The pathology of the immune response to Haemonchus contortus infection in sheep

Salman, Salman Kadhim (1980) The pathology of the immune response to Haemonchus contortus infection in sheep. PhD thesis, University of Glasgow.

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This thesis describes the results of various experiments on the response of sheep and lambs to Haemonchus contortus infection. Primary infections in adult sheep produced a high degree of protection against re-infection and this was associated with a marked cellular reaction in the abomasal mucosa together with a high level of local antibody production. In contrast primary infections in lambs had little or no protective effect and was associated with a weak cellular reaction in the mucosa and a poor local antibody response. There were similar qualitative changes in the type of mucin seen covering the surface mucosa after infection in both adult sheep and lambs; in worm-free animals only acid mucosubstances were detected whereas a mixture of neutral and acid mucin was observed after infection. Increased production of mucin was more obvious in the adult animals compared with the lambs. Attempts to stimulate immunity in young lambs by using different immunising regimens with various adjuvants and immunostimulants proved unsuccessful. There was little difference in the abomasal pathology of lambs clinically infected with small numbers of worms compared with worm-free controls. Similar infections in lambs maintained on either a high or low protein diet, however, showed that there was a marked reduction in faecal egg output and subsequent worm burdens in the group fed on a high protein diet compared with those maintained on a maintenance ration. An investigation of the significance of passive immunity showed that prior immunisation of ewes had little apparent effect on the subsequent response of their lambs to H. contortus infection. In naturally suckled lambs, however, there was reduced worm establishment compared with that in lambs bottle-fed a dried milk diet. The response to a challenge infection with normal H. contortus larvae in groups of previously uninfected and repeatedly vaccinated adult sheep and young lambs showed that after challenge in hyper-immune adult sheep there were increases in the size and number of lymphoid aggregates and this was associated with mild but diffuse cellular infiltrations of the mucosa. In contrast, in non-immunised adults there were fewer lymphoid aggregates but there was more obvious cellular infiltration and damage to the mucosal surface. Although hyperimmunised lambs showed a delay in the development of patent infections after challenge compared with non- immunised controls, the worm-burdens of both groups at necropsy were similar. Cellular reactions although present in both vaccinated and non-vaccinated lambs after challenge were, in contrast to the adult sheep, more marked in the vaccinated group. In the vaccinated ewes, intra-epithelial mast cells were present in all of the animals at all stages after challenge and they were always more numerous than in the non-vaccinated animals. In the vaccinated lambs intraepithelial mast cells were also present at all stages after challenge, although in smaller numbers than in the adult sheep, while in the non-vaccinated lambs only a few of these cells were detected three to four weeks after infection.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J L Duncan
Keywords: Animal diseases
Date of Award: 1980
Depositing User: Enlighten Team
Unique ID: glathesis:1980-72401
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 24 May 2019 15:12

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