NEW ParaFishControl article "Acting locally - affecting globally: RNA sequencing of gilthead sea bream with a mild Sparicotyle chrysophrii infection reveals effects on apoptosis, immune and hypoxia related genes"

Background: Monogenean flatworms are the main fish ectoparasites inflicting serious economic losses in aquaculture.The polyopisthocotylean Sparicotyle chrysophrii parasitizes the gills of gilthead sea bream (GSB,Sparus aurata) causing anaemia, lamellae fusion and sloughing of epithelial cells, with the consequent hypoxia, emaciation, lethargy andmortality. Currently no preventive or curative measures against this disease exist and therefore information on the host-parasite interaction is crucial to find mitigation solutions for sparicotylosis. The knowledge about gene regulation inmonogenean-host models mostly comes from freshwater monopysthocotyleans and almost nothing is known about polyopisthocotyleans. The current study aims to decipher the host response at local (gills) and systemic (spleen, liver) levels in farmed GSB with a mild natural S. chrysophrii infection by transcriptomic analysis.

Results: Using Illumina RNA sequencing and transcriptomic analysis, a total of 2581 differentially expressed transcripts were identified in infected fish when compared to uninfected controls. Gill tissues in contact with the parasite (P gills) displayed regulation of fewer genes (700) than gill portions not in contact with the parasite (NP gills) (1235), most likely due to a local silencing effect of the parasite. The systemic reaction in the spleen was much higher than that at the parasite attachment site (local) (1240), and higher than in liver (334). NP gills displayed a strong enrichment of genes mainly related to immune response and apoptosis. Processes such as apoptosis, inflammation and cell proliferation dominated gills, whereas inhibition of apoptosis, autophagy, platelet activation, signalling and aggregation, and inflammasome were observed in spleen. Proteasome markers were increased in all tissues, whereas hypoxia-related genes were down-regulated in gills and spleen.

Conclusions: Contrasting forces seem to be acting at local and systemic levels. The splenic down-regulation could be part of a hypometabolic response, to counteract the hypoxia induced by the parasite damage to the gills and to concentrate the energy on defence and repair responses. Alternatively, it can be also interpreted as the often observedaction of helminths to modify host immunity in its own interest. These results provide the first toolkit for future studiestowards understanding and management of this parasitosis.

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NEW ParaFishControl article "In vitro activity of chemicals and commercial products against Saprolegnia parasitica and Saprolegnia delica strains"

Oomycetes of the genus Saprolegnia are responsible for severe economic losses in freshwater aquaculture. Following the ban of malachite green in food fish production, the demand for new treatments pushes towards the selection of more safe and environment‐friendly products. In the present work, in vitro activity of ten chemicals and three commercial products was tested on different strains of Saprolegnia, using malachite green as reference compound. The compounds were screened in agar and in water to assess the minimum inhibitory concentration (MIC) and the minimum lethal concentration (MLC), respectively. Two strains of Saprolegnia parasitica and one isolate of Saprolegnia delica were tested in triplicate per each concentration. Among tested chemicals, benzoic acid showed the lowest MIC (100 ppm) followed by acetic acid, iodoacetic acid and copper sulphate (250 ppm). Sodium percarbonate was not effective at any tested concentration. Among commercial products, Virkon™S was effective in inhibiting the growth of the mycelium (MIC = MLC = 1,000 ppm). Actidrox® and Detarox® AP showed MIC = 5,000 and 1,000 ppm, respectively, while MLCs were 10‐fold lower than MICs, possibly due to a higher activity of these products in water. Similarly, a higher effectiveness in water was observed also for iodoacetic acid.


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The third ParaFishControl e-newsletter has now been published!

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Workshop on “Sustainable Fish Health Control”

The DAFINET workshop on Sustainable fish health control was organized in collaboration with Parafishcontrol and BANGFISH on October 23, 2018. In connection to the workshop the University of Copenhagen hosted a five day workshop on fish diseases. The 40 workshop participants comprised PFC partners and colleagues from various countries (Norway, Bangladesh, India, China, Indonesia, Italy, Denmark). The scientific fields touched upon ranged from PFC parasites (salmon lice, white spot disease parasite Ichthyophthirius multifiliis, zoonotic nematode Contracaecum osculatum), and environmental issues (arsenic substances and antibiotics in fish ponds), pigments in fish flesh, bacterial and viral infections of rainbow trout. The host species discussed ranged from Atlantic salmon and rainbow trout to tilapia and Asian catfish. Sonal Patel from Norway and Morten Limborg from Denmark presented new results and ideas from novel types of approaches in fish disease research – the holistic view on both host, microbiome and the environment. The connected fish disease course over five days focused on both basic classical techniques and more advanced methodologies such as ELISA, immunohistochemistry, histology, PCR, qPCR and DNA sequencing. The course addressed parasitic, bacterial and viral diseases in wild and farmed fish. The photo shows seven course participants from Bangladesh with professor Kurt Buchmann (KU) in the lab.


NEW ParaFishControl article "Hints on T cell responses in a fish-parasite model: Enteromyxum leei induces differential expression of T cell signature molecules depending on the organ and the infection status"

Hints on T cell responses in a fish-parasite model: Enteromyxum leei induces differential expression of T cell signature molecules depending on the organ and the infection status. Parasites & Vectors 11:443.

Enteromyxum leei is a myxozoan parasite that produces a slow-progressing intestinal disease. This parasite invades the paracellular space of the intestinal epithelium and progresses from the posterior to the anterior intestine. The aim of the present study was to gain insights into fish T cell responses in the gilthead sea bream-E. leei infection model using a PCR-array with 30 signature molecules for different leukocyte responses in head kidney, spleen, anterior and posterior intestine.
The PCR-array results suggest that E. leei induced migration of T cells from head kidney to intestines where TH1, CTL and TH17 profiles were activated and kept in balance by the upregulation of regulatory cytokines. These results were partially validated by the use of cross-reacting antibodies and BrdU immunostaining to monitor proliferation. Zap70 immunostaining supported the increased number of T cells in the anterior intestine detected by gene expression, but double staining with BrdU did not show active proliferation of this cell type at a local level, supporting the migration from lymphohaematopoietic tissues to the site of infection. Global analyses of the expression profiles revealed a clear separation between infected and exposed, but non-infected fish, more evident in the target organ. Exposed, non-infected animals showed an intermediate phenotype closer to the control fish.
These results evidence a clear modulation of the T cell response of gilthead sea bream upon E. leei infection. The effects occurred both at local and systemic levels, but the response was stronger and more specific at the site of infection, the intestine. Altogether, this research poses a promising basis to understand the response against this important parasite and establish effective preventive or palliative measures.


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