfare of Hens in Free-Range Egg Production Systems

“…This finding contrasts with an earlier study that found increasing Salmonella shedding over the sampling period (13). There was no significant effect of season on Salmonella prevalence during this study.…”

“…During our study, variabilities between the detected prevalence and shedding were observed between flocks and farms. This observation is in agreement with previous reports (13,16). There are numerous reports on the effects of the housing system on the shedding of Salmonella spp.…”

Salmonella spp. in poultry: a constant challenge and new insights

“…According to a longitudinal study of environmental Salmonella contamination in caged and free-range layer flocks carried out by Wales et al (2007), the timing of taking samples has been shown to have a significant influence on Salmonella spp. isolation.…”

“…Cleaning and disinfection in cases when organic matter had been substantially removed and disinfectants were adequately applied and in proper concentration, had a positive influence on Salmonella control. However, the wildlife reservoirs, multiage farming and lack of "all in all out" strategy highlight the need for vaccination and the use of probiotics in flocks with high and low incidence of the pathogen's load or even in cases that it is absent (Wales et al, 2007). Another study by Dewaele et al (2012) which aimed to examine the Salmonella enterica serovar Enteritidis environmental contamination on persistently positive layer farms in Belgium during successive laying cycles showed that in contaminated poultry houses, neither vaccination nor cleaning and disinfection are considered as the only prerequisite for successful elimination of Salmonella spp.…”

Scientific Opinion on the public health risks of table eggs due to deterioration and development of pathogens

“…Several studies have shown an increased tendency for flocks to be identified as Salmonella positive as the birds become older (Garber et al, 2003;van de Giessen et al, 2006;Wales et al, 2007;Bouzidi et al, 2012;Roberts et al, 2013) especially if birds have been moulted (Golden et al, 2008) In most cases, the initial infection resulted from residual contamination of laying houses that spread to pullets that are suffering from transport, handling and relocation/remixing stress at a time when hormonal changes associated with the onset of lay are also increasing susceptibility to infection (Line et al, 1997). This leads to a typical early peak of infection within three weeks of housing (Humbert et al, 1995;Gradel et al, 2002) but laying flocks are rarely sampled at this time (16-19 weeks of age).…”