Table 5.
Mixed-effect logistic regression of dogs infested with brown dog ticks and potential risk factors during a survey for proposed risk factors for brown dog tick infestation and Rocky Mountain spotted fever in Tijuana, México
| Predictors | No. (%) with Ticks/Total | OR | 95% CI | P-Value |
|---|---|---|---|---|
| Univariable Models | ||||
| House variables | ||||
| Case/control | ||||
| Case | 25/47 (53.2) | 0.65 | 0.25–1.71 | 0.38 |
| Control | 93/144 (64.6) | Reference | – | – |
| Marginalization | ||||
| Medium | 41/63 (65.1) | Reference | – | – |
| High | 50/85 (58.8) | 0.82 | 0.32–2.12 | 0.68 |
| Very high | 27/43 (62.8) | 1.02 | 0.32–3.21 | 0.98 |
| Debris | ||||
| None | 23/44 (52.3) | Reference | – | – |
| A little | 53/90 (58.9) | 1.36 | 0.57–3.25 | 0.49 |
| A lot | 33/45 (73.3) | 2.54 | 0.87–7.40 | 0.09 |
| On a hill | ||||
| No | 51/93 (54.8) | Reference | ||
| Yes | 66/96 (68.8) | 1.11 | 0.59–2.09 | 0.75 |
| On a dirt road | ||||
| No | 42/64 (65.6) | Reference | – | – |
| Yes | 76/127 (59.8) | 0.8 | 0.34–1.87 | 0.60 |
| Near a canal | ||||
| No | 105/164 (64.0) | Reference | – | – |
| Yes | 11/24 (45.8) | 0.46 | 0.14–1.52 | 0.20 |
| Cement | 0.99 | 0.98–1.00 | 0.03 | |
| Whether ticks were present at house | ||||
| None | 77/140 (55.0) | Reference | – | – |
| Present | 27/32 (84.4) | 5.24 | 1.60–17.19 | 0.006 |
| No. of dogs living at the house | 1.01 | 0.86–1.19 | 0.94 | |
| Total No. of dogs seen | 1.03 | 0.91–1.17 | 0.65 | |
| Some dogs at the house allowed to go inside* | ||||
| No | 69/99 (69.7) | Reference | – | – |
| Yes | 49/92 (53.3) | 0.49 | 0.25–0.99 | 0.05 |
| House infested with ticks (self-reported) | ||||
| No | 69/115 (60.0) | Reference | – | – |
| Yes | 49/76 (64.5) | 1.4 | 0.68–2.87 | 0.36 |
| Frequency of treating house with acaricide | ||||
| Rare to never | 39/59 (66.1) | Reference | – | – |
| Once or twice/year | 49/79 (62.0) | 1.03 | 0.45–2.37 | 0.95 |
| Multiple times/year | 30/47 (63.8) | 0.95 | 0.38–2.39 | 0.92 |
| Frequency of treating dogs with acaricide* | ||||
| Rare to never | 27/37 (73.0) | Reference | – | – |
| Once or twice/year | 29/44 (55.7) | 0.47 | 0.19–1.20 | 0.12 |
| Multiple times/year | 54/97 (65.9) | 0.8 | 0.28–2.33 | 0.69 |
| Dog variables | ||||
| Allowed to roam | ||||
| No | 44/94 (46.8) | Reference | – | – |
| Yes | 67/83 (80.7) | 5.93 | 2.59–13.57 | <0.001 |
| Body mass (kg) | ||||
| <10 | 47/88 (53.4) | Reference | – | – |
| 10–20 | 45/62 (72.6) | 2.27 | 1.07–4.83 | 0.03 |
| >20 | 26/41 (63.4) | 1.31 | 0.56–3.06 | 0.53 |
| Sex | ||||
| Female | 64/95 (67.4) | Reference | – | – |
| Male | 53/95 (55.8) | 0.55 | 0.29–1.06 | 0.08 |
| Body condition | ||||
| Normal (2–3) | 91/156 (58.3) | 2.53 | 0.94–6.84 | 0.07 |
| Abnormal (<2 or >3) | 24/31 (77.4) | Reference | – | – |
| Age | ||||
| Adult | 97/154 (63.0) | – | – | – |
| Juvenile | 21/36 (58.3) | 0.69 | 0.3–1.58 | 0.38 |
| Multivariable models | ||||
| (Intercept) | – | 1.79 | 0.82–3.88 | 0.14 |
| Allowed to roam | 6.94 | 2.87–16.8 | <0.001 | |
| Cement | 0.99 | 0.98–1.00 | 0.02 | |
| Male | 0.42 | 0.19–0.91 | 0.03 | |
OR = odds ratio.
*
Analysis restricted to houses with dogs.