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CHICKENPOX (VARICELLA). VZV. The Varicella-Zoster Virus (VZV) belongs to the HERPES group. Pathogenic only for man; occurs worldwide . Causes 2 distinct clinical patterns: primary and latent.

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CHICKENPOX (VARICELLA)


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chickenpox varicella

CHICKENPOX (VARICELLA)

DR (MRS) M.B. FETUGA

slide2
VZV
  • The Varicella-Zoster Virus (VZV) belongs to the HERPES group.
  • Pathogenic only for man; occurs worldwide .
  • Causes 2 distinct clinical patterns: primary and latent.
  • The primary infection is manifested as varicella (chickenpox) and results in establishment of a lifelong latent infection of sensory ganglion neurons.
  • The reactivated infections are known as herpes zosters (shingles).
  • It is predominantly a disease of childhood in tropical Africa.
  • Varicella is highly infectious in children.

DR (MRS) M.B. FETUGA

pathogenesis 1
PATHOGENESIS 1
  • Infection is spread by direct contact and by air droplets.
  • The virus may be contained in the pharyngeal secretions hence the infectivity via air droplets.
  • Patients are infectious for 2 days before the appearance of the rash and until the skin lesions have crusted although the crusts do not usually contain viable viruses.
  • The viruses gain entry via the mucosa of the conjunctivae, nasopharynx and URT.

DR (MRS) M.B. FETUGA

pathogenesis 2
PATHOGENESIS 2
  • Viral replication takes place at the point of entry and they invade through the local lymphatic and blood vessels resulting in viraemia.
  • At this stage, the viruses are seeded in the dorsal root ganglion cells where they remain dormant even after the acute infection has resolved.
  • Antibodies are formed which protect against re-infection but not against re-activation of latent infections.

DR (MRS) M.B. FETUGA

clinical features of varicella
CLINICAL FEATURES OF VARICELLA
  • Diagnosis- clinical
  • VARICELLA begins usually SUDDENLY after an IP of 14 – 17 days.
  • Rash is usually accompanied by fever, malaise and pruritus.
  • Rash 1st appears on scalp & face and spreads to the trunk. Distribution is typically centripetal (more on the trunk than on the limbs; but spares hands & soles of feet).
  • Lesions begin as macules then turn to papules and vesicles. They crust within 2-3 days.

DR (MRS) M.B. FETUGA

clinical features of varicella1
CLINICAL FEATURES OF VARICELLA
  • New vesicles continue to appear over the first week of the illness. Typically, the rashes are present in different crops at the same time.
  • In Atypical form- the rash is not characteristic in appearance & distribution. The rash involves the flexural areas and concavities like the axillae, groin and mucous membranes of the nasopharnyx, conjunctivae & cornea.
  • Healing is usually complete although very minimal scarring may be present unlike in smallpox where scarring is massive.

DR (MRS) M.B. FETUGA

clinical features of varicella2
CLINICAL FEATURES OF VARICELLA
  • The rash involves the flexural areas and concavities like the axillae, groin and mucous membranes of the nasopharnyx, conjunctivae & cornea.
  • Healing is usually complete although very minimal scarring may be present.

DR (MRS) M.B. FETUGA

complications of varicella
COMPLICATIONS OF VARICELLA
  • Generally benign in children with low mortality & few complications but may be fatal in neonates
  • Complications usually occur in debilitated and immunocompromised children, particularly those with: TB, severe malnutrition, Measles, HIV, malignancies and steroid therapy.
  • Secondary skin infection by Staphylococcus and Streptococcus.
  • CNS (due to post-infectious demyelination). e.g. encephalitis (cerebellar in form), polyneuritis, transverse myelitis and Reye syndrome.

DR (MRS) M.B. FETUGA

complications of varicella1
COMPLICATIONS OF VARICELLA
  • keratitis,conjunctivitis, carditis, appendicitis, glomerulonephritis, orchitis
  • DIC- thrombocytopenia

DR (MRS) M.B. FETUGA

clinical features of zoster
CLINICAL FEATURES OF ZOSTER
  • Zoster is uncommon in childhood.
  • Early onset dx more likely to be ffged by herpes zoster due to persistence & prolonged presence of virus in the body
  • It is heralded by pain in the affected dermatome.
  • Few days later, the rash appears along the painful dermatome: typically, unilateral, segmental and proximal.
  • Any cranial or spinal sensory nerve may be affected but the thoracic nerves are most frequently affected.
  • The rashes are similar to those of varicella but are deeper and tend to heal with scarring.

DR (MRS) M.B. FETUGA

neonatal varicella
NEONATAL VARICELLA
  • Most babies acquire protective antibodies transplacentally, hence they are protected for the first 6 months of life (ONLY IF THE MOTHER PREVIOUSLY HAD THE INFECTION AND FORMED ANTIBODIES)
  • If a susceptible mother develops varicella rash 7 days or less before delivery, NEONATAL VARICELLA may occur in the baby. If the mother develops the rash more than 7 days before delivery, there is adequate time for the synthesis and transfer of antibodies against the virus.
  • Affected babies usually manifest 5-10 days after birth.
  • Mortality in Neonatal Varicella: 10 - 20%.

DR (MRS) M.B. FETUGA

congenital varicella
CONGENITAL VARICELLA
  • Follows maternal varicella in the first 2 trimesters.
  • Xterised by multiple congenital anomalies including choroiditis and cerebral malformation.
  • Features include: skin scars, contractures, hypoplastic limb deformities with rudimentary digits, congenital cataract and microphthalmia.

DR (MRS) M.B. FETUGA

management
MANAGEMENT
  • Diagnosis is usually clinical.
  • Viral culture & serology may be done where facilities are available.
  • Treatment is largely symptomatic: calamine lotion to soothen the skin, oral antihistamines like promethazine and analgesia with paracetamol.
  • Secondary bacterial infection of skin lesions can be treated with topical silver sulphadiazine or chlorhexidine. Systemic antibiotics are only indicated when cellulitis occurs.
  • Post-exposure prophylaxis with IM Varicella-Zooster Immunoglobulin 2mL confers about 97% protection.
  • Clinical trials of a live attenuated vaccine are being done.

DR (MRS) M.B. FETUGA

prognosis
PROGNOSIS
  • Recovery is ffged by long immunization. 2nd infection occasionally occurs

DR (MRS) M.B. FETUGA

prevention
PREVENTION
  • Vaccine - available, safe & effective.
  • Mainly used for children about to be treated with immunosuppressive drugs (leukemia)

DR (MRS) M.B. FETUGA

differential diagnosis
DIFFERENTIAL DIAGNOSIS
  • Impetigo, scabies, dermatitis multiforme

DR (MRS) M.B. FETUGA