Viruses

Question 1

What is a mimivirus

Answer 1

A Microbe mimicking Virus

Question 2

What is a pandovirus

Answer 2

A virus with a significant genome size which codes for more structures than need

Question 3

How can you classify Viruses

Answer 3

1. TheirGenome (DNA or RNA)
2. The Form Of Their Genome (Single or Double Stranded
3. Host Range and Type
4. Virion Size and Shape - Pleiomorphic
5. The Chemical Characteristic of their coat

Question 4

What is the causative agent of WSSV

Answer 4

Whispoviridae

Question 5

What are the Symptoms of WSSV

Answer 5

Lethargy, Disorientation, Loss of Balance, Cuticle loosening, Red/brown flesh, White Spots

Question 6

How do you detect WSSV

Answer 6

Histiopathology, Dark Field Microscopy, PCR, qPCR

Question 7

What Impact Does WSSV have on The Farming Industry

Answer 7

• 90-100% Mortality in 7-10 Days
• Spreads via transport of infected shrimp heads
• Harvest at first sign of infection - can be sold as cat or fish feed
• Infects 14 Species including FW decapods
• Lytic Cycle Unknown

Question 8

What are the 4 main Proteins o WSSV and what do they code for

Answer 8

2 Viral Coat Proteins - VP19 and VP28

2 Viral Nuclear capsid Proteins - VP24 and VP26

Question 9

How does WSSV enter cells

Answer 9

Ingestion or Water Bourne - passage across gills and into hemocytes and connective tissue where it proliferates

Question 10

How can you treat WSSV

Answer 10

Preimmune Egg Yolk - inject with 0.5mg/ul 1.5 hours after first introduction to WSSV waters - 83% survival after 15 days

Question 11

What does PDV stand for and what is the causative agent?

Answer 11

Phocine Distemper Virus - it is a morbillivirus

Question 12

What are the Symptoms of PDV?

Answer 12

• Mucas secretion from eyes and nose
• Miscariage
• Diahrea
• Skin alopecia
• Coughing
• Respiratory Discharge
• Emphysemia

Question 13

What organisms does PDV affect - who are the carriers?

Answer 13

• Can cause mortality in cetaceans
• Started in Denmark
• Sleigh dogs and Grey seals are carriers
• Harbour seals are most susceptible
• 2009 saw PDV in pacific sea otters

Question 14

What is The PDV Aetiology

Answer 14

• Infects lymphoid tissues and cells
• Transmitted through droplets of milk
• effects of pollution on resistance are unknown
• replicates in cytoplasm

Question 15

How do You detect PDV

Answer 15

A. Serology

1. blood serum examined for antibodies
2. viral neutralisation test which measures amount of specific antibody to virus capsid in sample
3. create dilution series of known virus, isolate CDV
4. virus binds to antibodies and is inactive, unbound virus remains, assayed for cytopathic effects
5. antibody titre in sample is derived from the CDV dilution in which virus is bound

B. PCR

1. direct measurement of viral nucleic acid
2. allows quantification
3. can look at allelic variations and use qPCR to look at past history

Question 16

What are The Advantages of Serology

Answer 16

• reveals information about past exposure
• inexpensive
• requires no genomic information about virus
• although depends on antibody cross-reactivity

Question 17

What are the advantages of PCR

Answer 17

• Quantitative information about the presence of viral RNA
• Level of infection/information about infectivity
• very sensitive and highly specific
• can study allelic variation

Question 18

What does VHS stand for and what is the causative agent

Answer 18

Virus Haemorrhagic Speticaemia - Rhabdoviridae

Question 19

What are The Symptoms of VHS

Answer 19

• Reduced Feeding
• Swimming is lethargic or Hyperactive
• Anaemia and lethargy
• exophthalmia (pop-eye)
• liver Necrosis
• Myocardial mineralisation

Question 20

What are the characteristics of VHS

Answer 20

• Not lethal immediately
• Rainbow Trout and 10 other species
• fish of all ages but high mortality in juvenile fish
• Survivors act as vectors
• birds can also be vectors
• significant in aquaculture - >80%
  Effluent
  considered emergent disease
• Virus is most active at low temps - 14 degrees, at 20 it is inhibited