Table 2. .
Population Study, Follow-up Data, Incidence Rates, and Incidence Rate Ratios
| No. Examined in Baseline Study (% of Total) | No. With Information Collected in 2017 (% of Total) | SCE, No. | PY | IR (per 100 000 PY) (95% CI) | P a | Model Without Random-Effect | Model With a Random-Effect at HD Level | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| aIRRb (95% CI) | P | aIRRc (95% CI) | P | ||||||||
| Total | 1258 | 922 | 53 | 23 287.4 | 227.6 (173.9–297.9) | ||||||
| Age, y | 5 | 95 (7.6) | 59 (6.4) | 7 | 1445.8 | 484.1 (230.8–1015.6) | .380 | 3.60 (2.19–5.92) | <.0001 | 3.39 (1.25–9.14) | .016 |
| 6–7 | 273 (21.7) | 182 (19.7) | 6 | 4673.4 | 128.4 (57.7–285.8) | 0.83 (0.37–1.85) | .645 | 0.74 (0.26–2.09) | .572 | ||
| 8–9 | 222 (17.7) | 169 (18.3) | 8 | 4285.5 | 186.7 (93.4–373.3) | 1.03 (0.35–3.31) | .956 | 1.07 (0.42–2.74) | .889 | ||
| 10–11 | 273 (21.7) | 212 (23.0) | 10 | 5410.4 | 184.8 (99.4–343.5) | Ref | |||||
| 12–13 | 235 (18.7) | 182 (19.7) | 12 | 4556.2 | 263.4 (149.6–463.8) | 1.06 (0.54–2.07) | .868 | 0.99 (0.42–2.36) | .991 | ||
| 14–15 | 160 (12.7) | 118 (12.8) | 10 | 2916.0 | 342.9 (184.5–637.4) | 1.19 (0.436–3.86) | .775 | 1.17 (0.47–2.90) | .735 | ||
| Sex | Female | 637 (50.6) | 449 (48.7) | 25 | 11 216.6 | 222.9 (150.6–329.9) | .892 | Ref | Ref | ||
| Male | 621 (49.4) | 473 (51.3) | 28 | 12 070.8 | 232.0 (160.2–336.0) | 0.75 (0.33–1.73) | .505 | 0.78 (0.44–1.38) | .388 | ||
| CMFL, mf/snip | <4 | 395 (31.4) | 257 (27.9) | 13 | 6412.7 | 202.7 (117.7–349.1) | .004 | Ref | Ref | ||
| 4–19 | 250 (19.9) | 207 (22.4) | 4 | 5153.1 | 77.6 (29.1–206.8) | 0.24 (0.04–1.36) | .106 | 0.29 (0.08–1.02) | .054 | ||
| 20–29 | 291 (23.1) | 222 (24.1) | 10 | 5834.1 | 171.4 (92.2–318.6) | 0.32 (0.07–1.47) | .143 | 0.20 (0.10–0.93) | .036 | ||
| ≥30 | 322 (25.6) | 236 (25.6) | 26 | 5887.5 | 441.6 (300.7–648.6) | 0.51 (0.09–2.86) | .447 | 0.49 (0.15–1.66) | .251 | ||
| Ov in skin snip | Negative | 524 (41.7) | 367 (39.8) | 11 | 9341.8 | 117.8 (65.2–212.6) | .004 | ||||
| Positive | 734 (58.43) | 555 (60.2) | 42 | 13 945.6 | 301.2 (222.6–407.5) | ||||||
| MFD, mf/snip | 0 | 524 (41.7) | 367 (39.8) | 11 | 9341.8 | 117.8 (65.2–212.6) | <.001 | Ref | Ref | ||
| 1–7 | 241 (19.2) | 182 (19.7) | 4 | 4638.1 | 86.2 (32.4–229.8) | 0.96 (0.38–2.43) | .937 | 0.93 (0.28–3.07) | .909 | ||
| 8–70 | 245 (19.5) | 178 (19.3) | 10 | 4558.8 | 219.4 (118.0–407.7) | 2.76 (1.20–6.35) | .017 | 2.66 (0.98–7.19) | .054 | ||
| 71–200 | 129 (10.3) | 100 (10.9) | 7 | 2544.8 | 275.1 (131.1–577.0) | 3.67 (1.86–7.21) | <.001 | 3.29 (1.01–10.71) | .048 | ||
| >200 | 119 (9.5) | 95 (10.3) | 21 | 2203.9 | 952.8 (621.3–1461.4) | 11.87 (5.56–25.33) | <.001 | 11.60 (3.89–34.61) | <.0001 | ||
| Loa loa, mf/mL | Negative | 1077 (85.6) | 796 (86.3) | 47 | 20 046.7 | 234.5 (176.2–312.0) | .484 | Ref | Ref | ||
| Positive | 99 (7.9) | 72 (7.8) | 2 | 1848.7 | 108.2 (27.1–432.6) | 0.46 (0.14–1.55) | .211 | 0.46 (0.11–1.96) | .292 | ||
| Missing | 82 (6.5) | 54 (5.9) | 4 | 1391.9 | 287.4 (107.9–765.7) | 1.46 (0.75–2.83) | .265 | 1.52 (0.48–4.77) | .476 | ||
| Mansonella perstans, mf/mL | Negative | 1074 (85.4) | 788 (85.5) | 43 | 19 857.7 | 216.5 (160.6–292.0) | .679 | Ref | Ref | ||
| Positive | 102 (8.1) | 80 (8.7) | 6 | 2037.7 | 294.4 (132.3–655.4) | 0.93 (0.31–2.75) | .896 | 1.15 (0.45–2.97) | .770 | ||
| Missing | 82 (6.5) | 54 (5.9) | 4 | 1391.9 | 287.4 (107.9–765.7) | N.A. | N.A. | ||||
| CDTI | 1994 | 169 (13.4) | 111 (12.0) | 16 | 5589.4 | 617.9 (378.6–1008.6) | <.001 | Ref | Ref | ||
| 1999 | 1089 (86.6) | 811 (98.0) | 37 | 20 698.0 | 178.8 (129.5–246.7) | 0.63 (0.11–3.80) | .617 | 0.49 (0.13–1.75) | .270 |
Abbreviations: aIRR, adjusted incidence rate ratio; CDTI, start year of community-directed treatment with ivermectin; CI, confidence interval; CMFL, community microfilarial load (in mf/snip); HD, health district; IR, incidence rate (number of cases per PY); MFD, individual microfilarial density (in mf/snip); Ov, Onchocerca volvulus mf; PY, persons-years; SCE, suspected cases of epilepsy (number).
a P values were calculated within each variable and assessed using the log-rank test for sex, skin snip positivity, Loa loa microfilariae positivity, Mansonella perstans positivity, CDTI, and the trends modified log-rank test for age, CMFL, and skin snip in 5 categories of variables.
bMultivariate logistic model with a cluster-robust standard errors to account for possible intra-community clustering.
cMultivariate logistic model with a random effect at the HD level.