Table 2.
Bivariate and multivariable analysis of exposures in the 2 weeks before illness onset caused by Giardia infection in the Colorado and Minnesota giardiasis case-control study
| Exposure | Cases (N = 199) | Controls (N = 381) | Unadjusted ORa | Adjusted ORb | Population-Attributable |
|---|---|---|---|---|---|
| n(%) | n(%) | (95% CI) | (95% CI) | Fraction (%) | |
| International travel | 24 (12.1) | 5 (1.3) | 10.3 (3.9, 27.5) | 13.9 (4.9, 39.8) | 11.2 |
| Travel in USAc | 78 (39.2) | 123 (32.3) | 1.4 (0.9, 1.9) | 1.0 (0.7, 1.6) | 0.0 |
| Camp | 29 (14.6) | 26 (6.8) | 2.3 (1.3, 4.1) | 1.2 (0.6, 2.6) | 2.4 |
| Animal contactd | 129 (64.8) | 278 (73.0) | 0.7 (0.5, 0.99) | 0.7 (0.4, 1.1) | – |
| Contact with children wearing diaperse | 80 (40.2) | 138 (36.2) | 1.2 (0.8, 1.7) | 1.6 (1.01, 2.6) | 15.1 |
| Contact with person with diarrhoeaf | 24 (12.1) | 31 (8.1) | 1.5 (0.9, 2.7) | 1.5 (0.8, 2.8) | 4.0 |
| Contact with children in childcareg | 32 (16.1) | 54 (14.2) | 1.2 (0.7, 1.9) | 1.5 (0.8, 2.8) | 5.4 |
| Male–male sexual behaviourh | 17 (15.2) | 1 (0.7) | 26.5 (3.5, 202.0) | 45.7 (5.8, 362.0) | 8.4 |
| Female–female sexual behaviourh | 1 (1.2) | 5 (2.2) | 0.5 (0.1, 4.6) | 0.6 (0.1, 6.4) | ─ |
| Drink water from welli | 48 (24.1) | 87 (22.8) | 1.1 (0.7, 1.6) | 1.1 (0.7, 1.9) | 2.2 |
| Drink water from lake, river, stream, or spring | 22 (11.1) | 5 (1.3) | 9.3 (3.5, 25.1) | 6.5 (2.0, 20.6) | 9.4 |
| Swim in natural body of waterj | 30 (15.1) | 16 (4.2) | 4.1 (2.1, 7.6) | 3.3 (1.5, 7.0) | 10.5 |
| Swim in manmade aquatic venuek | 48 (24.1) | 61 (16.0) | 1.7 (1.1, 2.6) | 1.2 (0.7, 2.1) | 4.0 |
| Eat raw vegetables or fruitsl | 187 (94.0) | 374 (98.2) | 0.3 (0.1, 0.8) | 0.2 (0.1, 0.7) | |
| Take antibiotics | 21 (10.6) | 22 (5.8) | 1.9 (1.03, 3.6) | 2.5 (1.2, 5.0) | 6.3 |
| Take psychoactive medication | 21 (10.6) | 15 (3.9) | 2.9 (1.4, 5.7) | 1.7 (0.7, 4.1) | 4.3 |
| Chronic gastrointestinal condition or medicationm | 56 (28.1) | 68 (17.9) | 1.8 (1.2, 2.7) | 1.8 (1.1, 3.0) | 12.5 |
| Immunosuppressing condition, medication, or treatmentn | 21 (10.6) | 41 (10.8) | 1.0 (0.6, 1.7) | – | – |
Unadjusted odds ratio.
Odds ratio from full multivariable model adjusted for age, site, sex and all exposures that have been previously reported to be associated with giardiasis and showed an association with disease status with P < 0.2 in the bivariate models. Given these criteria, immunosuppressing condition, medication, or treatment was excluded from the multivariable analysis.
The variable ‘travel in the United States’ was derived by grouping travel within home state more than 100 miles and travel outside of home state within the USA.
The variable ‘animal contact’ was derived by grouping any contact with domestic pets (i.e., kitten, cat, puppy, dog) and contact with farm mammals (i.e., calf, cow, goat, sheep, horse, pig).
The variable ‘contact with children wearing diapers’ was derived by grouping children in home wear diapers, children at child's childcare location wear diapers, contact with children in diapers and change diapers.
The variable ‘contact with person with diarrhoea’ was derived by grouping direct contact with person with diarrhoea and provide care for person with diarrhoea.
The variable ‘contact with children in childcare’ was derived by grouping attends childcare, children in home attend out-of-home childcare, provide childcare outside of home, provide childcare in home.
Statistically significant interaction was identified between sex (male vs. female) and having a same-gender sex partner; this is presented stratified by individual sex.
The variable ‘drink water from well’ was derived by grouping well as source of drinking water at home and well as source of drinking water outside of home.
The variable ‘swim in natural body of water’ was derived by grouping swim, wade, or enter an ocean, lake, pond, river, stream, or hot spring.
The variable ‘swim in manmade aquatic venue’ was derived by grouping swim, wade, or enter a swimming pool, hot tub/spa, or waterpark.
The variable ‘eat raw vegetables or fruits’ was derived by grouping eat lettuce, garden salad, raw vegetables, raw berries, raw fruits with skin/peel and any organic produce.
The variable ‘chronic gastrointestinal (GI) condition’ was derived by grouping chronic lower GI conditions (i.e., chronic diarrhoea, Crohn's disease, irritable bowel syndrome), chronic upper GI conditions (i.e., stomach ulcer disease), chronic lower GI medications (i.e., laxatives, enemas, antidiarrhoeal medications) and chronic upper GI medications (i.e., stomach-acid reducing medications).
The variable ‘immunosuppressing condition, medication, or treatment’ was derived by grouping immunosuppressing conditions (i.e., diabetes, cancer, HIV/AIDS, other immunodeficiency), medications (i.e., steroids, cyclosporine) and treatments (i.e., organ transplant, chemotherapy, radiation).