Effects of different levels of nutrition and continuing dosing of poultry with Ascaridia galli eggs on the subsequent development of parasite populations

Publisher Website
Google Scholar
Abstract
SUMMARY: The population dynamics of Ascaridia galli infections of poultry was studied under repeated doses of 10, 100 and 1000 eggs. Daily doses were continued for 6 weeks only. At low dose rates patency is noted by the fifth week. At higher dose rates there is an accumulation of larvae whose development has been arrested at a precise developmental stage, i.e. the third larval stage. Sporadic development of some of these larvae to adults occurs later. Arguments are produced to show that this inhibition of larval development is a resistance and not a density-dependent phenomenon. The epidemiological significance of this inhibition is discussed. This resistance phenomenon is shown to occur in single infection experiments where 1000 eggs were used. This gives rise to the development of a worm population of two facies. The whole finding is suggested to be related in some way to the phenomenon of ‘tissue phase’, which is accepted as a normal life-cycle behaviour of this parasite. A brief review of previous work on this is given and it is postulated that the ‘tissue phase’ phenomenon is not an obligatory part of the normal life-cycle of the parasite but represents a reaction to factors of resistance inherent in chickens and controlled to a large extent by a complex dynamic interplay of dose size and the chickens.I wish to thank the Department of Technical Co-operation and the Federal Government of Nigeria for financing this project, Dr Boulton of the Poultry Research Centre, Edinburgh, for advice on nutrition, and the Department of Zoology, especially Dr J. A. Campbell, University of Edinburgh, for facilities and advice on the work. I am greatly indebted to the Ministry of Agriculture, Fisheries and Food, Poultry Research Laboratories, Lasswade, for the free supply of chickens used in this work.