Microbiological diagnosis of dengue virus infection

Tell microbiological diagnosis of dengue virus infection.

Microbiological diagnosis of dengue virus infection:

A.    Specimen collection:
a.    Blood

B.    Isolation: By cell culture—
a.    Acute phase protein
b.    Plasma

C.    Serological Test: [ This is enough for VIVA]

a.    Antibody detection:
1.    ELISA
2.    ICT (Immuno chromatography test)
3.    Immmuno blot (Western blot)

b.    Antigen detection:
1.    Fluorescence microscopy in tissue
2.    EIA in blood and plasma (Enzyme Immuno Assay)

c.    Routine blood test:
1.    Platelet count – Thrombocytopenia (<100,000/mm3)
2.    Haematocrit
3.    Prothrombin time increased

d.    Nucleic acid based technique:
1.    Plymerase chain reaction (PCR)

Pathogenesis of dengue fever

Tell pathogenesis of dengue shock syndrome.

Pathogenesis of dengue fever:

A.    Classical dengue fever (First exposure of dengue virus):
Dengue infection by one of the four serotypes
Antibody is formed
Formation of immune complex & activation of compliment
Increased vascular permeability and thrombocytopenia

B.    Dengue haemorrhagic fever (Re-exposure of dengue virus):
Patient infected with another serotype of dengue virus
An anamnestic, heterotypic response occurs
Large amount of cross-reacting antibody to the first serotype are produced
There are two hypotheses about what happens next—

a)    Immune complexes composed of virus and antibody are formed that activate complement, causing increased vascular permeability and thrombocytopenia. Ultimately shock and haemorrhage result.
b)    Antibodies increase the entry of virus into monocytes and moacrophages with the consequent liberation of a large amount of cytokines. Ultimately shock and haemorrhage result.

Ref: Lange /11th/283

Clinical types of Dengue

Mention clinical types of dengue.

Clinical types of Dengue:

  1. Primary Dengue (Classical dengue fever): When the patient is infected with any of four strain (DEN-1, DEN-2, DEN-3, DEN-4)
  2. Secondary Dengue (Dengue haemorrhagic fever): When the patient become infected with any of the rest 3 strains again.


What is dengue? Name vector & type of dengue virus.

Dengue ( breakbone fever):

Dengue is a mosquito-borne is an infectious tropical disease caused by the dengue virus.
Vector: Female Aedes aegypti mosquito

Types of dengue virus:

4 serological types:
1)    DEN-1
2)    DEN-2
3)    DEN-3
4)    DEN-4

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