Incidence of and risks associated with Giardia infections in herds on dairy farms in the New York City Watershed

Table 1 The impact of season of collection and the prior status of the herd on the hazard of shedding Giardia cysts among dairy cattle in the study population.

Risk factors	Regression coefficient	Standard error	Hazard ratio	95% CI
Prior risk of Giardia
Low risk	0		1.0
Moderate risk	0.328	0.109	1.4	1.1, 1.7
High risk	0.620	0.110	1.9	1.5, 2.3
Season of the year
Summer	0		1.0
Winter	0..058	0.080	1.1	0.9, 1.2
Spring	-0.266	0.083	0.7	0.6, 0.9

Low risk= Herds shedding neither Giardia or Cryptosporidium prior to start of the study
Intermediate risk= Herd shedding Giardia only prior to the start of the study
High risk= Herd shedding both Giardia and Cryptosporidium prior to the star of the study
Winter= November through March
Spring= April through June
Summer= July through October

ISSN: 1751-0147