Miscellaneous Viruses Flashcards
Examples of miscellaneous viruses
- Parvovirus
- Variola (poxvirus)
- Molluscum contagiosum (poxvirus)
- Rabies (rhabdovirus)
- JC virus (human polyomavirus) - progressive multifocal leucoencephalopathy - subacute spongioform encephalitis
- Prions
Structure of parvovirus
- simplest DNA animal virus, small
- non-enveloped
- ssDNA
Transmission of parvovirus
- only affects humans: Parvovirus B19
- mainly body fluids, blood, vertically from mother to fetus
Incubation period of parvovirus
4 days - 2 weeks
Symptoms of parvovirus
- common in chidhood, mostly asymptomatic
Fifth Disease (Erythema Infectiosum)
- 1st phase: viremic - URTI (site of shedding), symptoms occur at end of 1st wk (fever, malaise, myalgia, chills, itching)
- 2nd phase: mediated by immune complexes - rash, “slapped cheek”/”lacy” reticulated appearance
Complications of parvovirus
- targets human erythroid progenitor cells - cell lysis - anemia, can also affect lymphocytes, granulocytes, platelets
1. Transient aplastic crisis - in pt w chronic haemolytic anaemia
2. Severe aplastic anaemia - immunocompromised
3. Severe anaemia in non-immune hydrops fetalis
Diagnosis of parvovirus (3)
- Difficult to grow virus
- Serology
- IgM (4-7d), IgG (7-10d, persists)
- pregnancy: mother - IgM & IgG - rising titres - Pregnancy
- mother: PCR, detect B19 DNA in maternal serum
- fetus: ultrasound screening & percutaneous umbilical blood sampling
Treatment of parvovirus (4)
- No known specific treatment, no vaccine
- Blood transfusion for transient aplastic crisis
- Fetal infection: (A) watchful waiting (B) high dose IgG therapy (C) intrauterine fetal transfusion
- Avoid exposure during pregnancy
Transmission of variola
- respiratory route, from lesions in respiratory tract
- 12 day incubation period, virus distributed to internal organs
Features of variola
- smallpox - high mortality, eradicated
- rash appears suddenly - papular, vesicular, pustular, leaves pink scars
- search & containment (isolation, tracing, vaccination)
Features of vaccinia virus
- vaccination prepared from vesicular lesions produced in the skin of calves/sheep/grown in chick embryos
- complications - mild reactions, to fatal encephalitis
Eradication of smallpox (3)
- No other reservoir but man
- Only causes acute infections - infected person (A) dies (B) recovers w life long immunity
- Vaccinia is an effective immunogen
Incubation period of molluscum contagiosum
1 week to 6 months
Symptoms of molluscum contagiosum
- small papule, grows into discrete, waxy, smooth, dome-shaped, pearly/flesh coloured nodule
- 1-20 lesions, persist for 2m, disease lasts 6m
- children: trunk, proximal extremities
- adults: trunk, pubic area, thighs
Diagnosis of molluscum contagiosum (2)
- Clinical appearance
2. Confirmed by EM (semi solid caseous material can be expressed from lesions)