Prophylactic use of decoquinate for infections with Cryptosporidium parvum in experimentally challenged neonatal calves

Objective—To evaluate the effect of daily oral administration of decoquinate to neonatal calves experimentally challenged with various numbers of Cryptosporidium parvumo ocysts. Design—Clinical trial. Animals—75 calves. Procedure—Calves were purchased from a commercial dairy during a 5-week period. Calves were housed in individual hutches and fed milk replacer with or without decoquinate (2 mg/kg [0.9 mg/lb per day]). Calves were randomly assigned to treatment and 1 of 5 challenge groups (0, 50, 100, 1000, or 10,000 C parvum oocysts in 60 mL of saline [0.9% NaCl] solution administered PO on the day after arrival). Calves were maintained in the study for as long as 28 days. Calves were clinically assessed for diarrhea and dehydration. Fecal samples were submitted for oocyst enumeration 3 times each week. Results—Treatment did not affect number of days to first watery feces (diarrhea), number of days to first oocyst shedding, or duration of diarrhea or oocyst shedding. Duration of oocyst shedding was signif...