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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.

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

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