Cryptosporidium spp. in diarrheic calves less than 30 days old from farms across Northern Ireland were examined over a year period by microscopic, genotyping, and subtyping techniques to characterize the transmission dynamics. Cryptosporidium oocysts were detected in 291 of 779 (37.4%) animals. The prevalence rates of rotavirus, coronavirus, and Escherichia coli K99+ were lower as seen in 242 of 806 (30.0%), 46/806 (5.7%), and 16/421 (3.8%) of animals, respectively. Of the 224 Cryptosporidium-positive specimens available for molecular analysis, Cryptosporidium parvum was identified in 213 (95.1%) specimens, Cryptosporidium bovis in eight (3.6%), and Cryptosporidium deer-like genotype in three (1.3%). Sequence analysis of the 60-kDa glycoprotein gene identified 16 IIa subtypes and a new subtype family, with 120 of the 216 (55.6%) positive specimens having the subtype IIaA18G3R1. Eight of the IIa subtypes were previously seen in humans in Northern Ireland. Several subtypes were temporally or geographically unique. The genetic diversity in calves in Northern Ireland was much greater than that reported from other areas. This work demonstrates the utility of genotyping and subtyping tools in characterizing the transmission of Cryptosporidium spp. in calves and humans.

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Sixty multiparous crossbred ewes which had lambed within three days in the first week of April 1996, were divided into four groups. Each group consisted of 15 ewes plus 12 pairs of twins and three single lambs. Group 1 was left untreated, group 2 was treated with albendazole 2.5 per cent drench, group 3 received moxidectin 0.1 per cent drench and group 4 received ivermectin 0.08 per cent drench. The ewes in each group were dosed with their anthelmintic on April 4 (day 0) before being turned out to separate equal-sized paddocks within the same field on the following morning. The field had been used for grazing sheep annually for many years and was considered to be contaminated with infective larvae of the common gastrointestinal nematodes infecting sheep in the region. Faecal samples were collected every two weeks from the ewes and lambs until July 25 (day 112). The lambs in each group were dosed with the anthelmintic used for their dams on day 42, and the dose was repeated when more than 50 per cent of the lambs in any group had a faecal egg count of more than 200 eggs per gram (epg). The total faecal egg output of the treated ewes over days 14 to 70, compared with that of the untreated control group, was reduced by 78.9 per cent by the moxidectin drench, by 47.6 per cent by ivermectin, and by 21.5 per cent by albendazole. The lambs in the groups treated with moxidectin and ivermectin required only one treatment on day 42 before reaching finishing weight; those in the albendazole-treated group were treated twice and the control group once. The faecal egg outputs of the lambs from day 42 until the end of the experiment on day 112 were reduced by 75 per cent by the moxidectin drench, by 48.5 per cent by ivermectin, and by 9 per cent by albendazole. There were no significant differences between the rates of weight change of either ewes or lambs in any of the groups.

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