Prevalence of Cryptosporidium parvum infection in northwest Portugal dairy calves and efficacy of halofuginone lactate on the prevention of Cryptosporidiosis

Cryptosporidium parvum infection was detected in 137 of 183 dairy calves up to 12 weeks of age (74.8%) on a convenience sample of 30 farms with a history of calf diarrhoea. The prevalence was determined by using a formol-ether concentration and acid fast staining method (Ziehl Neelsen). All farms studied had infected calves at the time of sampling and within farm prevalence ranged from 25 to 100%. The higher percentages of oocysts excreted were recorded in calves with 7 to 14 days (89%) and 15 to 21 days old (90%). Eighty-four of the calves were diarrhoeic (46%) and 74 of these calves were shedding C parvum oocysts (88%). Cryptosporidiosis appears to be an important cause of dairy calf scours in this region. A second study was performed on 79 newborn calves from the later farms to assess the efficacy of halofuginone lactate (Halocur(R)) in the prevention of cryptosporidiosis. Halocur(R) was administered at 120 mu g /Kg/day for 7 days to 39 calves and the other 40 calves did not receive any antiprotozoal treatment. Over a period of 3 weeks the animals were examined four times for shedding of C. parvum oocysts and diarrhoea. The intensity of infection was determined by a semi-quantitative score of oocyst numbers in faeces. Oocyst excretion peaked on Day 7 and Day 14 in the control group (100% and 94%) being at the same time lower in the treated halofuginone-group (30.5 % and 55.6 %). During that period intensity of shedding was significantly lower (P<0.0001) in the treated group, thus contributing to decrease environmental contamination and zoonotic risks. Halocur(R) reduced significantly the number of calves presenting diarrhoea on Day 14 (P<0.001). Despite the low intensity of shedding on Day 7, the high prevalence of diarrhoea of the treated group (58%) may suggest the presence of other enteropathogens as the cause of scouring, such as Escherichia coli K99, rotavirus and coronavirus.