Herpes Viruses - 2013 (FN)

7/30/2019 Herpes Viruses - 2013 (FN)

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HERPES VIRUSES

Dr F Noordeen

Department of Microbiology

Faculty of Medicine

Peradeniya

April 2013


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Mechanisms by which herpes viruses cause

disease in humans

Host defenses against viruses

Main clinical features of viral infections/disease

Principles of diagnosis treatment and prevention

viral infections/disease in humans

Learning outcomes


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EM of a Herpes Virus


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CLASSIFICATION

Genome - DNA Viruses

Morphology - Icosahedral

- Large baggy envelope

Enzymes - DNA polymerase

- HSV & VZV thymidine kinase

Reproduction - Nucleus of host cell


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CLASSIFICATION

Alphaherpesvirinae

Herpes Simplex Virus type 1 HSV-1

Herpes Simplex Virus type 2 HSV-2

Varicella-Zoster Virus VZV

Betaherpesvirinae

Cytomegalovirus CMV

Human Herpesvirus type 6 HHV- 6



Gammaherpesvirinae

Epstein-Barr virus EBV


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HERPES SIMPLEX VIRUS

Primary infection - Contact with HSV

Latent infection - Virus persists in root ganglia

Reactivation - Production of infective virus

by latently infected cell

Recurrence - Clinical disease produced

by reactivation


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Pathogenesis

Entry by skin or mucous membranes

viral multiplication sensory nerve

lysis of cells root ganglia

vesicles latency

ulcersREACTIVATION

ColdFever

Surgery

Unknown


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Stomatitis with secondary skin lesions


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Primary infection of the skin


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Recurrent

infection


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Herpetic infection of the eye


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Herpetic whitlowHerpetic whitlow


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Vulvovaginitis in child


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Genital herpes inan adult male


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Genital herpes inan adult female


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Genital herpes in

adult female(Herpetic cervicitis)


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Epidemiology

Childhood infections common

Second peak at onset of sexual activity

Viral shedding/reservoirs

persons with recurrences infected but asymptomatic persons


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Laboratory diagnosis

Useful

Genital & eye infections

HVZ & HSV in immunocompromised

Herpes encephalitis

Specimens

Aspirate from vesicle

Scraping from base of ulcer

Serum/CSF for antibody


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Laboratory diagnosis

1. Microscopy

- Light - giant cells & inclusions

- Electron microscopy

2. Antigen detection - ELISA and IFT

3. Virus culture & identification

4. DNA detection - PCR (Encephalitis)

5. Antibody detection - ELISA and IFT


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Treatment for HSV infections

1. Acyclovir : Topical and oral formulations

2. Idoxyuridine


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HERPES VARICELLA ZOSTER - HVZ

Chicken pox - Fever + characteristic rash

Variable incubation period 14-21 days

Usually mild in children and more severe in adults

Complications

Secondary infection - uncommon

Varicella pneumonia

Secondary bacterial pneumonia S aureus & pneumococci

Post-infectious encephalitis

Generalised varicella (in immunocompromised patients)

Congenital and neonatal varicella


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Varicella rash in child


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Varicella vesicleson palate


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Varicella vesicles

on conjunctiva


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HERPES ZOSTER

Reactivation of VZV

Dermatomal distribution and may recur

Can disseminate in immunocompromised

patients

Complications

Post herpetic pain

Ophthalmic zoster - corneal scarring and loss of vision


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Diagnosis of Zoster

Clinical features and lesion distribution

EM/IFA of vesicle fluid

Serology - IgM detection


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Skin supplied by cervical roots 4 & 5 are affected


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Thoracic segments are affected


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Prevention of chicken pox

Children & adults living in close proximity

Do nothing Immunise with

live attenuated

vaccine

Protect contact

with patient with

chickenpox and

at risk of severe

disease

Zoster Immuno

Globulin (ZIG)


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EPSTEIN-BARR VIRUS - EBV

Discovered in 1964 by Epstein and Barr

Definite association with malignancy

Is able to transform cells resulting inimmortalisation of cells

2 types of virus A & B which may co-exist

in a same person


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Infectious mononucleosis

Affects adolescents and young adults

Worldwide distribution

Called kissing disease

IP - one month

Presents with fever,

sore throat, rash and swollen lymph nodes

DIAGNOSIS

Raised WBC with >20% lymphocytes

Paul-Bunnell test (heterophil antibodies) or mono spot

DIAGNOSIS

Raised WBC with >20% lymphocytes

Paul-Bunnell test (heterophil antibodies) or mono spot


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Blood film with abnormal

mononuclear cells

1st week - normal/raised

neutropenia

2nd week - leukoctosis with

(lymphoctosis)


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EnanthumEnanthum -- Rashes on the palateRashes on the palate


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Inflamed throat

without exudate


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Follicular

exudate

Patches of

white exudate

Patch of

white exudate


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Syndromes caused by EBV

Burkitts lymphoma Children 4-12 years

Subsaharan Africa and New Guinea

Nasopharyngeal carcinoma Adults 20-50 years old

Southern China

B cell lymphoma

Children and adults

Primary immunodeficiency

Patients with AIDS


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BURKITTS LYMPHOMA


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NASOPHARYNGEAL CARCINOMA


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Cytomegalovirus infections

Ubiquitous virus

Most populations - infections in early childhood

Often asymtomatic

Latency

Clinical disease increasing due to increasing

number of immunocompromised patients


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Foetal infection Transmission from mother via placenta

Clinically normal 80%

Causes congenital CMV

Death 1%

Cytomegalic inclusion disease 4%

Late onset hearing defect/mental retardation 15%

Infantile infections

Transmission during birth or breast feeding

Usually asymptomatic


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Young children Transmission from other children

Usually asymptomatic

Adolescent/adult Transmission during kissing, sexual intercourse or blood

transfusion

Occasionally IM like syndrome

Immunocompromised Exogenous PRIMARY INFECTION

Endogenous REACTIVATION

Pneumonitis, GI infection


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Diagnosis - Difficult Presence of virus or antibody to CMV does not indicate

a current CMV infection/disease

Different strategies used in different clinical situations

Isolation of virus from urine

within 30 days of birth

Antigen detection in

buffy coat - indicates

viraemia

* CMV specific IgG positive indicates past infection

Congenital CMV

Immunocompromised


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Treatment and prevention

Congenital CMV Prevention not possible

CMV in transplant recipients Prevention

Treatment

Test IgG before transplant

Use only seronegative donors

Early diagnosis

Reduce immunosuppression

Ganciclovir


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OTHER HUMAN HERPES VIRUSES

Human Herpes Virus 6 (HHV6) Discovered in 1988

Worldwide

Virus replicates in T and B cells

Infection occurs in first 3 years of life

Clinical disease - Exanthem subitum (Roseola infantum)

Mild acute febrile illness

Incubation period of 2 weeks

Fever lasts several days

Macular papular rash appears within 2 days of fever

85% of adults carry virus in saliva


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Exanthem subitum

(Roseola infantum)


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OTHER HUMAN HERPES VIRUSES

HHV7 Isolated from CD4 positive cells

Virus present in saliva of >75% of adults

Role in disease is unclear Evidence of infection present (seroconversion)

HHV8

Detected in epithelial cells of Kaposi sarcoma

Also present in semen

Postulated as cause of Kaposi sarcoma


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1.1 Name three (5) herpes viruses that causedisease in humans

(25 Marks)

1.2 How can you make an aetiological diagnosisof 3 diseases you have named in 1.1?

(75 Marks)

SAQ September 2011

Documents

Herpes Viruses - 2013 (FN)