P. L. Long

Bio: P. L. Long is an academic researcher. The author has contributed to research in topics: Schizogony. The author has an hindex of 1, co-authored 1 publications receiving 29 citations.

Studies on Eimeria praecox Johnson, 1930, in the chicken

Abstract: E. praeox has been isolated in Britain for the first time and is similar in regard to its oocyst size, prepatent time, life-cycle and the development of host immunity to the reports of Tyzzer et al. (1932). Oocysts had mean dimensions of 20·4 × 17·45 μm and the first oocysts were discharged 83½ h after infection. Oocyst production and life-cycle studies suggest that at least three generations of schizogony precede gametogony and that at least one further generation of schizogony is needed to explain the oocyst reproduction resulting from a small dose of oocysts. Young chickens 1½–3 weeks of age were not such suitable hosts as older chickens (6 weeks) and the reproduction of the parasite was seriously reduced when large numbers (e.g. 10 5 , 10 6 ) were used to infect chickens. A high degree of resistance to reinfection occurred after a single exposure to infection. Sporozoite infections of the caeca or cloaca resulted in the infection of the usual small intestine site; there was no development at the site of inoculation and attempts to infect the embryo allantois did not succeed. I wish to thank Dr M. Elaine Rose for the surgery required for the caecal infections, for her interest throughout and for help with the manuscript; Dr R. F. Gordon for help with the manuscript and permission to publish and Mr B. J. Millard for skilled technical assistance.

Problems in the Identification of Species of Eimeria

Abstract: The paper is concerned with the principles upon which coccidia of the genus Eimeria may be characterized. Reference strains for comparative purposes usually are not available and the limitations of morphological data for speciation are discussed. The value of other parameters are considered such as host and site specificity, pathogenicity, immunological specificity, pre-patent period, sporulation time, enzyme variation, and DNA buoyant density. The weight afforded to each of these parameters for specific identification may vary according to the parasite and host studied. Determinations of physiological and behavioral characteristics that are now becoming available should be included in species definitions wherever possible.

The specific characters of the Eimeria, with special reference to the Coccidia of the fowl

Abstract: Summary The differentiation of species of Eimeria is discussed with special reference to those occurring in the domestic fowl. Details of the morphology of the oocysts and other developmental stages of the parasites, their location in the host and, the characteristics of the lesions produced, the timing of the patent and prepatent periods, host‐ and site‐specificity and inimunological specificity may be used as aids for specific identification. A single criterion is usually insufficient for differentiation and depending upon the species, different characters vary in significance. Quantitative cross‐immunity tests appear to be the most satisfactory means available for the differentiation of species of Eimeria affecting chickens.

Enzyme variation in Eimeria species of the chicken

Abstract: A method for the biochemical identification of protozoa belonging to the genus Eimeria is described for the first time. Starch gel electrophoresis of the enzymes lactate dehydrogenase, glucose phosphate isomerase, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase from parasite extracts revealed both intra- and inter-species differences when 11 strains representative of 6 species of Eimeria were examined. Oocysts were the most accessible parasite stage for investigation but sporozoites and merozoites of an embryo-adapted strain of E. tenella were also examined for enzyme activity.

Mucosal transport of eimeria tenella in the cecum of the chicken

Abstract: A study of the early life history of Eimeria tenella with the electron microscope confirmed that sporozoites do not directly enter the enterocytes of the crypts, in which they develop, but are carried there by host cells. However, these cells are not macrophages, as previously thought, but intraepithelial lymphocytes. The evidence presented demonstrates that sporozoites first penetrate surface enterocytes and then enter intraepithelial lymphocytes that leave the epithelium, pass through the lamina propria and enter the crypts.

Host-Parasite Relationships in the Alimentary Tract of Domestic Birds

Abstract: Publisher Summary This chapter discusses host–parasite relationships in the alimentary tract of domestic birds. The functioning of the digestive system justifies assigning the status of a habitat to the alimentary tract and, therefore, that of a community to the organisms living therein. The chapter presents the aspects of the nutrition of domestic birds, including chemical nutrients, energy requirements, and nature of diet. The results of studies on the distribution, process of infection, and nutrition of organisms living in the alimentary tract of domestic birds have demonstrated, in a relatively superficial manner, something of the complexity of the various host–parasite relationships. Many parasites are dependent on the digestive physiology of their hosts, and some of the inhabitants of the tract also appear to be dependent on the activities of others, although it is not clear whether this dependence is direct or mediated through the host or some other environmental factor. The nature of the alimentary tract as an environment needs further investigation, and more studies should be undertaken to discover how the digestive physiology of the host, and the intraluminal conditions of the tract are affected by dietary changes and by parasites. Information of this type will facilitate both the design of experimental studies of host–parasite relationships and the in vitro cultivation of protozoan and metazoan parasites under chemically defined conditions. Satisfactory methods for in vitro cultivation are a prerequisite of the direct nutritional studies of parasites.