Pathogen

Pathophysiology& Immune response

ManagementVaccinations

Classical presentation

Complications

Chicken-pox

• Member of Herpesviridae • Sharing structural characteristics as a lipid

envelope surrounding a nuscleocapsid with icosahendral symmetry – total diameter 180-200nm

• Centrally located DNA 125000 bp in length• little genetic variation

• Reservoir – human, no animal reservoir• Highly contageous – attack rate ~90% in

seronegative individuals• Both sexes and all races – equivalent• Dermo & neutrotropic• Disease in children – well tolerated• More severe in adult, pregnant women and

immunocompromised often have hemorrhagic base

• Transmission– direct contact with the rash – Airborne respiratory droplets – vertical transmission (mother to baby) during pregnancy

Localize replication at undefined site (presumably the

nasopharynx)

Seeding to reticuloendothelial

system

Ultimately develop viremia

HSV• Mechanism of reactivation VZV resulting in Herpes

zoster is unknown• Presumedly virus infect dorsal roots ganglia during

chicken pox, remain latent until activated• Histopathologic examination Hemorrhage,

edema and lymphomcytic infiltration

Signs and symptoms • In healthy children – the disease is generally mild.

• The illness usually 14–16 days after exposure – Incubation period 10-21 days

• Prodromal symptoms : particularly in older children– Low-grade fever preceding skin manifestations by 1-2 D– 24-48 hr before rash • Mild abdominal pain • Mild cough and runny nose

– Mild headache – malaise or irritability

Signs and symptoms

• red, itchy rash appear first on the scalp, face, trunk• quickly turn into clear fluid-filled vesicles• 24-48 hr later, clouding and umbilication of lesions • initial lesions are crusting, new crops form on trunk and then

the extremities • Characteristics : various stages of evolution • oropharyngeal, vagina involvement : common• cornial involvement and serious ocular disease : rare• the average number of varicella lesion is about 300 lesions– <10 to >1,500 lesions

• Itching may range from mild to intense

• Diffuse and scattered nature of skin lesion• Vesicle involve cornium and dermis, • degenerative changes balloning, presence of

multinucleated giant cells and eosinophilic intranuclear inclusion

• Infection at localize blood vessels of the skin resulting in necrosis an epidermal hemorrhage

• Vesicular fluid become cloudy – recruitment of PNM leucocytes and presence of degenerated cells and debris.

• Ultimately vesicle may rupture and release fluid (infectious virus) or reabsorbed

Immune response

• Natural infection induces lifelong immunity• Newborn babies of immune mothers are protected by

passively acquired antibodies during their first months of life • Temporary protection of non-immune individuals can be

obtained by injection of varicella-zoster immune globulin within 3 days of exposure

• The immunity acquired in the course of varicella prevents neither the establishment of a latent VZV infection, nor the possibility of subsequent reactivation as zoster.

High-risk groups

• High risks of complications– Newborns and infants whose mothers

never had chickenpox or the vaccine – Teenagers – Adults – Pregnant women – People whose immune systems are impaired by another

disease or condition – People who are taking steroid medications for another

disease or condition, such as asthma – People with the skin inflammation eczema

• special consideration in Adults– not received the vaccine – not already had chickenpox – higher risk for exposure/transmission

Treatment

• Treatment approaches– supportive measures eg Hydration– antiviral therapy– varicella zoster immune globulin (VZIG)( 5g/day x 5days)– management of secondary bacterial infection. – Recognize underlying co-morbid eg: DKA

• Early recognition of secondary bacterial infections. Failure to recognize occult infection may result in serious illness and even death.

• Some case report review suggest steroid pulse therapy in severe conditoin ( IV methyprednisolone 1000mg/day x 3 days)

Acyclovir therapy

• Oral 800mg 5 times /day for 5-7days• Recommended for adolecents and adults < 24

hrs of infection• More effective in HZV infection – accelerated

healing of lesions, resolution of Zoster associated pain

• In Severe Chickenpox infection, should be treated at the onset reduce occurrence of visceral complications

• Penetration into CSF Excellent ~ 50% of serum level

• Complications:– Increase urea and increase creatinine ~5% – Thrombocytopenia ~ 6%– Gastrointestinal ~ 7%– Neurotoxicity ~ 1%

Varicella Vaccine

• Live attenuated vaccine (Oka)• Recommended in all children > 1 yr age and

seronegative adult

Varocella Immunoglobulin• special consideration in Adults– not received the vaccine – not already had chickenpox – higher risk for exposure/transmission

References• Harrison Principles of Internal Medicine, Vol 1, 17th

Edition, 2008• Davidson’s Principles & Practice of Medicine, 20th

Edition, 2006• Fulminant varicella Infection complicated with ARDS

and DIVC in Immunocompetent Young Adult, Soshoku et al, 2004

• Varicella pneumonia in adults, A.H. Mohsen*, M. McKendrick, Eur Respir J 2003; 21: 886–891

• Varicella-Zoster Virus Infection Associated with Acute Liver Failure, Hilde et al, 1998

Thank You….

.