The effect of stress on the parasitism of mallard ducklings by Echinuria uncinata (Nematoda: Spirurida)

Abstract

Mallard ducklings given a standardized inoculum of Echinuria uncinata and stressed by crowding or by injecting with cortisone retained greater numbers and larger nematodes at necropsy than infected nontreated controls. Stressed ducklings exhibited signs of the General Adaptation Syndrome; namely, involution of the bursae of Fabricius and thymus glands, hypertrophy of the adrenal glands (except in those birds injected with cortisone), and retardation of growth. Numerous eosinophils normally infiltrate granulomas in response to the nematode infection. Stress inhibited this reaction and may have contributed to the retention of larger nematode burdens. Bursectomy within 2 days of hatching failed to prevent antibody production in mallard ducklings infected with E. uncinata.