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. Author manuscript; available in PMC: 2022 Aug 12.
Published in final edited form as: Ticks Tick Borne Dis. 2017 Nov 22;9(2):340–348. doi: 10.1016/j.ttbdis.2017.11.010

Table 3.

Association between environmental predictors and the density of I. scapularis nymphs on residential properties in univariate Poisson models using all observations and after removing the two outlier residential sitesa one at a time to test the sensitivity of modelb.

Unit of increase Using all observations (n = 24) Removing conifer property (n = 23) Removing high density I. scapularis nymph property (n = 23)
Environmental variable RRc p-value RR p-value RR p-value
Percent forest within residential parcel 10% 1.2   < 0.001d 1.2   < 0.001d 1.0 0.67
Percent forest within 500 m of residential parcel 10% 1.5   < 0.0001d 1.5   < 0.0001d 0.9   < 0.0001d
Percent forest within 1 km of residential parcel 10% 1.4   < 0.0001d 1.4   < 0.0001d 0.9   < 0.0001d
Forest edge density within 500 m of residential parcel 10 m/m2 1.2   < 0.0001d 1.2   < 0.001d 0.9   < 0.001d
Forest edge density within 1 km of residential parcel 10 m/m2 1.2   < 0.0001d 1.2   < 0.0001d 0.9   < 0.001d
Signs of deer on property Presence 3.3 0.12 3.8 0.09 6.3   < 0.001d
Presence of fence on property Presence 1.4 0.01 1.4 0.06 2.0 0.22
Compost pile on property Presence 0.3   < 0.0001d 0.3   < 0.0001d 0.9 0.08
Log pile on property Presence 4.2 0.10 4.8 0.08 14.3   < 0.001d
Bird feeder on property Presence 0.4 0.29 0.4 0.27 0.8 0.02
Forest type (versus deciduous forest)
Coniferous forest Presence 1.0 0.98 – – 1.8 0.35
Mixed deciduous/coniferous forest Presence 3.9   < 0.01d 4.2   < 0.0001d 0.8 0.42
a

Two outlier residential sites that were tested are: (1) property with coniferous forest and 2) property with high I. scapularis nymphal density.

b

Offset variable included for number of drags completed on a residential property in order to account for sampling effort. Log (area of the property in km2) included as a fixed effect to account for differences in property size. Variable to indicate whether a residential property was located near Lake Elmo Park Reserve or William O’Brien State Park was included to account for correlation among households within a neighborhood.

c

RR = Risk Ratio.

d

Significant at α = 0.05.