Nematode worm egg output by ewes.

The results from routine monitoring of parasite burdens in ewe flocks from 1980 to 1991 by the Massey University Veterinary Clinic were analysed. Faecal strongylate nematode egg counts from 401 flock samples were analysed according to ewe age (two-tooth, 16-23 month-old vs mixed-age, greater than 2-year-old ewes) and month of the year. Each flock sample contained faeces from ten ewes and nematode egg counts were carried out on each faecal sample. ln the mixed-age ewes, the overall mean faecal egg count per gram of faeces (epg) was lowest during January (82 epg) and rose to a peak during October (539 epg). The overall mean faecal egg count in two-tooth ewes remained constant from January (240 epg) to June (294 epg) and dropped during July (156 epg). Overall, 8% of the mixed-age ewes and 12% of the two-tooth ewe submissions had a mean egg count equal to or greater than 500 epg. It is possible that these data over-estimate the pasture contamination by ewes as farmers are more likely to submit faecal samples and to seek veterinary assistance when parasitism is thought to be a problem. The role of ewes as a source of pasture contamination should be considered when developing parasite control regimes on farms.