Miscellaneous Viruses Flashcards
1
Q
Examples of miscellaneous viruses
A
- Parvovirus
- Variola (poxvirus)
- Molluscum contagiosum (poxvirus)
- Rabies (rhabdovirus)
- JC virus (human polyomavirus) - progressive multifocal leucoencephalopathy - subacute spongioform encephalitis
- Prions
2
Q
Structure of parvovirus
A
- simplest DNA animal virus, small
- non-enveloped
- ssDNA
3
Q
Transmission of parvovirus
A
- only affects humans: Parvovirus B19
- mainly body fluids, blood, vertically from mother to fetus
4
Q
Incubation period of parvovirus
A
4 days - 2 weeks
5
Q
Symptoms of parvovirus
A
- 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
6
Q
Complications of parvovirus
A
- 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
7
Q
Diagnosis of parvovirus (3)
A
- 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
8
Q
Treatment of parvovirus (4)
A
- 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
9
Q
Transmission of variola
A
- respiratory route, from lesions in respiratory tract
- 12 day incubation period, virus distributed to internal organs
10
Q
Features of variola
A
- smallpox - high mortality, eradicated
- rash appears suddenly - papular, vesicular, pustular, leaves pink scars
- search & containment (isolation, tracing, vaccination)
11
Q
Features of vaccinia virus
A
- vaccination prepared from vesicular lesions produced in the skin of calves/sheep/grown in chick embryos
- complications - mild reactions, to fatal encephalitis
12
Q
Eradication of smallpox (3)
A
- No other reservoir but man
- Only causes acute infections - infected person (A) dies (B) recovers w life long immunity
- Vaccinia is an effective immunogen
13
Q
Incubation period of molluscum contagiosum
A
1 week to 6 months
14
Q
Symptoms of molluscum contagiosum
A
- 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
15
Q
Diagnosis of molluscum contagiosum (2)
A
- Clinical appearance
2. Confirmed by EM (semi solid caseous material can be expressed from lesions)
16
Q
Transmission of molluscum contagiosum
A
- direct contact/fomites
- may be transmitted skin-to-skin after sexual intercourse
- tends to be in children
17
Q
Treatment of molluscum contagiosum
A
- infection is usually benign & painless
- spontaneous recovery, only treatment for cosmetic reasons
18
Q
Structure of rabies virus
A
- ssRNA
- enveloped
- characteristic bullet-shaped appearance
19
Q
Pathogenesis of rabies
A
- virus replicates in striated/connective tissue at site of inoculation
- enters peripheral nerves through NMJ
- spreads to CNS in endoneurium of Schwann cells
- terminally, there is widespread CNS involvement - almost invariably fatal
- prevalent in wildlife/domestic dogs
20
Q
Symptoms of rabies (3)
A
- Prodromal phase
- 1-2d, pain & parasthesia at site of bite, GI/URT symptoms, irritability, apprehension, sense of impending death, hydrophobia - Excitation phase
- hyperventilation, hyperactivity, disorientation, seizures - Paralytic phase
- early paralysis/lethargy esp in areas innervated by CNs & in somatic muscles, bladder, bowels, gradual involvement of cardiac muscles + paralysis of resp muscles lead to death
21
Q
Diagnosis of rabies (4)
A
- Histopathology - Negri bodies (70%)
- Rapid virus antigen detection - corneal impressions, neck skin biopsy, DFA
- Virus cultivation - from saliva & infected tissue
- Serology - less useful
22
Q
Treatment of rabies (3)
A
- Post exposure prophylaxis
- wound treatment
- passive immunization (short term protection - human rabies Ig around wound)
- active immunization - Vaccines - human diploid cell vaccine (HDCV) (IM/SC, 5 doses)
- Control against canine rabies - stray dog control, vaccination of dogs, quarantine of imported animals
23
Q
Features of JC virus
A
- human polyomavirus
- circular, dsDNA - infects oligodendrocytes
- reactivation of latent JCV infection, dissemination via blood
24
Q
Symptoms of JC virus
A
- mental status changes
- speech/language deficits
- visual/sensory deficits/loss
- generalised/focal weakness
- unsteadiness, lack of coordination
- CN palsies
25
Diagnosis of JC virus (3)
1. Definitive diagnosis - brain biopsy
2. Clinically - detect focal lesion & abnormalities of white matter on CT/MRI
3. PCR from CSF
- no effective treatment
26
Features of subacute spongioform encephalopathies
- neurological diseases due to unconventional agents
- characterised by spongioform/vacuolating degeneration in the brain
- caused by abnormal prions combined w normal cellular protein - induce replication of abnormal form
27
Features of Creutzfeldt-Jacob Disease
- long incubation period
- dementia, ataxia, myoclonic jerks, death within 1yr
- degeneration of CNS w vacuolated neurons, fibrous gliosis (neuronal cells cannot regenerate, replaced by fibrous tissue)
