Dr. Murai Éva szerk.: Parasitologia Hungarica 22. (Budapest, 1989)

samples taken at each visit depended upon the accessibility and number of animals grazing, with up to 50 samples/site/visit being taken. The samples were placed in Para-Pak formalin kits* and returned to St. John's, where they were analysed as above (6). Loss of fluid and variations in the amount of feces per vial precluded any accurate assessment of epg of feces. However, trends were evident. RESULTS AND DISCUSSION (1) Prevalence The mean prevalence of parasites was 55% (655 of 1200 samples positive; Fig. 2), with statistically significant differences being noted In the prevalence of parasitism between herds (prevalence range 33-67%: X

2

=55„9, df=9, p < 0.001). The overall mean is similar to those determined for cattle in Ontario (58%, (16)) and Quebec (50 %, (8)), but much lower than for cattle in Maine (96%, (22)), or the rest of the United States (> 80%, (9)). A wide variety of environmental factors, both geographic and climatic, might account for these differences (14). A statistically significant difference was noted in the monthly prevalence of parasitism (X

2

=31.0, df=ll, p< 0.005), although this pattern was not evident in all herds, e.g. one herd showed a consistently high monthly prevalence (X

2

=10.1. dt'= 11. u<' 0.80). Prevalence generally rose from 59% in January-February to a peak in April-May (71 %) representing the spring or parturient rise. This Is followed by a decline and then a small rise In AugustSeptember (60%) before a drop-off to a low of 39% in December-January. 80-1 Fig. 2. Prevalence of gastrointestinal helminths in dairy cattle from ten farms In the region of St. John's, Newfoundland, as determined by fecal egg counts ^Meridian Diagnostics, Inc., 3471 River Hills Drive, Cincinnati, Ohio 45244.