Epidemiologic study of Giardia sp. infection in dairy cattle in southeastern New York State.

To identify animal and management factors associated with the risk of Giardia sp. infection in dairy cattle in southeastern New York State, an observational analytical epidemiologic study was conducted. A random sample of 2943 animals in 109 dairy herds located in five counties of southeastern New York was selected from the target population. Fecal samples were collected from animals in the study population and examined for the presence of Giardia sp. using a quantitative centrifugation concentration flotation technique. Data on each animal, and on general management, maternity, preweaning, and postweaning practices were collected by personal interview with the farmer or farm manager. The significance of association of these factors, within each management practice group, with the risk of infection was evaluated using the logistic regression analysis. Weighted indices for each of these four groups were developed, and were evaluated together with the age of the animal and season of sampling for their significance of association with the risk of infection using mixed effect logistic regression analysis. Only the maternity management practices, age of the animal, and the season of sampling were significantly associated with the risk of infection with Giardia sp. Summer housing of bred heifers, on pasture or in tie stalls, was associated with increased risk of infection. Calves that were fed fresh colostrum or separated immediately after birth from the dam were at decreased risk of infection. The risk of infection decreased with the age of the animal and varied by the season of sampling. There was no significant extra binomial variation in the risk of infection in this data. If consideration is to be given to reducing the risk of infection with this parasite, management must be a top priority, especially in younger animals.