Biology of intestinal nematode parasites in relation to host immunity : a study of Nematospiroides dubius Baylis, 1926, in mice, and Oesophagostomum columbianum (Curtice, 1890) in sheep

Dash, Keith Macdonald (1970). Biology of intestinal nematode parasites in relation to host immunity : a study of Nematospiroides dubius Baylis, 1926, in mice, and Oesophagostomum columbianum (Curtice, 1890) in sheep PhD Thesis, School of Molecular and Microbial Sciences, The University of Queensland. doi:10.14264/uql.2015.475

       
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Author Dash, Keith Macdonald
Thesis Title Biology of intestinal nematode parasites in relation to host immunity : a study of Nematospiroides dubius Baylis, 1926, in mice, and Oesophagostomum columbianum (Curtice, 1890) in sheep
School, Centre or Institute School of Molecular and Microbial Sciences
Institution The University of Queensland
DOI 10.14264/uql.2015.475
Publication date 1970
Thesis type PhD Thesis
Supervisor C. Dobson
Total pages 191
Language eng
Subjects 070205 Animal Protection (Pests and Pathogens)
Formatted abstract
The host-parasite relationships of Nematospiroides dubius in mice and Oesophagostomum columbianum in sheep were studied as examples of associations at different levels of adaptation. 

The development of Nematospiroides dubius in initial infections was characterised by the establishment of a high percentage of infective larvae and by a uniform rate of development to the adult stage. Resistance to reinfection was not observed even after three immunizing infections with 50 third-stage larvae. However there was a progressive inhibition of worm growth and development from the second to the fourth infection, but this, did not prevent the parasites from completing their development to the adult stage. These features are interpreted as being indicative of a well developed host-parasite relationship. 

Immediate skin reactions were elicited with Nematospiroides dubius antigen as early as the fourth day after initial infections. Anaphylactic and reaginic antibodies were first detected in sera on the fifth and twentieth days respectively. Both types of antibodies were also found in the mucosa of the small intestine in the area parasitized by the larval and adult worms. No association was evident between reaginic antibodies and resistance to reinfection. 

Passively transferred immune sera had an inhibitory effect on the growth of female Nematospiroides dubius during the first five days after infection; male worms were less affected. There was no relationship between the degree of growth inhibition and the immune status of the donor. 

The life-cycle of Oesophagostomum columbianum in sheep was unique. Most third-stage larvae encysted in the small intestine; metamorphosis from the third to the fourth-larval stage commenced during this tissue phase. Some fourth-stage larvae subsequently entered a second histotropic phase in the large intestine, while others appeared to develop directly to the adult stage in the lumen without undergoing a second tissue migration. 

It is thought that larvae which undergo a second tissue migration are those which return prematurely to the intestinal lumen from the first histotropic phase before they have completed the third moult. 

Two distinct types of nodule were seen in the intestinal wall of sheep infected with Oesophagostomum columbianum. Small nodules 1-3 mm in diameter were formed in response to the third and early fourthstage larvae in the first histotropic phase. These became progressively smaller in size after the larvae had returned to the lumen. Large caseous nodules 5-10 mm in diameter were formed in the large Intestine in response to fourth-stage larvae in the second histotropic phase. In effect, the one larva was responsible for both lesions, although at different stages of its development. 

Single infections in adult sheep with 600 larvae failed to stimulate any appreciable resistance to the establishment of a challenge infection given 80 days later. The immunolcgical response of the host was expressed by the arrested development of some fourth-stage larvae in the first histotropic phase, by the inhibition of worm growth, by the failure of the majority of re-infecting larvae to develop to the adult stage, and by an increase in the prepatent period. 

The relationship between Oesophagostomum columbianum and the sheep appears to be a poorly adapted one. It is proposed that the reason for this is that O. columbianum may be a natural parasite of African antelopes and that its association with domestic sheep is of recent origin.
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