Annex O8.1:

COMPARISON OF EU LAYER SURVEY – NON-EU SURVEY SALMONELLA POSITIVE FARMS

Prior to the EU layer survey, a total of 18 farms had been investigated by VLA, primarily as a result of a trace-back investigation of a Salmonella Enteritidis (SE) food-borne poisoning outbreak, or as a consequence of monitoring due to clinical disease of birds or monitoring of Salmonella (14 of these were investigated under OZ0321). The first farm was recruited in July 1998. Two farms were recruited after the EU layer survey but were not included in the EU survey. Therefore a total of 20 layer farms had been investigated by VLA for reasons other than the EU survey. In addition, a total of 23 laying farms when Salmonella was detected in the EU survey were followed-up. In total 560 separate flocks were investigated by VLA.

The list of these farms, the number of houses by type of production and the number of flocks investigated in these farm is presented in Tables 1 and 2.

The distribution of laying houses investigated as a result of the EU survey and for other reasons data indicates a similar (Table 1).

Table 1. Distribution of houses by type of production among farms recruited at the EU survey and farms not recruited at the EU survey.

Non-EU-survey / EU-survey
No. houses / % / No. houses / %
Conventional cage / 61 / 67.0 / 96 / 75.6
Barn / 10 / 11.0 / 6 / 4.7
Colony cage / 3 / 3.3 / 2 / 1.6
Free-range / 17 / 18.7 / 23 / 18.1
91 / 100 / 127 / 100

Percentage of infected flocks in EU survey and non-EU survey holdings

A total of 266 and in 297 flocks were investigated in VLA and EU survey-recruited farms, respectively. Among holdings that were not recruited as part of the EU survey, the percentage of positive flocks with Salmonella, SE, ST and other serovars was 76%, 66%, 3%, and 22%. The equivalent percentage for EU-survey holdings was 68.4%, 56%, 5% and 16%. In general the proportion of infected flocks among VLA farms was greater, although these differences were small. Only in the case of other serovars this difference was of a considerable magnitude, with VLA study flocks being infected in a greater proportion with other serovars (Table 2).

Table 2. No. flocks investigated and positive with different serovars of Salmonella

No. flocks investigated / % flocks with Salmonella spp. / % flocks with SE / % flocks with STM / % flocks with other serovars

Non-EU survey holdings†

Cage / 214 / 85.5 / 74.3 / 4.3 / 26.6
Barns / 38 / 50 / 47.3 / 0.0 / 5.3
Free-range / 41 / 51.2 / 41.5 / 0.00 / 12.2
Colony cage / 4 / 75.0 / 50.0 / 0.00 / 25.0
/ 297 / 76.1 / 66.0 / 3.0 / 21.9

EU survey holdings

Cage / 208 / 75.0 / 61.5 / 5.8 / 17.8
Barns / 18 / 11.1 / 11.1 / 0.0 / 0.0
Free-range / 38 / 57.9 / 47.4 / 2.6 / 10.5
Colony cage / 2 / 100.0 / 50.0 / 0.0 / 100.0
Total / 266 / 68.4 / 56.0 / 5.3 / 16.2

†Holdings recruited by VLA for reasons other than the EU layer survey