lecture tropmed 2013 dhf nata
TRANSCRIPT
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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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