Table 2.
Drinking water sources used during the period of infection* among case patients and controls in a case-control study of Guinea worm disease transmission—Chad, 2010–2011
| Drinking water sources | Case patients (N = 19) n (%) | Controls (N = 45) n (%) | mOR | 95% CI |
|---|---|---|---|---|
| Source type (any use) | ||||
| Lagoon or pond | 18 (95) | 35 (78) | 11.9 | 0.4–372.5 |
| Unprotected dug well | 9 (47) | 9 (20) | 29.6 | 1.3–693.3 |
| Cistern | 3 (16) | 6 (13) | 9.1 | 0.1–851.2 |
| Borehole | 12 (63) | 22 (49) | 2.0 | 0.5–8.1 |
| River | 5 (26) | 13 (29) | 0.9 | 0.2–4.1 |
| Canal | 1 (5) | 2 (4) | 1.0 | 1.0–1.0 |
| Primary source† | ||||
| Lagoon or pond | 11 (58) | 24 (53) | 1.0 | 0.2–6.0 |
| Unprotected dug well | 3 (16) | 6 (13) | 2.2 | 0.2–26.7 |
| Cistern | 1 (5) | 5 (11) | 0.3 | 0.0–30.8 |
| Borehole | 4 (21) | 5 (11) | 4.0 | 0.4–38.9 |
| River | 0 (0) | 4 (9) | 0.1 | 0.0–6.2 |
| Canal | 0 (0) | 1 (2) | 0.6 | 0.01-62.1 |
| Secondary sources‡ | ||||
| Any secondary source | 17 (89) | 20 (44) | 38.1 | 1.6–728.2 |
| Lagoon or pond | 12 (63) | 15 (33) | 3.6 | 1.1–12.5 |
| Unprotected dug well | 7 (37) | 3 (7) | 11.1 | 1.7–74.6 |
| Cistern | 2 (11) | 2 (4) | 9.1 | 0.1–585.8 |
| Borehole | 2 (11) | 3 (7) | 3.2 | 0.2–40.8 |
| River | 1 (5) | 4 (9) | 0.7 | 0.07–6.2 |
| Canal | 1 (5) | 1 (2) | 1.6 | 0.02–152.8 |
| Travel-related sources§ | ||||
| Any travel-related source | 14 (74) | 29 (64) | 1.9 | 0.4–9.2 |
| Lagoon or pond | 10 (53) | 12 (27) | 3.6 | 0.9–14.5 |
| Borehole | 10 (53) | 15 (33) | 2.6 | 0.7–10.1 |
| Unprotected dug well | 3 (16) | 6 (13) | 2.6 | 0.2–33.3 |
| River | 5 (26) | 9 (20) | 1.5 | 0.4–6.1 |
| Cistern | 1 (5) | 1 (2) | 3.0 | 0.2–48.0 |
| Canal | 0 (0) | 0 (0) | — | — |
mOR = matched odds ratio; 95% CI = 95% confidence interval. Bolded values are statistically significant.
The period of infection (POI) for the case patient was the 10- to 14-month time period before the emergence of the first worm, corresponding to the incubation period of Guinea worm disease. Controls were questioned about their drinking water sources during the same POI as the case patients to whom they were matched.
The primary drinking water source was the single main source of drinking water used at home by the respondent on a daily basis
Secondary drinking water sources were any sources used on a regular basis in addition to the primary source and were not mutually exclusive. These were typically sources used outside the village of residence (such as those used during farming and fishing) or other nonprimary sources used at home, but did not include sources used while traveling or at school.
Travel-related drinking water sources were all sources used when traveling far away from home, even if only once, and were not mutually exclusive. Water sources used at school were included in the travel-related drinking water source category, unless respondents brought water with them from home (i.e., from their primary water sources).