The type of Atlantic salmon immune response to amoebic gill disease was investigated by analysis of cytokine genes possibly related to the TH1, TH17 and Treg pathways, which were significantly down regulated, while il-4/13 isoforms, possibly related to the TH2 pathway, were found to be significantly up regulated. Moreover, the injection of Atlantic salmon with rIfn-γ, which might initiate the TH1 immune pathway, did not reduce infection load of Paramoeba perurans or severity of gill pathology in challenged fish. Different arginase isoforms present in salmonids were also characterised and the data supported the concept that arginase type II may be a more relevant marker of alterantive activate macrophages in teleost fish induced by rIl-4/13. Regarding the biology of P. perurans, the susceptibility of amoebae to different environmental conditions showed that amoebae exposed to salinities lower than 3 ppt were disrupted or did not recover after 16 days, while all amoebae cultures showed a significant difference between the two temperatures (10°C and 15°C) studied over time. Significant differences were also found in relative abundance of the 30 most prevalent bacterial genera present in the isolated P. perurans cultures (16S rRNA). The impact of stress on the host response to AGD was tested for the presence of an association between temperature (10°C and 15°C) and variation in severity of AGD in Atlantic salmon. This association was demonstrated for the histopathology and P. perurans load analysis, reflecting an earlier and stronger AGD infection at the higher temperature (15°C) treatment. No significant difference between the two temperature treatments was shown in hormonal and molecular responses. Therefore, temperature might not act as a chronic stressor but its effect could be linked to the higher amoebae attachment seen at higher temperatures in the in vitro experiment reported.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:731634 |
| Date | January 2017 |
| Creators | Benedicenti, Ottavia |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235409 |
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