The history of avian medicine in the United States. IV. Some milestones in American research of poultry parasites.

Most of the major contributions of Americans to knowledge of poultry parasites have been made in the last 100 years. Factors responsible for this tardiness differed somewhat according to the disease. The first parasitic diseases to receive attention were usually those with distinctive characteristics as well as serious consequences, such as "gapes" and lousiness. Since helminths could usually be readily observed, whereas protozoa could be observed only by persons skilled in microscopy, disorders attributable to the former usually received attention earlier than did protozoan diseases. The control of ectoparasites, before the use of modern insecticides, became vastly simplified as mechanical incubators and brooders replaced the hen, and as the birds were provided with better housing. The major contributions of Americans to our understanding of parasitic diseases of poultry are detailed for five disorders attributable to helminths, and two attributable to protozoa. The latter are histomoniasis of turkeys and coccidiosis of chickens. No attempt has been made to evaluate the impact of contemporary research.