An outbreak of cyclosporiasis in 1996 associated with consumption of fresh berries: RESULTS part 2
For cases, the predominant symptoms were diarrhea (96%), fatigue (96%), weight loss (96%), increased gas or bloating (88%), abdominal pain (77%), nausea (61%), headache (54%) and fever (38%). The median weight loss was 3 kg (maximum 8.0 kg). The onsets of illness were from May 16 to June 26, 1996. All 26 cases consulted physicians for their illness; none were hospitalized. Trimethoprim/sulphamethoxazole was prescribed to 81% of the cases. The median duration of diarrhea was 13 days (range zero to 28 days), not accounting for whether the cases had been treated. Three cases reported having a medical condition affecting their immune system, but none reported having HIV infection, organ transplantation, diabetes or inflammatory bowel disease, or taking oral steroid medication. Five cases reported taking antacids, and two reported taking ulcer medication. Six patients had made overnight trips outside Ontario but within North America.
All cases and 96% (n=50) of the controls reported eating fresh fruit during the two-week exposure period. All cases and 98% (n=51) of the controls reported that they usually washed fruit before they ate it. There were no differences between cases and their matched controls in the number of servings of fresh fruit or raw vegetables consumed daily. In the univariate analyses, illness was associated with consumption of strawberries (MOR=28.5, 95% CI 4.02 to 478), raspberries (MOR=21.0, 95% CI 3.48 to 448), blackberries (MOR=undefined, 95% CI 0.82 to infinity) and blueberries (MOR=6.5, 95% CI 1.38 to 44.8). Illness was not associated with consumption of other fruits, place of fruit purchase, consumption of tap water or exposure to untreated water or animals. Analyses are summarized in Table 3.
TABLE 3 Results of the matched case-control study (cases 26; controls 52) in an outbreak of cyclosporiasis in Ontario in 1996
|
Variable |
Cases n |
Controls n |
Matched odds |
95% |
|
Univariate analysis |
|
|
|
|
|
Completed postsecondary education |
21 (81) |
23 (44) |
7.3 |
1.89-28.0 |
|
Strawberries |
24 (92) |
19 (36) |
28.5 |
4.02-478 |
|
Cantaloupes |
17 (65) |
21 (40) |
3.8 |
1.21-13.6 |
|
Raspberries |
11 (42) |
2 (4) |
21.0 |
3.48-448 |
|
Blueberries |
8 (31) |
4 (8) |
6.5 |
1.38-44.8 |
|
Peaches |
5 (19) |
13 (25) |
0.7 |
0.18-2.31 |
|
Blackberries |
3 (12) |
0 |
Undefined |
0.82-infinity |
|
Fruit consumption more than one serving/day |
12 (46) |
16 (31) |
0.9 |
0.34-2.69 |
|
Place of fruit purchase |
|
|
|
|
|
Supermarket |
20 (77) |
40 (77) |
1.0 |
0.33-3.36 |
|
Street vendor |
3 (12) |
2 (4) |
3.0 |
0.45-25.2 |
|
Farmer’s market |
3 (12) |
5 (10) |
1.2 |
0.22-6.21 |
|
Green grocer |
10 (38) |
13 (25) |
2.4 |
0.66-5.55 |
|
Any raw vegetables |
23 (88) |
46 (88) |
1.2 |
0.25-9.30 |
|
Raw vegetable consumption more than one |
5 (21) |
18 (35) |
0.5 |
0.12-1.84 |
|
Tap water more than two glasses/day |
9 (36) |
29 (55) |
0.5 |
0.17-1.21 |
|
Any untreated drinking water |
2 (8) |
6(12) |
0.6 |
0.08-3.38 |
|
Pets at home |
13 (50 ) |
21 (40) |
1.4 |
0.56-3.81 |
|
Multivariate analysis |
|
|
|
|
|
Strawberries |
|
|
13.8 |
2.35-infinity* |
|
Raspberries |
|
|
6.3 |
0.86-277* |
|
Completed postsecondary education |
|
|
5.3 |
0.77-infinity* |
Consumption of strawberries was the only statisically significant risk factor in a conditional logistics regression model that included all types of berry consumption and education. The final model excluded blueberries and blackberries, in part, because of the infrequent consumption of these berries.
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