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Saturday, January 28, 2012

Chicken Pox - Epidemiology, Clinical Features, Diagnosis, Prevention and Control and Complications of Chicken Pox

I. What is chickn pox?

Chicken Pox Rashes caused by Varicella Zoster Virus
Chicken Pox or Varicella is an acute, highly infectious disease caused by varicella zoster virus (VZV). It is characterised by vesicular rash that may be accompanied by fever and malaise.


II. Epidemiology of Chickenpox

A. Occurence of Chickenpox

Chickenpox occurs world-wide in both epidemic and endemic forms.

B. Ecological Triad of Chickenpox

1. AGENT:

Varicella Zoster Virus (VZV) - VZV is a DNA virus - member of the family herpes virus.

2. HOST:

Humans are the natural host.
  • Age: Children under 10 years suffer more, where the disease is mild and self-limiting. A number of infections occur in adulthood which is called Shingles and is usually severe.
  • Sex-Both sexes are susceptible.
  • Immunity: One attack of chickenpox usually gives life-long immunity

3. ENVIRONMENT:

  • Season: Chickenpox occurs in all seasons. In temperate climates it is common in winter, but in the tropics it is common in summer.
  • Overcrowdin favours the spread of this disease.

C. Natural histroy of Chickenpox:

1. RESERVOIR (SOURCE OF INFECTION):

Usually a case of chickenpox.

2. INFECTIVE MATERIALS:

  • Oropharyngeal secretions
  • Lesions of skin and mucosa

3. INFECTIOUS PERIOD:

1-2 days before the appearance of rahs and 4-5 days after the appearance of the first crop of vesicles.

4. MODE OF TRANSMISSION:

  • Respiratory droplet
  • Direct contact

5. INCUBATION PERIOD: 2-3 WEEKS


III. Clinical Features of Chickenpox:

Rashes in Chicken Pox

A. Prodromal symptoms:

  • Fever
  • Malaise
  • Anorexia

B. First Sign:

Stages of Chicken Pox
  • Appearance of a characteristics rash in crops on the trunk on 2nd day of illness
  • The rahs spreads to the head and extremities
  • The rash will be found in different stages: Macules > Papules > Vesicles > Crusts.

C. Itching is marked.


IV. Diagnosis of Chickenpox:

A. Clinical of chickenpox:

The disease is usually recognized by the characteristic clinical sings mentioned above.

B. Laboratory Diagnosis of chickenpox:

  • Cytology and Electron Microscopy of vesicular fluid or scraping. This may reveal inclusions, giant cells and virus particles.
  • Detection of varicella specific antigen in vesicular fluid with immunoflourescence of monoclonal antibodies.
  • Serelogy: Complement Fixation Test
  • Culture of Vesicular Fluid: VZV is difficult to culture.

V. Prevention and Control of Chickenpox:

1. Notification:

Chickenpox is a locally notifiable disease.

2. Isolation:

The patient is infectious in early first week. During this period isolation of the patient is necessary.

3. Disinfection:

All the contaminated articles soiled by discharges from nose, throat, and skin lesions should be disinfected by boiling.

4. Immunization against chickenpox:

A. PASSIVE IMMUNIZATION

It is done with human varicella zoster immunoglobulin. This should be given for prophylaxis to immunosuppressed patients, neonates, and pregnant women who have no antibody to VZV and have had significant contact with chickenpox.

B. ACTIE IMMUNIZATION

It is now available with a live attenauted vaccie.

VI. Treatment of Chickenpox:

In the majority of patients (healthy children) no specific treatment is required for chickenpox.
However the following treatment plan is indicated in special cases:

1. Antiviral therapy

Aciclovir is indicated for:
  • the immunodeficient or immunocompromised (10mg/kg 8 hourly by intravenous infusion).
  • the adults and older adolescents (over 16 years of age by oral or intravenous infusion).

2. Local antiseptics:

Chlorhexidine is applied to the skin if there is secondary bacterial infection (due to itching).

3. Antibiotic therapy:

An antibiotic such as Flucoxacillin 500 mg 6 hourly is prescribed if secondary infection progresses.

4. Other symptomatic treatment

Such as analgesics, antipyretics and antipuritics are given.

VII. Complications immuomplications of chickenpox:

A. Viral effects:

  1. Pneumonitis (usually adults or immunosuppressed)
  2. Diffuse encephalitis (within first week)
  3. Cerebellar syndrome (in second week)
  4. Trannsverse myelitis, optic neuritis
  5. Myocarditis (usually in adults or immunosuppressed)
  6. Glomerulonephritis

B. Secondary Bacterial Infection:

  1. Skin
  2. Septicaemia
  3. Osteomylitis
  4. Septic arthritis

C. Intrauterine Infection:

  1. Congenital limb defects (varicella embryopathy - rare)


That's all for today!
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