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Factors associated with Cryptosporidium and Giardia infection in preweaned dairy heifer calves
The objective of this study was to evaluate the presence of Cryptosporidium (Crypto) and Giardia in U.S. dairy heifer calves based on different management practices and environmental factors. This study was conducted as part of the calf component of the National Animal Health Monitoring System’s Dairy 2014 study, which included 104 dairy operations in 13 states. The calf component was an 18-mo longitudinal study focused on dairy heifer calves from birth to weaning. Fecal samples were collected from 2,009 calves: 1,258 calves in the East region (IA, MI, MN, MO, NY, OH, PA, VT, VA, WI) and 751 calves in the West region (CA, CO, WA). Calves were sampled from 3 to 66 days of age, with a mean of 22 d (SE=0.13). Calves were evenly sampled throughout the spring (n=491), summer (n=539), fall (n=536), and winter (n=443) seasons. Overall, 43.6% of calves were infected with Crypto and 30.0% of calves were infected with Giardia. Backward elimination model selection in Proc Genmod of SAS® was used after univariate screening (P<0.2) to determine which environmental factors and management practices significantly impacted the presence of Crypto or Giardia. The final Crypto model included days of age at fecal collection (P<0.001), herd size (P=0.03), and season (P=0.04). Calves £28 days of age were 1.24 times more likely to be infected with Crypto compared with calves >28 days of age. Large herds (500+ cows) were 1.12 times more likely to be infected with Crypto compared with small herds (30 to 99 cows). Calves sampled in the fall were 1.1 times more likely to be to be infected with Crypto than calves sampled in the spring. The final Giardia model included season (P<0.001), region (P=0.001), liquid diet additives (P=0.002), and average daily gain (ADG) (P=0.003). Calves sampled in spring, summer, or fall were 1.14 times more likely to be infected with Giardia than calves sampled in the winter. Calves in the East region were 1.15 times more likely to be positive for Giardia than calves in the West region. Calves fed additives other than antibiotics and direct fed microbials, such as larvicides and coccidiostats, in their liquid diet were 1.12 time more likely to be infected with Giardia. Additionally, ADG had a negative association with Giardia. These results highlight the factors associated with the presence of Crypto and Giardia in preweaned dairy heifer calves.
Keywords: dairy heifers; Cryptosporidium, Giardia