In this chapter, we discuss the diseases and related pathologic alterations that may be encountered in the gastrointestinal tract and associated organs of various species of laboratory animals, birds, fish, reptiles, and amphibians. Diseases of various segments of the gastrointestinal tract, the salivary glands, liver, and pancreas are discussed and categorized as inflammatory, parasitic, neoplastic, or miscellaneous. The latter category includes developmental anomalies and metabolic lesions. Due to space limitations, this presentation is not an all-inclusive review, but it does provide a rather extensive review of these lesions. We have also included a rather comprehensive literature review, with a list of references for those readers who want more detailed information with respect to specific diseases.

The Digestive System

Captive flocks of red jungle fowl ( Gallus gallus ) experimentally infected with the intestinal nematode Ascaridia galli were used to test Hamilton and Zuk's (1982 ) hypothesis that parasites adversely affect male secondary sex characters and that females prefer unparasitized over parasitized males. Infected chicks grew more slowly than uninfected controls, with the effect particularly pronounced on comb length rather than tarsus length or body weight. At sexual maturity, infected roosters had duller combs and eyes, shorter combs and tail feathers, and paler hackle feathers than control roosters. In experimental mate choice tests, females preferred unparasitized over parasitized roosters by about 2: 1, and an analysis of covariance revealed that the hens were using the traits on which the two groups differed to make their mate choice decisions. Finally, in a test of an extension of the Hamilton and Zuk hypothesis, control and infected males were not distinguishable based on non sexually-selected characters such as bill size, suggesting that parasites have a disproportionately larger effect on ornamental traits.

Parasites and mate choice in red jungle fowl.

1. The effect of infections with Dermanyssus gallinae (poultry red mite or chicken mite) and Ascaridia galli (roundworm) on the behaviour and health of laying hens was investigated. 2. Six groups of 15 pullets (Isa Brown) were kept in indoor pens from 18 weeks of age. Two groups were artificially infected with D. gallinae, two groups with A. galli and two groups were kept as uninfected controls. The hens were observed for behavioural reactions and physiological changes (weight gain and various blood variables) to the parasitic infections. 3. Infections with D. gallinae resulted in reduced weight gain, anaemia and even death of some of the hens. Behavioural changes were also observed, as the mite-infected hens showed higher self-grooming and head scratching both during the day and night. 4. A. galli resulted in a lower weight gain but no significant changes were seen in blood variables or behavioural activities.

Influence of Dermanyssus gallinae and Ascaridia galli infections on behaviour and health of laying hens (Gallus gallus domesticus)

Important parasites in poultry production systems.

Publisher Summary This chapter discusses the occurrence, physiological effects, and possible causes of a voluntary reduction of food consumption in parasitic infections with protozoa and helminths. A study of anorexia is justified by its widespread occurrence in protozoal infections and helminthiases, particularly of the gastrointestinal tract (GIT), and its association with poor growth or loss of weight of the host. Viral, bacterial, and noninfectious diseases of man and domestic animals are also briefly described because anorexia in these and protozoal and helminthic infections may have common causes and responses. The hosts cover most groups of animals, including man. Anorexia may occur with infections in different parts of the GIT or in other organs and tissues. In acute infections of pigeons, the schizonts of Haemoproteus columbae are located in the endothelial cells of blood vessels. In the infections of ducks and geese with Leucocytozoon simondi, schizonts are present in the parenchymal cells of the liver, and megaloschizonts are present in brain, liver, lungs, kidneys, intestinal tissue, and lymphoid cells. The chapter discusses the relevance of anorexia to the physiological responses to infection, which is frequently assessed by the pair-feeding technique.

Anorexia: Occurrence, Pathophysiology, and Possible Causes in Parasitic Infections

The pathogenicity and pathology of Ascaridia galli infections of poultry were studied using repeated doses of varying numbers of eggs No significant effect due to infection was seen on pcv and Hb values of infected chickens Haemo concentration occurred parallel with sporadic diarrhoea, which follows high levels of repeated dosing This phenomenon complicated the interpretation of blood protein values A/G ratios were, however, worked out and analysed No significant differences were noticed between the groups and it was concluded that under the levels of inoculation employed during the study there were no significant effects of A galli infections on blood protein values as well as pcv and Hbvalues of infected chickensSymptomatic developments, macroscopic lesions and pathological changes of intestinal tissues due to infection were followed up in detail They were most severe in chickens on the least nutritive diet and sustaining the highest levels of repeated doses Pathogenicity of larval and adult parasites was described The presence of large numbers of adult parasites was associated with intestinal obstruction in host This was seen mostly in chickens on low nutrition and sustaining either low or high levels of repeated inoculation, and very rarely also in chickens under high plane of nutrition but sustaining repeated inoculation of small numbers of eggs Cellular infiltration as a result of infection was found to be extremely rareIt was present as fibroblasts and only in association with dead larvaeThe author is indebted to the Department of Technical Cooperation, under whose Fellowship the study was carried out; the Department of Zoology, Edinburgh University, for facilities provided; the Ministry of Agriculture, Fisheries and Food; Lasswode Poultry Research Laboratories, for the free supply of chickens used here; Dr J A Campbell of Edinburgh University for his keen interest, encouragement and advice throughout this work; and finally to G Obiwelozor for reproducing the photographs from the original manuscript

Observations on the pathogenicity and pathology of Ascaridia galli.

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.

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

M. M. Ikeme

Papers

Observations on the pathogenicity and pathology of Ascaridia galli.

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

Weight changes in chickens placed on different levels of nutrition and varying degrees of repeated dosage with Ascaridia galli eggs.