Observations on the faecal egg count of calves naturally infected with Ostertagia ostertagi

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Abstract
The faecal egg counts of seven groups of calves exposed to infection with O. ostertagi on pastures were found to follow a similar course to those of calves experimentally infected on one occasion or of calves infected daily. They declined from an early peak according to an apparently logarithmic curve. It was concluded that faecal egg counts were largely independent of worm numbers and tended to follow a stereotyped pattern. Acute clinical ostertagiasis was as liable to lead to high egg counts as was poor thriving due to the other causes. The relevance of these findings to the epidemiology of ostertagiasis and to the use of faecal egg counts in the diagnosis of parasitic gastro-enteritis are discussed.The author thanks Miss C. N. Herbert for the calculations and curve fitting in this paper.