The epidemiology of ostertagiasis in cattle in Finland

It has been shown that Ostertagia ostertagi, the brown stomach -worm, may have its prevalence all over Finland where cattle husbandry exists. The infection was able to over-winter on the pasture. The infection rate caused by the overwintered infection reached its maximum early in the spring and declined then successively until the middle of the summer. Thereafter, the number of the infective larvae on pasture began to increase again. The infection rate on pasture was markedly higher close to the droppings than further away from them. It was shown that the vertical distribution of larvae on grass depends on the environmental humidity, temperature and light. The weight gain of all experimental animals, controls as well as those of treated with anthelmintics was modest. Consequently the effect of the anthelmintic treatment could not be estimated. Pathological changes in the abomasal wall caused by Ostertagia ostertagi were common, but only in a few cases were they severe. Neither did the abomasal pH-value or the serum pepsinogen content suggest a severe ostertagiasi