Mcb 8 Flashcards
(27 cards)
What are the criteria for classifying viruses?
Host types, Disease syndrome, Viral structure & symmetry, Nucleic acid types (Genome), mRNA production mechanism, Modern taxonomy (Phylogenetic)
What is the Baltimore classification of viruses based on?
Nucleic Acid types and mRNA production mechanism
What are the six groups of viruses in Baltimore’s classification?
- ds-DNA viruses
- ss-DNA viruses
- ds-RNA viruses
- ss-RNA viruses with positive strands (+ve polarity)
- ss-RNA viruses with negative strands (-ve polarity)
- ss-RNA viruses associated with the enzyme reverse transcriptase
Name three medically important double-stranded DNA viruses.
- Poxviridae
- Herpesviridae
- Hepadnaviridae
DNA viruses can be classified into what categories?
- Enveloped viruses
- Non-enveloped viruses
What family does Parvovirus belong to?
Family: Parvoviridae
What is the order of the Parvovirus?
Order: Piccovirales
What is the class of Parvovirus?
Class: Quintoviricetes
What are the unique properties of Parvoviruses?
- Smallest DNA virus
- Icosahedral
- Non-enveloped
- ssDNA, 4000-6000 bases
- Predilection for erythroid progenitor cells
What diseases do Parvoviruses cause in animals?
- Distemper in cats
- Enteric disease in dogs
- Fatal cardiac infection in puppies
Which Parvovirus is the only member that causes infections in humans?
B19
What is the serotype situation for Parvovirus?
Has only one serotype
What is the temperature resistance of Parvovirus?
Resistant at 53°C for 30 minutes
What is the pH stability of Parvovirus?
Stable at pH 3-9
What inactivates Parvovirus?
- Formalin
- Propiolactone
- Oxidizing agents
What proteins does Parvovirus code for?
- 3 structural proteins
- 1 major non-structural protein
- Many smaller proteins
What are the genera included in the classification of parvoviruses?
- Erythrovirus
- Parvovirus
- Dependovirus
What characterizes Dependoviruses?
- Replicate only in the presence of helper virus (Adenoviruses)
- Do not alter the infection caused by the helper virus
What diseases are associated with the Parvovirus genus?
- Aleutian mink disease
- Canine parvovirus
- Immune complex disease
- Enteritis, myocarditis
What is the transmission route for B19 infection?
- Aerosol droplet
- Fecal–oral route
- Direct inoculation of conjunctivas by fingers
- Vertical transmission during birth
- Percutaneous inoculation with blood contaminated items
- Transfusion of blood & blood related products
When is the infected individual contagious for B19?
From 24-48 hours before prodrome to rash appearance
What is the pathogenesis of B19 virus infection?
- Tropism for RBC precursors
- Infects rapidly dividing RBC precursors in the bone marrow
- Destroys infected cells leading to anaemia
What clinical syndromes are associated with B19 infection?
- Flu-like illness
- Erythema infectiosum (5th Disease)
- Infection in pregnant women
- Chronic B19 infection
What is the classic clinical presentation of Erythema infectiosum?
Cutaneous rash, arthralgia, aplastic anaemia
