Lecture Tropmed 2013 Dhf Nata

8/10/2019 Lecture Tropmed 2013 Dhf Nata

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Natural history of dengue virus infection.

Dengue case classification and level ofseverity according to WHO 2009.

Dengue management and delivery clinical

services. Basic principle of volume replacement in

dengue cases.

Laboratory diagnosis methods for confirming

the dengue cases and know the efficiencyand accuracy of diagnostic tests in denguecases.


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HEMORRH GIC


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Epidemiology

Most important arthropod-borne viraldiseases in terms of human morbidity andmortality.

Important public health problem.

Tropical & subtropical regions around the

worldurban and semi urban areas


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Virology

Dengue virus

mosquito-borne flavivirus.

Transmitted by Aedes aegypti

Aedes albopictus.

DEN-1, 2, 3 and 4.


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Virology

Each episode of infection

a life-long protective immunity to thehomologous serotype

partial & transient protection against subsequentinfection by the other three serotypes.

Secondary infection is a DHF major risk factor


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Spectrum of Infection

The incubation period is 4-7 days (range 3-14)

Asymptomatic a spectrum of illness

Undifferentiated mild febrile illness severedisease (plasma leakage (-/+_) & organimpairment

Systemic & dynamic disease with Clinical

Haematological

Serological

profiles changing from day to day.


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Pathophysiology

Increased vascular permeability is the primarypathophysiological abnormality in DHF/ DSS.

Increased vascular permeability leads toplasma leakage and results in hypovolaemia/shock.


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Pathophysiology

The pathogenetic mechanism for the increased

vascular permeability (?) Destructive vascular lesions (-)

post-mortem (microscopically),

perivascular oedema loss of integrity of endothelial junctions

endothelial dysfunction

AbN immune response

production of cytokines or chemokines, activation of T-lymphocytes

disturbances of haemostatic system

C3a, C5a, TNF-, IL-2, 6 & 10, IFN-, histamine


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TOURNIQUET TEST

In DHF grade 1 (+) tourniquet test serves as

the only indicator of haemorrhagic tendency. Sensitivity0% to 57% (phase of illness)

5-21%false positive

How to perform tourniquet test Inflate the blood pressure cuff on the upper arm

to a point midway between the systolic and

diastolic pressures for 5 minutes. A positive test is when 20 or more petechiae

per 2.5 cm (1 inch) square are observed.


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The 1997 WHO classification of dengue virus infection.


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DFProbable

An acute febrile illness with two or more of the following manifestations:headache, retro-orbital pain, myalgia, arthralgia, rash, haemorrhagicmanifestations and leucopeniaAnd

Supportive serology (a reciprocal haemagglutination-inhibition antibody titre>1280, a comparable IgG enzyme-linked immunosorbent assay (ELISA, seechapter 455) titre or a positive IgM antibody test on a late acute orconvalescent-phase serum specimen)

Or

Occurrence at the same location and time as other DF cases

Confirmed

A case confirmed by one of the following laboratory criteria: Isolation of the dengue virus from serum/autopsy samples

At least a four-fold change in reciprocal IgG/IgM titres to one or more dengue virusantigens in paired samples

Demonstration of dengue virus antigen in autopsy tissue, serum or cerebrospinal fluidsamples by immunohistochemistry, immunofluorescence or ELISA

Detection of dengue virus genomic sequences in autopsy tissue serum or cerebrospinalfluid samples by polymerase chain reaction (PCR)

Reportable

Any probable or confirmed case should be reported


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DHFFor a diagnosis of DHF, a case must meet all four of thefollowing criteria:

Fever or history of fever lasting 27 days, occasionallybiphasic

A haemorrhagic tendency shown by at least one of thefollowing: a positive tourniquet test*; petechiae, ecchymosesor purpura; bleeding from the mucosa, gastro-intestinal tract,injection sites or other locations; haematemesis or melaena

Thrombocytopenia [(100,000 cells/mm3 (1006109/L)]{

Evidence of plasma leakage due to increased vascularpermeability shown by: an increase in the haematocrit >20%above average for age, sex and population; a decrease in thehaematocrit after intervention >20% of baseline; signs ofplasma leakage such as pleural effusion, ascites orhypoproteinaemia


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DSS

For a case of DSS, all four criteria for DHF must

be met, in addition to evidence of circulatoryfailure manifested by:

Rapid and weak pulse

And Narrow pulse pressure (,20 mmHg or 2.7 kPa)

or manifested by

Hypotension for age

And

Cold, clammy skin and restlessness


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World Health Organization. Dengue Guidelines for

Diagnosis, Treatment, Prevention and Control

New Edition 2009. WHO: Geneva; 2009


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The following manifestations are importantin dengue infection but are often under-recognised or misdiagnosed

Acute abdomen :

Hepatitis and liver failure :

Neurological manifestation :

Haemophagocytic syndrome


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DISEASE MONITORING LABORATORY TESTS

Full Blood Count (FBC)

1. White cell count (WCC) :

2. Haematocrit (HCT) :

3. Thrombocytopaenia :

Liver Function Test


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Diagnostic Tests

DENGUE SEROLOGY TESTS

Haemagglutination Inhibition Test

Dengue IgM test

Indirect IgG ELISA test Cross-react with:

other flavivirus Japanese Encephalitis

non-flavivirusmalaria, leptospirosis, toxoplasmosis,syphilis

connective tissue diseases

rheumatoid arthritisVIRUS ISOLATION

POLYMERASE CHAIN REACTION (PCR)

NON-STRUCTURAL PROTEIN-1 (NS1 Antigen)


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Clinical and Laboratory Criteria for Patients Who Can be Treated at Home


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The following should be taken intoconsideration before discharging a patient.

Afebrile for 48 hours

Improved general condition

Improved appetite

Stable haematocrit Rising platelet count

No dyspnoea or respiratory distress from pleuraleffusion or ascites

Resolved bleeding episodes

Resolution/recovery of organ dysfunction


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Lecture Tropmed 2013 Dhf Nata