Table 4. Multivariate analyses by logistic regression for determination of risk factors (odds ratio) associated to four serologic profiles of domestic dogs tested by immunofluorescence assay (IFA).

Independent variables		Dependent variable: seroreactivity to Rickettsia spp. (titer ≥64)
	Cases	Exposure	P value	Odds Ratio	CI (95%)	r2
Rural area	137	823	0.000	1.843	[1.314–2.586]
Hunting activity	54	213	0.000	2.132	[1.465–3.104]	0.066
Ticks*	23	196	0.001	2.492	[1.433–4.334]
		Dependent variable: seroreactivity to R. amblyommatis (titer ≥64)
	Cases	Exposure	P value	Odds Ratio	CI (95%)	r2
Rural area	115	823	0.001	1.952	[1.338–2.848]
Hunting activity	47	213	0.000	2.203	[1.476–3.290]	0.075
Ticks*	22	160	0.000	2.941	[1.670–5.180]
		Dependent variable: seroreactivity to R. amblyommatis (titer ≥512)
	Cases	Exposure	P value	Odds Ratio	CI (95%)	r2
Rural area	76	823	0.000	2.453	[1.492–4.034]
Hunting activity	32	213	0.001	2.311	[1.437–3.717]	0.077
Ticks*	12	99	0.009	2.433	[1.246–4.751]
		Dependent variable: seroreactivity to R. amblyommatis with titers 4-fold higher than the titers for other Rickettsia species
	Cases	Exposure	P value	Odds Ratio	CI (95%)	r2
Rural area	53	823	0.020	1.946	[1.111–3.409]
Hunting activity	25	213	0.000	2.606	[1.522–4.460]	0.068
Ticks*	11	73	0.010	2.576	[1.259–5.270]

CI–Confidence interval

*Infestation by ticks different from R. sanguineus s.l.