Iridoviridae

Question 1

Morphology

Answer 1

Nonenveloped, or enveloped (membrane derived) with a spherical shape
- pleomorphic

Question 2

Nucleic acid

Answer 2

One molecule of linear dsDNA

• icosahedral
• large genome length
• may be circularly permuted (ends of each packaged DNA genome differs between viral particles)
• direct terminal repeats
• each virion may contain a single or multiple copies of genome (2 copies per particle)

Question 3

Taxonomic structure

Answer 3

• iridovirus: insects
• chloriridovirus: insects, mosquitoes
• ranavirus: fish, frogs, turtles
• lymphocryptovirus, lymphocystis virus: teleosts fish

Question 4

Iridovirus and chloriridovirus are known to be ______

Answer 4

Iridescent, forms paracrystal arrays in the host that reflects light
- makes host change color

Question 5

Ranavirus morphology

Answer 5

Enveloped, spherical virions

• isometric nucleocapsids with icosahedral symmetry
• infected larvae produce yellow-green iridescence

Question 6

Ranavirus nucleic acid

Answer 6

11-18% nucleic acid, with one molecule of linear dsDNA

• dsDNA is circularly permuted
• direct terminal repeats
• each virion contains a single copy of the genome
• contain 9% lipid without envelope

Question 7

CPE

Answer 7

• basophilic cytoplasmic inclusion bodies
• rounding of infected cells
• lifting from substrate
• extensive destruction of the monolayer by 24-48 hrs postinfection

Question 8

What is the most common virus of aquarium fish?

Answer 8

Lymphocystis

• chronic, self limiting viral disease
• freshwater, estuarine, and marine fish in warm, cool, and cold water are susceptible
• low mortality rate

Question 9

Lumphocystis pathogenesis

Answer 9

Viral replication and subsequent inhibition of mitosis in host connective tissue cells –> macroscopic, nodular lesions that resemble warts
- lymphocysts occur on skin or fins

Question 10

Iridoviruses replicate in the _______

Answer 10

Cytoplasm

Question 11

What are the 2 strains of lymphocystivirus?

Answer 11

Described based on DNA and polypeptide evaluation

• LCDV-1: fish species
• LCDV-2: dabs

Question 12

Transmission of lymphocystivirus

Answer 12

Direct contact with infected individuals

• infected via introduction of infected fish or exposure to contaminated fish products
• trauma to skin accelerates viral transmission

Question 13

Diagnosis of lymphocystivirus

Answer 13

Wet mounts or touch impressions of skin and fin lesions

- skin or fin biopsies are a definitive diagnosis