Tolerance of Fowls for Moderate Infections of Intestinal Helminths 1

Summary 1. Experiments involving parastized and control fowls were made to test the tolerance of growing chickens to moderate infections of ascarids and tapeworms. 2. The criteria for judging the tolerance included growth, blood sugar level, and hemoglobin content of parasitized fowls comparable to those of the control chickens. The criteria for the tapeworm tests included also differential blood counts. 3. Chickens 23 days of age parasitized with 200 infective eggs of the fowl ascarid, Ascaridia galli, were able to tolerate infections of from one to 46 worms without manifesting definite harm from the worms in four weeks. The average of 17.9 ascardis per fowl is above the average infection in range fowls. 4. Growing chickens parasitized at 40 days of age with 200 larval tapeworms (Raillietina cesticillus) were not significantly harmed by infections of from two to 172 tapeworms during a period of eight weeks. The average of 61.5 tapeworms per fowl is more than an average infection found under conditions of general poultry production.