Volume 9, Number 5—May 2003
Research
Vero Cytotoxin–Producing Escherichia coli O157 Gastroenteritis in Farm Visitors, North Wales
Table 1
Exposure | Cases | Controls | Univariable analysis | ||||
---|---|---|---|---|---|---|---|
Exposed/ not exposed |
Exposed/ not exposed |
Odds ratio |
p value |
95% CI |
|||
Contact with animals |
|||||||
Cows |
11/2 |
16/20 |
6.88 |
0.01 |
1.15 to 52.69 |
||
Goats (any contact) |
13/0 |
27/9 |
Undef |
0.09 |
Undef |
||
Goat (high contact) |
10/3 |
17/19 |
3.72 |
0.06 |
0.75 to 20.70 |
||
Rabbit |
9/4 |
20/16 |
1.80 |
0.39 |
0.40 to 8.62 |
||
Sheep |
10/3 |
27/9 |
1.11 |
1.00 |
0.21 to 6.48 |
||
Pigs |
5/7 |
11/24 |
1.56 |
0.72 |
0.33 to 7.32 |
||
Pony |
4/9 |
20/16 |
0.36 |
0.12 |
0.07 to 1.61 |
||
Shire horse |
4/9 |
13/23 |
0.79 |
1.00 |
0.16 to 3.64 |
||
Areas of farm visited |
|||||||
Play area |
5/7 |
27/9 |
0.24 |
0.07 |
0.05 to 1.13 |
||
Paddock |
6/7 |
28/8 |
0.24 |
0.08 |
0.05 to 1.13 |
||
Pony ride |
4/9 |
15/21 |
0.62 |
0.49 |
0.13 to 2.84 |
||
Tractor ride |
9/4 |
28/8 |
0.64 |
0.71 |
0.13 to 3.31 |
||
Main barn |
13/0 |
35/1 |
Undef |
1.00 |
Undef |
||
Food consumption and personal behaviors |
|||||||
Sucks thumb |
1/11 |
6/30 |
0.45 |
0.66 |
0.02 to 4.74 |
||
Bites nails |
2/10 |
6/30 |
1.00 |
1.00 |
0.12to 7.08 |
||
Ate any food while on farm |
13/0 |
33/3 |
Undef |
0.56 |
Undef |
||
Ate immediately after barn |
6/6 |
11/23 |
2.09 |
0.31 |
0.45 to 9.81 |
||
Ate food bought on farm |
8/5 |
14/21 |
2.40 |
0.18 |
0.55 to 10.85 |
||
Ate ice cream |
9/4 |
14/22 |
3.54 |
0.06 |
0.77 to 17.19 |
||
Ate cotton candy |
7/6 |
4/32 |
9.33 |
0.004 |
1.69 to 57.10 |
||
Bought animal feed |
10/3 |
32/4 |
0.42 |
0.36 |
0.06 to 2.88 |
||
Picked up animal feed from floor |
5/8 |
6/30 |
3.13 |
0.13 |
0.61 to 16.29 |
||
Ate animal feed |
1/12 |
0/36 |
Undef |
0.26 |
Undef |
||
Clung to animal barriers |
6/3 |
25/7 |
0.56 |
0.66 |
0.09 to 3.76 |
||
Fell over while on farm |
1/12 |
7/29 |
0.35 |
0.66 |
0.01 to 3.43 |
||
Washed hands at all |
10/3 |
24/9 |
1.12 |
1.00 |
0.23 to 7.35 |
||
Environmental observations |
|||||||
Wet underfoot |
3/10 |
6/30 |
1.50 |
0.68 |
0.24 to 8.85 |
||
Dirty hands, shoes, or clothes |
0/13 |
9/27 |
0.00 |
0.09 |
0.00 to 1.46 |
||
Noticed queue for toilets |
2/10 |
3/32 |
2.13 |
0.59 |
0.21 to 19.56 |
||
Type of visit |
|||||||
Family visit |
12/1 |
33/3 |
0.92 |
1.00 |
0.08 to 30.07 |
||
Bank Holiday Monday | 11/2 | 13/20 | 9.73 | 0.003 | 1.38 to 66.32 |
aCI, confidence interval; undef, undefined. (When one of the cells contains a zero, defining a confidence interval is not possible.) Bold typeface highlights variables with increased odds ratio statistically significant at 90% level.
1C. Payne designed the case-control study, drew up the questionnaire, and analyzed and wrote up the results. M. Petrovic helped design the questionnaire, organized the data collection, and wrote the sections describing the outbreak and microbiologic findings. R.J. Roberts contributed toward the study and questionnaire design, including devising the method of selecting controls; he also helped in the final drafts of the paper. R.L. Salmon originally conceived the study, commented on the questionnaire design, and helped interpret the findings. T. Cheasty was responsible for confirmation and typing of isolates. G. Willshaw performed DNA-based comparison of strains. Other authors made important contributions to the investigation and control of the outbreak and participated in writing the paper.