Studies on Bovine Gastro-Intestinal Parasites. II. Immunity to Hookworm and Nodular Worm Infection in Calves

Abstract

During experiments on the life cycle of the hookworm (Bunostomum phlebotomum) and the nodular worm (Oesophagostomnum radiatum), nematode parasites of cattle, four calves have developed a certain amount of resistance to infection as judged by egg counts. Since it is believed that these observations will be of considerable interest to parasitologists and veterinarians, a description of the experiments is presented in the following pages. The conditions under which the experiments were carried out were carefully controlled insofar as the parasitic infections were concerned. Only a brief description of the methods is given here, since a more complete statement is made in another paper (Mayhew, 1939). The calves used in these experiments were obtained as soon as possible after birth and placed in specially constructed cages in the animal building belonging to the Veterinary Science Department. The cement floors of the rooms, as well as the cages, were cleaned twice a week to remove the larvae before they reached the infective stage. The feed and water were parasite-free. Each animal was allowed as much hay as it desired and was given a measured amount of a commercial calf feed each day. Under these conditions of management the control animals remained consistently free of parasites. At least one and as many as four uninoculated controls have been maintained under the same conditions as