Protists Flashcards
What is the causative agent of Dermo Disea?
Perkinsus Marinus - Single Celled Protozoan Parasite
What Species does Dermo affects
Oysters - Crassostrea Virginia (eastern oysters) and other species
What are the effects of dermo on oysters?
Pale Digestive gland, Shrimkage of mantle away from shell, slowed growth, occasional puss like pockets, (FORD AND TRIPP 1996)
How does demo disease affect oysters biologically (internal)
- alters amino acid balance of host - depletes glycine and taurine by 40% - impacts salinity tolerance as osmoconformers use amino acids to create osmotic pressures
- supression of production of reactive oxygen (which is important in the immune system)
- MORTALITY when temp and salinity rises
- Trophozites in water column enter oysters paella cavity through filter feeding - gills
- Trophozites displaying oyster surface ligands are phagocytksed by hemocytes, where they then replicate and migrate out of host tissue by lysis
How is demo disease treated in aquaculture?
Erradication if possible
- restricted movement
- Low salinities and temps
- reduce densities
- early harvest of infected stock
How is demo disease detected
- Histology using H and E Stain - parasitic states an be detected in connective tissue
- EM of zoospore ultrastructure
- Immunoassay - poly/mono clonal antibodies developed
- RT-PR
- Fluid thiocollate medium (FTM) for 7 days, stain with iodine, examine for blue black prezoosporangia - causes swelling of up to 100um
- DNA probes developed for SSU rRNA genes
What species does bonamia affect?
Ostreae Species (Oysters)
What type of parasite is bonamia ostreae?
Haplosporidian
How can bonamia be treated?
There are no known treatments - notifiable disease by CEFAS - restricted movement
- Suspension culture, reduced stocking density
- Avoid use of wild oyster seed – use spat from hatcheries so you can test the seeds
- Mix cultures withdifferent oysters – so reducing susceptibility ofpopulations
- Selective breeding? Disease resistant populations
- GM? Genetically modified oysters in Japan
- Roselin institute in edinburugh – looking for traits restistant to bonamia
How can Bonamia be detected?
PCR rDNA and ITS region – code for functional proteins and are completely variable so use these regions as diagnostic
What are the Symptoms of Bonamia?
- Yellow to black dicoloured tissues and perforated ulcers in gills, mantle and hepatopancreas – cant sell
- Ultimately causes host mortality – not instantaneous
- Infection intensity not related to gonadal development stage
- Some evidence to suggest that a minimum age of 2 years is required for infection to develop in wild oysters
