Miscellaneous Viruses Flashcards

1
Q

Examples of miscellaneous viruses

A
  1. Parvovirus
  2. Variola (poxvirus)
  3. Molluscum contagiosum (poxvirus)
  4. Rabies (rhabdovirus)
  5. JC virus (human polyomavirus) - progressive multifocal leucoencephalopathy - subacute spongioform encephalitis
  6. Prions
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2
Q

Structure of parvovirus

A
  • simplest DNA animal virus, small
  • non-enveloped
  • ssDNA
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3
Q

Transmission of parvovirus

A
  • only affects humans: Parvovirus B19

- mainly body fluids, blood, vertically from mother to fetus

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4
Q

Incubation period of parvovirus

A

4 days - 2 weeks

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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
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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
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7
Q

Diagnosis of parvovirus (3)

A
  1. Difficult to grow virus
  2. Serology
    - IgM (4-7d), IgG (7-10d, persists)
    - pregnancy: mother - IgM & IgG - rising titres
  3. Pregnancy
    - mother: PCR, detect B19 DNA in maternal serum
    - fetus: ultrasound screening & percutaneous umbilical blood sampling
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8
Q

Treatment of parvovirus (4)

A
  1. No known specific treatment, no vaccine
  2. Blood transfusion for transient aplastic crisis
  3. Fetal infection: (A) watchful waiting (B) high dose IgG therapy (C) intrauterine fetal transfusion
  4. Avoid exposure during pregnancy
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9
Q

Transmission of variola

A
  • respiratory route, from lesions in respiratory tract

- 12 day incubation period, virus distributed to internal organs

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10
Q

Features of variola

A
  • smallpox - high mortality, eradicated
  • rash appears suddenly - papular, vesicular, pustular, leaves pink scars
  • search & containment (isolation, tracing, vaccination)
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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
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12
Q

Eradication of smallpox (3)

A
  1. No other reservoir but man
  2. Only causes acute infections - infected person (A) dies (B) recovers w life long immunity
  3. Vaccinia is an effective immunogen
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13
Q

Incubation period of molluscum contagiosum

A

1 week to 6 months

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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
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15
Q

Diagnosis of molluscum contagiosum (2)

A
  1. Clinical appearance

2. Confirmed by EM (semi solid caseous material can be expressed from lesions)

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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
  1. Prodromal phase
    - 1-2d, pain & parasthesia at site of bite, GI/URT symptoms, irritability, apprehension, sense of impending death, hydrophobia
  2. Excitation phase
    - hyperventilation, hyperactivity, disorientation, seizures
  3. 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
  1. Histopathology - Negri bodies (70%)
  2. Rapid virus antigen detection - corneal impressions, neck skin biopsy, DFA
  3. Virus cultivation - from saliva & infected tissue
  4. Serology - less useful
22
Q

Treatment of rabies (3)

A
  1. Post exposure prophylaxis
    - wound treatment
    - passive immunization (short term protection - human rabies Ig around wound)
    - active immunization
  2. Vaccines - human diploid cell vaccine (HDCV) (IM/SC, 5 doses)
  3. 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
Q

Diagnosis of JC virus (3)

A
  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
Q

Features of subacute spongioform encephalopathies

A
  • 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
Q

Features of Creutzfeldt-Jacob Disease

A
  • 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)