Table 2. Univariate conditional logistic regression analyses of potential risk factors.
| Exposure factors | Cases | Controls | χ2 | P-value | OR(95%CI) |
|---|---|---|---|---|---|
| n(%) | n(%) | ||||
| Presence of weeds and shrubs in working areas | |||||
| Yes | 64(92.8) | 210(79.2) | 3.42 | 0.072 | 2.66(0.92–7.71) |
| No | 5(7.2) | 55(20.8) | |||
| Presence of weeds and shrubs around the house | |||||
| Yes | 59(85.5) | 198(74.7) | 3.75 | 0.058 | 2.49(0.97–6.40) |
| No | 10(14.5) | 67(25.3) | |||
| Presence of ticks in working areas or around the house | |||||
| Yes | 49(71.0) | 138(52.1) | 4.91 | 0.030 | 2.35(1.09–5.09) |
| No | 20(29.0) | 127(47.9) | |||
| Presence of rats in home | |||||
| Yes | 63(91.3) | 228(86.0) | 0.96 | 0.330 | 1.62(0.61–4.30) |
| No | 6(8.7) | 37(14.0) | |||
| Presence of rats in the working areas | |||||
| Yes | 40(58.0) | 140(52.8) | 0.06 | 0.807 | 1.08(0.58–2.02) |
| No | 29(42.0) | 125(47.2) | |||
| Farming | |||||
| Yes | 59(85.5) | 195(73.6) | 2.04 | 0.157 | 1.78(0.80–3.97) |
| No | 10(14.5) | 70(26.4) | |||
| Hunting | |||||
| Yes | 3(4.3) | 7(2.6) | 0.01 | 0.918 | 1.08(0.24–4.85) |
| No | 66(95.7) | 258(97.4) | |||
| Picking tea or herbs | |||||
| Yes | 21(30.4) | 57(21.5) | 1.25 | 0.265 | 1.71(0.67–4.39) |
| No | 48(69.6) | 208(78.5) | |||
| Raising dogs | |||||
| Yes | 48(69.6) | 135(50.9) | 4.64 | 0.030 | 2.01 (1.06–3.82) |
| No | 21(30.4) | 130(49.1) | |||
| Raising cats | |||||
| Yes | 32(46.4) | 107(40.4) | 0.01 | 0.962 | 1.02(0.55–1.88) |
| No | 37(53.6) | 158(59.6) | |||
| Raising cattle | |||||
| Yes | 11(15.9) | 21(7.9) | 3.11 | 0.083 | 2.22(0.90–5.44) |
| No | 58(84.1) | 244(92.1) | |||
| Raising goats | |||||
| Yes | 4(5.8) | 12(4.5) | 0.02 | 0.886 | 1.09(0.33–3.56) |
| No | 65(94.2) | 253(95.5) | |||
| Raising pigs | |||||
| Yes | 15(21.7) | 59(22.3) | 1.54 | 0.217 | 0.60(0.26–1.35) |
| No | 54(78.3) | 206(77.7) | |||
| Raising poultry | |||||
| Yes | 57(82.6) | 201(75.8) | 0.11 | 0.736 | 1.14(0.53–2.49) |
| No | 12(17.4) | 64(24.2) | |||
| Domestic animals illness or death | |||||
| Yes | 6(8.7) | 8(3.0) | 3.25 | 0.083 | 2.77(0.88–8.74) |
| No | 63(91.3) | 257(97.0) | |||
| Contacting with a dead rat | |||||
| Yes | 6(8.7) | 41(15.5) | 0.91 | 0.344 | 0.61(0.22–1.69) |
| No | 63(91.3) | 224(84.5) | |||
| Contacting with wild animals | |||||
| Yes | 67(97.1) | 236(89.1) | 1.58 | 0.223 | 2.54(0.57–11.40) |
| No | 2(2.9) | 29(10.9) | |||
| Removing ticks from domestic animals | |||||
| Yes | 13(18.8) | 37(14.0) | 0.27 | 0.601 | 1.22(0.58–2.59) |
| No | 56(81.2) | 228(86.0) | |||
| Tick bites | |||||
| Yes | 30(43.5) | 32(12.1) | 35.86 | <0.001 | 9.13(3.92–21.27) |
| No | 39(56.5) | 233(81.9) | |||
| Other insects bites | |||||
| Yes | 26(37.7) | 93(36.5) | 2.12 | 0.149 | 1.85(0.80–4.26) |
| No | 43(62.3) | 162(63.5) | |||
| Taking preventative measures during outdoor activities# | |||||
| Yes | 1(1.5) | 25(10.7) | 8.19 | 0.020 | 0.09(0.01–0.68) |
| No | 65(98.5) | 209(89.3) | |||
| Resting on a grass field | |||||
| Yes | 54(78.3) | 176(66.4) | 1.62 | 0.206 | 1.59(0.78–3.26) |
| No | 15(21.7) | 89(33.6) | |||
| Working with broken skins | |||||
| Yes | 12(17.4) | 47(17.7) | 0.36 | 0.547 | 1.30(0.55–3.07) |
| No | 57(82.6) | 218(82.3) | |||
| Having underlying diseases | |||||
| Yes | 20(29.4) | 100(37.7) | 0.76 | 0.383 | 0.76(0.41–1.41) |
| No | 48(70.6) | 165(62.3) |
#: preventative measures included wearing gloves or boots, fastening cuffs and trouser mouths, wearing a long-sleeved shirt and using insect repellents.
All exposure factors were within the previous two weeks prior to disease onset. OR: odds ratio; CI: confidence interval.