The extreme susceptibility of ducks to Plasinodium lophurae was first reported by Wolfson (1940) who noted both the high parasitemia and mortality that followed blood-inoculation of these birds. The course of the infection in ducklings has been studied by a number of workers, among them Hewitt, Richardson and Seager (1942), Rigdon and Varnadoe (1945), and Becker, Brodine and Clappison (1949), all of whom support Wolfson\u27s findings. Marshall, Litchfield and White (1942) state that over a 4-month period they lost 95.1 % of a total of 205 infected control ducks, the average survival time being 9.3 ± 4 days. Hewitt et coll. made a study of mortality among infected ducks of different ages. The results of one study appearing in a table showed 50-60 percent mortality in birds 2-4 weeks of age and 80-85 percent mortality in birds 6-12 weeks of age. The results of another study reported graphically also tell the story of delayed death in the younger groups
