Effect of longitude and latitude on fecal egg and oocyst counts in cow–calf beef herds from the United States Northern Great Plains

This study evaluated potential relationships between parasite egg/oocyst outputs in cow–calf beef herds located within the United States Northern Great Plains and herd longitude and latitude. Management of study herds was typical of herds from this region. Parasite egg/oocyst counts were measured from 10 cows and 5 calves selected from each herd near the end of the traditional grazing season (October 1993). The types and numbers of eggs and oocysts recovered from both cows and spring-born calves were consistent with those described in other studies. No significant relationship between fecal egg/oocyst counts and latitude was observed in calves or cows. Monezia egg output exhibited no significant correlation with longitude for calves or cows. In cows, a significant negative correlation was detected between coccidian oocyst counts and herd longitude but not between helminth egg counts and longitude. In calves, Nematodirus, trichostrongyle and Trichuris egg output and coccidian oocyst output were all negatively correlated with longitude. This negative correlation suggests that nematode populations within the study area decreased slightly from an east to west direction.