Cyclical changes in seroprevalence of leptospirosis in California sea lions: endemic and epidemic disease in one host species?

Table 4 Risk factors for high-titer (≥ 1:800) and low-titer (≥ 1:100 and <1:800) seropositivity to L. interrogans serovar Pomona. Significant variables in the multinomial logistic regression model and corresponding relative risk ratios (RRR) are shown.^a

			High titer seropositivity vs seronegativity			Low titer seropositivity vs seronegativity
Variable	Value	N^b	RRR	95% CI	p-value	RRR	95% CI	p-value
Age	Yearling	450 (383)	1			1
	Juvenile^c	220 (99)	4.41	(2.80,6.95)	<0.001	5.99	(1.5,23.9)	0.011
	Subadult	331 (195)	3.79	(2.54,5.67)	<0.001	23.8	(6.85,82.6)	<0.001
	Adult	293 (241)	0.79	(0.49,1.27)	0.32	43.6	(12.9,147.4)	<0.001
Sex	Female	565 (456)	1			1
	Male	729 (462)	4.13	(2.89,5.89)	<0.001	8.29	(4.62,14.9)	<0.001
Season	Jan-Jul	629 (549)	1			1
	Aug-Dec	665 (369)	4.87	(3.53,6.72)	<0.001	1.15	(0.68,1.92)	0.60
Outbreak year	No	859 (710)	1			1
	Yes	435 (208)	6.97	(5.02,9.68)	<0.001	1.35	(0.76,2.39)	0.31

^a Model had residual deviance 1483.3 on 1287 df (chi-squared p = 1; Nagelkerke R ² = 0.51).
^b Sample size in each group is shown as a total number and as a number excluding leptospirosis-induced strands (in parentheses).
^c Note that the juvenile age class contains only males.

ISSN: 1471-2334