Poxviridae - Part 1 Flashcards
What is the subfamily of Poxviridae that causes poxvirus of vertebrates?
Chordopoxivinae
What is the subfamily of Poxviridae that causes poxvirus of insects?
Entomopoxvirinae
How many genera belong to the subfamily Chordopoxvirinae?
8 genera that infect humans, animals, and birds.
Describe the structure of poxviruses?
Large Sometimes enveloped DNA viruses Most are pleomorphic, typically brick shaped. Possess an irregular surface of projecting tubular or globular structures.
What do members of genus Parapoxvirus look like?
Ovid Covered with long thread-like surface tubules that appear to arranged in a crisscross fashion. Resembles a ball of yarn.
What are the two infectious poxvirus particles?
Intracellular mature virus (IMV) Extracellular enveloped virus (EEV) Both forms are infectious.
The extracellular forms contain which two membranes?
1) Envelope 2) Inner Membrane
T/F Virions that are released from cells by budding, rather than by cellular disruption, acquire the extra envelope that contains virus encoded-proteins from host cell membrane.
True.
T/F Intracellular viral particles (IMV) only have an inner membrane.
True. IMV may come out by disruption of host cell and only have an inner membrane.
What type of symmetry do Poxviruses have?
Complex symmetry. NOT icosahedral or helical!
What does the virion outer layer enclose?
A dumbbell-shaped core and two lateral bodies.
How many genes do Poxviruses have in their genome?
More than 200.
How many genes of the genome encode proteins that are contained in virions?
As many as 100.
What is the structural property of the genome of Poxviruses?
Single molecule of linear double-stranded DNA
What is the smallest type of Poxviruses? What is the size?
130 kbp – Parapoxvirus
What is the largest type of Poxviruses? What is the size?
375 kbp – Entomopoxviruses
Where does replication of Poxviruses occur predominantly?
Cytoplasm
Unlike other DNA viruses, Poxviruses have evolved to encode the enzymes required for what?
Transcription and replication of the viral genome.
How are virions released?
Budding (enveloped) Exocytosis Cell lysis- Most Common (non-enveloped)
T/F Both enveloped and non enveloped virions are infectious?
True
Are enveloped or non enveloped virions taken up by cells more readily?
Enveloped. They appear to be more important in the spread of virions through the body of the animal.
Which genus of Poxviruses produce a hemagglutinin?
Orthopoxviruses
What makes enveloped Poxviruses different from other enveloped viruses?
They have high environmental stability and remain infectious over a period of several months in an ambient environment.
Why are Poxviruses less sensitive to organic solvents/disinfectants compared to other enveloped viruses?
They have a low lipid content.
T/F Poxviruses show an extraordinary high resistance to drying
True.
T/F Poxviruses can survive for many years in dried scabs or other virus-laden material
True.
What are the three modes of transmission between animals?
1) Wounds– Poxviruses cannot infect intact skin. 2) Respiratory route– IE) sheeppox 3) Mechanical transmission through biting arthropods.
What type of cutaneous lesions do Poxviruses cause?
Epitheliotrophic.
In what types of animals can Poxviruses cause systemic diseases?
Birds Wild Animals
T/F Poxviruses are NOT species specific
FALSE. Most are host specific. The exception is Orthopoxvirus, which can infect a wide range of species.
How do Poxviruses usually gain access to the systemic circulation?
The lymphatic system. Then a second viremia disseminates the virus back to the skin and other target organs.
What are the steps of skin lesions in a Poxvirus infection?
1) Macule – flat red. 2) Papule – raise red. 3) Vesicle – Small blister 4) Pustule 5) Ulcer – epithelium ruptures/microbe discharged OR 5) Complication from ulcer or Scab/Scar
What is the other name for Orthopoxvirus?
Cow Pox
Where is cow pox endemic to?
Europe and Asia only.
What are the hosts for cow pox?
Cattle, wild and domestic cats, humans, zoo animals **Remember: This is the only Poxvirus that is not species specific.
What are the reservoir hosts for cow pox?
Rodents
What are the three modes of transmission for cow pox in cows?
1) Cow-Cow transmission through an infected milker’s hands or teat cups. 2) Farm cats-Cow 3) Rodents–Cow
What are the economic implications of cowpox in cows?
1) Losses to milk production due to soreness of teats 2) Mastitis that results from secondary bacterial infections
What are the three modes of transmission of cowpox in cats?
1) Skin inoculation through a bite or wound. Rodents are the common source of infection. 2) Oro-nasal 3) Viral pneumonia in exotic cats.
What are the clinical signs of cowpox in cats?
Primary- Single skin lesion on head, neck, or forelimb. It can be a small scabbed wound to a large abscess. Secondary- 1) 7-10 days later, widespread lesions begin to appear. 2) They become ulcerated papules in days 2-4. 3) Scab over and healing is complete by ~6 weeks.
Other than skin lesions, what other clinical signs do ~20% of cats show when infected with cow pox?
Mild coryza or conjunctivitis
How is cowpox transmitted to humans?
1) Direct contact to “cuddly” cats. 2) Rarely from zoo animals and rodents. 3) Virus is not commonly found in cattle, so chances of getting the virus is much less.
What are the clinical signs of cowpox in humans?
1) Macropapular lesions on hands and face. 2) Enlarged painful local lymph nodes 3) Sore throat, vomiting, fever
What is another type of Orthopoxvirus?
Monkey pox
How is monkeypox transmitted to humans?
Primary- Direct contact with blood, bodily fluids, or rashes of infected animals– Squirrels, monkeys, rats. Secondary- Human to human through infected respiratory tract excretions.
Where is monkeypox endemic to?
Remote villages in Central and West Africa, near rainforests
What are the clinical signs of monkeypox in humans?
1) Invasion period (0-5 days): Fever, intense headache, lymphadenopathy, muscle pain. 2) Skin eruption period: Evolution of rash from maculo-papules (lesions with flat bases) to vesicles (small fluid filled blisters), pustules, followed by crusts.
What are the other types of orthopoxviruses?
